Zero 2 Infinity
Zero 2 Infinity: Introduction of a game-changing launch technology for small satellites
Founded in 2009, the private aerospace company Zero 2 Infinity – which is headquartered in Barcelona, Spain – was created with the vision of delivering orbital payloads and providing space tourism on a budget. But unlike your conventional aerospace companies – i.e. SpaceX, Blue Origin, Orbital ATK, etc. — their plan is to do it all using high-altitude stratospheric balloons.
Our mission: enable people with a project and a passion to place themselves above the Earth in order to collect rich data, take high definition images, manage communications and more, much more. "In 2009 we recognized that Space should not just be for big companies. Small companies, schools, universities and lovers of our Earth and Space should be able to contribute. Why shouldn't they join the next big adventure? We want people to be able to quickly and affordably get their projects into orbit and to capitalize on the exciting opportunities created by innovations in Space technology. That is why Jose Mariano Lopez-Urdiales and the team launched Zero 2 Infinity and that is why we haven't stopped working for it." — Since 2009 we've been successfully lifting heavy commercial payloads into Near Space using our balloon technology. By helping these projects succeed we fuel our future economies and expand our knowledge of the world and universe we live in. Collectively, our team has track records in aerospace management, aerospace engineering, avionics engineering, international Space law, innovation, marketing and communications. 1)
On March 1, 2017, the Zero 2 Infinity team passed a major milestone, deploying a prototype "rockoon" craft from the National Institute of Aerospace Technology's (INTA) facility in El Arenosillo (Huelva), on the south coast of Spain. Known as Bloostar, this two-stage craft (which consists of a balloon and a rocket) is one of the latest technologies seeking to drastically reduce the costs of launching people and payloads into space. 2) 3)
Figure 1: Bloostar ignition closeup after balloon delivery/deployment to ~22 km (image credit: Zero 2 Infinity) 4)
The goals of the mission were: (i) validation of the telemetry systems in Space conditions, (ii) controlled ignition, (iii) stabilization of the rocket, (iv) monitoring of the launch sequence, (v) parachute deployment, and finally, (vi) sea recovery. All these goals were achieved in full.
This mission is part of the development of Bloostar, the first small satellite launcher to use a stratospheric balloon as a first stage. By initiating the rocket ignition from above airspace, the targeted orbit can be reached with expediency and efficiency.
This patented technique is less risky than any systems used until now. The rocket-powered phase starts already from above 95% of the mass of the atmosphere (~ 22 km), getting there with no polluting emissions. Besides the environmental angle, this new method lets Zero 2 Infinity launch satellites with more flexibility (2 weeks notice), at a drastically lower cost and more often than ever before.
From the day it was presented, Bloostar has attracted the attention of the leading satellite companies around the world. Zero 2 Infinity already has gathered upwards of 250 million euros in Letters of Intent for future launches.
The Space sector has become more open to private initiatives and is nowadays living a revolution. From global communication services to meteorological predictions, interconnection of machines through the Internet of Things and even the possibility of having a daily picture of the entire Planet. These advances have paved the way for the creation of hundreds of companies that need efficient and safe transportation services like the ones Zero 2 Infinity is offering and developing.
Zero 2 Infinity, a private company headquartered in Barcelona, Spain, with subsidiaries around the world, is radically simplifying access to Space. It is the only company in Europe specialized in the elevation to the Edge of Space of components that require testing and certifying in Space conditions. At the moment, it is working on sending small satellites into orbit through its project Bloostar and has mid-term plans to send people to Near Space for science and leisure (project Bloon).
With Bloostar, Zero 2 Infinity is simplifying access to Space so that more problems can efficiently be solved from Space. By means of a hybrid Balloon-Rocket solution (a "Rockoon"), Bloostar uses a stratospheric balloon as the initial ascent stage followed by three rocket stages to reach orbit. The balloon stage, launched from open seas on board a standard ship, eliminates the need for a launch facility and delivers the rocket stage to a near-space environment which enables significant advantages. Bloostar thus leverages the atmosphere and gravity (through buoyancy) and becomes an elegantly efficient solution to affordable and responsive Space transportation for micro and nano class payloads.
Advantages of a stratospheric release: 6)
Launching a rocket above 99% of the mass of the atmosphere, where the aerodynamic resistance is near-negligible, yields several significant advantages compared to a standard ground-based launch. Extensive mission analysis with the ASTOS (Aerospace Trajectory Optimization Software), a software tool (used by e.g. ESA in launcher designs), comparing Bloostar and a ground-ignited equivalent, shows a ~8% ΔV decrease required for Bloostar to reach orbit. This improvement originates from lower drag losses, lower gravity losses and nozzles working at optimum performance. What seems like a small improvement in ΔV, results in a significant payload increase due to the exponential relation between vehicle mass and ΔV (Tsiolkowsky equation). As seen in Figure 3 (left), drag can be 20 times less when the launcher is ignited from the stratosphere compared to igniting form the ground.
