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SLS (Space Launch System)

Development Status    References

The SLS is the new heavy launch system for NASA. The SLS configuration for EM-1 is considered Block 1, the first configuration of the SLS evolution plan. The Shuttle-derived design takes advantage of resources established for the Space Shuttle, including the workforce, tooling, manufacturing processes, supply chain, transportation logistics, launch infrastructure, and LOX/LH2 propellant infrastructure. An overview of the initial SLS Block 1 configuration that will first fly with the Orion in 2020 is shown in Figure 1. The SLS enables many aspects of the NASA core capabilities in addition to human exploration initiatives. These include the reduction in mission duration, increased mass margins, reductions in total spacecraft complexity, and significant increases in payload volume. 1) 2) 3) 4)

Created to provide sufficient launch capability to enable human exploration missions beyond Earth orbit and ultimately to Mars, NASA’s Space Launch System (SLS) rocket represents a new asset, not only for human spaceflight, but also for a variety of other payloads and missions with launch requirements beyond what is currently available. The initial configuration of the vehicle, on track for launch readiness in 2020, is designed to offer substantial launch capability in an expeditious timeframe and to support evolution into configurations offering greater launch capability via an affordable and sustainable development path.

NASA is developing SLS in parallel with two other exploration systems development efforts – the Orion crew vehicle program and the Ground Systems Development and Operations (GSDO) program. Orion is a four-person spacecraft designed to carry astronauts on exploration missions into deep space. GSDO is converting the facilities at NASA’s Kennedy Space Center (KSC) in Florida into a next-generation spaceport capable of supporting launches by multiple types of vehicles.

These capabilities are part of a larger NASA strategy of working with commercial partners that will support crew and cargo launches to the International Space Station, while the agency focuses its development efforts on an incremental approach to developing the systems necessary for human exploration beyond Earth orbit and eventually to Mars. SLS is being designed with performance margin and flexibility to support an evolvable human exploration approach. (Figure 2).

Currently under construction, the initial configuration of the vehicle will have the capability to deliver a minimum of 70 t into low Earth orbit (LEO) and will be able to launch a crew aboard the Orion spacecraft on into cislunar space on its first flight, Exploration Mission-1 (EM-1) in 2020. The vehicle will evolve to a full capability of greater than 130 t to LEO and will be able to support a stepping-stone approach to human exploration leading to the first footsteps on Mars.

The SLS initial Block 1 configuration stands 97 meters tall, including the Orion crew vehicle. The vehicle’s architecture reflects NASA’s desire to meet the mandates for heavy-lift capability in the U.S. congressional NASA Authorization Act of 2010 in a manner that is safe, affordable, and sustainable. After input was received from industry and numerous concepts were reviewed, a shuttle-derived design was found to enable the safest, most-capable transportation system in the shortest amount of time for the anticipated near-term and long-range budgets.

The SLS operational scheme takes advantage of resources established for the Space Shuttle Program, including workforce, tooling, manufacturing processes, supply chains, transportation logistics, launch infrastructure, and liquid oxygen and hydrogen (LOX/LH2) propellants and allows the initial configuration of the vehicle to be delivered with only one clean-sheet new development, the Core Stage. In October 2015, the SLS Program completed its Critical Design Review (CDR), the first time a NASA human-class launch vehicle has reached that milestone since the Shuttle Program almost 40 years ago.

The SLS Core Stage, which stores the liquid oxygen (LOX) and liquid hydrogen (LH2) propellant for four Core Stage engines, will stand 61 m tall and will have a diameter of 8.4 m, sharing commonality with the space shuttle’s external tank in order to enhance compatibility with equipment and facilities at Kennedy Space Center and elsewhere. At Michoud Assembly Facility (MAF), outside New Orleans, Louisiana, the last of six major welding manufacturing tools for the Core Stage, the world’s largest space vehicle welding tool, the 52m-tall Vertical Assembly Center (VAC), has been installed and is being used by The Boeing Company, Core Stage prime contractor, to weld barrel sections, rings and domes together to form the propellant tanks for the stage.

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Figure 1: SLS Block 1 70t Initial Configuration (image credit: NASA)

The Core Stage will be powered by four RS-25 engines, which previously served as the Space Shuttle Main Engine (SSME), taking advantage of 30 years of U.S. experience with liquid oxygen and liquid hydrogen, as well as an existing U.S. national infrastructure that includes specialized manufacturing and launching facilities. These human-rated engines support the SLS goal of safety, with a record of 100 percent mission success for the engines over 135 flights. At the end of the Space Shuttle Program, 16 RS-25 flight engines and two development engines were transferred to the SLS Program and placed in inventory at NASA’s Stennis Space Center, providing enough engines for the first four flights of SLS.

While the SLS Program is heavily focused on working toward first flight, efforts are already underway on the evolution of SLS beyond the 70 t Block 1. As early as the second launch of SLS, Exploration Mission-2, the vehicle will be augmented with a low-thrust dual-use Exploration Upper Stage (EUS), providing both ascent and in-space propulsion capabilities. This stage, which is working toward a preliminary design review in late 2016, will upgrade SLS to a performance of 105 t to LEO, and create a configuration that will serve as a workhorse for “Proving Ground” missions in cislunar space that will pave the way for further exploration. From there, additional upgrades, including enhancements to the RS-25 engines and upgraded boosters will ultimately evolve SLS to a configuration capable of delivering more than 130 metric tons to LEO, the capability identified as necessary for human missions to Mars.

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Figure 2: Evolutionary development path of SLS (Space Launch System), image credit: NASA

Modifications to Stennis Test Stand A-1 to support RS-25 testing were completed in 2014, and two test series have already been completed in preparation for flight certification of the SLS configuration of the engine, including a new engine controller unit. The testing includes propellant pressure and temperature inlet conditions that will both be higher with SLS than with the shuttle, as well as other SLS-specific performance requirements such as 109 percent thrust versus the shuttle’s 104.5 percent thrust. Stennis Test Stand B-2 is being refitted for the SLS “green run” – the test firing of the first Core Stage with four RS-25 engines beginning in 2017, which will be NASA’s largest engine ground firing since stage tests of the Saturn V in the 1960s.

The majority of the thrust for the first two minutes of flight will come from a pair of Solid Rocket Boosters, also of Space Shuttle Program heritage. The SLS is upgrading the boosters from the four-segment version flown on the shuttle to a more-powerful five-segment version. Each booster measures 54 m long and 3.7 m in diameter and is capable of generating up to 3.6 million pounds of thrust, the most powerful flight boosters in the world. Although largely similar to the SRBs used on the space shuttle, this upgraded five-segment SRB includes improvements such as a larger nozzle throat and an environmentally-benign insulation and liner material. In March 2015, the SLS configuration of the booster successfully underwent the first of two Qualification Motor tests, and the second test is scheduled for summer 2016.

In-space propulsion for the 70 t Block 1 version of SLS will be provided by the Interim Cryogenic Propulsion Stage (ICPS), a modified version of United Launch Alliance’s Delta Cryogenic Second Stage (DCSS) flown on more than 20 launches of the Delta IV Evolved Expendable Launch Vehicle (EELV). In order to support the currently planned initial test flight that would send Orion on a circumlunar trajectory, the LH2 tank of the SLS ICPS will be stretched 46 cm longer than the standard DCSS.

