Technologies and Applications
Technologies and Applications
This file is intended to present some technology topics that cannot be assigned to a particular mission. The following chapters contain only short descriptions, they are presented in reverse order. The topics should be of interest to the reader community.
ESA helps industry for 5G innovation
25 September 2019: Connecting people and machines to everything, everywhere and at all times through 5G networks promises to transform society. People will be able to access information and services developed to meet their immediate needs but, for this to happen seamlessly, satellite networks are needed alongside terrestrial ones. 1)
Figure 1: Space's part in the 5G revolution. Everybody is talking about 5G, the new generation of wireless communication. We are at the start of a revolution in connectivity for everything, everywhere, at all times. Space plays at important roll in this revolution. We need satellites to ensure businesses and citizens can benefit smoothly from 5G (video credit: ESA)
The European Space Agency is working with companies keen to develop and use space-enabled seamless 5G connectivity to develop ubiquitous services. At the UK Space Conference, held from 24 to 26 September in Newport, South Wales, UK, ESA is showcasing its work with several British-based companies, supported by the UK Space Agency.
The companies are working on applications that range from autonomous ships to connected cars and drone delivery, from cargo logistics to emergency services, from media and broadcast to financial services.
Spire is a satellite-powered data company that provides predictive analysis for global maritime, aviation and weather forecasting. It uses automatic identification systems aboard ships to track their whereabouts on the oceans.
Spire's network of 80 nanosatellites picks up the identity, position, course and speed of each vessel. Thanks to intelligent machine-learning algorithms, it can predict vessel locations and the ship's estimated time of arrival at port, enabling port authorities to manage busy docks and market traders to price the goods carried aboard.
Peter Platzer, chief executive of Spire, said: "ESA recognized the value of smaller, more nimble satellites and was looking for a provider that could bring satellites more rapidly and cheaper to orbit. That really was the start of our collaboration. ESA was instrumental in the fact that Spire's largest office today is in the UK and most of its workforce is in Europe."
Integrating the ubiquity and unprecedented performance of satellites with terrestrial 5G networks is fundamental to the future success of 'Project Darwin', a project to develop connected cars in a partnership between ESA, Telefonica 02, a satellite operator, the universities of Oxford and Glasgow and several UK-based start-up companies.
Connected cars need to switch seamlessly between terrestrial and satellite networks, so that people and goods can move across the country without any glitches.
Darwin relies on a terminal that will allow seamless switching between the networks.
Daniela Petrovic of Telefonica O2, who founded Darwin, said: "There is a really nice ecosystem of players delivering innovation. ESA provided the opportunities to start discussions with satellite operators and helped us create this partnership.
"There is a good body of knowledge within ESA on innovation and science hubs and this gave us the opportunity to see what other start-ups are doing. Through ESA, we are getting exposure to 22 member state countries which can see the opportunity and maybe get involved."
Magali Vaissiere, Director of Telecommunications and Integrated Applications at ESA, said: "We are very excited to see the response of industry to our Space for 5G initiative, which aims to bring together the cellular and satellite telecommunications world and provide the connectivity fabric to enable the digital transformation of industry and society.
"The showcase of flagship 5G projects today confirms the strategic importance of our Space for 5G initiative, which will be a significant strategic part of the upcoming ESA Conference of Ministers to be held in November."
Other companies that formed part of the showcase include: Cranfield University, which as part of its Digital Aviation Research and Technology Centre is set to spearhead the UK's research into digital aviation technology; HiSky, a satellite virtual network operator that offers global low-cost voice, data and internet of things communications using existing telecommunications satellites; Inmarsat, a global satellite operator that is showcasing a range of new maritime services enabled by the seamless integration of 5G cellular and satellite connectivity; Open Cosmos, a small satellite manufacturer based at Harwell in Oxfordshire, which is investigating how to deliver 5G by satellite; and Sky and Space Global based in London that plans a constellation of 200 nanosatellites in equatorial low Earth orbit for narrowband communications.
Glowing solar cell
25 September 2019: A solar cell is being turned into a light source by running electric current through it. Such ‘luminescence' testing is performed routinely in ESA's Solar Generator Laboratory, employed to detect cell defects – such as the cracks highlighted here. 2)
By happy accident the solar (or ‘photovoltaic') cell was invented in 1954, just before the start of the Space Age, allowing satellites to run off the abundant sunshine found in Earth orbit and beyond.
Figure 2: Made from the same kind of semiconductor materials as computer circuits, solar cells are designed so that incoming sunlight generates an electric current. But the process can be reversed for test purposes: apply an electric charge and a solar cell will glow (image credit: ESA–SJM Photography)
Solar cells, carefully assembled together into arrays, are an essential part of space missions, together with specially-designed batteries for times when a satellite needs more power, passes into darkness or faces a power emergency – plus the power conditioning and distribution electronics keeping all parts of a mission supplied with the power they require.
"Space power technologies are second only to launchers in ensuring European competitiveness and non-dependence," comments Véronique Ferlet-Cavrois, Head of ESA's Power Systems, EMC & Space Environment Division.
"Without the research and development ESA performs with European industry to ensure the continued availability of high-performance space power systems and components we would be left utterly reliant on foreign suppliers, or missions wouldn't fly at all. We will be taking a look back at the important work done during the last three decades during this month's European Space Power Conference."
The 12th European Space Power Conference (ESPC) is taking take place in Juan-les-Pins, Côte d'Azur, France, from 30 September to 4 October, with almost 400 participants. Véronique is chairing the event.
"It will begin 30 years to the week from the very first conference in the series," adds ESA power conditioning engineer Mariel Triggianese, ESPC's technical coordinator.
"So we'll be commemorating our past but also looking forward. Our theme is ‘Space Power, Achievements and Challenges'. The chief technology officers from Airbus, Thales, Ariane Group and OHB will be joined by ESA's Director of Technology Engineering and Quality, Franco Ongaro, to discuss the space power needs of their markets into the future."
Quantum light sources pave the way for optical circuits
05 August 2019: An international team headed up by Alexander Holleitner and Jonathan Finley, physicists at the Technical University of Munich (TUM), has succeeded in placing light sources in atomically thin material layers with an accuracy of just a few nanometers. The new method allows for a multitude of applications in quantum technologies, from quantum sensors and transistors in smartphones through to new encryption technologies for data transmission. 3) 4)
Previous circuits on chips rely on electrons as the information carriers. In the future, photons which transmit information at the speed of light will be able to take on this task in optical circuits. Quantum light sources, which are then connected with quantum fiber optic cables and detectors are needed as basic building blocks for such new chips.
Figure 3: By bombarding thin molybdenum sulfide layers with helium ions, physicists at TUM succeeded in placing light sources in atomically thin material layers with an accuracy of just a few nanometers. The new method allows for a multitude of applications in quantum technologies (image credit: TUM)
First step towards optical quantum computers: "This constitutes a first key step towards optical quantum computers," says Julian Klein, lead author of the study. "Because for future applications the light sources must be coupled with photon circuits, waveguides for example, in order to make light-based quantum calculations possible."
The critical point here is the exact and precisely controllable placement of the light sources. It is possible to create quantum light sources in conventional three-dimensional materials such as diamond or silicon, but they cannot be precisely placed in these materials.
Deterministic defects: The physicists then used a layer of the semiconductor molybdenum disulfide (MoS2) as the starting material, just three atoms thick. They irradiated this with a helium ion beam which they focused on a surface area of less than one nanometer.
In order to generate optically active defects, the desired quantum light sources, molybdenum or sulfur atoms are precisely hammered out of the layer. The imperfections are traps for so-called excitons, electron-hole pairs, which then emit the desired photons.
Technically, the new helium ion microscope at the Walter Schottky Institute's Center for Nanotechnology and Nanomaterials, which can be used to irradiate such material with an unparalleled lateral resolution, was of central importance for this.
On the road to new light sources: Together with theorists at TUM, the Max Planck Society, and the University of Bremen, the team developed a model which also describes the energy states observed at the imperfections in theory.
In the future, the researchers also want to create more complex light source patterns, in lateral two-dimensional lattice structures for example, in order to thus also research multi-exciton phenomena or exotic material properties.
This is the experimental gateway to a world which has long only been described in theory within the context of the so-called Bose-Hubbard model which seeks to account for complex processes in solids.
Quantum sensors, transistors and secure encryption: And there may be progress not only in theory, but also with regard to possible technological developments. Since the light sources always have the same underlying defect in the material, they are theoretically indistinguishable. This allows for applications which are based on the quantum-mechanical principle of entanglement.
"It is possible to integrate our quantum light sources very elegantly into photon circuits," says Klein. "Owing to the high sensitivity, for example, it is possible to build quantum sensors for smartphones and develop extremely secure encryption technologies for data transmission."
10 July 2019: ESA's technical heart will be serving as a testbed for this driverless shuttle in the coming months. 5)
The Agency's ESTEC establishment in Noordwijk, the Netherlands, is working with vehicle owner Dutch Automated Mobility, provincial and municipal governments and the bus company Arriva to assess its viability as a ‘last mile' solution for public transport.
The fully autonomous vehicle calculates its position using a fusion of satellite navigation, lidar ‘laser radar', visible cameras and motion sensors. Once it enters service in October it will be used to transport employees from one side of the ESTEC complex to the other.
The fully-electric, zero-emission shuttle will respect the on-site speed limit of 15 km/h, and for its first six months of service will carry a steward to observe its operation along its preprogrammed 10-minute-long roundtrip.
Figure 4: This driverless shuttle will soon be tested at ESA/ESTEC in the Netherlands (image credit: ESA, B. Smith)
New Method Can Spot Failing Infrastructure from Space
09 July 2019: We rely on bridges to connect us to other places, and we trust that they're safe. While many governments invest heavily in inspection and maintenance programs, the number of bridges that are coming to the end of their design lives or that have significant structural damage can outpace the resources available to repair them. But infrastructure managers may soon have a new way to identify the structures most at risk of failure. 6)
Figure 5: A satellite view of the Morandi Bridge in Genoa, Italy, prior to its August 2018 collapse. The numbers identify key bridge components. Numbers 4 through 8 correspond to the bridge's V-shaped piers (from West to East). Numbers 9 through 11 correspond to three independent balance systems on the bridge. In the annotated version, the black arrows identify areas of change based on data from the Cosmo-SkyMed satellite constellation (image credit: NASA/JPL-Caltech/Google)
Scientists, led by Pietro Milillo of NASA's Jet Propulsion Laboratory in Pasadena, California, have developed a new technique for analyzing satellite data that can reveal subtle structural changes that may indicate a bridge is deteriorating - changes so subtle that they are not visible to the naked eye.
In August 2018, the Morandi Bridge, near Genoa, Italy, collapsed, killing dozens of people. A team of scientists from NASA, the University of Bath in England and the Italian Space Agency used synthetic aperture radar (SAR) measurements from several different satellites and reference points to map relative displacement - or structural changes to the bridge - from 2003 to the time of its collapse. Using a new process, they were able to detect millimeter-size changes to the bridge over time that would not have been detected by the standard processing approaches applied to spaceborne synthetic aperture radar observations.
They found that the deck next to the bridge's collapsed pier showed subtle signs of change as early as 2015; they also noted that several parts of the bridge showed a more significant increase in structural changes between March 2017 and August 2018 - a hidden indication that at least part of the bridge may have become structurally unsound.
"This is about developing a new technique that can assist in the characterization of the health of bridges and other infrastructure," Millilo said. "We couldn't have forecasted this particular collapse because standard assessment techniques available at the time couldn't detect what we can see now. But going forward, this technique, combined with techniques already in use, has the potential to do a lot of good."
The technique is limited to areas that have consistent synthetic aperture radar-equipped satellite coverage. In early 2022, NASA and the Indian Space Research Organization (ISRO) plan to launch the NASA-ISRO Synthetic Aperture Radar (NISAR), which will greatly expand that coverage. Designed to enable scientists to observe and measure global environmental changes and hazards, NISAR will collect imagery that will enable engineers and scientists to investigate the stability of structures like bridges nearly anywhere in the world about every week.
"We can't solve the entire problem of structural safety, but we can add a new tool to the standard procedures to better support maintenance considerations," said Milillo.
The majority of the SAR data for this study was acquired by the Italian Space Agency's COSMO-Skymed constellation and the European Space Agency's (ESA's) Sentinel-1a and -1b satellites. The research team also used historical data sets from ESA's Envisat satellite. The study was recently published in the journal Remote Sensing. 7)
Atomic motion captured in 4-D for the first time
27 June 2019: Everyday transitions from one state of matter to another—such as freezing, melting or evaporation—start with a process called "nucleation," in which tiny clusters of atoms or molecules (called "nuclei") begin to coalesce. Nucleation plays a critical role in circumstances as diverse as the formation of clouds and the onset of neurodegenerative disease. 8)
A UCLA-led team has gained a never-before-seen view of nucleation—capturing how the atoms rearrange at 4-D atomic resolution (that is, in three dimensions of space and across time). The findings, published in the journal Nature, differ from predictions based on the classical theory of nucleation that has long appeared in textbooks. 9)
"This is truly a groundbreaking experiment—we not only locate and identify individual atoms with high precision, but also monitor their motion in 4-D for the first time," said senior author Jianwei "John" Miao, a UCLA professor of physics and astronomy, who is the deputy director of the STROBE National Science Foundation Science and Technology Center and a member of the California NanoSystems Institute at UCLA.
Research by the team, which includes collaborators from Lawrence Berkeley National Laboratory, University of Colorado at Boulder, University of Buffalo and the University of Nevada, Reno, builds upon a powerful imaging technique previously developed by Miao's research group. That method, called "atomic electron tomography," uses a state-of-the-art electron microscope located at Berkeley Lab's Molecular Foundry, which images a sample using electrons. The sample is rotated, and in much the same way a CAT scan generates a three-dimensional X-ray of the human body, atomic electron tomography creates stunning 3D images of atoms within a material.
Miao and his colleagues examined an iron-platinum alloy formed into nanoparticles so small that it takes more than 10,000 laid side by side to span the width of a human hair. To investigate nucleation, the scientists heated the nanoparticles to 520 º Celsius ( 968º Fahrenheit), and took images after 9 minutes, 16 minutes and 26 minutes. At that temperature, the alloy undergoes a transition between two different solid phases.
Figure 6: The image shows 4D atomic motion is captured in an iron-platinum nanoparticle at three different annealing times. The experimental observations are inconsistent with classical nucleation theory, showing the need of a model beyond
SUN-to-LIQUID (Fuels from concentrated sunlight)
June 2019: The EU (European Union) energy roadmap for 2050 aims at a 75% share of renewables in the gross energy consumption. Achieving this target requires a significant share of alternative transportation fuels, including a 40% target share of low carbon fuels in aviation. 10) Therefore the European Commission calls for the development of sustainable fuels from non-biomass non-fossil sources.