Figure 3: ASTOS plots of drag vs. altitude (left graph) and heat flux vs. altitude (right graph) for a generic launcher ignited from ground (red) and from 20 km (blue), image credit: Zero 2 Infinity
It should be noted that lower atmospheric density has more benefits than solely decreased ΔV. It also influences the vibrations the payload needs to withstand and the mass of the launcher structure because of reduced load cases. Figure 3 (right) shows that also the thermal heat flux is reduced by a factor of 10. This implies even further significant mass savings because of the decreased thermal insulation the vehicle needs to carry and the early separation of the fairing.
On the propulsion side, the low chamber pressure experienced in near-space makes feasible the utilization of pressure fed systems while not requiring thick/heavy tank structures. This significantly decreases the mass and complexity of the vehicle reducing development and operating costs. As a consequence, the pressure fed systems allow the use of differential throttling for trajectory control, eliminating the need for TVC (Thrust Vector Control) gimbals on some engines.
On the ground segment side, additional cost can be saved by using the remaining balloon segment as a high altitude communication relay after the rocket has been release and ignited. This eliminates the need for costly ground stations along the initial flight path.
All these factors combined reveal the true advantage of launching from the stratosphere. And in the long run, such simplified rocket configurations that only a near-space launch allows, will be the easiest to make reusable - further reducing the cost and increasing the rates of launch to satisfy the growing demand for constellations.
Key customer advantages:
The gains listed in the previous chapter translate into the following unique advantages for the customer compared to other launch vehicles:
• Cheapest dedicated nanosatellite launcher on the market
• Availability: less risk of launch delay due to bad weather (wind is compensated by the ship's aligned course)
• Most benign vibrational and shock environment
- Use of lighter spacecraft structure
- Less need for costly and time consuming launch qualification tests
• Double payload volume
• ITAR-free launch
• Possibility to launch from different places around the world.
Bloostar development program:
The Bloostar development program is based on an iterative design-build-test approach – a philosophy in which all Zero 2 Infinity projects rely on. The project incorporates the most advanced technologies in rapid prototyping like 3D printing to ensure fast iteration and improvement cycles. All new systems will undergo a rigorous testing program, with opportunities for gradually scaled up performance and operations.
1) Phase 1: High-altitude subsystem tests – This phase has already started and includes continued testing of key subsystems and operational procedures, while the technical design is finalized in parallel.
2) Phase 2: Nanobloostar – This phase will cover the development of a Balloon-Launched single-stage suborbital launcher with the ability to carry out a precise suborbital flight with a 75 kg payload to 180 km altitude. The suborbital launcher will be identical to the third stage of the subsequent orbital launcher. The timeline for this phase is estimated to 1 year.
3) Phase 3: Bloostar – After a second round of investment, the development continues with the full 3-stage launcher with capacity to insert 75 kg into a polar 600 km orbit. The third stage will be re-used from the suborbital launcher. The other stages share key commonalities that are slightly upgraded such as pressurization system, tanks configuration, avionics and launch operations.
Bloostar is a dedicated nanosatellite and microsatellite launching system that will put payloads of 75 kg into a 600 km sun-synchronous orbit. It is based on the Rockoon method: an orbital launcher which is ignited from a balloon platform in near-space at an altitude of 20-25 km.
Having already mastered stratospheric balloon missions, the next natural step for Zero 2 Infinity is to build upon this expertize and develop the Bloostar launch vehicle. It is designed with simplicity in mind to ensure lower development and operational costs.
Bloostar configuration (Ref. 6):
The Bloostar craft consists of a balloon in the first phase of flight that carries a launch vehicle to altitudes of about 25 km, where it then engages its engine.
The rocket segment of the vehicle consists of three toroidal stages arranged concentrically as seen in Figure 4 and Figure 5. The first stage wraps around the second stage with a torus-shaped structural tank. Similarly, the second stage tank wraps around the third and final stage. Several structural rings around each toroidal tank acts as fixture points for engines and other subsystems. The compact toroidal shape of Bloostar makes the launcher more controllable and easier to integrate (no need for erection systems or towers).
Figure 4: Bloostar shape and dimensions (image credit: Zero 2 Infinity)
Figure 5: Exploded view of the Bloostar launch vehicle (image credit: Zero 2 Infinity)
The payload will be located in the center of the launcher on top (attached to the third stage). The geometry of the system takes advantage of the fact that the vehicle is launched from near-space where the aerodynamic resistance is near-negligible. The rocket segment of the Bloostar vehicle has a total mass of 4.9 metric tons, a mass breakdown is listed in Table 1.
Table 1: Bloostar mass budget, excluding the 75 kg payload
Structure and mechanisms: The structure of Bloostar's stages consists mainly of the tanks, who fulfill a structural function as well as storing the propellants. The engines, avionics, communication and power units will be attached to hardpoints on the tanks. The engines are additionally connected through dedicated engine mounts and struts.