While the SLS Program is heavily focused on working toward first flight, efforts are already underway on the evolution of SLS beyond the 70 t Block 1. As early as the second launch of SLS, Exploration Mission-2, the vehicle will be augmented with a low-thrust dual-use Exploration Upper Stage (EUS), providing both ascent and in-space propulsion capabilities. This stage, which is working toward a preliminary design review in late 2016, will upgrade SLS to a performance of 105 t to LEO, and create a configuration that will serve as a workhorse for “Proving Ground” missions in cislunar space that will pave the way for further exploration. From there, additional upgrades, including enhancements to the RS-25 engines and upgraded boosters will ultimately evolve SLS to a configuration capable of delivering more than 130 metric tons to LEO, the capability identified as necessary for human missions to Mars.

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Figure 3: Welding is complete on the largest piece of the core stage that will provide the fuel for the first flight of NASA's new rocket, the Space Launch System, with the Orion spacecraft in 2018. The core stage liquid hydrogen tank has completed welding on the Vertical Assembly Center at NASA's Michoud Assembly Facility in New Orleans. Standing more than 40 m tall and 8.4 m in diameter, the liquid hydrogen tank is the largest cryogenic fuel tank for a rocket in the world. The liquid hydrogen tank and liquid oxygen tank are part of the core stage — the "backbone" of the SLS rocket that will stand at more than 61 m tall. Together, the tanks will hold 733,000 gallons (2775 m3) of propellant and feed the vehicle's four RS-25 engines to produce a total of 2 million pounds of thrust (8896 kN) This is the second major piece of core stage flight hardware to finish full welding on the Vertical Assembly Center. The core stage flight engine section completed welding in April 2016. More than 1.7 miles of welds have been completed for core stage hardware at Michoud. Traveling to deep space requires a large rocket that can carry huge payloads, and SLS will have the payload capacity needed to carry crew and cargo for future exploration missions, including NASA's Journey to Mars. 5)

The secondary payload initiative for EM-1 takes advantage of several of these capabilities and enables new opportunities for small spacecraft developers. By utilizing planned unoccupied volume within the upper stage adapter ring, the OSA (Orion Stage Adapter), increased mission science and technology missions can be accommodated.

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Figure 4: David Osborne, an Aerie Aerospace LLC machinist at NASA's Marshall Space Flight Center in Huntsville, Alabama, takes measurements prior to the start of precision machining of the Orion stage adapter for NASA's new rocket, the SLS (Space Launch System). The adapter will connect the Orion spacecraft to the ICPS (Interim Cryogenic Propulsion Stage) for the first flight of SLS with Orion in late 2018. The ICPS is the liquid oxygen/liquid hydrogen-based system that will give Orion the big, in-space push needed to fly beyond the moon before it returns to Earth. The adapter also will carry 13 CubeSats that will perform science and technology investigations that will help pave the way for future human exploration in deep space, including the Journey to Mars (image credit: NASA, Sept. 29, 2016)

SLS Block 1 is capable of deploying 70 metric tons of payload into LEO (Low Earth Orbit). The characteristic energy (C3) curve for SLS is provided in Figure 2, illustrating SLS’s evolved thrust capabilities.

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Figure 5: SLS Net-Payload System Mass-Earth Escape (image credit: NASA)




Status of SLS development

• October 6, 2021: NASA has completed the design certification review (DCR) for the Space Launch System Program (SLS) rocket ahead of the Artemis I mission to send the Orion spacecraft to the Moon. The review examined all the SLS systems, all test data, inspection reports, and analyses that support verification, to ensure every aspect of the rocket is technically mature and meets the requirements for SLS’s first flight on Artemis I. 6)

- “With this review, the NASA has given its final stamp of approval to the entire, integrated rocket design and completed the final formal milestone to pass before we move forward to the SLS and Artemis I flight readiness reviews,” said John Honeycutt, the SLS Program Manager who chaired the DCR board held at NASA’s Marshall Space Flight Center in Huntsville, Alabama.

- In addition to the rocket’s design, the review certified all reliability and safety analyses, production quality and configuration management systems, and operations manuals across all parts of the rocket including, interfaces with the Orion spacecraft and Exploration Ground Systems (EGS) hardware. With the completion of the SLS DCR, NASA has now certified the SLS and Orion spacecraft designs, as well as the new Launch Control Center at the agency’s Kennedy Space Center in Florida, for the mission.

- The DCR is part of the formal review system NASA employs as a systematic method for manufacturing, testing, and certifying space hardware for flight. The process starts with defining what the rocket needs to do to achieve missions, such as its performance; these are called systems requirements. Throughout this process the design of the hardware is refined and validated by many processes: inspection, analysis, modeling, and testing that ranges from single components to major integrated systems. As the design matures, the team evaluates it during a preliminary design review, then a critical design review, and finally after the hardware is built and tested, the design certification review. The review process culminates with the Artemis I Flight Readiness Review when NASA gives a “go” to proceed with launch.

- “We have certified the first NASA super heavy-lift rocket built for human spaceflight in 50 years for missions to the Moon and beyond," said David Beaman, the manager for SLS Systems Engineering and Integration who led the review team. “NASA’s mature processes and testing philosophy help us ask the right questions, so we can design and build a rocket that is powerful, safe, and makes the boldest missions possible.”

- Artemis I will be the first integrated flight test of the SLS and Orion spacecraft. In later Artemis missions, NASA will land the first woman and the first person of color on the surface of the Moon, paving the way for a long-term lunar presence and serving as a steppingstone on the way to Mars.

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Figure 6: NASA has completed the design certification review (DCR) for the Space Launch System Program (SLS) rocket ahead of the Artemis I mission to send the Orion spacecraft to the Moon. This close-up view shows the SLS rocket for Artemis I inside High Bay 3 of the Vehicle Assembly Building (VAB) at NASA’s Kennedy Space Center in Florida on Sept. 20, 2021. Inside the VAB, the rocket recently completed the umbilical retract and release test and the integrated modal test. With the completion of the SLS design, NASA has now certified the SLS and Orion spacecraft designs, as well as the new Launch Control Center at Kennedy for the Artemis I mission (image credit: NASA/Frank Michaux)

• July 8, 2021: A limited supply chain and the demands of the Artemis program will prevent the use of the Space Launch System for alternative roles, such as launching science missions, until at least late this decade. 7)

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Figure 7: While NASA is developing a cargo version of the SLS that could be used for science missions, the limited supply chain and requirements of the Artemis program will limit its use to missions launching no earlier than the late 2020s (image credit: NASA)

- In a briefing about the SLS to the steering committee of the planetary science decadal survey July 7, Robert Stough of NASA’s Marshall Space Flight Center said that if scientists are contemplating missions that require the use of the SLS, they should be talking with NASA now to secure manifest slots no earlier than the late 2020s or early 2030s.

- “Given the demands of the Artemis program between now and the late 2020s,” he said, “it’s going to be very difficult to squeeze a science mission in that time frame.”

- While NASA has a goal of being able to launch three SLS missions in a 24-month period, and two in 12 months, the supply chain is currently limited to one SLS per year. That will change by the early 2030s, he said, growing to two per year and thus creating opportunities for additional SLS missions beyond the Artemis program. That will be enabled by changes to at the Michoud Assembly Facility to increase core stage production and a “block upgrade” to the RS-25 engine used on that core stage that will be cheaper and faster to produce.

- NASA also expects to shift to the Block 2 versions of the SLS by the late 2020s. The Block 2 will be based on the Block 1B version, with the larger Exploration Upper Stage, to be introduced on the fourth SLS mission, but will replace the existing five-segment solid rocket boosters with a new design that will further increase the vehicle’s performance.