In contrast to biofuels, solar energy is undisputedly scalable to any future demand and is already utilized at large scale to produce heat and electricity. Solar energy may also be used to produce hydrogen, but the transportation sector cannot easily replace hydrocarbon fuels, with aviation being the most notable example. Due to long design and service times of aircraft the aviation sector will critically depend on the availability of liquid hydrocarbons for decades to come . 11) Heavy duty trucks, maritime and road transportation are also expected to rely strongly on liquid hydrocarbon fuels. 12) Thus, the large volume availability of ‘drop-in' capable renewable fuels is of great importance for decarbonizing the transport sector.
This challenge is addressed by the four year solar fuels project SUN-to-LIQUID kicked off in January 2016.
The European H2020 project aims at developing a solar thermochemical technology as a highly promising fuel path at large scale and competitive costs.
Solar radiation is concentrated by a heliostat field and efficiently absorbed in a solar reactor that thermochemically converts H2O and CO2 to syngas which is subsequently processed to Fischer-Tropsch hydro-carbon fuels. Solar-to-syngas energy conversion efficiencies exceeding 30% can potentially be realized (13)) thanks to favorable thermodynamics at high temperature and utilization of the full solar spectrum . 14)
The following key innovations are expected from the SUN-to-LIQUID project:
• Advanced modular solar concentration technology for high-flux/high-temperature applications.
• Modular solar reactor technology for the thermochemical production of syngas from H2O and CO2 at field scale and with record-high solar energy conversion efficiency.
• Optimization of high-performance redox materials and reticulated porous ceramic (RPC) structures favorable thermodynamics, rapid kinetics, stable cyclic operation, and efficient heat and mass transfer.
• Pre-commercial integration of all subsystems of the process chain to solar liquid fuels, namely: the high-flux solar concentrator, the solar thermochemical reactor, and the gas-to-liquid conversion unit.
SUN-to-LIQUID will design, fabricate, and experimentally validate a large-scale, complete solar fuel production plant.
The preceding EU-project SOLAR-JET has recently demonstrated the first-ever solar thermochemical kerosene production from H2O and CO2 in a laboratory environment. 15) A total of 291 stable redox cycles were performed, yielding 700 standard liters of high-quality syngas, which was compressed and further processed via Fischer-Tropsch synthesis to a mixture of naphtha, gasoil, and kerosene. 16)
As a follow-up project, SUN-to-LIQUID will design, fabricate, and experimentally validate a more than 12-fold scale-up of the complete solar fuel production plant and will establish a new milestone in reactor efficiency. The field validation will integrate for the first time the whole production chain from sunlight, H2O and CO2 to liquid hydrocarbon fuels.
Figure 7: SUN-to-LIQUID will realize three subsystems (image credit: EC)
1) A high-flux solar concentrating subsystem — Consisting of a sun-tracking heliostat field, that delivers radiative power to a solar reactor positioned at the top of a small tower.
2) A 50 kW solar thermochemical reactor subsystem — For syngas production from H2O and CO2 via the ceria-based thermochemical redox cycle, with optimized heat transfer, fluid mechanics, material structure, and redox chemistry.
3) A gas-to-liquid conversion subsystem — Comprising compression and storage units for syngas and a dedicated micro FT unit for the synthesis of liquid hydrocarbon fuels.
SUN-to-LIQUID will run a long-term operation campaign: SUN-to-LIQUID will parametrically optimize the solar thermochemical fuel plant on a daily basis over the time scale of months under realistic steady-state and transient conditions relevant to large-scale industrial implementation.
Concept and Approach
The SUN-to-LIQUID approach uses concentrated solar energy to synthesize liquid hydrocarbon fuels from H2O and CO2. This reversal of combustion is accomplished via a high-temperature thermochemical cycle based on metal oxide redox reactions which convert H2O and CO2 into energy-rich synthesis gas (syngas), a mixture of mainly H2 and CO.17) This two-step cycle for splitting H2O and CO2 is schematically represented by:
The thermochemical process
Since H2/CO and O2 are formed in different steps, the problematic high-temperature fuel/O2 separation is eliminated. The net product is high-quality synthesis gas (syngas), which is further processed to liquid hydrocarbons via Fischer-Tropsch (FT) synthesis. FT synthetic paraffinic kerosene derived from syngas is already certified for aviation.
SUN-to-LIQUID uses concentrated solar radiation as the source of high-temperature process heat to drive endothermic chemical reactions for solar fuel production. 18) A variety of redox active materials have been explored by different research groups. 19) Among them, non-stoichiometric cerium oxide (ceria) has emerged as an attractive redox active material because of its high oxygen ion conductivity and cyclability, while maintaining its fluorite-type structure and phase.
The laboratory-scale solar reactor for a radiative power input of 4 kW has been designed, fabricated, and experimentally demonstrated at ETH Zurich. The reactor configuration, which was used in the FP7-project SOLAR-JET, is schematically shown in Figure 8.
It consists of a cavity receiver containing a reticulated porous ceramic (RPC) foam-type structure made of pure CeO2 that was directly exposed to concentrated solar radiation. The production of H2 from H2O, CO from CO2, and high quality syngas suitable for FT synthesis by simultaneously splitting a mixture of H2O and CO2 has been demonstrated (Ref. 16).
The main objective of SUN-to-LIQUID is the scale-up and experimental demonstration of the complete process chain to solar liquid fuels from H2O and CO2 at a pre-commercial size, i.e. moving from a 4 kW setup in the laboratory to a 50 kW pre-commercial plant in the field. SUN-to-LIQUID will demonstrate an enhanced solar-to-fuel energy conversion efficiency and validate the field suitability.
Figure 8: Schematic of the reactor configuration in the FP7-project SOLAR-JET (image credit: FC)
SUN-to-LIQUID will demonstrate an enhanced solar-to-fuel energy conversion efficiency and validate the field suitability.
The high-flux solar concentrating subsystem consists of an ultra-modular solar heliostat central receiver that provides intense solar radiation for high temperature applications beyond the capabilities of current commercial CSP installations. This subsystem is constructed at IMDEA Energía at Móstoles Technology Park, Madrid, in 2016. The customized heliostat field makes use of most recent developments on small size heliostats and a tower with reduced height (15 m) to minimize visual impact. The heliostat field consists of 169 small size heliostats (1.9 m x 1.6 m). When all heliostats are aligned, it is possible to fulfil the specified flux above 2500 kW/m2 for at least 50 kW and an aperture of 16 cm, with a peak flux of 3000 kW/m2. A reliable road map for competitive drop-in fuel production from H2O, CO2, and solar energy will be established.
Figure 9: The SUN-to-LIQUID project develops an alternative fuel technology that promises unlimited renewable transportation fuel supply from water, CO2 and concentrated sunlight. The project, which is funded by the EU and Switzerland, can have important implications for the transportation sectors, especially for the long-haul aviation and shipping sectors, which are strongly dependent on hydrocarbon fuels (video credit: ARTTIC, Published on 12 June 2019)
SUN-to-LIQUID Field Test Project
The SUN-to-LIQUID four-year project, which finishes at the end of this year, is supported by the EU's Horizon 2020 research and innovation program and the Swiss State Secretariat for Education, Research and Innovation. It involves leading European research organizations and companies in the field of solar thermochemical fuel research. In addition to ETH Zurich, IMDEA Energy and HyGear Technology & Services, other partners include the German Aerospace Center (DLR) and Abengoa Energía. Project coordinator Bauhaus Luftfahrt is also responsible for technology and system analyses and ARTTIC International Management Services is supporting the consortium with project management and communication. 20)
The preceding EU-project SOLAR-JET developed the technology and achieved the first-ever production of solar jet fuel in a laboratory environment. The SUN-to-LIQUID project scaled up this technology for on-sun testing at a solar tower. For that purpose, a unique solar concentrating plant was built at the IMDEA Energy Institute in Móstoles, Spain. "A sun-tracking field of heliostats concentrates sunlight by a factor of 2500 – three times greater than current solar tower plants used for electricity generation," explains Manuel Romero of IMDEA Energy. This intense solar flux, verified by the flux measurement system developed by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) makes it possible to reach reaction temperatures of more than 1500 ºC within the solar reactor positioned at the top of the tower. 21)
Figure 10: The sun-tracking heliostat field delivers radiative power to a solar reactor positioned at the top of the tower (image credit: Christophe Ramage ©ARTTIC 2019)
The solar reactor, developed by project partner ETH Zurich, produces synthesis gas, a mixture of hydrogen and carbon monoxide, from water and carbon dioxide via a thermochemical redox cycle. An on-site gas-to-liquid plant that was developed by the project partner HyGear processes this gas to kerosene.
DLR has many years of experience in the development of solar-thermal chemical processes and their components. In the SUN-to-LIQUID project, DLR was responsible for measuring the solar field and concentrated solar radiation, for developing concepts for optimized heat recovery and – as in the previous SOLAR-JET project – for computer simulations of the reactor and the entire plant. Researchers from the DLR Institute of Solar Research and the DLR Institute of Combustion Technology used virtual models to scale up the solar production of kerosene from the laboratory to a megawatt-scale plant and to optimize the design and operation of the plant. For SUN-to-LIQUID, DLR solar researchers developed a flux density measurement system that makes it possible to measure the intensity of highly concentrated solar radiation directly in front of the reactor with minimal interruption of its operation. This data is necessary to operate the plant safely and to determine the efficiency of the reactor.
Unlimited supply of sustainable fuel: Compared to conventional fossil-derived jet fuel, the net carbon dioxide emissions to the atmosphere can be reduced by more than 90 percent. Furthermore, since the solar energy-driven process relies on abundant feedstock and does not compete with food production, it can thus meet the future fuel demand at a global scale without the need to replace the existing worldwide infrastructure for fuel distribution, storage, and utilization.
Melting a satellite, a piece at a time
17 June 2019: Researchers took one of the densest parts of an Earth-orbiting satellite, placed it in a plasma wind tunnel then proceeded to melt it into vapor. Their goal was to better understand how satellites burn up during reentry, to minimize the risk of endangering anyone on the ground. 22)
Figure 11: A rod-shaped magnetorquer – made of an external carbon fiber reinforced polymer composite, with copper coils and an internal iron-cobalt core – being melted at thousands of degrees C inside a DLR plasma wind tunnel. This atmospheric reentry simulation was performed as part of ESA's 'Design for Demise' efforts to reduce the risk of reentering satellites reaching the ground (image credit: ESA/DLR)
Taking place as part of ESA's Clean Space initiative, the fiery testing occurred inside a plasma wind tunnel, reproducing reentry conditions, at the DLR German Aerospace Center's site in Cologne.
The test subject was a magnetorquer, designed to interact magnetically with Earth's magnetic field to shift satellite orientation.
Figure 12: Melting a piece of a satellite. Researchers took one of the heaviest, bulkiest parts of an Earth-orbiting satellite, placed it in a plasma wind tunnel, then proceeded to melt it into vapor. Their goal was to better understand how satellites burn up during reentry, to minimize the risk of endangering anyone on the ground (video credit: ESA/DLR/Belstead Research)
The mysterious crystal that melts at two different temperatures
06 June 2019: In a little-known paper published in 1896, Emil Fischer—the German chemist who would go on to win the 1902 Nobel Prize in Chemistry for synthesizing sugars and caffeine—said his laboratory had produced a crystal that seemed to break the laws of thermodynamics. To his puzzlement, the solid form of acetaldehyde phenylhydrazone (APH) kept melting at two very different temperatures. A batch he produced on Monday might melt at 65 °C, while a batch on Thursday would melt at 100 °C. 23)
Colleagues and rivals at the time told him he must have made a mistake. Fischer didn't think so. As far as he could tell, the crystals that melted at such different points were identical. A few groups in Britain and France repeated his work and got the same baffling results. But as those scientists died off, the mystery was forgotten, stranded in obscure academic journals published in German and French more than a century ago.
There it would probably have remained but for Terry Threlfall, an 84-year-old chemist at the University of Southampton, UK. Stumbling across Fischer's 1896 paper in a library about a decade ago, Threlfall was intrigued enough to kick-start an international investigation of the mysterious crystal. Earlier this year in the journal Crystal Growth and Design, Threlfall and his colleagues published the solution: APH is the first recorded example of a solid that, when it melts, forms two structurally distinct liquids. Which liquid emerges comes down to contamination so subtle that it's virtually undetectable. 24)
Figure 13: Crystals of acetaldehyde phenylhydrazone appear colorful when exposed to polarized light under a microscope (image credit: Terry Threlfall)
A forgotten mystery
he quest began in 2008 when Threlfall, a fluent speaker of German and a keen student of the history of science, was searching the pages of the 140-year-old Berichte der deutschen chemischen Gesellschaft for interesting solid-state work relevant to his research on second-order phase transitions. After learning of the long-lost puzzle from Fischer's paper, Threlfall followed the reported recipe and found that his own samples of APH melted according to the same peculiar pattern. One batch melted at around 60 °C, the other at 90–95 °C.
As Fischer knew 125 years ago, the laws of thermodynamics do not allow such a molecule. If a pair of solids have different melting points, then they must be structurally distinct. Yet all the modern structural analysis techniques that Threlfall and some colleagues tried on Fischer's compound confirmed the 19th-century claim. X-ray diffraction, nuclear magnetic resonance, IR spectroscopy: All showed the crystals that behaved so differently were identical.
"For two years we wondered whether to believe the evidence of our own eyes and think that we needed to rewrite the laws of the universe, or to believe thermodynamics and think that we were simply incompetent experimentalists," Threlfall says.
Figure 14: Nobel laureate Emil Fischer works in his lab in 1904, eight years after describing a mysterious solid with multiple melting points (image credit: Nicola Perscheid)
Piecing together the puzzle
The first clue for solving the mystery came from the way APH crystals are prepared. The molecule (C8H10N2) is made up of a benzene ring attached to a pair of nitrogen atoms, one of which is attached to a hydrogen atom and a methyl group that can point either up or down. Chemists make APH by dissolving solid acetaldehyde (a precursor for many useful chemical reactions and a compound found naturally in fruit) into aqueous ethanol and adding drops of liquid phenylhydrazine (also first made and characterized by Fischer, who used it in his seminal studies of sugars). If the mixture is chilled and stirred, jagged flakes and then thicker chunks of APH crystals start to appear.
Figure 15: Terry Threlfall and his colleagues confirmed that there are low-melting-point and high-melting-point forms of APH. The y axis represents the heat absorbed in melting; the measured absorption is the area under the curve (image credit: Terry Threlfall)
According to reports from Fischer's time, there were hints that impurities could play a role in the puzzling behavior of APH. Adding drops of an acid could steer the crystallization process toward the low-melting-point version of the molecule; with added alkali, the high-melting-point crystal would emerge. Threlfall confirmed that claim and found that he could convert between the two forms. The low-melting version could be made to melt at the higher temperature by exposing it to ammonia vapor. And the high-melting crystal just needed a whiff of acid to bring its melting point down.