Traditional fairings need to withstand significant structural and acoustic loads. This is not the case for Bloostar, which can carry a much lighter fairing. The purpose of Bloostar's fairing is to keep the payload protected during the balloon ascent and to prevent damage of the sensitive parts of the payload because of the (limited) aero heating from the first phase of the rocket propelled flight. For this purpose, a flexible, retractable fairing, with rigid carbon fiber ribs and a multilayer canvas of betacloth (Teflon-coated fiberglass), has been designed. A gas barrier layer is included as the innermost layer.
Bloostar's stage separation is performed by synchronized pyro devices. These units are reliable but expensive and produce some shock. The long term goal is to switch to low-shock mechanisms found in the military aircraft sector.
Avionics: The avionics system is responsible for sensing the motion of the launcher, running the GNC software, controlling actuators, monitoring each subsystem's state, communicating with ground and supplying electrical power. Many of these systems are based on our existing flight-proven and robust avionics set, with added features to be qualified under stratospheric and suborbital flights as a part of the Bloostar development program.
The GNC (Guidance, Navigation and Control) subsystem calculates the optimum trajectory and controls the elements for modifying the trajectory. It uses a set of redundant sensors (3-axis gyros, accelerometers, ambient pressure gages, GPS, sun sensors etc.) and redundant flight computers. The trajectory is controlled using TVC (Thrust Vector Control) and engine.
The compact configuration of Bloostar makes control much simpler than the very slender bodies of traditional launch vehicles. Figure 4 shows the definition of the axes for the Bloostar launch vehicle, where the X-axis is the roll axis, and therefore the vertical axis for any vertically mounted payload.
TVC (Thrust Vector Control): Each engine will be equipped with a set of TVC actuators. Due to the many engines, the TVC system mass will be a significant part of the dry mass. It is therefore necessary to use low mass units such as Electro Mechanical Actuators. A range of commercially available units exist that fulfil the requirements for performance and reliability.
The first and second stage TVCs can provide torques around the x, y and z axis, but the third stage, equipped with a single rocket engine, can only produce torques about the y and z axes. For the x axis (roll) of stage 3, a simple RCS (Reaction Control System) is implemented using excess Helium pressurant gas.
Future improvements: Differential Throttling
The baseline method for controlling Bloostar's trajectory is using TVC, but future improved versions may progressively switch some engines to Differential Throttling. The toroidal shape of Bloostar, the symmetrically spaced engines and the pressure-fed system allows for this simpler control method which have typically only been used on small UAVs (Unmanned Air Vehicles) such as quad-rotors. As the radius of Bloostar is significantly larger than its height, it is possible to use Differential Throttling of the rocket engines to produce the required torques in a similar fashion to that employed by quad-rotors.
Zero 2 Infinity has conducted a research project to investigate the suitability of Differential Throttling versus TVC. In order to compare the two control systems, a model of Bloostar was produced in MatLab/Simulink and a series of simulations was conducted, testing the control systems in various flight phases. We found that if the throttle response rate of the engines was fast enough, the Differential Throttling controller performed better than a TVC system. The throttling itself can be achieved by a simple propellant flow regulation. As the propellant is pressure-fed into the engines this can be easily achieved using fast variable-amplitude valves. Consequently, the conclusion was that using such a propellant feed system and regulation allows the thrust level to be adjusted quickly enough to maintain sufficient control of the vehicle – while saving on mass, cost and overall vehicle complexity.
Communication: Communication between ground and the launcher is crucial throughout the entire flight, both with the balloon segment and rocket segment. Bloostar is designed to provide a two-way link for real-time flight data (telemetry) and ground safety commands (telecommand). Moreover, off-line data is provided for post-mission processing and diagnostics. A redundant C-band communications system, already flight-qualified in previous stratospheric flights, is envisaged for Bloostar.
Propulsion: Bloostar is powered by liquid oxygen (LOX) and liquid methane (LCH4). This bi-propellant combination is the perfect match between performance, simplicity of combustion and green propulsion. The engines are optimized to work efficiently in the very low pressure environment where ignition takes place; between 20 and 25 km. Bloostar's first stage contains 6 engines with a vacuum thrust of 15 kN. The second stage has another 6 engines with 2 kN of vacuum thrust. The third stage's single engine is identical to the ones used in the second stage (2 kN). All 13 engines are ignited upon launch from the balloon platform, resulting in a total thrust of 104 kN. Table 2 gives specific data about the engines and propulsion of each stage.
The propulsion system utilized cross-tanking. This function optimizes the capabilities of every stage by allowing each tank to be full of propellants when the previous stage is detached. It also saves dry mass since all engines can be ignited during the whole trajectory.
Table 2: Bloostar propulsion characteristics
Rocket engines: Simplicity and robustness is the key driver for our engine development. The two different types of engines used are designed with high structural margin and redundant ignition systems. Because the launcher operates in a low-pressure to vacuum environment (near-space to Space), the engine nozzle can be optimized for maximum performance in a single pressure environment (that of vacuum).