- The performance of the SLS is of interest to scientists proposing missions to the outer solar system in particular. The SLS Block 2 will be able to send payloads of nearly 10 tons directly to Jupiter, and nearly as much to Saturn with a Jupiter gravity assist. The use of additional stages, such as versions of the Centaur, can double that payload, as well as enable direct missions to Uranus and Neptune.

- NASA is continuing to study various SLS upper stage configuration options to support such missions, he said, along with what would be needed to certify the SLS for carrying the radioisotope power sources required for missions in the outer solar system. However, Stough said that if proposed missions wanted to use SLS, they needed to start discussions with the Human Exploration and Operations Mission Directorate (HEOMD) now to secure a spot on the manifest in roughly a decade.

- “While the manifest for SLS is not fully established for the 2030s or the late 2020s, I would say right now is the optimal time to engage with HEOMD to make sure that these missions get on the docket,” he said.

- That may be difficult since it’s not clear what missions NASA will pursue that would require, or could benefit from, an SLS launch. The ongoing planetary science decadal, which will provide recommendations on the highest priority missions for the next decade, won’t be completed until the spring of 2022, and NASA will take some time to decide which recommended missions to implement and when.

- Stough said NASA’s Jet Propulsion Laboratory has shown an interest for using SLS for the Mars Sample Return campaign, but the next mission in that effort, the Sample Retrieval Lander, is scheduled for launch as soon as 2026.

- The experience of Europa Clipper offers a cautionary tale for those seeking to launch missions on SLS. Congress for several years directed NASA to use SLS for the mission, allowing the spacecraft to get to Jupiter several years faster than if launched on alternative vehicles. NASA fought that directive, arguing that using a commercially procured launch vehicle would be less expensive and free up the SLS for the early Artemis missions.

- Congress relented in the fiscal year 2021 appropriations bill, but only after NASA warned of a potential torsional loading issue if the Europa Clipper spacecraft was launched on SLS. NASA is now in the process of buying a commercial launch for Europa Clipper.

- That issue came up during the steering committee meeting, particularly after Stough emphasized the “benign launch loads” of the SLS. He said later that, because of work already underway to analyze the initial Artemis missions, engineers decided to use “very conservative” limits when examining Europa Clipper to streamline the analysis.

- “We didn’t understand that that was going to cause a problem for Europa Clipper,” he said, but could have been corrected. “It really was a nonissue at the end of the day.”

- Another issue for those considering SLS is the cost of the vehicle. Stough took issue with some cost estimates for the vehicle. “The cost numbers you hear in the media are typically inflated,” he said, by taking into account fixed costs. He didn’t give specific examples, but some estimates assume an SLS cost of $2 billion each, based on the program’s annual budget and flight rate.

- Asked for his estimate of SLS costs, he said “we are close to $1 billion per launch right now.” He projected that to decrease by 20 to 30% by the early 2030s as the flight rate increases.

• April 23, 2021: The first core stage of NASA’s Space Launch System (SLS) rocket departs Stennis Space Center near Bay St. Louis, Mississippi, following completion of the Green Run series of tests of its design and systems. The stage now is in route to the agency’s Kennedy Space Center in Florida, its final stop prior to NASA’s launch of the Artemis I mission around the Moon. At Kennedy, the core stage will be integrated with the rest of the SLS rocket and the Orion spacecraft in preparation for launch. Through the Artemis program, NASA will return humans, including the first woman and first person of color, to the Moon and prepare for eventual journeys to Mars. 8)

- NASA is building SLS as the world’s most powerful rocket to serve as the backbone of the Artemis program and the nation’s future deep space exploration missions. The SLS core stage, measuring 212 feet (64.6 m) tall and 27.6 feet (8.4 m) in diameter, is the tallest flight component ever built by NASA. It is equipped with four RS-25 engines to help power the SLS rocket at launch. Built by prime contractor Boeing at NASA’s Michoud Assembly Facility in New Orleans, the stage was delivered to Stennis aboard the agency’s Pegasus barge in January 2020. Once installed on the B-2 Test Stand at Stennis, the series of eight Green Run tests began. After pausing for about two months at the start of the COVID-19 pandemic, the work continued with new safety and health protocols in place. The team also endured a record-setting hurricane season that featured multiple storms. Nevertheless, each stage system – including avionics, hydraulics, and propulsion – were turned on and checked out during the eight-test campaign that concluded with a hot fire of the stage’s RS-25 engines, just as during an actual launch.

- After an initial hot fire test of the engines experienced an automatic shutdown early this year, teams conducted a second test on March 18, characterized by agency spokespersons as “flawless.” During the test, the engines fired for more than eight minutes, generating a combined 1.6 million pounds of thrust and representing the most powerful test conducted at Stennis in more than 40 years. The test team then worked to refurbish the stage for launch and to remove it from the B-2 Test Stand, a precise operation that requires optimal weather and wind conditions.

- Teams succeeded in removing the stand April 19-20, lifting it from its vertical installed position and using a pair of cranes to break it over and lower it to a horizontal position on the B-2 Test Stand tarmac. Following operations to prepare the stage, teams used specially designed transporters to load and hold the massive stage on the Pegasus barge. The work at Stennis was conducted by a multifaceted team of employees from NASA; Boeing, lead contractor for the SLS core stage; Aerojet Rocketdyne, lead contractor for the RS-25 engines; and Syncom Space Services, lead contractor for facility maintenance and operations at Stennis and Michoud.

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Figure 8: The first core stage of NASA's Space Launch System (SLS) rocket departs Stennis Space Center near Bay St. Louis, Mississippi, following completion of the Green Run series of tests of its design and systems (image credit: NASA)

• March 18, 2021: The largest rocket element NASA has ever built, the core stage of NASA’s Space Launch System (SLS) rocket, fired its four RS-25 engines for 8 minutes and 19 seconds Thursday at NASA’s Stennis Space Center near Bay St. Louis, Mississippi. The successful test, known as a hot fire, is a critical milestone ahead of the agency’s Artemis I mission, which will send an uncrewed Orion spacecraft on a test flight around the Moon and back to Earth, paving the way for future Artemis missions with astronauts. 9)

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Figure 9: The core stage for the first flight of NASA’s Space Launch System rocket is seen in the B-2 Test Stand during a second hot fire test, Thursday, March 18, 2021, at NASA’s Stennis Space Center near Bay St. Louis, Mississippi. The four RS-25 engines fired for the full-duration of 8 minutes during the test and generated 1.6 million pounds of thrust. The hot fire test is the final stage of the Green Run test series, a comprehensive assessment of the Space Launch System’s core stage prior to launching the Artemis I mission to the Moon. This and additional images can be found by going to: https://images.nasa.gov/album/Green_Run (image credits: NASA/Robert Markowitz)

- Engineers designed the eight-part Green Run test campaign to gradually bring the SLS core stage to life for the first time, culminating with the hot fire. The team will use data from the tests to validate the core stage design for flight.

- “The SLS is the most powerful rocket NASA has ever built, and during today’s test the core stage of the rocket generated more than 1.6 million pounds of thrust within seven seconds. The SLS is an incredible feat of engineering and the only rocket capable of powering America’s next-generation missions that will place the first woman and the next man on the Moon,” said acting NASA Administrator Steve Jurczyk. “Today’s successful hot fire test of the core stage for the SLS is an important milestone in NASA’s goal to return humans to the lunar surface – and beyond.”