That behavior seemed to suggest that the acid worked like rock salt does in lowering the melting point of water ice. But for salt to make a difference, a significant amount must be added—certainly enough to show up in a close examination of the ice's structure. At as little as a thousandth of a molar equivalent, the quantities of acid or alkali needed to make the switch in APH were vanishingly small. Whatever contamination occurred did so with no detectable physical change to the crystal structure.
Threlfall got some important help from Hugo Meekes, a solid-state physicist at Radboud University in Nijmegen, the Netherlands. After hearing of a 2012 lecture that Threlfall had given about the conundrum, Meekes wondered if the solution might relate to a different, but equally curious, phenomenon called the disappearing polymorph problem. A scourge of drug companies, the problem manifests as the production of a solid that's slightly but consequentially different from the desired product. The polymorphs are identical except for varying crystalline structures, which can give them different properties. In the late 1990s, for example, Abbott Laboratories learned that it had produced a less-soluble polymorph of its antiviral crystalline compound ritonavir.
The cause of disappearing polymorphs is disputed, but Meekes says it seems to come down to imperceptible contamination—perhaps a single molecule in the air can disrupt the process by seeding crystallization of the problematic form. "It sounds rather unbelievable, but it's the only explanation," he says. "We thought the situation with the APH must be something like this."
But the APH case didn't fit the pattern. The crystals of APH that melted at different temperatures weren't polymorphs; they were identical. The researchers failed to find any other structural discrepancies either. For example, some molecules show different physical properties when their same atoms are arranged in different patterns, which is called isomerization. But both solid forms of APH contained the Z isomer, in which the methyl group points down.
Meekes too was stumped.
Enter Manuel Minas da Piedade, a solid-state physicist and thermodynamics researcher at the University of Lisbon, whom Threlfall met at a conference in 2011. After initially offering a hunch that led to another dead end, the Portuguese physicist did what many scientists do when faced with something that doesn't add up: He went back to first principles. Because it is impossible for the same material to melt at different temperatures if the initial and final states are the same, he says, "either we don't have the same crystal state, or the final state cannot be the same."
Until then, all the tests performed by Threlfall and a growing number of interested colleagues had focused on solid APH, since differences in melting point typically stem from differences in the solid form. But, out of options on the solid front, in 2015 the researchers took a look at the liquids that emerged.
Back in the Netherlands, Meekes spun tiny tubes of the hot, molten APH in a solid-state NMR machine, once with the low-melting-point sample and once with the high-melting-point one. Occasional forays to temperatures higher than the delicate equipment's 100 °C limit led to "frowning technicians," Meekes says, but the risk was worth it. He discovered that the spectra of the two liquids were different. The same solid crystal was melting to form two liquids with distinct compositions—an unprecedented finding. "We think we have a clue as to what's going on," Meekes recalls telling Threlfall at a conference.
Figure 16: Study coauthors Simon Coles (left) and Terry Threlfall performed some of their APH detective work at the UK National Crystallography Service at the University of Southampton (image credit: Simon Coles)
The difference, Meekes, Threlfall, and colleagues soon found as they probed further, comes down to isomerization, but only in the liquid phase. Although solid APH consists of solely the Z isomer, liquid APH also contains E isomer, in which the methyl group points up. In the liquid state, with the molecules spaced farther apart and therefore with more room to maneuver, APH can flit between the two forms, and it does so until it finds the most stable mix. That turns out to be a blend of about one-third of the Z isomer and two-thirds of the E form.
The relative amounts of each isomer at equilibrium are determined by the molecules' Gibbs free energies, a measure of their thermodynamic potential. As the difference in Gibbs energy increases, so does the ratio of one isomer to the other. What makes APH so unusual, Threlfall says, is that the optimal isomer combination for liquid APH doesn't match that of the solid form. "That the [solid] crystal is composed entirely of Z molecules shows that these must have a more favorable packing," he says.
Figure 17: An NMR analysis of liquid APH revealed structural differences between the low-melting-point (black line) and high-melting-point (red) forms (image credit: Terry Threlfall)
Tests showed that the high-melting solid crystal melted to a liquid that was also all Z. Then the Z-type molecules started to flip to E-type and continued until they hit that stable mix. But when the low-melting solid APH melted, it did so almost immediately to the stable mix of two-thirds E. The two liquids are different—and so the melting points are different—only because one represents an intermediate stage.
It was a melting-point suppression effect, just like salt and ice, but it was much larger than anyone on the team had thought possible. So what was behind it? Like the salt, they thought it must be an impurity. And like the disappearing polymorphs that plague the pharmaceutical industry, that impurity is too small to see or measure. Threlfall says hydrogen ions must be clinging to the surface of the solid crystal and catalyzing the shift from the Z form to the E form. To do so, those protons shift the electron density of the nitrogen atoms, which loosens the connection between nitrogen and carbon atoms in the APH molecules from a strong double bond to a weaker single one. The bond is therefore free to rotate, allowing a much more rapid switch between the Z and E forms.
Figure 18: Two isomers of APH. As a solid, molecules of APH take the Z form (left), in which the methyl group points down. But liquid APH also contains the E isomer, in which the methyl group points up (image credit: Leyla-Cann Söğütoğlu and Hugo Meekes)
With no acid present, the Z-form solid melts to Z-form liquid, and then this Z-form liquid starts the transition to E-form liquid until it reaches the stable 1:2 ratio. But when acid is there, the catalysis effect speeds the switch from Z form to E form, so much so that it happens as the solid melts.
Overall, the starting solid is the same, the finishing liquid is the same, and the amount of energy used is the same. The laws of the universe are safe. Gérard Coquerel, who works on thermodynamics and solid-state physics at the University of Rouen, France, and was not involved in the project, says it's an important discovery that organic chemists and others who rely on melting points to help characterize compounds should take into account. "It shows that sometimes there is a need to be careful about what we consider as the melting point," he says.
Fischer would have been delighted to see the answer, Threlfall says, and the 19th-century chemist would probably have understood it. Although the team's work breaks genuinely new ground, Meekes cheerfully admits that the circumstances under which the melting-point suppression occurs are so specific that the research is unlikely to have useful applications. The team hasn't even coined a name for the physical process by which identical solids can melt into distinct liquids. "If someone else wants to name it, then they can," Threlfall says. "But if you ask me, the scientific literature is already cluttered with too many needless terms."
Mission Control 'Saves Science'
17 May 2019: Every minute, ESA's Earth observation satellites gather dozens of gigabytes of data about our planet – enough information to fill the pages on a 100-meter long bookshelf. Flying in low-Earth orbits, these spacecraft are continuously taking the pulse of our planet, but it's teams on the ground at ESA's Operations Center in Darmstadt, Germany, that keep our explorers afloat. 25)
Figure 19: ESA has been dedicated to observing Earth from space ever since the launch of its first Meteosat weather satellite back in 1977. With the launch of a range of different types of satellites over the last 40 years, we are better placed to understand the complexities of our planet, particularly with respect to global change. Today's satellites are used to forecast the weather, answer important Earth-science questions, provide essential information to improve agricultural practices, maritime safety, help when disaster strikes, and all manner of everyday applications (image credit: ESA)
From flying groups of spacecraft in complex formations to dodging space debris and navigating the ever-changing conditions in space known as space weather, ESA's spacecraft operators ensure we continue to receive beautiful images and vital data on our changing planet.
Get in formation
Many Earth observation satellites travel in formation. For example, the Copernicus Sentinel-5P satellite follows behind the Suomi-NPP satellite (from the National Oceanic and Atmospheric Administration). Flying in a loose trailing formation, they observe parts of our planet in quick succession and monitor rapidly evolving situations. Together they can also cross-validate instruments on board as well as the data acquired.
ESA's Earth Explorer Swarm satellites are another example of complex formation flying. On a mission to provide the best ever survey of Earth's geomagnetic field, they are made up of three identical satellites flying in what is called a constellation formation.
Swarm's individual satellites operate together under shared control in a synchronized manner, accomplishing the same objective of one giant – and more expensive – satellite.
"Formation flying has all the challenges of flying many single spacecraft, except with the added complexity that we need to maintain a regular distance between all of these high-speed and high-tech eyes on Earth," explains Jose Morales Santiago, ESA's Head of the Earth Observation Mission Operations Division. "Every decision we make, every command we send, has to be the right one for each spacecraft – particularly when it comes to maneuvers. These must be planned properly so that they do not endanger companion satellites, while keeping a consistent configuration across the formation."
Figure 20: Swarm is ESA's first Earth observation constellation of satellites. The three identical satellites are launched together on one rocket. Two satellites orbit almost side-by-side at the same altitude – initially at about 460 km, descending to around 300 km over the lifetime of the mission. The third satellite is in a higher orbit of 530 km and at a slightly different inclination. The satellites' orbits drift, resulting in the upper satellite crossing the path of the lower two at an angle of 90° in the third year of operations. The different orbits along with satellites' various instruments optimize the sampling in space and time, distinguishing between the effects of different sources and strengths of magnetism (image credit: ESA/AOES Medialab)
Last year, ESA's Earth observation missions performed a total of 28 ‘collision avoidance maneuvers'. These maneuvers saw operators send the orders to a spacecraft to get out of the way of an oncoming piece of space debris.
An impact with a fast-moving piece of space junk has the potential to destroy an entire satellite and in the process create even more debris. As a spacecraft ‘swerves' to avoid collision, science instruments may need to be turned off to ensure their safety and avoid being contaminated by the thrusting engine.
Teams at mission control consider how to keep Europe's fleet of Earth observers safe while maximizing the vital work they are able to do. Recently, they came up with an ingenious concept to ‘save science' during such maneuvers of the Sentinel-5P satellite.
The Sentinel team quickly realized that during a collision avoidance maneuver they would have to suspend science collection for almost a day, because of the emergency firing of the thrusters.
"That's a lot of data to miss out on. As the amount of space debris is currently increasing, this would be something we would need to do more and more often," explains Pierre Choukroun, Sentinel-5P Spacecraft Operations Engineer, who came up with the fix. "So we designed and validated a new on-board function to enhance the spacecraft's autonomy, such that the science data loss is reduced to a bare minimum. We are very much looking forward to securing more data for the science community in the near future!"
With this new strategy, the science instruments on Sentinel-5P would be shut off for around on hour compared with an entire day!
As if dodging bits of space debris weren't enough for Europe's Earth explorers, they also have to navigate the turbulent weather conditions in space.
Space weather refers to the environmental conditions around Earth due to the dynamic nature of our Sun. The constant mood swings of our star influence the functioning and reliability of our satellites in space, as well as infrastructure on the ground.
Figure 21: SOHO's view of the September 2017 solar flares. The Sun unleashed powerful solar flares on 6 September, one of which was the strongest in over a decade. An M-class flare was also observed two days earlier on 4 September. The flares were launched from a group of sunspots classified as active region 2673. The shaded disc at the center of the image is a mask in SOHO's LASCO instrument that blocks out direct sunlight to allow study of the faint details in the Sun's corona. The white circle added within the disc shows the size and position of the visible Sun. (video credit: SOHO (ESA & NASA)
When the Sun is particularly active, it adds extra energy to Earth's atmosphere, changing the density of the air at low-Earth orbits. Increased energy in the atmosphere means that satellites in this region experience more ‘drag' – a force that acts in the opposite direction to the motion of the spacecraft, causing it to decrease in altitude.
Operators need this information to know when to perform maneuvers to "boost" the satellite's speed in order to counter drag and keep it in its proper orbit.
This drag effect also changes the speed and position of space debris around Earth, meaning our understanding of the debris environment needs to be constantly updated in light of changing space weather.
"While Earth observation satellites monitor the weather on Earth, we have to stay aware of the changing weather in space," says Thomas Ormston, Spacecraft Operations Engineer at ESA. "This is vital because understanding atmospheric drag is fundamental to predicting when we will be threatened by space debris and determining when and how big our spacecraft maneuvers need to be to keep delivering great science to our users."
Space weather also impacts communication between ground stations and satellites due to changes in the upper atmosphere, the ionosphere, during solar events. Because of this, satellite operators avoid critical satellite operations like maneuvers or updates of the on board software during periods of high solar activity.
Figure 22: It's difficult to comprehend the size and sheer power of our Sun, a churning ball of hot gas has a mass that is 1.3 million times larger than Earth, it dominates our Solar System. Unpredictable and temperamental, it blasts intense radiation and colossal amounts of energetic material in every direction, creating the ever-changing conditions in space known as 'space weather'. The solar wind is a constant stream of electrons, protons and stripped-down atoms emitted by the Sun, while coronal mass ejections are the Sun's periodic outbursts of colossal clouds of solar plasma. The most extreme of these events disturb Earth's protective magnetic field, creating geomagnetic storms at our planet. — These storms can cause serious problems for modern technological systems, disrupting or damaging satellites in space and the multitude of services – like navigation and telecoms – that rely on them, and blacking out power grids and radio communication. They can even serve potentially harmful doses of radiation to astronauts on future missions to the Moon or Mars (image credit: ESA)
Testing satellite marker designs
24 April 2019: Akin to landing lights for aircraft, ESA is developing infrared and phosphorescent markers for satellites, to help future space servicing vehicles rendezvous and dock with their targets. 26)
Developed by the Hungarian company Admatis (Advanced Materials in Space) as part of an ESA Clean Space project, these markers would offer robotic space servicing vehicles a steady target to home in on, providing critical information on the line of sight, distance and pointing direction of their target satellite.
Figure 23: Initial testing of these ‘Passive Emitting Material at end-of-life' or PEMSUN markers took place at the end of March 2019 inside ESA's GNC Rendezvous, Approach and Landing Simulator, part of the Agency's Orbital Robotics and Guidance, Navigation and Control Laboratory, at its ESTEC technical center in Noordwijk, the Netherlands (image credit: ESA)
"The idea itself is not new, but this is the first time we've manufactured and tested sample patches, cut into spacecraft multi-layer insulation covering," comments ESA Clean Space trainee Sébastien Perrault. "For the design we've looked into one larger pattern incorporating smaller versions for when the space servicing vehicle comes close enough that its camera's field of view is filled.
"These markers would be very useful during eclipse states for instance, when Earth obscures the Sun in low Earth orbit, to allow the chaser vehicle to stay fixed on its target, potentially in combination with radio tags."
ESA is studying space servicing vehicles to carry out a wide range of roles in orbit, from refurbishment and refuelling to mission disposal at their end of life.
Figure 24: GRALS Testbed. This robotic arm, attached to a 33 m track is ESA's GRALS (GNC Rendezvous, Approach and Landing Simulator), is part of the Agency's Orbital Robotics and Guidance, Navigation and Control Laboratory. GRALS is used to simulate close approach and capture of uncooperative orbital targets, such as drifting satellites or to rendezvous with asteroids. It can also be used to test ideas for descending to surfaces, such as a lunar or martian landing (image credit: ESA, M. Grulich)
Legend to Figure 24: The moveable arm can be equipped with cameras to test vision-based software on a practical basis to close on a scale model of its target. Image-processing algorithms recognize various features on the surface of the model satellite seen here, and uses those features to calculate the satellite's tumble, allowing the chaser to safely come closer. Alternatively, the robotic arm can be fitted with a gripper, to test out actually securing a target, or with altimeters or other range sensors.