The engine size allows for 3D printing manufacturing techniques, easing the rapid prototyping-test-improvement cycle. Ceramic thermal protection can be deposited on parts of the chamber through thermal spray. The injector plate is a classical co-axial system and the thrust chamber is regeneratively cooled with methane.
Propellant tanks: The first and second stage's toroidal volume are composed mostly by toroidal carbon fiber filament wound tanks. They are kept at pressure and provide structural rigidity to the rocket. They are made in one piece by filament winding, and they are equipped with an internal liner to avoid micro-cracking in the composite walls. T1000G fibers provide the right strength to weight ratio for this application. Internal baffles have been added to prevent low frequency sloshing modes. Several axial reinforcements made by hand lay-up will be placed at the attachment points between the stages, tanks and fairing.
For the third stage, where every kg saved in dry mass is a kg of payload, an even more optimized solution has been adopted; flexible multilayer tanks - previously tested in flight with NASA and Zero 2 Infinity itself. This light and flexible cryogenic tank maintains the liquid methane and liquid oxygen separated thanks to a multilayer leak-proof isotensoid. The tanks remain pressurized thanks to helium gas which has the triple purpose of 1) feeding the engines, 2) maintaining the rigidity of the structure and 3) feeding the cold gas thrusters of the RCS (Reaction Control System).
All tanks carry a certain amount of external MLI to limit the boil-off, which has been estimated to be 5 kg of liquid methane and 15 kg of liquid oxygen for a 2-hour ascent to launch altitude. In the event of larger boil-off amounts, there is furthermore the possibility to use super-cooled fuels or having the balloon gondola carry a top-off tank.
Propellant Feed System: The pressure fed propellant feed system consists of piping, valves, filters, pressure regulators, vents, gages, pyro disconnectors and more. One critical point taken into consideration is the matching of fluid impedances of the pipes, so that propellant arrives equally to each stage and engine at any time. This is modelled in software suits such as EcosimPro using components from the ESPSS libraries.
Figure 6 depicts the feed line configuration with respect to the cross tanking from stage 1 to stage 2 and 3, and from stage 2 to stage 3.
Figure 6: Overview of propellant feed system (image credit: Zero 2 Infinity)
The pyro feed line disconnectors of each stage (marked C1 and C2 in Figure 6) are of standard self-sealing fitting; when detached they self-seal. There are several brands (e.g. Schrader) and this type of unit is routinely used with LOX and LNG for healthcare and vehicle use, respectively. They are only activated after a safety sequence, where the pressurizing gas has scavenged and cleaned the surrounding feed lines and valves of all the propellant residue.
Although the Propellant Feed System is non-trivial, the system in its entirety is still very reliable thanks to its pressure-fed and not pump-fed nature.
Figure 7: Illustration of the launch vehicle elements (image credit: Zero 2 Infinity) 7)
The balloon segment handles the first phase of the flight by lifting Bloostar to near-space. It also isolates the rocket from the rotation of the balloon and provides a telemetry/telecommand relay from the ground to the launcher. Consequently, the link range is extended significantly, eliminating the need for ground stations located along the initial flight path – further decreasing overall launch costs.
The balloon segment consists of (in order of vertical flight position up to down):
• the high-altitude balloon
• the flight train
• the Gondola.
High-altitude balloon: The balloon required for lifting the launch vehicle, communications gondola and other equipment to the stratosphere is a 90,000 m3 balloon, which is comfortably within the range of high-altitude balloons that are commercially available.
Flight train: The flight train, located between the balloon and the gondola, hosts all the necessary equipment for a successful balloon operation, it consists of:
• several redundant GNSS beacons for recovery
• two C-band transponders (for the balloon operation and to comply with Air traffic rules)
• two radar reflectors
• a flight termination system
• a telemetry system
• a ballasting system.
Gondola: The balloon gondola (Figure 8) has the capacity to point the launcher towards the preferred azimuthal direction for the rocket ignition. It also carries all the communication equipment dedicated for relaying rocket telemetry/telecommand.
Figure 8: Balloon gondola configuration (image credit: Zero 2 Infinity)
Bloostar is launched on international waters from a ship. International waters enable regulatory ease and sea launch itself reduces the risk of launch delays due to bad weather by compensating the ground wind speed and direction with the ship's speed and direction. Furthermore, it allows for flexible mission needs or range safety requirements by having a movable launch site and adapting the point of rocket-ignition.
The launch ship itself does not need any significant adaptation for the launch operation (the reader is reminded that the ship only releases the Balloon-Powered assembly – there is no ignition of the rocket engines from the ship). Any ship with a sufficiently wide flat area could be rented to perform the flight. The effective launch area on deck should be of around 50 x 17 meters.
One ideal location for launches is the south-west of the Canary Islands due to the generation of near zero wind speeds because of the geographic characteristics of the islands. This location is also excellent to reach any azimuth.