- NASA previously conducted a hot fire test of the SLS core stage Jan. 16. The four RS-25 engines fired together for the first time for about one minute before the test ended earlier than planned. Following data analysis, NASA determined a second, longer hot fire test would provide valuable data to help verify the core stage design for flight, while posing minimal risk to the Artemis I core stage.

- During the second hot fire test, the stage fired the engines for a little more than eight minutes, just like it will during every Artemis launch to the Moon. The longer duration hot fire tested a variety of operational conditions, including moving the four engines in specific patterns to direct thrust and powering the engines up to 109% power, throttling down and back up, as they will during flight.

- “This longer hot fire test provided the wealth of data we needed to ensure the SLS core stage can power every SLS rocket successfully,” said John Honeycutt, manager for the SLS Program at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “During this test, the team conducted new operations with the core stage for the first time, repeated some critical operations, and recorded test data that will help us verify the core stage is ready for the first and future SLS flights for NASA’s Artemis program.”

- The two propellant tanks in the SLS core stage collectively hold more than 733,000 gallons of supercold liquid hydrogen and liquid oxygen to help fuel the RS-25 engines at the bottom of the stage. The core stage has a complex network of flight software and avionics systems designed to help fly, track, and steer the rocket during launch and flight. Prior tests in the Green Run test series evaluated the integrated functionality and performance of the core stage’s avionics systems, propulsion systems, and hydraulic systems.

- “Today is a great day for NASA, Stennis and this nation’s human space exploration program. This final test in the Green Run series represents a major milestone for this nation’s return to the Moon and eventual mission to Mars,” said Stennis Center Director Richard Gilbrech. “So many people across the agency and the nation contributed to this SLS core stage, but special recognition is due to the blended team of test operators, engineers, and support personnel for an exemplary effort in conducting the test today.”

- Test teams at Stennis supervised a network of 114 tanker trucks and six propellant barges that provided liquid propellant through the B-2 Test Stand to the core stage. Test teams also delivered operational electrical power, supplied more than 330,000 gallons of water per minute to the stand’s flame deflector, and monitored structural interfaces of both the hardware and the stand.

- Testing the SLS rocket’s core stage is a combined effort for NASA and its industry partners. Boeing is the prime contractor for the core stage and Aerojet Rocketdyne is the prime contractor for the RS-25 engines.

- Next, the core stage for SLS will be refurbished, then shipped to NASA’s Kennedy Space Center in Florida. There, the core stage will be assembled with the solid rocket boosters and other parts of the rocket and NASA’s Orion spacecraft on the mobile launcher inside the Vehicle Assembly Building at Kennedy in preparation for Artemis I.

- SLS, Orion, and the ground systems at Kennedy, along with the human landing system and the Gateway in orbit around the Moon, are NASA’s backbone for deep space exploration. SLS is the only rocket that can send Orion, astronauts, and supplies to the Moon on a single mission. The exploration of the Moon with NASA’s Artemis program includes preparations to send astronauts to Mars as part of America’s Moon to Mars exploration approach.

• January 17, 2021: NASA conducted a hot fire Saturday (Jan. 16) of the core stage for the agency’s Space Launch System (SLS) rocket that will launch the Artemis I mission to the Moon. The hot fire is the final test of the Green Run series. 10)

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Figure 10: The core stage for the first flight of NASA’s Space Launch System rocket is seen in the B-2 Test Stand during a hot fire test Jan. 16, 2021, at NASA’s Stennis Space Center near Bay St. Louis, Mississippi (image credit: NASA Television)

- The test plan called for the rocket’s four RS-25 engines to fire for a little more than eight minutes – the same amount of time it will take to send the rocket to space following launch. The team successfully completed the countdown and ignited the engines, but the engines shut down a little more than one minute into the hot fire. Teams are assessing the data to determine what caused the early shutdown, and will determine a path forward.

- For the test, the 212-foot core stage generated 1.6 million pounds of thrust, while anchored in the B-2 Test Stand at NASA’s Stennis Space Center near Bay St. Louis, Mississippi. The hot fire test included loading 733,000 pounds of liquid oxygen and liquid hydrogen – mirroring the launch countdown procedure – and igniting the engines.

- "Saturday’s test was an important step forward to ensure that the core stage of the SLS rocket is ready for the Artemis I mission, and to carry crew on future missions,” said NASA Administrator Jim Bridenstine, who attended the test. “Although the engines did not fire for the full duration, the team successfully worked through the countdown, ignited the engines, and gained valuable data to inform our path forward.”

- Support teams across the Stennis test complex provided high-pressure gases to the test stand, delivered all operational electrical power, supplied more than 330,000 gallons of water per minute to protect the test stand flame deflector and ensure the structural integrity of the core stage, and captured data needed to evaluate the core stage performance.

- “Seeing all four engines ignite for the first time during the core stage hot fire test was a big milestone for the Space Launch System team” said John Honeycutt, the SLS program manager at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “We will analyze the data, and what we learned from today’s test will help us plan the right path forward for verifying this new core stage is ready for flight on the Artemis I mission.”

- The Green Run series of tests began in January 2020, when the stage was delivered from NASA’s Michoud Assembly Facility in New Orleans and installed in the B-2 test stand at Stennis. The team completed the first of the eight tests in the Green Run series before standing down in March due to the ongoing coronavirus pandemic. After resuming work in May, the team worked through the remaining tests in the series, while also standing down periodically as six tropical storms or hurricanes affected the Gulf Coast. Each test built upon the previous test with increasing complexity to evaluate the stages’ sophisticated systems, and the hot fire test that lit up all four engines was the final test in the series.

- “Stennis has not witnessed this level of power since the testing of Saturn V stages in the 1960s,” said Stennis Center Director Rick Gilbrech. “Stennis is the premier rocket propulsion facility that tested the Saturn V first and second stages that carried humans to the Moon during the Apollo Program, and now, this hot fire is exactly why we test like we fly and fly like we test. We will learn from today’s early shutdown, identify any corrections if needed, and move forward.”

- In addition to analyzing the data, teams also will inspect the core stage and its four RS-25 engines before determining the next steps. Under the Artemis program, NASA is working to land the first woman and the next man on the Moon in 2024. SLS and the Orion spacecraft that will carry astronauts to space, along with the human landing system and the Gateway in orbit around the Moon, are NASA’s backbone for deep space exploration.

• January 5, 2021: NASA is targeting the final test in the Green Run series, the hot fire, for as early as Jan.17. The hot fire is the culmination of the Green Run test series, an eight-part test campaign that gradually brings the core stage of the Space Launch System (SLS) — the deep space rocket that will power the agency’s next-generation human Moon missions — to life for the first time. 11)

- NASA conducted the seventh test of the SLS core stage Green Run test series – the wet dress rehearsal – on Dec. 20 at NASA’s Stennis Space Center near Bay St. Louis, Mississippi and marked the first time cryogenic, or super cold, liquid propellant was fully loaded into, and drained from, the SLS core stage’s two immense tanks. The wet dress rehearsal provided structural and environmental data, verified the stage’s cryogenic storage capabilities, demonstrated software with the stage’s flight computers and avionics, and conducted functional checks of all the stage’s systems. The end of the test was automatically stopped a few minutes early due to timing on a valve closure. Subsequent analysis of the data determined the valve’s predicted closure was off by a fraction of a second, and the hardware, software, and stage controller all performed properly to stop the test. The team has corrected the timing and is ready to proceed with the final test of the Green Run series.