Mirror array for LSS (Large Space Simulator)
17 April 2019: The mirror array (Figure 25) remains an integral element of ESA's Large Space Simulator at the ESTEC Test Center in Noordwijk, the Netherlands. It is used to subject entire satellites to space-like conditions ahead of launch. At 15 m high and 10 m in diameter, the chamber is cavernous enough to accommodate an upended double decker bus. 27)
Satellites are lowered down through a topside hatch. Once the top and side hatches are sealed, high-performance pumps create a vacuum a billion times lower than standard sea level atmosphere, held for weeks at a time during test runs.
This mirror array is made of 121 separate hexagonal segments. Its task is to reflect a 6-m diameter beam of simulated sunlight into the chamber, at the same time as the walls are pumped full of –190°C liquid nitrogen, together recreating the extreme thermal conditions prevailing in orbit.
By re-orienting the individual segments a much tighter beam can be focused, helping to simulate higher intensity sunlight, such as the 10 solar constants experienced in the vicinity of Sun-scorched Mercury, for testing the ESA/JAXA BepiColombo mission.
Figure 25: The giant 121-segment mirror array used to reflect simulated sunlight into the largest vacuum chamber in Europe seen being hoisted into position within ESA's technical heart back in 1986 (image credit: ESA, CC BY-SA 3.0 IGO)
Cold plasma tested on ISS
10 April 2019: Low-temperature plasma – electrically charged gas – that was originally tested aboard the International Space Station is now being harnessed to kill drug-resistant bacteria and viruses that can cause infections in hospital. 28)
Professor Gregor Morfill of Germany's Max Planck Institute for Extraterrestrial Physics made use of the ISS to investigate complex three-dimensional plasmas that Earth gravity would have flattened. His very first plasma chamber was installed aboard the Station back in 2001, by cosmonaut Sergei Krikalev. The latest fourth-generation follow-on is still running on the ISS to this day.
Plasmas are usually hot gases but Prof. Morfill's team developed a method of generating room temperature ‘cold plasma'. Exposure to this forms small holes in the membranes of bacterial cells and destroy their DNA, while human cells are not so easily damaged.
So the idea was born to make use of cold plasma against bacteria in infected wounds without harming the patient. Initial treatment was for infected chronic wounds such as leg ulcers. Initial clinical trials showed significant reduction in bacterial burden of infected wounds, supporting healing and pain relief.
As a next step, new company terraplasma medical was set up to develop a smaller portable, battery-driven cold plasma medical device. The company has been supported through ESA's Business Incubation Center Bavaria.
Starting this May, this ‘plasma care' device will be evaluated in a medical trial across multiple German healthcare institutes.
Figure 26: Technology image of the week: Cold plasma tested aboard the International Space Station is now being harnessed against drug-resistant bacteria (image credit: Max Planck Institute for Extraterrestrial Physics)
3D printing and milling Athena optic bench
03 April 2019: Twin robotic arms work together as part of a project to construct what will be the largest, most complex object ever 3D printed in titanium: a test version of the 3-m diameter ‘optic bench' at the heart of ESA's Athena X-ray observatory. 29)
Figure 27: Technology image of the week: twin robotic arms work together to 3D print and mill a test version of the optical heart of ESA's Athena X-ray observatory (image credit: Fraunhofer IWS)
- The first multi-axis robotic arm builds up each new layer of metal using a laser to melt titanium powder. The second robotic arm then immediately cuts away any imperfections using a cryogenically cooled milling tool. The bench itself is placed on a slowly moving 3.4 m diameter turntable.
- "ESA has teamed up with Germany's Fraunhofer Institute for Material and Beam Technology for this exploratory activity," explains ESA materials and processes engineer Johannes Gumpinger. "The final design of Athena's optic bench is still to be decided, but if it will be built in titanium then its size and complexity is such that it could not be built in any other way."
- Due to launch in 2031, ESA's Athena mission will probe 10 to 100 times deeper into the cosmos than previous X-ray missions, to observe the very hottest, high-energy celestial objects.
- The mission requires entirely new X-ray optics technology, with stacks of ‘mirror modules' arranged carefully to capture and focus high-energy X-rays.
- The optic bench aligns and secures around 750 mirror modules in a complex structure with many deep pockets that tapers out to a maximum height of 30 cm. Its overall shape needs to be precise down to a scale of a few tens of micrometers – or thousandths of a centimeter.
- "The optic bench's complexity requires each addition to be milled immediately after printing," comments André Seidel, overseeing the project at the Fraunhofer Institute for Material and Beam Technology. "Any subsequent modification could risk introducing contamination, weakening the space-quality titanium.
- "Similarly, the entire process has been designed to minimize any risk of contamination. The titanium powder is swept into the laser using the noble gas argon that also prevents any contamination with air. And the milling tool is kept cool using liquid carbon dioxide that evaporates as it warms up, preventing any harmful deposition on the freshly-laid metal surface."
- Precision sensors immediately detect any out of tolerance elements for milling or more extensive repair – including milling away for reprinting.
- Smaller segments have been manufactured so far, with a 1.5 m diameter demonstrator optic bench set to follow. The full scale 3 m bench is expected to take about a year to produce.
- "It will be a huge task, taking a lot of time and energy," adds Johannes. "But if we manage it, it will be the largest titanium object ever 3D printed – and the process will be available to manufacture other large parts, potentially in other metals."
- Last month more than 150 experts from all across Europe met at ESA's technical heart in the Netherlands to share the latest results from ESA Advanced Manufacturing projects covering topics including 3D printing and the latest composite materials as well as friction stir-welding.
Figure 28: 3D printing titanium for Athena. A close-up view of laser melting being used to 3D print in titanium to produce test versions of the ‘optic bench' at the heart of our Athena X-ray observatory. A multi-axis robotic arm is being used to produce the complex structure, including deep pockets to place optical mirror modules (video credit: Fraunhofer IWS)
Legend to Figure 28: "The essential technological achievement is the fact that 3D printing takes place under local protective gas shielding, without a protective gas chamber," comments André Seidel, overseeing the project at the Fraunhofer Institute for Material and Beam Technology in Germany. "This is enabled by a specially-developed process head called COAXShield which uses the noble gas argon to sweep titanium powder into the path of the laser, in the process protecting the newly-printed titanium from contact with the atmosphere."
This gas protection enables a rapid change between additive manufacturing – laser metal deposition with powder – and subtractive manufacturing – as cryogenically cooled milling tool operated by a second robotic arm removes surplus titanium.
The optic bench itself is placed on a slowly moving 3.4-m diameter turntable between the two robotic arms. The end goal of this ESA Technology Development Element project is to produce a 3-m diameter optical bench, but in principle the procedure can be applied to a wide variety of sizes.
"You can see the metallic bright surface of the titanium, reflecting the honeycomb structure of the protective gas nozzle," adds André. "Taking account of this for laser melting was a very big challenge, and an absolute milestone in the project."
Introduction of SmartSat architecture in spacecraft
20 March 2019: Lockheed Martin of Denver, CO, announced a new generation of space technology launching this year that will allow satellites to change their missions in orbit. Satellites that launched one, ten or even fifteen years ago largely have the same capability they had when they lifted off. That's changing with new architecture that will let users add capability and assign new missions with a software push, just like adding an app on a smartphone. This new tech, called SmartSat, is a software-defined satellite architecture that will boost capability for payloads on several pioneering nanosats ready for launch this year. 30)
Figure 29: Lockheed Martin SmartSat Infographic. Lockheed Martin's nanosatellite bus, the LM 50, will host the first SmartSat-enabled missions set for delivery this year (image credit: Lockheed Martin)
"Imagine a new type of satellite that acts more like a smartphone. Add a SmartSat app to your satellite in-orbit, and you've changed the mission," said Rick Ambrose, executive vice president of Lockheed Martin Space. "We are the first to deploy this groundbreaking technology on multiple missions. SmartSat will give our customers unparalleled resiliency and flexibility for changing mission needs and technology, and it unlocks even greater processing power in space."
This year Lockheed Martin is integrating SmartSat technology on ten programs and counting, including the Linus and Pony Express nanosats, which will be the first to launch. These are rapid-prototype, testbed satellites using internal research and development funding, ready for 2019 launches on the first LM 50 nanosatellite buses:
• The Linus project delivers two 12U cubesats performing a technology demonstration mission, validating SmartSat capabilities as well as 3D-printed spacecraft components.
• Pony Express builds multiple 6U satellites destined for a low earth orbit and will space qualify state-of-the-art networking technologies. Pony Express 1 is a pathfinder for a software-defined payload that will test cloud computing infrastructure and was developed in nine months. Follow-on Pony Express missions will prove out RF-enabled swarming formations and space-to-space networking.
"SmartSat is a major step forward in our journey to completely transform the way we design, build and deliver satellites," said Ambrose. "The LM 50 bus is the perfect platform for testing this new, groundbreaking technology. We're self-funding these missions to demonstrate a number of new capabilities that can plug into any satellite in our fleet, from the LM 50 nanosat to our flagship LM 2100. And the same technology not only plugs into ground stations, improving space-ground integration, it will one day connect directly with planes, ships and ground vehicles, connecting front-line users to the power of space like never before."
Cyber security is at the core of this new technology. SmartSat-enabled satellites can reset themselves faster, diagnose issues with greater precision and back each other up when needed, significantly enhancing resiliency. Satellites can also better detect and defend against cyber threats autonomously, and on-board cyber defenses can be updated regularly to address new threats.
SmartSat uses a hypervisor to securely containerize virtual machines. It's a technology that lets a single computer operate multiple servers virtually to maximize memory, on-board processing and network bandwidth. It takes advantage of multi-core processing, something new to space. That lets satellites process more data in orbit so they can beam down just the most critical and relevant information—saving bandwidth costs and reducing the burden on ground station analysts, and ultimately opening the door for tomorrow's data centers in space.
SmartSat uses a high-power, radiation-hardened computer developed by the National Science Foundation's Center for Space, High-performance, and Resilient Computing, or SHREC. Lockheed Martin helps fund SHREC research, and in turn gains access to world-class technologies and student researchers.
Radiation tolerance of 2D material-based devices for space applications
15 March 2019: A new study from The Australian National University (ANU) has found a number of 2D materials can not only withstand being sent into space, but potentially thrive in the harsh conditions. It could influence the type of materials used to build everything from satellite electronics to solar cells and batteries - making future space missions more accessible, and cheaper to launch. 31) 32)
Figure 30: Tobias Vogl, ANU Research School of Physics & Engineering (image credit: Lannon Harley, ANU)
PhD candidate and lead author Tobias Vogl was particularly interested in whether the 2D materials could withstand intense radiation.
"The space environment is obviously very different to what we have here on Earth. So we exposed a variety of 2D materials to radiation levels comparable to what we expect in space," Mr Vogl said. "We found most of these devices coped really well. We were looking at electrical and optical properties and basically didn't see much difference at all."
During a satellite's orbit around the Earth, it is subjected to heating, cooling, and radiation. While there's been plenty of work done demonstrating the robustness of 2D materials when it comes to temperature fluctuations, the impact of radiation has largely been unknown - until now.
The ANU team carried out a number of simulations to model space environments for potential orbits. This was used to expose 2D materials to the expected radiation levels. They found one material actually improved when subjected to intense gamma radiation.
"A material getting stronger after irradiation with gamma rays - it reminds me of the hulk," Mr Vogl said. "We're talking about radiation levels above what we would see in space - but we actually saw the material become better, or brighter."
Mr Vogl says this specific material could potentially be used to detect radiation levels in other harsh environments, like near nuclear reactor sites.
"The applications of these 2D materials will be quite versatile, from satellite structures reinforced with graphene - which is five-times stiffer than steel - to lighter and more efficient solar cells, which will help when it comes to actually getting the experiment into space."
Among the tested devices were atomically thin transistors. Transistors are a crucial component for every electronic circuit. The study also tested quantum light sources, which could be used to form what Mr Vogl describes as the "backbone" of the future quantum internet.
"They could be used for satellite-based long-distance quantum cryptography networks. This quantum internet would be hacking proof, which is more important than ever in this age of rising cyber attacks and data breaches."
"Australia is already a world leader in the field of quantum technology," senior author Professor Ping Koy Lam said. "In light of the recent establishment of the Australian Space Agency, and ANU's own Institute for Space, this work shows that we can also compete internationally in using quantum technology to enhance space instrumentation."
Light from Exotic Crystal Semiconductor Could Lead to Better Solar Cells
15 March 2019: Scientists have found a new way to control light emitted by exotic crystal semiconductors, which could lead to more efficient solar cells and other advances in electronics, according to a Rutgers-led study in the journal Materials Today. 33) 34)
Figure 31: A conceptual view of a transistor device that controls photoluminescence (the light red cone) emitted by a hybrid perovskite crystal (the red box) that is excited by a blue laser beam after voltage is applied to an electrode (the gate), image credit: Vitaly Podzorov and Yaroslav Rodionov
Their discovery involves crystals called hybrid perovskites, which consist of interlocking organic and inorganic materials, and they have shown great promise for use in solar cells. The finding could also lead to novel electronic displays, sensors and other devices activated by light and bring increased efficiency at a lower cost to manufacturing of optoelectronics, which harness light.
The Rutgers-led team found a new way to control light (known as photoluminescence) emitted when perovskites are excited by a laser. The intensity of light emitted by a hybrid perovskite crystal can be increased by up to 100 times simply by adjusting voltage applied to an electrode on the crystal surface.
"To the best of our knowledge, this is the first time that the photoluminescence of a material has been reversibly controlled to such a wide degree with voltage," said senior author Vitaly Podzorov, a professor in the Department of Physics and Astronomy in the School of Arts and Sciences at Rutgers University–New Brunswick. "Previously, to change the intensity of photoluminescence, you had to change the temperature or apply enormous pressure to a crystal, which was cumbersome and costly. We can do it simply within a small electronic device at room temperature."
Semiconductors like these perovskites have properties that lie between those of the metals that conduct electricity and non-conducting insulators. Their conductivity can be tuned in a very wide range, making them indispensable for all modern electronics.
"All the wonderful modern electronic gadgets and technologies we enjoy today, be it a smartphone, a memory stick, powerful telecommunications and the internet, high-resolution cameras or supercomputers, have become possible largely due to the decades of painstaking research in semiconductor physics," Podzorov said.
Understanding photoluminescence is important for designing devices that control, generate or detect light, including solar cells, LED lights and light sensors. The scientists discovered that defects in crystals reduce the emission of light and applying voltage restores the intensity of photoluminescence.