Bloostar trajectory and performance
While each mission is unique, a typical flight profile can consist of the following sequence: the first phase of the flight is a balloon ascent to near-space (20-25 km) lasting 1.5-2 hr. The second (powered) phase of the flight starts once the rocket is released from the balloon. Shortly thereafter, all 13 engines are ignited. The first stage burns for 110 seconds, upon which the vehicle reaches an altitude of 80 km and an inertial speed of 2.3 km/s. After ejecting the first stage, the vehicle reaches 400 km and 4.4 km/s in 230 seconds. Upon third and final stage separation, the third stage performs multiple firings, the first one lasting 340 seconds and reaching 600 km of altitude while still slightly below the target orbital speed. Then, after coasting and later finalizing the orbit, the payload is released. Finally, a last engine boost is performed to deorbit the third stage in order to minimize space debris left by the mission.
Figure 9: Simulation of altitude and inertial speed over flight time (image credit: Zero 2 Infinity)
Performance capability: Bloostar vehicle's payload capabilities are shown in Figure 10. The performance shown is the maximum capability from the Canary Islands. An additional payload spin (up to 10 rpm) can be provided before separation.
Figure 10: Bloostar performance for circular orbits from the Canary Islands (image credit: Zero 2 Infinity)
Payload insertion accuracy: Bloostar is capable to provide precise orbit insertion according to Table 3.
Table 3: Orbital insertion accuracy (1σ)
Reliability and anomaly response: The unlikely anomaly events, that can occur during a flight, are described and how risk has been retired already at the architectural level by designing a robust vehicle from the ground up. Each unlikely event has a dedicated response strategy that will contain the anomaly and ensure a successful mission.
Engine ignition delay: Since it is not possible to ignite the rocket engines while the vehicle is attached to the balloon, the rocket segment will be released first and shortly thereafter ignited. Therefore, it is necessary to ignite all engines simultaneously in order to avoid the vehicle entering into a spin. However, it is unlikely that all 13 engines will ignite at the exact same time. We have simulated whether the GNC is capable of controlling the vehicle while all the engines ignite and throttle up. A realistic delay was introduced between the time the vehicle was dropped from the balloon and the ignition of each individual engine. The steadfast results show that Bloostar remains securely controlled despite non-simultaneous engine start.
Engine out capability: Once the rockets are ignited the GNC checks that all engines are delivering delivering the correct thrust. In the unlikely event of thrust deviation or or failed ignition on an engine, the opposing symmetrical pair on the same same stage is shut down. The engines that remain on are actuated and and throttled to ensure adherence to the nominal trajectory. Thanks to the Bloostar's highly redundant configuration, mission success is assured in the event of an engine-out on both the first and second stage.
Figure 11: This has been confirmed by Matlab, ZOOM and ASTOS simulations, indicating that the Bloostar is able to perform its mission successfully in a wide range of off-nominal conditions, from initial torque at separation to engine out events (image credit: Zero 2 Infinity)
Figure 12: Bottom view of tolerable engine out capability - stage 1 and 2 can have one engine out each (marked red), plus their opposing pair (image credit: Zero 2 Infinity)
Launch: The first launch of Bloostar with a payload (most probably a microsatellite) into LEO (Low Earth Orbit) is expected by the end of 2019.
Fairing volume: The fairing is attached to the first stage of the launcher. The payload has to fit within the dynamic envelope within the fairing. Figure 13 shows the dimensions. The volume is approximately 2.4 m3. Oversized payloads can be accommodated as special flights.
The fairing is nearly transparent to RF so that the customer can continuously communicate with the satellite during ascent and launch. The internal pressure decay is controlled by a set of redundant valves.
The large volume available inside the Bloostar payload area provides flexibility about the size and shape of the satellites to be launched. This simplifies satellite design, it allows the customer to pack more powerful features and reduces the need for folding parts. The customer's satellite is kept safe through the launch by a lightweight fairing that covers the payload.
Figure 13: Bloostar fairing available inner dimensions in mm (image credit: Zero 2 Infinity)
Figure 14: Side view of Bloostar craft with its fairing closed (image credit: Zero 2 Infinity) 8)
Mechanical interfaces:The payload is attached to a mating plane at the center of the third stage. Depending on payload interface and size, Bloostar offers to accommodate most Primary and Secondary customer needs. The most commonly used small satellite separation systems and nanosatellite deployers are supported, such as:
• Planetary Systems' Mark II Motorized LightBand (8-38.8 inch diameter)
• Planetary Systems' Canisterized Satellite Dispenser (3, 6, 12, 27U form factors)
• Innovative Solutions in Space's ISIPOD CubeSat Deployer (inclusive Quadpack)
• Dassault ASAP 5
• Ruag Clamp Band Separation Systems
• Spaceflight Industries' P-PODs (one or multiple CubeSats up to 34 cm in length) and Nanobox (6U, 12U, 24U sizes)
• Spaceflight Industries' Adapter Mounts for Microsat-class <70 kg (8 inch separation ring) and ESPA-class <190 kg (15 inch separation ring).
Electric al interfaces: Bloostar provides standard payload electrical interfaces. Details surrounding connector type and pinouts will be specified in future versions of the PUG (Payload User Guide). The connection will provide power, data communication lines, and separation detection systems. Regulated 28 V, 1 A power is available to the payload during the flight.