- “During our wet dress rehearsal Green Run test, the core stage, the stage controller, and the Green Run software all performed flawlessly, and there were no leaks when the tanks were fully loaded and replenished for approximately two hours,” said Julie Bassler, SLS Stages manager at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “Data from all the tests to date has given us the confidence to proceed with the hot fire.”

- The upcoming hot fire test will fire all four of the stage’s RS-25 engines simultaneously for up to eight minutes to simulate the core stage’s performance during launch. After the firing at Stennis, the core stage for SLS will be refurbished and shipped on the agency's Pegasus barge to NASA’s Kennedy Space Center in Florida. The stage will then be assembled with the other parts of the rocket and NASA’s Orion spacecraft in preparation for Artemis I, the first integrated flight of SLS and Orion and the first mission of the agency’s Artemis program.

- “The next few days are critical in preparing the Artemis I rocket stage, the B-2 Test Stand at NASA’s Stennis Space Center, and the test team for the finale of the Green Run test series,” said Barry Robinson, project manager for SLS core stage Green Run testing at Stennis. “The upcoming Green Run hot fire test is the culmination of a lot of hard work by this team as we approach a key milestone event for NASA’s Artemis missions.”

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Figure 11: Fully loading the propellant and detecting no leaks is a major milestone for the Green Run test series. A total of 114 tanker trucks delivered propellant to six propellant barges next to the B-2 Test Stand at NASA’s Stennis Space Center near Bay St. Louis, Mississippi. The barges deliver more than 733,000 gallons of liquid hydrogen and liquid oxygen to the core stage for NASA’s Space Launch System (SLS) rocket as part of the seventh test in the Green Run test series. The wet dress rehearsal test marks the first time propellant is loaded and drained from the propellant tanks of the stage that will help power Artemis I. Six propellant barges send fuel through a special feed system and lines in the test stand to the rocket stage (image credit: NASA)

- Testing the SLS rocket’s core stage is a combined effort for NASA and its industry partners. Boeing is the prime contractor for the core stage and Aerojet Rocketdyne is the lead contractor for the RS-25 engines. Prior tests in the Green Run test series evaluated the stage’s avionics systems, propulsion systems, and hydraulic systems.

Figure 12: NASA completed the wet dress rehearsal, the seventh test of the Space Launch System (SLS) rocket core stage Green Run test series at the agency’s Stennis Space Center near Bay St. Louis, Mississippi, on Dec. 20. During the test, 733,000 gallons filled the liquid hydrogen and liquid oxygen tank. A key part of the test was to load the propellant and the replenish it to keep the tanks full as the gas naturally boils off. The mist around the stage in this video is actually the propellant boiling off during the test. The wet dress rehearsal test is one of the most extensive tests of the entire series and marks the first time that the rocket stage is filled and drained of liquid propellant. The next time the propellant tanks are filled, NASA will be moving toward Green Run hot fire testing (video credit: NASA)

- NASA is working to land the first woman and the next man on the Moon by 2024. SLS, and Orion, along with the human landing system and the Gateway in orbit around the Moon, are NASA’s backbone for deep space exploration. SLS is the only rocket that can send Orion, astronauts, and supplies to the Moon on a single mission.

• October 20, 2020: NASA’s mobile launcher that will carry the Space Launch System (SLS) and Orion spacecraft for Artemis I is on the road again. The Exploration Ground Systems and Jacobs teams rolled the mobile launcher, atop crawler-transporter 2, out of the Vehicle Assembly Building for its slow trek to Launch Pad 39B at Kennedy Space Center in Florida on Oct. 20. 12)

- The roll began just after midnight, and the mobile launcher arrived at the top of the pad Tuesday morning. This trek to the pad will help prepare the launch team for the actual wet dress rehearsal and launch of SLS and Orion on Artemis I next year. The wet dress rehearsal is when SLS and Orion will be rolled out to the pad atop the mobile launcher to practice fueling operations a couple months before launch. The last time the mobile launcher was rolled to the pad was in December 2019.

- During its two-week stay at the pad, engineers will perform several tasks, including a timing test to validate the launch team’s countdown timeline, and a thorough, top-to-bottom wash down of the mobile launcher to remove any debris remaining from construction and installation of the umbilical arms.

- “While these tasks have been rehearsed individually, the return to Pad 39B allows the team to perform this sequence altogether,” said Charlie Blackwell-Thompson, Artemis launch director.

- To begin, technicians will lower the engine service platform that is under the core stage RS-25 engines from the mobile launcher and move it to the launch position. The platform allows access to the engines for routine work or inspections. Engineers and technicians will rehearse a timely completion of removing platforms used to access SLS core stage engines. They will position both side flame deflectors in the flame trench and raise the extensible columns to launch configuration that are critical to support an on-time launch. The extensible columns are designed to provide extra support to the mobile launcher at liftoff, when the loads are the greatest. The team also will perform preparations of mobile launcher umbilical arms along with other mobile launcher and pad subsystems.

- “During the Artemis launch countdown, this work will be performed prior to tanking,” Blackwell-Thompson said. “As part of this demonstration, the team will exercise the ground hardware in order to determine the timing of these critical elements.”

- During its time at the pad, the mobile launcher also will receive a bath.

- “The wash down will reduce the risk to the SLS/Orion during launch,” said Cliff Lanham, EGS flow director. “Some of the debris are inaccessible without using high-pressure water, available at the pad, to get into hard-to-reach areas.”

- To accomplish the wash down, the team will use the mobile launcher’s fire protection system, which has hoses on each level and the deck. The high-pressure flow rate will wash debris into the flame trench, industrial wastewater retention tanks, and percolation ponds. Lanham said this is an added safety measure, in addition to the walk downs performed prior to launch.

- While at the pad, the mobile launcher’s fire suppression system also will be recertified. The last certification was in December 2019 and is due before launch in November 2021.

- Artemis I will test the Orion spacecraft and SLS as an integrated system ahead of crewed flights to the Moon. Under the Artemis program, NASA will land the first woman and the next man on the Moon in 2024.

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Figure 13: The mobile launcher for Artemis I begins rollout from the Vehicle Assembly Building atop crawler-transporter 2 in the early morning on Oct. 20, 2020, at NASA's Kennedy Space Center in Florida (image credit: NASA, Ben Smegelsky)

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Figure 14: In the early morning on Oct. 20, 2020, the mobile launcher for Artemis I rolls along the crawlerway atop crawler-transporter 2 after departing the Vehicle Assembly Building at NASA’s Kennedy Space Center in Florida (image credit: NASA, Ben Smegelsky)

• June 19, 2020: NASA’s Space Launch System (SLS) Program is concluding its structural qualification test series with one upcoming final test that will push the design for the rocket’s liquid oxygen tank to its limits at NASA’s Marshall Space Flight Center in Huntsville, Alabama. 13)

- In the name of science, engineers will try to break a structural test article of the tank-on purpose. The liquid oxygen tank’s structure is identical to the tank that is part of the SLS core stage, which will provide power to help launch the Artemis missions to the Moon. The tank is enclosed in a cage-like structure that is part of the test stand. Hydraulic systems will apply millions of pounds of force to push, pull and bend the liquid oxygen tank test article to see just how much pressure the tank can take. The forces simulate what the tank is expected to experience during launch and flight. For the test, the tank will be filled with water to simulate the liquid oxygen propellant used for flight, and when the tank ruptures, the water may create a loud sound as it bursts through the tank’s skin.