Hybrid perovskites are more efficient and much easier and cheaper to make than standard commercial silicon-based solar cells, and the study could help lead to their widespread use, Podzorov said. An important next step would be to investigate different types of perovskite materials, which may lead to better and more efficient materials in which photoluminescence can be controlled in a wider range of intensities or with smaller voltage, he said.
The study included lead author Hee Taek Yi in Rutgers' Department of Physics and Astronomy and co-authors Assistant Research Professor Sylvie Rangan and Professor Robert A. Bartynski, department chair. Researchers at the University of Minnesota and University of Texas at Dallas contributed to the study.
Converting Wi-Fi Signals to Electricity with New 2-D Materials
• 8 March 2019: Devices that convert AC electromagnetic waves into DC electricity are known as "rectennas." MIT Researchers have demonstrated a new kind of rectenna, that uses a flexible radio-frequency (RF) antenna to capture electromagnetic waves — including those carrying Wi-Fi. The antenna is connected to a novel device made out of a two-dimensional semiconductor just a few atoms thick, which converts the AC signal into a DC voltage. In this way, the battery-free device passively captures and transforms ubiquitous Wi-Fi (Wireless Fidelity) signals into useful DC power. Moreover, the device is flexible and can be fabricated in a roll-to-roll process to cover very large areas. 35) 36) 37)
Figure 32: Researchers from MIT and elsewhere have designed the first fully flexible, battery-free "rectenna" -- a device that converts energy from Wi-Fi signals into electricity — that could be used to power flexible and wearable electronics, medical devices, and sensors for the "internet of things" (image credit: Christine Daniloff)
- "What if we could develop electronic systems that we wrap around a bridge or cover an entire highway, or the walls of our office and bring electronic intelligence to everything around us? How do you provide energy for those electronics?" says paper co-author Tomás Palacios, a professor in the Department of Electrical Engineering and Computer Science and director of the MIT/MTL Center for Graphene Devices and 2D Systems in the Microsystems Technology Laboratories. "We have come up with a new way to power the electronics systems of the future — by harvesting Wi-Fi energy in a way that's easily integrated in large areas — to bring intelligence to every object around us."
- Promising early applications for the proposed rectenna include powering flexible and wearable electronics, medical devices, and sensors for the "internet of things." Flexible smartphones, for instance, are a hot new market for major tech firms. In experiments, the researchers' device can produce about 40 µW of power when exposed to the typical power levels of Wi-Fi signals (around 150 µW). That's more than enough power to light up an LED or drive silicon chips.
- Another possible application is powering the data communications of implantable medical devices, says co-author Jesús Grajal, a researcher at the Technical University of Madrid. For example, researchers are beginning to develop pills that can be swallowed by patients and stream health data back to a computer for diagnostics.
- "Ideally you don't want to use batteries to power these systems, because if they leak lithium, the patient could die," Grajal says. "It is much better to harvest energy from the environment to power up these small labs inside the body and communicate data to external computers."
- All rectennas rely on a component known as a "rectifier," which converts the AC input signal into DC power. Traditional rectennas use either silicon or gallium arsenide for the rectifier. These materials can cover the Wi-Fi band, but they are rigid. And, although using these materials to fabricate small devices is relatively inexpensive, using them to cover vast areas, such as the surfaces of buildings and walls, would be cost-prohibitive. Researchers have been trying to fix these problems for a long time. But the few flexible rectennas reported so far operate at low frequencies and can't capture and convert signals in gigahertz frequencies, where most of the relevant cell phone and Wi-Fi signals are.
- To build their rectifier, the researchers used a novel 2-D material called molybdenum disulfide (MoS2), which at three atoms thick is one of the thinnest semiconductors in the world. In doing so, the team leveraged a singular behavior of MoS2: When exposed to certain chemicals, the material's atoms rearrange in a way that acts like a switch, forcing a phase transition from a semiconductor to a metallic material. The resulting structure is known as a Schottky diode, which is the junction of a semiconductor with a metal.
- "By engineering MoS2 into a 2-D semiconducting-metallic phase junction, we built an atomically thin, ultrafast Schottky diode that simultaneously minimizes the series resistance and parasitic capacitance," says first author and EECS postdoc Xu Zhang, who will soon join Carnegie Mellon University as an assistant professor.
- Parasitic capacitance is an unavoidable situation in electronics where certain materials store a little electrical charge, which slows down the circuit. Lower capacitance, therefore, means increased rectifier speeds and higher operating frequencies. The parasitic capacitance of the researchers' Schottky diode is an order of magnitude smaller than today's state-of-the-art flexible rectifiers, so it is much faster at signal conversion and allows it to capture and convert up to 10 gigahertz of wireless signals.
- "Such a design has allowed a fully flexible device that is fast enough to cover most of the radio-frequency bands used by our daily electronics, including Wi-Fi, Bluetooth, cellular LTE, and many others," Zhang says.
- The reported work provides blueprints for other flexible Wi-Fi-to-electricity devices with substantial output and efficiency. The maximum output efficiency for the current device stands at 40 percent, depending on the input power of the Wi-Fi input. At the typical Wi-Fi power level, the power efficiency of the MoS2 rectifier is about 30 percent. For reference, today's rectennas made from rigid, more expensive silicon or gallium arsenide achieve around 50 to 60 percent.
- "This very nice teamwork from MIT demonstrates the first real application [of] atomically thin semiconductors for a flexible rectenna for energy harvesting," says Philip Kim, a professor of physics and applied physics at Harvard University whose research focuses on 2-D materials. "I am amazed by the innovate approach that the team has set up to utilize the waste energy from RF power around us."
- The team is now planning to build more complex systems and improve efficiency. The work was made possible, in part, by a collaboration with the Technical University of Madrid through the MIT International Science and Technology Initiatives (MISTI). It was also partially supported by the Institute for Soldier Nanotechnologies, the Army Research Laboratory, the National Science Foundation's Center for Integrated Quantum Materials, and the Air Force Office of Scientific Research.
NICU (Neonatal Intensive Care Units)
• 28 February 2019: An interdisciplinary Northwestern University team (Chicago and Evanston, Illinois) has developed a pair of soft, flexible wireless body sensors that replace the tangle of wire-based sensors that currently monitor babies in hospitals' neonatal intensive care units (NICU) and pose a barrier to parent-baby cuddling and physical bonding. 38) 39)
The team recently completed a collection of first human studies on premature babies at Prentice Women's Hospital and the Ann & Robert H. Lurie Children's Hospital in Chicago and concluded that the wireless infant sensors provided data as precise and accurate as that from traditional monitoring systems. The wireless patches also are gentler on a newborn's fragile skin and allow for more skin-to-skin contact with the parent.
The study includes initial data from more than 20 babies who wore the wireless sensors alongside traditional monitoring systems, so Northwestern researchers could do a side-by-side, quantitative comparison. Since then, the team has conducted successful tests with more than 70 babies in the NICU.
The study — involving materials scientists, engineers, dermatologists and pediatricians, was published in the journal Science. 40)
The study includes initial data from more than 20 babies who wore the wireless sensors alongside traditional monitoring systems, so Northwestern researchers could do a side-by-side, quantitative comparison. Since then, the team has conducted successful tests with more than 70 babies in the NICU.
"We wanted to eliminate the rat's nest of wires and aggressive adhesives associated with existing hardware systems and replace them with something safer, more patient-centric and more compatible with parent-child interaction," says John A. Rogers, a bioelectronics pioneer, who led the technology development. "Our wireless, battery-free, skin-like devices give up nothing in terms of range of measurement, accuracy and precision — and they even provide advanced measurements that are clinically important but not commonly collected."
Cutting the cords: The mass of wires that surround newborns in the NICU are often bigger than the babies themselves. Typically five or six wires connect electrodes on each baby to monitors for breathing, blood pressure, blood oxygen, heartbeat and more. Although these wires ensure health and safety, they constrain the baby's movements and pose a major barrier to physical bonding during a critical period of development.
"We know that skin-to-skin contact is so important for newborns — especially those who are sick or premature," says Paller, a pediatric dermatologist. "It's been shown to decrease the risk of pulmonary complications, liver issues and infections. Yet, when you have wires everywhere and the baby is tethered to a bed, it's really hard to make skin-to-skin contact."
The benefits of the Northwestern team's new technology reach beyond its lack of wires — measuring more than what's possible with today's clinical standards.
The dual wireless sensors monitor babies' vital signs — heart rate, respiration rate and body temperature — from opposite ends of the body. One sensor lies across the baby's chest or back, while the other sensor wraps around a foot. This strategy allows physicians to gather an infant's core temperature as well as body temperature from a peripheral region.
"Differences in temperature between the foot and the chest have great clinical importance in determining blood flow and cardiac function," Rogers says. "That's something that's not commonly done today."
Figure 33: Northwestern team shows new wireless sensors (video credit: Northwestern University)
Figure 34: Dual wireless sensors – The chest sensor (left) measures 5 x 2.5 cm; the foot sensor (right) is 2.5 x 2 cm. Both sensors weigh as much as a raindrop (image credit: Northwestern)
Introduction of 5G communication connectivity
• March 2019: 5G mobile telecommunication standards stand for fifth-generation advancements made in the mobile communications field. These comprise packet switched wireless systems using orthogonal frequency division multiplexing (OFDM) with wide area coverage, high throughput at millimeter waves (10 mm to 1 mm) covering a frequency range of 30 GHz to 300 GHz, and enabling a 20 Mbit/s data rate to distances up to 2 km. The millimeter-wave band is the most effective solution to the recent surge in wireless Internet usage. These specifications are capable of providing ‘wireless world wide web' (WWWW) applications. 41)
The WWWW allows a highly flexible network (flexible channel bandwidth between 5 and 20 MHz, optimally up to 40 MHz), and dynamic ad-hoc wireless network (DAWN). This technique employs intelligent antennae (e.g., switched beam antennae and adaptive array antennae) and the flexible modulation method, which helps in obtaining bidirectional high bandwidth, i.e., transfer of a large volume of broadcasting data in GB (giga bytes), sustaining more than 60,000 connections and providing 25 Mbit/s connectivity.
Users of 5G technology can download an entire film to their tablets or laptops, including 3D movies; they can download games and avail of remote medical services. With the advent of 5G, Piconet and Bluetooth technologies will become outdated. The 5G mobile phones would be akin to tablet PCs, where you could watch TV channels at HD clarity without any interruption.
Chronological evolution of mobile technologies: Although the 1G system (NMT) was introduced in 1981, 2G (GSM) started to come out in 1982, and 3G (W-CDMA)/FOMA first appeared in 2001, the complete development of these standards (e.g., IMT-2000 and UMTS) took almost 10 years. It is still unclear how much time it will take to launch the standards for 5G.
5G technology will ensure the convergence of networks, technologies, applications and services, and can serve as a flexible platform. Wireless carriers will have an opportunity to shorten their return-on-investment periods, improve operating efficiency and increase revenues. In short, this will change people's lives in numerous ways.
In 2019, after years of hype about Gb (gigabit) speeds that will let you download full-length movies in mere seconds, 5G is close to becoming a reality. Last year gave us a taste of 5G as Verizon launched a home broadband service using the next-generation wireless technology and AT&T brought 5G service to a dozen cities. 42)
The fifth generation of connectivity, pithily called 5G, will be ready for prime time this year. Software is being tested, hardware is in the works, and carriers are readying their plans to flip the switch on their 5G network in the first half of 2019.
The new networking standard is not just about faster smartphones. Higher speeds and lower latency will also make new experiences possible in augmented and virtual reality, connected cars and the smart home — any realm where machines need to talk to each other constantly and without lag.
Where 5G Is Now:
The 3rd Generation Partnership Project, the standards body that writes the rules for wireless connectivity, agreed in late 2017 on the first specification for 5G. The Non-Standalone Specification of 5G New Radio standard covers 600 and 700 MHz bands and the 50 GHz millimeter-wave end of the spectrum. That agreement paved the way for hardware makers to start developing handsets with 5G modems inside. But the non-standalone specification applies to 5G developed with LTE as an anchor.
In June of 2018, the standards body completed the rules for standalone 5G. Network operators are now fine-tuning their software using equipment that complies with the completed standard.
"[The standard] really sets [the stage] for interoperable systems and field trials with operators in 2018, and it starts the clock for being able to build standards-compliant devices heading toward the last half of 2018 and early 2019 launches," Qualcomm's Matt Branda, who oversees 5G marketing, told us last year.
It's important to note that 5G devices have to play nice with existing LTE networks, because in areas where 5G coverage will be spotty or nonexistent, the new radios will be optimized for available LTE connections. That's why the non-standalone specification came down first.
Companies such as Qualcomm and Intel are working on 5G modems that will fit into phones, cars, smart-home devices and other device forms that have yet to take shape. Those radios are in the midst of testing to make sure they're interoperable with network operators and infrastructure companies.
Space's part in the 5G revolution
The communications industry is in a period of unprecedented change, and consumers and enterprises across all regional and demographic sectors increasingly view mobile connectivity – and mobile broadband specifically – as an essential part of everyday life and business. 43)
5G represents an opportunity for the mobile industry to address that phenomenon. While the transition from 3G to 4G was an evolution in speed that paved the way for mobile broadband services, 5G is a revolution – an entirely new architecture that delivers exponential improvements in not only speed, but also latency, capacity, power consumption and number of connections supported. This opens the door to a broad new range of use cases, from enhanced mobile broadband to massive machine-type communications to ultra-low latency communications.
The Third Generation Partnership Project (3GPP), the industry association driving 5G development, is studying the challenges and has identified the value satellite coverage can bring to the enablement of 5G use cases, particularly mission-critical and industrial applications where ubiquitous coverage is crucial. By partnering with satellite operators, MNOs (Mobile Network Operators) can expand their footprint into regions that are difficult or impossible to serve via their terrestrial assets. Satellite represents a path for mobile network operators to expand their footprint and thus deliver on the promise of seamless, universal 5G coverage and services.
Figure 35: 5G, the next generation of communication services, will deliver ultra-fast speeds, connect all people and devices to the internet and minimize delays. It will affect everybody, changing the way we communicate, work and interact with technology. Space has an invaluable role to play in the 5G ecosystem. Satellites can extend, enhance, and provide reliability and security to 5G like no other, helping to deliver its promise of global, ubiquitous connectivity, with no noticeable difference to the end-user. ESA's Satellite for 5G (S45G) program aims to promote the value-added benefits of space to 5G, by developing and demonstrating integrated satellite- and terrestrial-based 5G services, across multiple markets and use cases (video credit: ESA) 44)
NASA to Advance Unique 3D Printed Sensor Technology
• 15 February 2019: A NASA technologist is taking miniaturization to the extreme. Mahmooda Sultana won funding to advance a potentially revolutionary, nanomaterial-based detector platform. The technology is capable of sensing everything from minute concentrations of gases and vapor, atmospheric pressure and temperature, and then transmitting that data via a wireless antenna — all from the same self-contained platform that measures just two-by-three-inches in size. 45)
Under a $2 million technology development award, Sultana and her team at NASA's Goddard Space Flight Center in Greenbelt, Maryland, will spend the next two years advancing the autonomous multifunctional sensor platform. If successful, the technology could benefit NASA's major science disciplines and efforts to send humans to the Moon and Mars. These tiny platforms could be deployed on planetary rovers to detect small quantities of water and methane, for example, or be used as monitoring or biological sensors to maintain astronaut health and safety.