Payload requirements: Documentation required by the payload user is kept to a minimum and limited to that which is absolutely required in order to execute a mission successfully and safely.
The single most important required document, containing the most relevant information, is the Launch Vehicle to Spacecraft ICD ( Interface Control Document). This should include details of all interfaces (mechanical, electrical, etc.), but also all information needed to describe the mission and the interactions between launch vehicle and payload.
Other documentation evidencing compliance to Qualification, Acceptance and Safety rules may be required as well.
Payload environments: The lack of a high dynamic pressure flight, acoustic ground reflections and turbo pumps significantly reduces the overall harshness of the trip for the satellite. However, all the environments should be taken into account, from transportation to final delivery into the desired orbit. Table 4 lists all the foreseen environmental conditions that the payload will experience.
Table 4: Summary of environmental conditions at various flight events
Figure 13 describes the Quasi-Static Loads (QSL) envelop to be considered for the spacecraft qualification. This envelop corresponds to the static acceleration of the launcher during the ascent phase multiplied by a development and a qualification factor. Also a small contribution for the dynamic environment is added to the value.
A maximum of 6.5 g in compression and 1g in tension is expected for the longitudinal QSL. ±0.5 g is the maximum lateral QSL expected. These values will be updated with flight experience and the reduction of the development factor.
Figure 15: QSLs (Quasi-Static Loads), image credit: Zero 2 Infinity)
Dynamic environment: As there is no dense atmospheric phase and no turbo pump, the dynamic environment generated by the Bloostar flight is very low and mostly transient. The sine environment to be considered is <0.1 g for longitudinal and lateral direction on the low frequency range (0-200 Hz).
Shock Environment: The maximum shock encountered by the payload occurs during payload separation. Several low-shock hold down release technologies, both pyrotechnic and free-of-pyrotechnics, are currently being evaluated. As an example the Pyrosoft from La Croix offers the Shock Response Spectrum (SRS) depicted in Figure 16.
Figure 16: Bloostar shock response spectrum (image credit: Zero 2 Infinity)
The following flight campaigns are listed in reverse order.
Zero 2 Infinity successfully launched its first rocket from the Edge of Space on March 1, 2017. This milestone opens the door for safer and more efficient Space access for small satellites (Ref. 2).
Figure 17: Bloostar ignition closeup after balloon delivery/deployment to ~22 km (image credit: Zero 2 Infinity) 9)
Part of the Zero 2 Infinity team sailed a few miles off the Spanish coast to launch the balloon carrying the rocket. After soaring to 25 km (more than twice the cruising altitude of commercial airplanes), the other part of the launch team gave the order of the controlled ignition of the first Bloostar prototype from the facilities of the National Institute of Aerospace Technology (INTA) in El Arenosillo (Huelva, Spain).
The goals of the mission were: (i) validation of the telemetry systems in Space conditions, (ii) controlled ignition, (iii) stabilization of the rocket, (iv) monitoring of the launch sequence, (v) parachute deployment, and finally, (vi) sea recovery. All these goals were achieved in full.
Figure 18: Photo of Bloostar flying away (image credit: Zero 2 Infinity)
Figure 19: The Bloostar prototype is elevated up to 25 km with the coast line of southern Spain in the background (image credit: Zero 2 Infinity)
• From January 16 to 23, 2017, the Spanish company Zero 2 Infinity prepared and carried out a launch rehearsal of Bloon. 10)
Bloon is a pod for Space tourism that flies up to 36 km to allow its travellers to observe the Earth. At this altitude, voyagers can already see the blackness of Space and the curvature of the Earth. The fact that Bloon flies thanks to a helium balloon makes for a safe, relaxed and enjoyable trip.
The engineers at Zero 2 Infinity spent some days in Lleida-Alguaire Airport (Spain) carrying out flight preparations. The team was joined by Steven Peterzén from ISTAR (International Science Technology and Research) who consulted and offered advice in the overall ballooning operation.
Despite the windy weather – an important flight constraint – the team was able to find a calm window to carry on with the mission and balloon inflation was given a go. The 35,000 m3 balloon was filled with helium through two pipelines. The flight train was 63 m long and included the trackers and the parachute. At the end of it, a real-size Bloon model stood.
Figure 20: Top photo: The Bloon pod is suspended by a crane prior to launch. Bottom Photo: The stratospheric balloon is being filled with helium (image credit: Zero 2 Infinity)
Legend to Figure 20: Zero 2 Infinity does not use the crane for unloading the bloon pod, but for launching the payload. Bloon with the payload needs to be suspended in the crane and attached to the flight train that leads to the balloon. When the balloon is launched, the crane needs to move a bit too to get a successful launch.