- “We take rocket tanks to extreme limits and break them because pushing systems to the point of failure gives us a data to help us build rockets more intelligently,” said Neil Otte, chief engineer for the SLS Stages Office at Marshall. “Breaking the propellant tank today on Earth will provide us with valuable data for safely and efficiently flying SLS on the Artemis missions to the Moon.”

- Earlier this year, NASA and Boeing engineers subjected the tank to 23 baseline tests that simulate actual flight conditions, and the tank aced the tests. The tank is fitted with thousands of sensors to measure stress, pressure and temperature, while high-speed cameras and microphones capture every moment to identify buckling or cracking in the cylindrical tank wall. This final test will apply controlled forces stronger than those engineers expect the tank to endure during flight, similar to the test that ruptured the liquid hydrogen tank and created noise heard in some Huntsville neighborhoods near Marshall.

- This is final test in a series of structural qualification tests that have pushed the rocket’s structures to the limits from top to bottom to help ensure the rocket is ready for the Artemis lunar missions. Completion of this upcoming test will mark a major milestone for the SLS Program.

- The Marshall team started structural qualification testing on the rocket in May 2017 with an integrated test of the upper part of the rocket stacked together: the Interim Cryogenic Propulsion Stage, the Orion stage adapter and the launch vehicle stage adapter. Then the team moved on to testing the four largest structures that make up the 212-foot-tall core stage. The last baseline test for Artemis I was completed in March 2020 before the team’s access to Marshall was restricted because of the COVID-19 pandemic. The NASA and Boeing team returned to work the first week in June to prepare for conducting the final liquid oxygen test to failure.

- The structural qualification tests help verify models showing the structural design can survive flight. Structural testing has been completed on three of the largest core stage structures: the engine section, the intertank, and the liquid hydrogen tank. The liquid oxygen tank has completed baseline testing and will now wrap up core stage testing with the upcoming test to find the tank’s point of failure.

- "The liquid oxygen tests and the other tests to find the point of failure really put the hardware through the paces," said April Potter, the SLS test project manager for liquid oxygen and liquid hydrogen structural tests. "NASA will now have the information to build upon our systems and push exploration farther than ever before."

- The SLS rocket, Orion spacecraft, Gateway and human landing system are part of NASA’s backbone for deep space exploration. The Artemis program is the next step in human space exploration. It is part of America’s broader Moon to Mars exploration approach, in which astronauts will explore the Moon and gain experience to enable humanity’s next giant leap, sending humans to Mars.

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Figure 15: The liquid oxygen tank structural test article, shown here, for NASA’s Space Launch System (SLS) rocket’s core stage was the last test article loaded into the test stand July 10, 2019. The liquid oxygen tank is one of two propellant tanks in the rocket’s massive core stage that will produce more than 2 million pounds of thrust to help launch Artemis-1, the first flight of SLS and NASA’s Orion spacecraft to the Moon. Now, the tank will undergo the final test completing a three-year structural test campaign at NASA’s Marshall Space Flight Center in Huntsville, Alabama. Tests conducted during this campaign put the rocket’s structures from the top of the upper stage to the bottom of the core stage through strenuous tests simulating the forces that the rocket will experience during launch and flight. All four of the core stage structural test articles were manufactured at NASA’s Michoud Assembly Facility in New Orleans and delivered by NASA’s barge Pegasus to Marshall (image credit: NASA/Tyler Martin)

• February 26, 2020: Northrop Grumman Corporation, along with NASA and Lockheed Martin, successfully completed its third and final qualification test of the Attitude Control Motor (ACM) for NASA's Orion spacecraft Launch Abort System (LAS). 14)

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Figure 16: Attitude Control Motor (ACM) for NASA's Orion spacecraft Launch Abort System (LAS), image credit: Northrop Grumman

- "The qualification test is a critical step toward Artemis II, Orion's first flight with astronauts," said Pat Nolan, vice president, missile products, Northrop Grumman. "Completion of this milestone emphasizes Northrop Grumman's commitment to deliver innovative and reliable technology that will keep our astronauts safe during launch."

- The test was performed under cold operating conditions, to complement the earlier tests conducted at nominal and high-temperature conditions. In an effort to demonstrate worst case conditions, the motor was ignited using one of the two initiators and simulated high altitude vacuum conditions.

- Preliminary results showed excellent performance, meeting the stringent design criteria for this critical application. All eight high thrust valves operated nominally over the 35 second motor burn time. The valves provided more than 7,000 lbs. of thrust during the high thrust portion of the duty cycle.

- The ACM is one of three motors comprising Orion's LAS. The system is designed to carry astronauts inside the spacecraft to safety if an emergency arises on the launch pad or during Orion's climb to orbit. In the unlikely event of an abort, the attitude control motor would steer the Orion crew module away from the launch vehicle. The ACM also orients the capsule for parachute deployment once the crew module is clear of all hazards.

- NASA is working to land the first woman and next man on the Moon by 2024. Orion is part of NASA's backbone for deep space exploration, along with the Space Launch System rocket and Gateway in orbit around the Moon. Orion will sustain astronauts in deep space, provide emergency abort capability, and support a safe re-entry from lunar return velocities.

- Exploring the Moon helps create a vibrant future and advance technologies, capabilities and new opportunities for future missions to Mars. Northrop Grumman is responsible for the LAS ACM through a contract with Lockheed Martin, prime contractor for Orion.

• February 3, 2020: - Aerojet Rocketdyne recently delivered four RL10 upper stage engines to NASA's Stennis Space Center that will help power NASA’s Space Launch System (SLS) rocket as it carries astronauts aboard the Orion spacecraft to deep space. These missions are part of NASA’s Artemis program, which will land the first woman and next man on the Moon, and set the stage to send astronauts to Mars. 15)

- “Nearly 500 Aerojet Rocketdyne RL10 engines have powered launches into space,” said Eileen Drake, Aerojet Rocketdyne CEO and president.“Aerojet Rocketdyne continues to upgrade and improve this highly-reliable, flight-proven engine. The RL10’s we just delivered to NASA will power the SLS upper stage on missions that safely launch our astronauts to explore deep space destination.”

- A single RL10 engine will provide nearly 25,000 pounds of thrust (~11 kN) and serve as the main propulsion for the Interim Cryogenic Propulsion Stage (ICPS)that will fly atop the SLS rocket Block 1 in support of each of the first three Artemis missions. Later Artemis missions will use the evolved SLS Block 1Brocket configuration that includes the Exploration Upper Stage (EUS) powered by four RL10 engines to send Orion and large cargos to the Moon. The four RL10 engines on EUS provide more than 97,000 pounds of thrust (~43 kN).

- Aerojet Rocketdyne is under contract to deliver 10 RL10 engines to NASA to support the Artemis program. One of the four engines that were recently delivered will be used to support the Artemis II mission that will use the ICPS upper stage, while the other three are slated to support future Artemis missions aboard the EUS. Delivery of the remaining six engines will be completed by 2021.

- ”The EUS is really a game changer for SLS and NASA’s lunar exploration program in terms of payload mass,” said Steve Wofford, Space Launch System Program Liquid Engines manager at NASA’s Marshall Space Flight Center. “These RL10 deliveries are a key stepping stone toward that future success.”

- Evolving the SLS rocket to the Block 1B version that uses EU'S significantly increases the amount of payload that can be carried to lunar orbit; up to 40metric tons compared to the 26 metric ton capability provided by the SLS Block 1 configuration. It also provides the option for “co-manifested”payloads such as large components for NASA’s Gateway orbiting lunar outpost, landers, or surface system.