Central to the effort, funded by NASA's Space Technology Mission Directorate's (STMD) Early Career Initiative (ECI) is a 3D printing system developed by Ahmed Busnina and his group at Northeastern University in Boston. The 3D printing system is like printers used to produce money or newspapers. However, instead of ink, the printer applies nanomaterials, layer-by-layer, onto a substrate to create tiny sensors. Ultimately, each is capable of detecting a different gas, pressure level or temperature.
Nanomaterials, such as carbon nanotubes, graphene, molybdenum disulfide and others, exhibit interesting physical properties. They are highly sensitive and stable at extreme conditions. They are also lightweight, hardened against radiation and require less power, making them ideal for space applications, Sultana said.
Under her partnership with Northeastern University, Sultana and her group will design the sensor platform, determining which combination of materials are best for measuring minute, parts-per-billion concentrations of water, ammonia, methane and hydrogen — all important in the search for life throughout the solar system. Using her design, Northeastern University will then use its Nanoscale Offset Printing System to apply the nanomaterials. Once printed, Sultana's group will functionalize the individual sensors by depositing additional layers of nanoparticles to enhance their sensitivity, integrate the sensors with readout electronics, and package the entire platform.
The approach differs dramatically from how technologists currently fabricate multifunctional sensor platforms. Instead of building one sensor at a time and then integrating it to other components, 3D printing allows technicians to print a suite of sensors on one platform, dramatically simplifying the integration and packaging process.
Figure 36: Technologist Mahmooda Sultana holds an early iteration of an autonomous multifunctional sensor platform, which could benefit all of NASA's major scientific disciplines and efforts to send humans to the Moon and Mars Image credit: NASA/W. Hrybyk)
Also innovative is Sultana's plan to print on the same silicon wafer partial circuitry for a wireless communications system that would communicate with ground controllers, further simplifying instrument design and construction. Once printed, the sensors and wireless antenna will be packaged onto a printed circuit board that holds the electronics, a power source, and the rest of the communications circuitry.
"The beauty of our concept is that we're able to print all sensors and partial circuity on the same substrate, which could be rigid or flexible. We eliminate a lot of the packaging and integration challenges," Sultana said. "This is truly a multifunctional sensor platform. All my sensors are on same chip, printed one after another in layers."
Figure 37: Meet Mahmooda Sultana, Associate Branch Head, Systems Engineering Branch at NASA's Goddard Space Flight Center in Maryland. Mahmooda uses her love of math and puzzles to develop new technologies and miniaturize instruments for NASA missions (video credit: NASA)
Wide-Ranging Uses: The research picks up where other NASA-funded efforts ended. Under several previous efforts funded by Goddard's Internal Research and Development Program and STMD's Center Innovation Fund, Sultana and her team used the same technique to manufacture and demonstrate individual sensors made of carbon nanotubes and molybdenum disulfide, among other materials. "The sensors were found to be quite sensitive, down to low parts per million. With our ECI funding, we are targeting the instrument's sensitivity to parts per billion by improving sensor design and structure," Sultana said.
According to her, the project addresses NASA's need for low-power, small, lightweight, and highly sensitive sensors that can distinguish important molecules other than by measuring the masses of a molecule's fragments, which is how many missions currently detect molecules today using mass spectrometers.
In fact, the agency has acknowledged that future sensors need to detect minute concentrations of gases and vapors in the parts per billion level. Although mass spectrometers can detect a wide spectrum of molecules — particularly useful for unknown samples — they have difficulty distinguishing between some of the important species, such as water, methane and ammonia. "It's also difficult to reach the parts per billion or beyond level with them," she said.
"We're really excited about the possibilities of this technology," Sultana said. "With our funding, we can take this technology to the next level and potentially offer NASA a new way to create customized, multifunctional sensor platforms, which I believe could open the door to all types of mission concepts and uses. The same approach we use to identify gases on a planetary body also could be used to create biological sensors that monitor astronaut health and the levels of contaminants inside spacecraft and living quarters."
New Geodesy Application for Emerging Atom-Optics Technology
• 20 December 2018: NASA and the Sunnyvale, California-based AOSense, Inc., have successfully built and demonstrated a prototype quantum sensor capable of obtaining highly sensitive and accurate gravity measurements — a stepping stone toward next-generation geodesy, hydrology, and climate-monitoring missions in space.46)
The prototype sensor, developed in collaboration with NASA's Goddard Space Flight Center in Greenbelt, Maryland, employs a revolutionary measurement technique called atom interferometry, which former U.S. Energy Department Secretary Steven Chu and his colleagues invented in the late 1980s. In 1997, Chu received the Nobel Prize in Physics for his work.
Since the discovery, researchers worldwide have attempted to build practical, compact, more sensitive quantum sensors, such as atom interferometers, that scientists could use in space-constrained areas, including spacecraft.
Figure 38: This image demonstrates the control that the Goddard-AOSense team has over the paths of atoms. In this demonstration, they manipulated the path to form the acronym, NASA (image credit: AOSense, Inc.)
With funding from NASA's Small Business Innovation Research, Instrument Incubator, and Goddard's Internal Research and Development programs, the Goddard-AOSense team developed an atom-optics gravity gradiometer primarily for mapping Earth's time-varying gravitational field. Although Earth's gravitational field changes for a variety of reasons, the most significant cause is a change in water mass. If a glacier or an ice sheet melts, this would affect mass distribution and therefore Earth's gravitational field.
"Our sensor is smaller than competing sensors with similar sensitivity goals," said Babak Saif, a Goddard optical physicist and collaborator in the effort. "Previous atom interferometer-based instruments included components that would literally fill a room. Our sensor, in dramatic comparison, is compact and efficient. It could be used on a spacecraft to obtain an extraordinary data set for understanding Earth's water cycle and its response to climate change. In fact, the sensor is a candidate for future NASA missions across a variety of scientific disciplines."
Atom interferometry, however, hinges on quantum mechanics, the theory that describes how matter behaves at sub-microscopic scales. Atoms, which are highly sensitive to gravitational signals, can also be cajoled into behaving like light waves. Special pulsing lasers can split and manipulate atom waves to travel different paths. The two atom waves will interact with gravity in a way that affects the interference pattern produced once the two waves recombine. Scientists can then analyze this pattern to obtain an extraordinarily accurate measure of the gravitational field.
In particular, the team is eying its quantum sensor as a potential technology to gather the type of data currently produced by NASA's Gravity Recovery and Climate Experiment (GRACE) Follow-On mission. GRACE-FO is a two-satellite mission that has generated monthly gravity maps showing how mass is distributed and how it changes over time. Due to its extraordinary precision, the quantum sensor could eliminate the need for a two-satellite system or provide even greater accuracy if deployed on a second satellite in a complementary orbit, said Lee Feinberg, a Goddard optics expert also involved in the effort.
"With this new technology, we can measure the changes of Earth's gravity that come from melting ice caps, droughts, and draining underground water supplies, greatly improving on the pioneering GRACE mission," said John Mather, a Goddard scientist and winner of the Nobel Prize in Physics in 2006 for his work on NASA's Cosmic Background Explorer that helped cement the big-bang theory of the universe.
The instrument, however, could be used to answer other scientific questions.
"We can measure the interior structure of planets, moons, asteroids, and comets when we send probes to visit them. The technology is so powerful that it can even extend the Nobel-winning measurements of gravitational waves from distant black holes, observing at a new frequency range," Mather said, referring to the confirmation in 2015 of cosmic gravitational waves — literally, ripples in the fabric of space-time that radiate out in all directions, much like what happens when a stone is thrown into a pond. Since that initial confirmation, the Laser Interferometer Gravitational Wave Observatory and the European Virgo detectors have detected other events.
Since 2004, AOSense has developed quantum sensors and atomic clocks, with broad expertise and capabilities spanning all aspects of development and characterization of advanced sensors for precision navigation and timing. 47)
Figure 39: Real-world atomic sensors and other exacting applications require laser sources with specific size, environmental, and optical characteristics, placing unique constraints that most commercial laser systems do not meet. AOSense has developed a line of external cavity diode lasers (ECDLs) designed to meet these needs, offering narrow linewidth in a compact package (image credit: AOSense)
Our AOSense ECDL is built on a semi-monolithic bench with a cat's-eye design for stable operation in demanding environments. The wavelength is factory-set to the desired user wavelength; no subsequent mechanical adjustment is required. A PZT may be used for ~GHz tuning in addition to current and temperature controls. Current wavelengths include alkali (767 nm, 780 nm, 852 nm) and alkaline earth (423 nm, 461 nm, 657 nm, 689 nm, 698 nm) transitions. Additional UV/blue models at 369 and 399 nm are currently in development. The flexible design is fully translatable to additional wavelengths. The output beam is circularized to optimize fiber coupling (not available for all wavelengths). The compact laser enclosure dimensions are only 7.5 x 3.8 x 2.8 cm.
New Standard for Wireless Transmission Speed at 100 Gbit/s
• 22 August 2018: Northrop Grumman Corporation and DARPA (Defense Advanced Research Projects Agency) have set a new standard for wireless transmission by operating a data link at 100 Gbit/s over a distance of 20 kilometers in a city environment. 48)
The blazing data rate is fast enough to download a 50 GB blue ray video in four seconds. The demonstration marked the successful completion of Northrop Grumman's Phase 2 contract for DARPA's 100 Gbit/s (100G) RF Backbone program.
Figure 40: Northrop Grumman and DARPA 100 Gbit/s link demonstrated over 20 km city environment on 19 January 2018 in Los Angeles (image credit: Northrop Grumman)
The 100G system is capable of rate adaptation on a frame by frame basis from 9 to 102 Gbit/s to maximize data rate throughout dynamic channel variations. Extensive link characterization demonstrated short-term error-free performance from 9 to 91 Gbit/s, and a maximum data rate of 102 Gbit/s with 1 erroneous bit received per ten thousand bits transmitted.
The successful data link results from the integration of several key technologies. The link operates at millimeter wave frequencies (in this case, 71-76 GHz and 81-86 GHz with 5 GHz of bandwidth, or data carrying capacity, and uses a bandwidth efficient signal modulation technique to transmit 25 Gbit/s data streams on each 5 GHz channel. To double the rate within the fixed bandwidth, the data link transmits dual orthogonally polarized signals from each antenna. Additionally, the link transmits from two antennas simultaneously (spatial multiplexing) and uses multiple-input-multiple-output (MIMO) signal processing techniques to separate the signals at the two receiving antennas, thus again doubling the data rate within the fixed bandwidth.
According to Louis Christen, director, research and technology, Northrop Grumman, "This dramatic improvement in data transmission performance could significantly increase the volume of airborne sensor data that can be gathered and reduce the time needed to exploit sensor data. Next generation sensors such as hyperspectral imagers typically collect data faster, and in larger quantity than most air-to-ground data links can comfortably transmit," said Christen. "Without such a high data rate link data would need to be reviewed and analyzed after the aircraft lands."
By contrast, a 100G data link could transmit high-rate data directly from the aircraft to commanders on the ground in near real time, allowing them to respond more quickly to dynamic operations.
The successful 100G ground demonstration sets the stage for the flight test phase of the 100G RF Backbone program. This next phase, which started in June, demonstrates the 100G air-to-ground link up to 100 Gbit/s over a 100 km range and extended ranges with lower data rates. The 100G hardware will be flown aboard the Proteus demonstration aircraft developed by Northrop Grumman subsidiary Scaled Composites.
Northrop Grumman's 100G industry team includes Raytheon, which developed the millimeter wave antennas and related RF electronics and Silvus Technologies, which provides the key spatial multiplexing and MIMO signal processing technologies.
Figure 41: The 100G hardware will be flown aboard the Proteus demonstration aircraft developed by Northrop Grumman subsidiary Scaled Composites (image credit: Northrop Grumman)
Researchers develop novel process to 3D print one of the strongest materials on Earth
• 15 August 2018: Researchers from Virginia Tech (Blacksburg, VA) and Lawrence Livermore National Laboratory (Livermore, CA) have developed a novel way to 3D print complex objects of one of the highest-performing materials used in the battery and aerospace industries. 49)
Previously, researchers could only print this material, known as graphene, in 2D sheets or basic structures. But Virginia Tech engineers have now collaborated on a project that allows them to 3D print graphene objects at a resolution an order of magnitude greater than ever before printed, which unlocks the ability to theoretically create any size or shape of graphene.
Because of its strength - graphene is one of the strongest materials ever tested on Earth - and its high thermal and electricity conductivity, 3D printed graphene objects would be highly coveted in certain industries, including batteries, aerospace, separation, heat management, sensors, and catalysis.
Graphene is a single layer of carbon atoms organized in a hexagonal lattice. When graphene sheets are neatly stacked on top of each other and formed into a three-dimensional shape, it becomes graphite, commonly known as the "lead" in pencils.
Because graphite is simply packed-together graphene, it has fairly poor mechanical properties. But if the graphene sheets are separated with air-filled pores, the three-dimensional structure can maintain its properties. This porous graphene structure is called a graphene aerogel.
"Now a designer can design three-dimensional topology comprised of interconnected graphene sheets," said Xiaoyu "Rayne" Zheng, assistant professor with the Department of Mechanical Engineering in the College of Engineering and director of the Advanced Manufacturing and Metamaterials Lab. "This new design and manufacturing freedom will lead to optimization of strength, conductivity, mass transport, strength, and weight density that are not achievable in graphene aerogels."
Zheng, also an affiliated faculty member of the Macromolecules Innovation Institute, has received grants to study nanoscale materials and scale them up to lightweight and functional materials for applications in aerospace, automobiles, and batteries.
Previously, researchers could print graphene using an extrusion process, sort of like squeezing toothpaste, but that technique could only create simple objects that stacked on top of itself. "With that technique, there's very limited structures you can create because there's no support and the resolution is quite limited, so you can't get freeform factors," Zheng said. "What we did was to get these graphene layers to be architected into any shape that you want with high resolution."
This project began three years ago when Ryan Hensleigh, lead author of the article and now a third-year Macromolecular Science and Engineering Ph.D. student, began an internship at the LLNL (Lawrence Livermore National Laboratory in Livermore), California. Hensleigh started working with Zheng, who was then a member of the technical staff at Lawrence Livermore National Laboratory. When Zheng joined the faculty at Virginia Tech in 2016, Hensleigh followed as a student and continued working on this project.