Figure 21: Photo of the real-size Bloon model (2.88 m in diameter and a mass of xx kg) with Jose Mariano Lopez-Urdiales, the CEO and founder of the company.(image credit: Zero 2 Infinity)
The flight rehearsal finished with the tethered balloon taking off. The Zero 2 Infinity team is happy with the rehearsal results. The flight also allowed for the testing of the new valve the engineering team implemented in the balloon as a new flight termination redundancy system.
• September 6, 2013: The Spanish company Zero 2 Infinity took another decisive step in the development of its high performance stratospheric balloon systems when it launched microbloon 3.0 on September 6, 2013. An ideal launch location for high-altitude balloons, the airport of Cordoba in Spain, was selected for this test flight. With perfect meteorology and effective support from airport and the civil aviation authorities AESA and AENA, the project suffered no delays. With an exemplary 3 hour and 10 minute flight, microbloon 3.0 spent 53 minutes at its designated floating altitude of 27 km, ultimately landing on target about 60 km north of Cordoba, where the team was in place to promptly effect recovery. 11)
- A key objective of the flight was to test the behavior, strength and suitability of an inflatable pressurized payload capsule for the microbloon. The pod was designed and manufactured by Thin Red Line Aerospace, the Canadian company known for providing the inflatable pressure hulls for the Bigelow Aerospace Genesis spacecraft. The pod behaved flawlessly during the flight and confirmed superior performance and resistance of inflatable structures. "Inflatable structures are very efficient compared to advanced materials such as carbon fiber or light alloys. They hold promise of safer, more affordable applications in Near Space and beyond," says Jose Mariano Lopez-Urdiales, CEO of Zero 2 Infinity. Maxim de Jong, Thin Red Line Aerospace Chief Engineer, also expressed his enthusiasm: "We based the Zero 2 Infinity pod entirely on our proprietary UHPV (Ultra High Performance Vessel) architecture. Developed largely in a NASA Space exploration program context, we welcomed this exciting flight opportunity to support Zero 2 Infinity's visionary project while further validating UHPV technology as the inflatable pressure vessel with highest performance and low test mass." As with previous launches, the operations and recovery were led by Steven Peterzén, from The ISTAR Group, a leading expert in stratospheric balloons. This launch served as further training for the Zero 2 Infinity crew. The company is currently operational to send scientific and technical payloads to Near Space and aims to start its manned test program next year. Commercial operations should start soon after to offer the view from Near Space to private passengers.
Figure 22: Image of the microbloon 3.0 model taken at high altitude (27 km) from the balloon camera above on Sept. 6, 2013 (image credit: Zero 2 Infinity) 12)
Figure 23: Photo of the microbloon 3.0 system (25 kg) at the Cordoba Airport (image credit: Zero 2 Infinity)
• November 12, 2012: The Zero 2 Infinity company has successfully launched its newest prototype (Figure 24), the microbloon 2.0, to the edge of Space at almost 32 km in altitude, that is above 99% of the mass of the atmosphere . It was a major step in Zero 2 Infinity's mission to bring Space closer to society. Founder Jose Mariano Lopez-Urdiales said: "It's very exciting to be this close to flying people on Bloon. The environmental conditions inside the pod remained comfortable at all times. The efficiency of the aviation safety agencies (AENA, AESA), local governments and especially the Spanish Air Force was key for this success. When everyone works together, anything can be achieved in Spain." 13)
- The microbloon 2.0, designed by Zero 2 Infinity, is 2 m in diameter and is a scale model of Bloon, the commercial vehicle that is soon to take 4 passengers and 2 pilots to the edge of Space. On the flights, passengers will conduct scientific experiments at a fraction of the cost of other Space missions and enjoy the view of the curvature of the Earth through the pod's panoramic windows during the 2 hours spent at an altitude of 36 km. On Monday 12th November 2012 at 5 hr (GMT), the whole team was ready at the airport of Virgen del Camino (León, Spain) to get all systems and equipment in flight position. At 12:15 hr (GMT) inflation of the balloon started and at 1:10 hr (GMT) the 43,000 m3 balloon was released and lifted the capsule gently for an hour up to 31.8 km. As planned, the balloon initially flew south as it was ascending, then moved eastward during the 2 hour-float at 31.8 km until it finally initiated a gentle descent with parachutes and landed in Encinas de Esgueva at 5:10 hr (GMT), where the recovery team was waiting and recovered the capsule and the balloon. Over the next few months, all data from the sensors will be thoroughly scrutinized. The first results show that the temperature inside the capsule remained above 15ºC throughout the flight, with 20% humidity. The pressure remained stable between 900 and 950 mb, which is equivalent to the pressure experienced at 1,000 m above sea level. The trajectory prediction was flawless. The android pilot was kindly provided by the robotics group of the University of León.
- Steven Peterzén (The ISTAR Group) is the leading expert in stratospheric balloons who orchestrated the preparation, launch and recovery. The weather forecast and trajectories were calculated by Pierre Dedieu, a meteorologist with years of experience with CNES's (the French Space Agency) high altitude balloon program. Back in the 1990s, CNES launched balloons from the same air force base in León.