- Aerojet Rocketdyne has completed engine qualification testing for EU'S and all other engineering activities, including providing NASA with the information necessary for the agency to human rate the RL10 engines. Qualification of the engines for ICPS will be completed in 2020.

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Figure 17: Four Aerojet Rocketdyne RL10 rocket engines – shown here at the company’s facility in West Palm Beach, Florida – were recently delivered to NASA. The engines will be used to help power the upper stage of the agency’s Space Launch System (SLS) rocket (image credit: Aerojet Rocketdyne)

• December 4, 2019: Engineers are preparing to push a test article identical to the world’s largest rocket fuel tank beyond its design limits and find its breaking point during upcoming tests at NASA’s Marshall Space Flight Center in Huntsville, Alabama. 16)

- Earlier this year, a NASA and Boeing test team subjected a test version of the Space Launch System (SLS) liquid hydrogen tank to a series of 37 tests that simulate liftoff and flight stresses by using large hydraulic pistons to push and pull on the test tank with millions of pounds of force. The test article aced these tests and showed no signs of cracks, buckling or breaking and qualified the design for flight. Now, the team wants to see just how much the tank can take.

- Space exploration involves risk,” said Julie Bassler, manager of the Space Launch System Stages Office. “This is a different kind of exploration that happens before we launch. A test to failure of the largest liquid hydrogen tank ever produced will expand our knowledge to ensure we can safely get the most performance out of the rocket that will send astronauts and large cargo to the Moon and then to Mars.”

- The hydrogen tank is part of the SLS core stage. Measuring more than 130 feet tall and 27.6 feet in diameter, it stores 537,000 gallons of super cooled liquid hydrogen to help power the four SLS core stage RS-25 engines for the 8-minute climb to orbit at more than 17,000 miles per hour. The test article’s structure is identical to that of the flight hardware.

- Having certified the tank for both the current version of SLS, called Block 1, as well as the more powerful Block 1B version in development, engineers are preparing their 215-foot-tall test stand for one final test to see exactly how much stress the hydrogen tank can take before it fails structurally.

- Built by Boeing at NASA’s Michoud Assembly Facility in New Orleans and barged to Marshall last December, the hydrogen tank test article has been fitted with thousands of sensors measuring, stress, pressure, and temperature, while high-speed cameras and microphones capture every inch for the expected telltale buckling or cracking in the cylindrical tank wall.

- “The core stage hardware structures are brand new, first-time developments, so this testing is crucial to ensuring mission success,” said Luke Denney, qualification test manager for Boeing’s Test & Evaluation Group. “The tests were designed to prove that each component of the stage will be able to survive its own unique set of extreme environmental conditions during liftoff, ascent and flight.”

- In fact, this will be the largest-ever controlled test-to-failure of a NASA rocket stage fuel tank, said Mike Nichols, Marshall’s lead test engineer for the tank.

- “The failure mechanism of a slender multi-segment rocket stage is not very well understood,” he said. “By taking this test article to failure, we can better understand the phenomenon. This test will benefit all rocket engineers, providing valuable data for their propellant tank designs for future rocket stages.”

- Engineers have computer calculations that predict when and where and how the tanks should fail. But without a carefully planned test they won’t know exactly. That difference is important for NASA’s plans to return human explorers to the Moon.

- “In spaceflight, especially human spaceflight, we always walk the line between performance and safety, said Neil Otte, the chief engineer for the SLS Stages Office. “Pushing systems to the point of failure gives us additional data to walk that line intelligently. We will be flying the Space Launch System for decades to come, and we have to take all the opportunities we have to maximize our understanding of the system so we may safely and efficiently evolve it as our desired missions evolve.

- This is not the first SLS test article to be tested to structural failure. Test versions of the engine section and intertank were also tested until they broke above 140% of anticipated flight stresses.

- While engineers predict the test will not create a sizable hole in the tank, should that happen, areas of the community close to Redstone Arsenal hear a low-level sound as the nitrogen gas used to pressurize the tank is vented.

- The 212-foot-tall core stage is the largest, most complex rocket stage NASA has built since the Saturn V stages that powered the Apollo missions to the Moon. SLS and Orion, along with the Gateway in orbit around the Moon, are NASA’s backbone for deep space exploration and the Artemis program, which will send the first woman and next man to the lunar surface by 2024. SLS is the only rocket that can send Orion, astronauts, and supplies to the Moon on a single mission.

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Figure 18: Engineers are preparing to push a test article identical to the world’s largest rocket fuel tank beyond its design limits and find its breaking point during upcoming tests at NASA’s Marshall Space Flight Center in Huntsville, Alabama. This will be the largest-ever controlled test-to-failure of a NASA rocket stage fuel tank. Earlier this year, a NASA and Boeing test team subjected a test version of the Space Launch System (SLS) liquid hydrogen tank to a series of 37 tests that simulate liftoff and flight stresses. Inside a 220-foot-tall test stand, they used large hydraulic pistons to push and pull on the test tank with millions of pounds of force. The test article aced these tests and showed no signs of cracks, buckling or breaking and qualified the design for flight. Now, the team will test the tank’s limits. The test article’s structure is identical to the hydrogen tank that is part of the SLS core stage. This tank will store 537,000 gallons of super cooled liquid hydrogen to help power the four SLS core stage RS-25 engines for the 8-minute climb to orbit at more than 17,000 miles per hour (image credit: NASA/MSFC)

• November 21, 2019: To launch the Artemis I Moon mission, NASA’s powerful SLS (Space Launch System) rocket must go from 0 to more than 17,000 miles per hour. The rocket’s flight software and avionics systems control all that power to ensure the rocket and NASA’s Orion spacecraft make it to space. The SLS avionics and flight software came a step closer to the Artemis I mission when NASA certified the Systems Integration Laboratory for final integrated avionics and flight software testing Nov. 14. 17)

- “The System Integration Lab’s test environment is the most accurate representation of the rocket’s entire avionics and software system,” said Dan Mitchell, lead SLS integrated avionics and software engineer. “Certification means the lab has completed a series of tests and analyses to assert that the facility, its simulation environment and the avionics and flight software have been properly integrated and ready for formal system verification testing.”

- This lab at NASA’s Marshall Space Flight Center in Huntsville, Alabama, not only includes the flight computers and avionics identical to the core stage avionics but also includes emulators for the rocket’s boosters and engines, the Launch Control Center and Orion. Now that the lab is ready, software engineers can test the software both under normal and unplanned scenarios.

- Using unique software programs, engineers in the lab create real-time launch vehicle simulations for the rocket’s extensive and incredibly intricate flight software and avionics hardware. These simulations include numerous nominal and off nominal real-time pre-launch and ascent SLS mission scenarios.

- Equipped with two propellant tanks that can hold a combined 733,000 gallons of fuel and four RS-25 engines, the 212-foot-tall core stage serves as the powerhouse of the rocket. The core stage, along with the two, five-segment solid rocket boosters, produces more than 8.8 million pounds of thrust to launch it and NASA’s Orion spacecraft to the Moon.

- The internal flight software and avionics outfitted throughout the boosters and core stage operate with three SLS flight computers and interface with the avionics systems to control all that power and safely guide the rocket beyond Earth’s orbit. The software also works with software for the Exploration Ground Systems team at NASA’s Kennedy Space Center in Florida, from where SLS will launch.

- “The flight software and avionics systems are considered the brain and nervous system of the rocket,” Mitchell said. “They control the rocket from launch through the first eight minutes of flight, and the test scenarios we create in the lab can simulate any part of an SLS rocket’s launch or even the entire mission.”