To create these complex structures, Hensleigh started with graphene oxide, a precursor to graphene, crosslinking the sheets to form a porous hydrogel. Breaking the graphene oxide hydrogel with ultrasound and adding light-sensitive acrylate polymers, Hensleigh could use projection micro-stereolithography to create the desired solid 3D structure with the graphene oxide trapped in the long, rigid chains of acrylate polymer. Finally, Hensleigh would place the 3D structure in a furnace to burn off the polymers and fuse the object together, leaving behind a pure and lightweight graphene aerogel.
"It's a significant breakthrough compared to what's been done," Hensleigh said. "We can access pretty much any desired structure you want."
The key finding of this work, which was recently published with collaborators at LLNL in the journal Materials Horizons, is that the researchers created graphene structures with a resolution an order of magnitude finer than ever printed. Hensleigh said other processes could print down to 100 µm, but the new technique allows him to print down to 10 µm in resolution, which approaches the size of actual graphene sheets. 50)
"We've been able to show you can make a complex, three-dimensional architecture of graphene while still preserving some of its intrinsic prime properties," Zheng said. "Usually when you try to 3D print graphene or scale up, you lose most of their lucrative mechanical properties found in its single sheet form."
Figure 42: (A) Four ‘‘Green'' MAG parts of differing unit-cell structures before pyrolysis from left to right octet-truss, gyroid, cubo-octahedron, and Kelvin foam; (B) optical image of pyrolyzed gyroid; (C) SEM image of pyrolyzed gyroid with intricate overhang structures (D) zoomed image of pyrolyzed gyroid in ‘‘C''; (E) optical image of pyrolyzed MAG octet-truss, of a different design than shown in ‘‘A'' supported by a single strawberry blossom filament; (F) SEM image of pyrolyzed octet-truss MAG in ‘‘E''; (G) zoomed image of octet-truss in ‘‘E'' showing the very high 10 µm resolution achievable in our process (image credit: 3D print graphene study team of Virginia Tech and Lawrence Livermore National Laboratory)
Prototype nuclear battery packs 10 times more power
• May 2018: Russian researchers from the Moscow Institute of Physics and Technology (MIPT), the Technological Institute for Superhard and Novel Carbon Materials (TISNCM), and the National University of Science and Technology, MISIS, have optimized the design of a nuclear battery generating power from the beta decay of nickel-63 (63Ni), a radioactive isotope. Their new battery prototype packs about 3,300 mW-hours of energy per gram, which is more than in any other nuclear battery based on 63Ni, and 10 times more than the specific energy of commercial chemical cells. The paper was published in the journal Diamond and Related Materials. 51) 52)
Figure 43: A nuclear battery (image credit: Elena Khavina/MIPT)
Ordinary batteries powering clocks, flashlights, toys, and other electrical devices use the energy of so-called redox chemical reactions in which electrons are transferred from one electrode to another via an electrolyte. This gives rise to a potential difference between the electrodes. If the two battery terminals are then connected by a conductor, electrons start flowing to remove the potential difference, generating an electric current. Chemical batteries, also known as galvanic cells, are characterized by a high power density—that is, the ratio between the power of the generated current and the volume of the battery. However, chemical cells discharge in a relatively short time, limiting their applications in autonomous devices. Some of these batteries, called accumulators, are rechargeable, but even they need to be replaced for charging. This may be dangerous, as in the case of a cardiac pacemaker, or even impossible, if the battery is powering a spacecraft.
Fortunately, chemical reactions are just one of the possible sources of electric power. In 1913, Henry Moseley invented the first power generator based on radioactive decay. His nuclear battery consisted of a glass sphere silvered on the inside with a radium emitter mounted at the center on an isolated electrode. Electrons resulting from the beta decay of radium caused a potential difference between the silver film and the central electrode. However, the idle voltage of the device was way too high—tens of kV (kilovolt)—and the current was too low for practical applications.
In 1953, Paul Rappaport proposed the use of semiconducting materials to convert the energy of beta decay into electricity. Beta particles—electrons and positrons—emitted by a radioactive source ionize atoms of a semiconductor, creating uncompensated charge carriers. In the presence of a static field of a p-n structure, the charges flow in one direction, resulting in an electric current. Batteries powered by beta decay came to be known as betavoltaics. The chief advantage of betavoltaic cells over galvanic cells is their longevity. Radioactive isotopes used in nuclear batteries have half-lives ranging from tens to hundreds of years, so their power output remains nearly constant for a very long time. Unfortunately, the power density of betavoltaic cells is significantly lower than that of their galvanic counterparts. Despite this, betavoltaics were used in the 1970s to power cardiac pacemakers, before being phased out by cheaper lithium-ion batteries, even though the latter have shorter lifetimes.
Betavoltaic power sources should not be confused with RTGs (Radioisotope Thermoelectric Generators), which are also called nuclear batteries, but operate on a different principle. Thermoelectric cells convert the heat released by radioactive decay into electricity using thermocouples. The efficiency of RTGs is only several percent and depends on temperature. But owing to their longevity and relatively simple design, thermoelectric power sources are widely used to power spacecraft such as the New Horizons probe and Mars rover Curiosity. RTGs were previously used on unmanned remote facilities such as lighthouses and automatic weather stations. However, this practice was abandoned, because used radioactive fuel was hard to recycle and leaked into the environment.
A research team led by Vladimir Blank, the director of TISNCM and chair of nanostructure physics and chemistry at MIPT, came up with a way of increasing the power density of a nuclear battery almost tenfold. The physicists developed and manufactured a betavoltaic battery using nickel-63 as the source of radiation and Schottky barrier-based diamond diodes for energy conversion. The prototype battery achieved an output power of about 1 µW (microwatt), while the power density per cubic centimeter was 10 µW, which is enough for a modern artificial pacemaker. Nickel-63 has a half-life of 100 years, so the battery packs about 3,300 mW-hours of power per 1 gram—10 times more than electrochemical cells.
Figure 44: A nuclear battery design (image credit: V. Bormashov et al./Diamond and Related Materials)
The nuclear battery prototype consisted of 200 diamond converters interlaid with nickel-63 and stable nickel foil layers (Figure 44). The amount of power generated by the converter depends on the thickness of the nickel foil and the converter itself, because both affect how many beta particles are absorbed. Currently available prototypes of nuclear batteries are poorly optimized, since they have excessive volume. If the beta radiation source is too thick, the electrons it emits cannot escape it. This effect is known as self-absorption. However, as the source is made thinner, the number of atoms undergoing beta decay per unit time is proportionally reduced. Similar reasoning applies to the thickness of the converter.
The goal of the researchers was to maximize the power density of their nickel-63 battery. To do this, they numerically simulated the passage of electrons through the beta source and the converters. It turned out that the nickel-63 source is at its most effective when it is 2 µm thick, and the optimal thickness of the converter based on Schottky barrier diamond diodes is around 10 µm.
The main technological challenge was the fabrication of a large number of diamond conversion cells with complex internal structure. Each converter was merely tens of micrometers thick, like a plastic bag in a supermarket. Conventional mechanical and ionic techniques of diamond thinning were not suitable for this task. The researchers from TISNCM and MIPT developed a unique technology for synthesizing thin diamond plates on a diamond substrate and splitting them off to mass-produce ultrathin converters.
The team used 20 thick boron-doped diamond crystal plates as the substrate. They were grown using the temperature gradient technique under high pressure. Ion implantation was used to create a 100 nm thick defective, "damaged" layer in the substrate at the depth of about 700 nm. A boron-doped diamond film 15 µm thick was grown on top of this layer using chemical vapor deposition. The substrate then underwent high-temperature annealing to induce graphitization of the buried defective layer and recover the top diamond layer. Electrochemical etching was used to remove the damaged layer. Following the separation of the defective layer by etching, the semi-finished converter was fitted with ohmic and Schottky contacts.
All converters were connected in parallel in a stack as shown in Figure 44. The technology for rolling 2 µm thick nickel foil was developed at the Research Institute and Scientific Industrial Association LUCH. The battery was sealed with epoxy.
The prototype battery is characterized by the current-voltage curve shown in Figure 46. The open-circuit voltage and the short-circuit current are 1.02 V and 1.27 µA, respectively. The maximum output power of 0.93 µW is obtained at 0.92 volts. This power output corresponds to a specific power of about 3,300 mW-hours per gram, which is 10 times more than in commercial chemical cells or the previous nickel-63 nuclear battery designed at TISNCM.
Figure 45: Photo of a prototype nuclear battery (image credit: Technological Institute for Superhard and Novel Carbon Materials)
In 2016, Russian researchers from MISIS had already presented a prototype betavoltaic battery based on nickel-63. Another working prototype, created at TISNCM and LUCH, was demonstrated at Atomexpo 2017. It had a useful volume of 1.5 cm3.
The main setback in commercializing nuclear batteries in Russia is the lack of nickel-63 production and enrichment facilities. However, there are plans to launch nickel-63 production on an industrial scale by mid-2020s.
There is an alternative radioisotope for use in nuclear batteries: Diamond converters could be made using radioactive carbon-14, which has an extremely long half-life of 5,700 years. Work on such generators was earlier reported by physicists from the University of Bristol (UK).
Figure 46: Prototype battery is characterized by the current-voltage curve (image credit: Study Team)
Nuclear batteries: Prospects:
The work reported in this story has prospects for medical applications. Most state-of-the-art cardiac pacemakers are over 10 cm3 in size and require about 10 µW of power. This means that the new nuclear battery could be used to power these devices without any significant changes to their design and size. "Perpetual pacemakers" whose batteries need not be replaced or serviced would improve the quality of life of patients.
The space industry would also greatly benefit from compact nuclear batteries. In particular, there is a demand for autonomous wireless external sensors and memory chips with integrated power supply systems for spacecraft. Diamond is one of the most radiation-proof semiconductors. Since it also has a large bandgap, it can operate in a wide range of temperatures, making it the ideal material for nuclear batteries powering spacecraft.
The researchers are planning to continue their work on nuclear batteries. They have identified several lines of inquiry that should be pursued. Firstly, enriching nickel-63 in the radiation source would proportionally increase battery power. Secondly, developing a diamond p-i-n structure with a controlled doping profile would boost voltage and therefore could increase the power output of the battery at least by a factor of three. Thirdly, enhancing the surface area of the converter would increase the number of nickel-63 atoms on each converter.
TISNCM Director Vladimir Blank, who is also chair of nanostructure physics and chemistry at MIPT, commented on the study: "The results so far are already quite remarkable and can be applied in medicine and space technology, but we are planning to do more. In the recent years, our institute has been rather successful in the synthesis of high-quality doped diamonds, particularly those with n-type conductivity. This will allow us to make the transition from Schottky barriers to p-i-n structures and thus achieve three times greater battery power. The higher the power density of the device, the more applications it will have. We have decent capabilities for high-quality diamond synthesis, so we are planning to utilize the unique properties of this material for creating new radiation-proof electronic components and designing novel electronic and optical devices."
The Kilopower Project of NASA
17 January 2018: When astronauts someday venture to the Moon, Mars and other destinations, one of the first and most important resources they will need is power. A reliable and efficient power system will be essential for day-to-day necessities, such as lighting, water and oxygen, and for mission objectives, like running experiments and producing fuel for the long journey home. 53)
That's why NASA is conducting experiments on Kilopower, a new power source that could provide safe, efficient and plentiful energy for future robotic and human space exploration missions. This pioneering space fission power system could provide up to 10 kW of electrical power — enough to run two average households — continuously for at least ten years. Four Kilopower units would provide enough power to establish an outpost.
Currently, power is usually generated in space by solar arrays that convert the Sun's energy into electricity or by radioisotope power systems that convert the heat from naturally decaying plutonium238 into electricity. Solar or radioisotope power systems may be impractical for future NASA missions to places where sunlight is dim or unavailable, and where more than a few hundreds of watts of power are needed. 54)
Fission power from nuclear reactors could provide abundant energy anywhere that humans or our robotic science probes might go. Fission, the splitting of an atom's nucleus, releases a great amount of heat energy: 1 pound of uranium fuel can produce as much energy as about 3 million pounds of burnable coal. With such a high energy density, fission power systems present an ideal solution for space missions that require large amounts of power, especially where sunlight is limited or not available.
Technology Demonstration Goal: Because of fission power's great potential for space exploration, the NASA Space Technology Mission Directorate's Game Changing Development (GCD) Program is funding the Kilopower project, an effort led by NASA's Glenn Research Center to demonstrate space fission power systems technology. Building on prior work by a joint NASA and Department of Energy team, the project's main goal is to assemble and test an experimental prototype of a space fission power system. In 2012, Los Alamos National Laboratory and NASA Glenn demonstrated how an innovative, small-scale heat pipe-cooled fission reactor could provide electrical power using Stirling power conversion. This proof of physics demonstration provided the basis for the Kilopower project, the goal of which is to demonstrate the readiness of a monolithic-core heat-pipe reactor power system for use in NASA's exploration missions.
Accomplishing the Goal: The NS (Nuclear Systems) Kilopower project is a partnership between NASA and the Department of Energy's National Nuclear Security Administration (NNSA). Together, NASA and NNSA have designed and developed a 1 kWe reactor prototype with technology that is relevant for systems up to 10 kWe. It consists of a highly enriched uranium core built by NNSA, heat pipes provided by Advanced Cooling Technologies through a NASA Small Business Innovation Research contract, and Stirling generators provided by Sunpower, Inc. The core is a solid block of a uranium alloy, and heat pipes are clamped around the core to transfer heat to Stirling power conversion units to generate electrical power. Much smaller than terrestrial nuclear plants, Kilopower systems are small enough to be demonstrated here on Earth in existing facilities at the Nevada National Security Site.
Space Exploration Uses for Fission Power: The Kilopower project was initiated because NASA mission planning includes exploration of places in the solar system—such as deep space beyond Jupiter's orbit and the surfaces of Earth's moon and Mars—where power generation from sunlight is difficult and power from radioisotope systems is limited by the fuel supply. For human exploration, multiple 10 kWe Kilopower systems could provide the 40 kWe initially estimated to be needed by NASA's preliminary concepts for a human outpost, with the ability to add power as the outpost grows. For robotic exploration, 1 kWe Kilopower units enable abundant, reliable power for science and communications, and the potential to field deep space missions based on science return while conserving the limited supply of radioisotope fuel for its best opportunities. Characteristics of fission power that make it so beneficial for Mars outposts and deep space robotics also apply to other space missions. Nuclear fission systems could be scaled up to power nuclear electric propulsion vehicles to efficiently transport heavy cargo beyond Mars, and they could potentially shorten crewed trip times to Mars and other distant planets.
Game Changing Development Program: The Game Changing Development (GCD) program is part of NASA's Space Technology Mission Directorate. The GCD program aims to advance exploratory concepts and deliver technology solutions that enable new capabilities or radically alter current approaches.