Figure 24: Photo of the microbloon 2.0 system of 347 kg (image credit: Zero 2 Infinity)
• On May 29th, 2012, the team was ready on the launch pad in León, Spain, for the first test flight of microbloon 2.0, a 2 m-diameter pressurized pod designed by Zero 2 Infinity as a scaled model of the full Bloon pod that will carry 4 passengers and 2 pilots to 36 km, providing Near Space conditions for over 2 hours. The team had designed and built all the launch equipment. The primary aim of the test was to validate launch procedures and, if everything was nominal and the flight was completed, to perform on-board remote robotic tests and environmental and life support system testing for future inhabited flight scenarios for Bloon's scientific, technological and experiential missions. 14)
Up through the inflation of the 35,000 m3 Zodiac balloon to just before the release of the balloon from the spool, all launch activities were smooth and flight systems were 100% functional. However, just prior to the release, a strong and unpredictable wind gust caused the balloon to sail and spill and load air several times. Initial inspection of the balloon did not reveal damage, so the launch operations continued. The balloon was released when the wind dropped, and quickly climbed up and over the launch vehicle. As the payload was released, the launch team quickly realized that the balloon had been damaged as the flight system slowly ascended approximately 5 m above the launch vehicle and then began to descend setting the payload on the surface. Winds pushed the balloon a short distance along the grass near the runway until it was stopped by vegetation and quickly recovered. Once the balloon was laid out and inspected, a gore tear was discovered and it is believed to be the point of initial failure. The pod and its pilot, an android named Ironman (provided by Universidad Jaume I from Castelló, Spain), both had a shorter than expected flight, but were fully recovered along with the entire flight system, which is now being reconfigured for the next launch attempt. Although disappointed for not having completed the test, the Zero 2 Infinity team still records this as a success of their flight systems and procedures.
Jose Mariano Lopez-Urdiales, CEO and founder of Zero 2 Infinity said: "There are literally hundreds of steps up to completing inflation and release: getting to this stage is a very important milestone in our program. The team has performed with mastery under the expert guidance of Steven Peterzén from The ISTAR Group, and supported by Dr. Silvia Masi from the University of Rome. I am very proud of them all. We introduced and tested several new components in stratospheric balloon flight operations. The team is now analyzing the wealth of data obtained from the sensors, and also documenting the experience of everybody involved in order to fully maximize the value of the test and prepare for the next launch. This campaign has also allowed us to deepen the trusting relationships with both the Virgen del Camino Base of the Spanish Air Force and the Spanish Civil Aviation Authorities, AESA and AENA. Their support of innovative Near Space operations shows a lot for what can be done from Spain in the 21st century." Jose Mariano is also confident about the future: "We are in this for the long run. Given the amount of time and resources applied, what we've already achieved is nothing short of outstanding. This test will make us stronger and better prepared for the next one. I am 100% confident we are off to a great future, both for the upcoming experimental test flights and for the commercial operations that will follow."
Figure 25: Photo of the balloon filling preparations of the first flight campaign at the León launch pad (image credit: Zero 2 Infinity)
1) "How it all began," Zero 2 Infinity, URL: http://www.zero2infinity.space/company/
2) "Zero 2 Infinity Successfully Launches its First Rocket from the Edge of Space," Zero 2 Infinity, March 13, 2017, URL: http://www.zero2infinity.space/updates/zero-2-infinity-successfully-launches-first-rocket-edge-space/
3) Matt Williams, "Zero 2 Infinity successfully test launches its Bloostar prototype," Universe Today, March 17, 2017, URL: http://www.universetoday.com/134408/zero2infinity-successfully-test-launches-bloostar-prototype/
4) "Flight campaigns," Zero 2 Infinity, URL: http://www.zero2infinity.space/media/flight-campaigns/
9) "Flight campaigns," Zero 2 Infinity, URL: http://www.zero2infinity.space/media/flight-campaigns/
10) "Zero 2 Infinity's Flight Simulation with the real-size Bloon Model at Lleida-Alguaire Airport;" Zero 2 Infinity, Jan. 24, 202017, URL: http://www.zero2infinity.space/updates/zero-2-infinitys-flight-simulation-real-size-bloon-model-lleida-alguaire-airport/
11) "Microbloon 3.0 Flies to the Edge of Space from Córdoba," Zero 2 Infinity, Sept. 6, 2013, URL: http://www.zero2infinity.space/updates/microbloon-3-0-flies-to-the-edge-of-space-from-cordoba/
12) Information provided by Marta Lebron of Zero 2 Infinity.
13) "Microbloon 2.0 Soars to the Edge of Space," Zero 2 Infinity, Nov. 12, 2012, URL: http://www.zero2infinity.space/updates/microbloon-2-0-soars-to-the-edge-of-space/
14) "Zero 2 Infinity's Microbloon 2.0 Begins Test Program," Zero 2 Infinity, June 01,2012, URL: http://www.zero2infinity.space/updates/zero-2-infinitys-microbloon-2-0-begins-test-program/
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 (firstname.lastname@example.org).