Unlike previous technologies, the Kilopower reactor is simple, inexpensive and relies on fuels and technologies that are already well understood, NASA officials said. It uses active nuclear fission, like a conventional nuclear reactor, which will enable it to harvest far more energy from its uranium alloy core than an RTG (Radioisotope Thermoelectric Generator) could. A heat pipe clamped around the reactor core will transfer heat to the unit's power generators: small Stirling engines, a technology that was developed in 1816. The engines are simple pistons that convert heat into motion, which is then converted to electricity. The reactor will radiate excess heat from an umbrella-like cooling array.
Figure 47: The Kilopower reactor will take advantage of active nuclear fission and Stirling engines — simple devices that convert heat into motion — to increase its efficiency compared with previous nuclear power sources (image credit: NASA)
KRUSTY (Kilopower Reactor Using Stirling Technology) Experiment Results
• On 2 May 2018, NASA announced the results of the KRUSTY experiment during a news conference at GRC (Glenn Research Center). The Kilopower experiment was conducted November 2017 through March 2018 at the Nevada National Security Site (NNSS). 55)
- NASA and the Department of Energy's National Nuclear Security Administration (NNSA) have successfully demonstrated a new nuclear reactor power system that could enable long-duration crewed missions to the Moon, Mars and destinations beyond.
- "Safe, efficient and plentiful energy will be the key to future robotic and human exploration," said Jim Reuter, NASA's acting associate administrator for the Space Technology Mission Directorate (STMD) in Washington. "I expect the Kilopower project to be an essential part of lunar and Mars power architectures as they evolve."
- Kilopower is a small, lightweight fission power system capable of providing up to 10 kW of electrical power - enough to run several average households - continuously for at least 10 years. Four Kilopower units would provide enough power to establish an outpost.
- The prototype power system uses a solid, cast uranium-235 reactor core, about the size of a paper towel roll. Passive sodium heat pipes transfer reactor heat to high-efficiency Stirling engines, which convert the heat to electricity.
- According to David Poston, the chief reactor designer at NNSA's Los Alamos National Laboratory, the purpose of the recent experiment in Nevada was two-fold: to demonstrate that the system can create electricity with fission power, and to show the system is stable and safe no matter what environment it encounters. "We threw everything we could at this reactor, in terms of nominal and off-normal operating scenarios and KRUSTY passed with flying colors," said Poston.
- The Kilopower team conducted the experiment in four phases. The first two phases, conducted without power, confirmed that each component of the system behaved as expected. During the third phase, the team increased power to heat the core incrementally before moving on to the final phase. The experiment culminated with a 28-hour, full-power test that simulated a mission, including reactor startup, ramp to full power, steady operation and shutdown.
- Throughout the experiment, the team simulated power reduction, failed engines and failed heat pipes, showing that the system could continue to operate and successfully handle multiple failures.
- "We put the system through its paces," said Gibson. "We understand the reactor very well, and this test proved that the system works the way we designed it to work. No matter what environment we expose it to, the reactor performs very well."
- The Kilopower project is developing mission concepts and performing additional risk reduction activities to prepare for a possible future flight demonstration. The project will remain a part of the STMD's Game Changing Development program with the goal of transitioning to the Technology Demonstration Mission program in Fiscal Year 2020.
- Such a demonstration could pave the way for future Kilopower systems that power human outposts on the Moon and Mars, including missions that rely on In-situ Resource Utilization to produce local propellants and other materials.
Figure 48: Artist's concept of new fission power system on the lunar surface (image credit: NASA)
• Testing: As of September 2017 a test reactor has been constructed, called KRUSTY (Kilopower Reactor Using Stirling Technology). It is designed to produce up to 1 kW of electric power and is about 1.9 m tall. The goal of the KRUSTY experiment is to closely match the operational parameters that would be required in NASA deep space missions. The prototype Kilopower uses a solid, cast uranium-235 reactor core, about the size of a paper towel roll. Reactor heat is transferred via passive sodium heat pipes, with the heat being converted to electricity by Stirling engines. 56)
- Testing to gain TRL 5 started in November 2017 and continued into 2018. The first tests used a depleted uranium core manufactured by Y-12 National Security Complex in Tennessee. The depleted uranium core is exactly the same material as the regular high-enriched uranium (HEU) core with the only difference being the level of uranium enrichment. The testing of KRUSTY represents the first time the United States has conducted ground tests on any space reactor since the SNAP-10A experimental reactor was tested and eventually flown in 1965.
Figure 49: Marc Gibson, Kilopower lead engineer, and Jim Sanzi, Vantage Partners, install hardware on the Kilopower assembly at the Nevada National Security Site in March 2018 (image credit: NASA) 57)
Top Tomatoes thanks to Mars Missions
11 April 2018: Inspired by an Obama speech in 2010 on human missions to Mars, the Dutch company Groen Agro Control started investigating the best way to grow and fertilize plants in space, and whether that could also lead to improving the growth of vegetables on Earth. 58)
"In space, you can fertilize plants only with the minerals you take with you, but you still want them to produce the best possible crops," explains the company's Lex de Boer. "Ideally, you would also use the water that evaporates from the plants as a source of drinking water, with the minimum amount of purification. That means you have to apply doses of each mineral extremely carefully, so that as little as possible ends up unused in the drain water."
To study this, the company built an enclosed system in which tomato and pepper plants received doses of 16 different minerals, looking at how the uptake of each mineral correlated with growth.
In 2013, the company met an ESA team at the Space-MATCH event organized by Netherlands Organization for Applied Scientific Research TNO and ESA's Technology Transfer Office to bring ESA engineers and industry together to exchange knowhow. Here, the company was inspired to spin off a smart service helping horticulturalists to fertilize plants better on Earth.
Figure 50: Next time you eat a tomato or sweet pepper, take a closer look, because there's a good chance that its healthy appearance is thanks to one of former US President Barack Obama's speeches and ESA research for sending people on long-duration space missions (image credit: M. Barel (CC BY-NC 2.0))
To study the optimal dosing of minerals for growing tomato and pepper plants, Dutch Groen Agro Control built an enclosed system in which the plants received doses of 16 different minerals. The doses of each mineral were extremely carefully controlled, so that as little as possible ends up unused in the drain water.
Figure 51: Dosing of minerals for growing tomato and pepper plants (image credit: Groen Agro Control)
Triggered by the requirement to provide for the needs of humans on long missions to the Moon and Mars, ESA's MELiSSA (Micro-Ecological Life Support System Alternative) project focuses on a ‘closed' life support system, where all supplies are reused and recycled. So, for example, organic waste and carbon dioxide should be entirely converted into oxygen, water and food.
"MELiSSA recognizes that we have to develop a self-supporting system for long missions, as astronauts will not be able to rely on regular deliveries of supplies, especially as they move further from Earth," explains ESA's Christel Paille. "One key issue is food and water supplies. Astronauts will need to grow their own food with limited resources, and reclaim as much water as possible from that growth cycle. Hence it's vital that we develop a scheme that tells them exactly the right amount of fertilizer to apply at every stage in the plant growth."
Figure 52: The AlgoSolis facility is offering researchers and industry an opportunity to experiment with microalgae on larger scales than before. Based in Saint-Nazaire, France, the site is a stepping stone to industrial production of algae-based products (image credit: Université de Nantes) 59)
Legend to Figure 52: Microalgae offer huge benefits because they promise many products for human use, from biofuels to oxygen and food, as well as clean contaminated water or extract carbon dioxide from the atmosphere. ESA's MELiSSA project is using algae and other organisms and chemicals to develop a compact closed ecosystem to keep astronauts alive on long missions.
Spin-off from research as if in space
Based on its initial experiments, and the results it gained from growing vegetables in closed and well-controlled environments conceptually as if in space, the company developed a scheme for horticulturists, this time with the goal of maximizing plant growth and yield through very careful use of fertilizers.
In the service now offered to growers, samples are taken every week of both the fertilizer solution dripped into the plants – including tomatoes, peppers, cucumbers, eggplant, roses and gerbera – and the liquid that drains away.
These are analyzed at the company's laboratory and the results sent back to the growers, with advice on any changes they should make to the amounts of each of the 16 minerals given to the plants.
"There is a separate approach for each mineral, but these are also linked with each other because the uptake of certain minerals – such as potassium, magnesium and calcium – are closely related," says Lex. "The amount of each mineral that a plant needs also varies across its lifecycle. It will need a different combination when it is producing stalks and leaves early in its life compared with when it is producing flowers and fruit."
Horticulturalists also face challenges in altering fertilizer doses to match changing growing conditions. For example, rising energy prices have encouraged growers to keep greenhouse windows closed. However, this causes higher humidity, resulting in a fall in evaporation from plants.
That, in turn, makes it harder for tomato plants to transport calcium to the top of the plant, which can result in a condition that leaves and the plant top becomes necrotic. The company's scheme shows growers how to compensate for this by altering not just the amount of calcium in the drop water, but also magnesium and potassium levels.
Production increase: In less than one season, Dutch customer Zwingrow has already started to see positive results from using the scheme for its crop of orange bell peppers.
"We're always trying to improve the health and quality of the plants we grow, but using this weekly analysis means we are acting proactively, delving deeper into the needs of the plants and getting better results," says Ted Zwinkels, co-owner of Zwingrow. "Even though we started using it after the start of the season last year, the plants grew better and were healthier. I'd estimate that overall production increased by around 5%. It's impossible to know how much of this was due to the new regime, as variations in sunlight from year to year also play a part. However, already this season, using the service from the very start, we've seen stronger, better plants, and fewer vulnerable ones."
Groen Agro Control now has clients across the world. While it still has plans for experiments on crop growth in space, it is also widening its horizons on Earth, including a potential service for crops grown outside using drop water application of fertilizers, such as asparagus.
Production of NEXT-C ion propulsion engine
• 10 April 2018: Aerojet Rocketdyne's (Redmond WA) NEXT-C ion propulsion engine has successfully cleared NASA's CDR (Critical Design Review), confirming the technology achieved all program requirements and is ready for final production of the flight units. NEXT-C (NASA's Evolutionary Xenon Thruster-Commercial) was developed by NASA and is being commercialized by Aerojet Rocketdyne. NEXT-C has 7 kW of maximum power and an Isp > 4100 s. Its high Isp (Specific Impulse) and flexible operational capabilities make NEXT ideal for scientific space missions. 60)
NEXT-C will be the ion thruster used on a 2021 mission, named DART (Double Asteroid Redirection Test), led by the Johns Hopkins University Applied Physics Laboratory for NASA. DART is a kinetic impact mission designed to collide with a moonlet around the Didymos asteroid and slightly alter its orbit. This mission will be a critical step in demonstrating NASA's impact threat mitigation capabilities for redirection of a potentially hazardous object such as an asteroid.
"Serving as the primary propulsion source for DART, NEXT-C will establish a precedent for future use of electric propulsion to enable ambitious future science missions," said Eileen Drake, CEO and President of Aerojet Rocketdyne. "Electric propulsion reduces overall mission cost without sacrificing reliability or mission success."
Under a cost-sharing agreement with NASA's Science Mission Directorate through the agency's Glenn Research Center, Aerojet Rocketdyne is developing the NEXT-C electric propulsion engine and power processing unit. In addition to DART, additional NEXT-C units may be launched on future NASA planetary missions.
New dimension in design
• 11 April 2018: An alternative to conventional circuit boards, these 3D-molded interconnect devices (Figure 53) add electrical connectivity to the surface of three-dimensional structures. The aim is to combine mechanical, electronic and potentially optical functions in a single 3D part, allowing the creation of intricate, precisely aligned designs using fewer parts while delivering significant savings in space and weight compared to conventional electronic manufacturing. 61)
"These prototype interconnect devices were produced using injection-moulded plastics incorporating electrical metallisation," explains ESA's Jussi Hokka. "In principle, however, other materials can also be used, allowing the incorporation of sensors or the integration of shielding or cooling systems."
Figure 53: Illustration of 3D-molded prototype interconnect devices procuded for ESA by Art of Technology AG in Switzerland, through the Agency's Advanced Research in the Telecommunications Systems program (image credit: ESA/Art of Technology AG)
Twisting laser light offers the chance to probe the nano-scale
• 5 April 2018: A new method to sensitively measure the structure of molecules has been demonstrated by twisting laser light and aiming it at miniscule gold gratings to separate out wavelengths. The technique could potentially be used to probe the structure and purity of molecules in pharmaceuticals, agrochemicals, foods and other important products more easily and cheaply than existing methods. 62)
Developed by physicists at the University of Bath (Bath UK), working with colleagues at the University of Cambridge and UCL (University College London), the technique relies on the curious fact that many biological and pharmaceutical molecules can be either 'left-handed' or 'right-handed'.
Figure 54: A twisted laser beam hits a nanoscopic U-shaped gold grating which further twists the beam in either a right or left-handed direction. This deflects the beam in many directions and further splits it into its constituent wavelengths across the color spectrum (image credit: University of Bath, Ventsislav Valev)
Although such molecules are built from exactly the same elements they can be arranged in mirror images of each other, and this configuration sometimes changes their properties drastically.
Notoriously the morning sickness drug Thalidomide caused birth defects and deaths in babies before it was pulled from the market in the 1960s. Investigation showed that the drug existed in two mirror images - the right-handed form was effective as a morning sickness drug, but the left-handed form was harmful to foetuses. This is one example of why testing what 'handedness', or chirality, a molecule has is essential for many valuable products.
The research team from the Centre for Photonics and Photonic Materials, and the Centre for Nanoscience and Nanotechnology at the University of Bath, used a special white-light laser built in-house and directed it through several optical components to put a twist on the beam. The twisted laser beam then hits a nano-scopic U-shaped gold grating which serves as a template for the light, further twisting the beam in either a right or left-handed direction. This deflects the beam in many directions and further splits it into its constituent wavelengths across the colour spectrum.
By carefully measuring the deflected light scientists can detect tiny differences in intensity across the spectrum which inform them about the chirality of the grating the laser beam interacts with.
The study, published in the journal Advanced Optical Materials, demonstrates the technique as a proof of principle. 63)
Christian Kuppe, the PhD student who conducted the experiments, said: "At the moment chiral sensing requires high molecular concentrations because you're looking for tiny differences in how the light interacts with the target molecule. By using our gold gratings we aim to use a much smaller amount of molecules to conduct a very sensitive test of their handedness. The next step will be to continue to test the technique with a range of well-known chiral molecules. We hope that this will become a valuable way to perform really important tests on all sorts of products including pharmaceuticals and other high-value chemicals."
Dr Ventsislav Valev, who oversaw the work, said: "There's a great deal of scientific excitement about miniaturisation and working on nano-sized dimensions at the very small scale. However, in the rush to go as small as possible, some opportunities have been overlooked. Working with chiral nano-gratings is a great example of that."
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The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (email@example.com).