- In the same room as the lab, the Software Integration and Test Facility integrates and tests hardware for the avionics systems in the core stage of the rocket. These two facilities provide a comprehensive scope of the rocket’s “internal organs” as teams of engineers run hundreds of virtual launches to verify the rocket’s thousands of functional lines of code to evaluate how it will perform in space.

- The facilities contain a complete set of avionics and software for the rocket’s core stage, boosters and engines to support end-to-end avionics and software system testing.

- “Across the lab in roughly the same positions as they would be inside the core stage, SLS avionics boxes are mounted around a cylinder frame that matches the size of the rocket,” said Lisa Espy, SLS core stage avionics lead. “Inside the skeleton of the rocket, the boxes are even connected with the same sized cables and connectors that will be used on the flight vehicle itself.”

- With the certification of the lab complete, formal system testing will be conducted in two phases. First, engineers and developers will focus on the critical avionics hardware and software for flight. Following that, testing will be conducted on the engineering and developmental data acquisition hardware and the hardware for the imagery and flight safety systems.

- With the certification of the lab complete, formal system testing will be conducted in two phases. First, engineers and developers will focus on the critical avionics hardware and software for flight. Following that, testing will be conducted on the engineering and developmental data acquisition hardware and the hardware for the imagery and flight safety systems.

- NASA is working to land the first woman and next man on the Moon by 2024. SLS and Orion, along with the Gateway in orbit around the Moon, are NASA’s backbone for deep space exploration. SLS is the only rocket that can send Orion, astronauts and supplies to the Moon on a single mission.

• November 12, 2019: Media and social media influencers are invited to NASA’s Michoud Assembly Facility in New Orleans Monday, Dec. 9, for Artemis Day: Michoud/Stennis. Those attending will get a rare, up-close look at the core stage for NASA’s Space Launch System (SLS) rocket that will help power the first Artemis mission to the Moon. 18)

- Artemis Day will begin at 9 a.m. EST (8 a.m. CST) and feature a news conference with NASA Administrator Jim Bridenstine, who will discuss the status of the agency’s Artemis program. A question-and-answer session will follow the discussion. The news conference will be carried live on NASA Television and agency website.

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Figure 19: On Nov. 6, engineers and technicians attached the last of four RS-25 engines that will provide the necessary thrust for the SLS rocket to reach space. To complete assembly of the stage, technicians now are attaching the engines to propulsion and avionics systems inside the core stage, which also houses the flight computers that control the rocket during its first eight minutes of flight. NASA will showcase the completed core stage in December (image credit: NASA)

• October 23, 2019: Engineers and technicians at NASA's Michoud Assembly Facility in New Orleans have structurally mated the first of four RS-25 engines to the core stage for NASA's Space Launch System (SLS) rocket that will help power the first Artemis mission to the Moon. 19)

- Integration of the RS-25 engines to the recently completed core stage structure is a collaborative, multistep process for NASA and its partners Boeing, the core stage lead contractor, and Aerojet Rocketdyne, the RS-25 engines lead contractor.

- To complete the installation, the technicians will now integrate the propulsion and electrical systems. The installation process will be repeated for each of the four RS-25 engines. The four RS-25 engines used for Artemis I were delivered to Michoud from Aerojet Rocketdyne’s facility at NASA’s Stennis Space Center near Bay St. Louis, Mississippi, in June.

The engines, located at the bottom of the core stage in a square pattern, are fueled by liquid hydrogen and liquid oxygen. During launch and flight, the four engines will fire nonstop for 8.5 minutes, emitting hot gases from each nozzle 13 times faster than the speed of sound. The completed core stage with all four engines attached will be the largest rocket stage NASA has built since the Saturn V stages for the Apollo Program.

- NASA is working to land the first woman and next man on the Moon by 2024. SLS is part of NASA's backbone for deep space exploration, along with Orion and the Gateway in orbit around the Moon. SLS is the only rocket that can send Orion, astronauts and supplies to the Moon on a single mission.

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Figure 20: Photo of the first RS-25 engine attached to the SLS rocket stage (image credit: NASA)

• September 27, 2019: NASA’s Pegasus barge arrived Sept. 27 at the agency’s Kennedy Space Center in Florida with the core stage pathfinder for NASA’s Space Launch System (SLS) rocket. The pathfinder will be used for lift and transport practice techniques inside Kennedy’s Vehicle Assembly Building to prepare for the first lunar mission of SLS and NASA’s Orion spacecraft, Artemis I. 20)

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Figure 21: NASA’s Space Launch System (SLS) core stage pathfinder is positioned in the B-2 Test Stand at NASA’s Stennis Space Center near Bay St. Louis, Mississippi. The Pathfinder is the same shape, size and weight (without propellants loaded) as the actual SLS core stage flight hardware. Stennis work crews used it in August to train and practice handling and lifting techniques needed for the core stage flight hardware when it arrives at Stennis for testing in 2020 (image credit: NASA)

- The core stage pathfinder is one of three pathfinder structures used by NASA to train lift crews on best practices for moving and handling the SLS rocket flight hardware. In addition to the core stage pathfinder, there is an RS-25 engine pathfinder and a solid rocket booster pathfinder. Designed as full-scale mockups of the flight hardware, the three SLS pathfinders each reflect the shape and size of the individual components of the rocket.

- The number of pathfinders for the rocket allow multiple teams to use the pathfinders for different operations and procedures at several processing locations. After teams at Kennedy practice with the core stage pathfinder in the VAB, NASA’s Exploration Ground Systems will begin stacking operations with the booster pathfinder structures to simulate an aft booster assembly and bottom center segment stacking operation. All this practice prepares teams for the same upcoming tasks with the actual flight hardware.

- Engineers previously used the core stage pathfinder in August at NASA’s Stennis Space Center near Bay St. Louis, Mississippi, where crews practiced similar lift and handling procedures into the B-2 Test Stand ahead of the Green Run test series for the core stage.

- “After the pathfinder lift operations were complete, the unit was installed into the B-2 Test Stand at Stennis,” said Barry Robinson, B-2 Test Stand core stage test project manager at Stennis. “Among other things, the exercise helped us identify minor facility modifications early enough to provide the time needed to make the corrections prior to the arrival of the core stage flight hardware.”

- Equipped with the largest rocket stage NASA has ever produced and the largest twin boosters ever built for flight, the SLS rocket for the Artemis missions will be the most powerful rocket in the world, enabling astronauts in Orion to travel to the Moon’s south pole. The two massive propellant tanks in the rocket’s 212-foot-tall core stage power the four RS-25 engines at the bottom of the rocket. On either side of the core stage are two, five-segment solid rocket boosters. Together, the engines and the boosters will produce a combined thrust of 8.8 million pounds during launch and flight. The rocket for Artemis I will tower at 322 feet.

- “Practicing operations with pathfinders offers teams hands-on experience for managing and handling the immense structures before this one-of-a-kind flight hardware arrives,” Robinson said.

- Because the pathfinders replicate the flight hardware, the various pathfinders validate ground support equipment, and flight hardware access techniques as well as train handlers to transport the equipment on a variety of terrains with different vehicles, like the Pegasus barge and Kennedy’s mobile launcher, and demonstrate how the equipment can be integrated within facilities.

- “Experience is the best teacher,” said Jim Bolton, EGS core stage operations manager. “Pathfinders allow crews to practice lifting, accessing and transporting techniques that we prefer not to do for the first time with the flight hardware. Practicing with a pathfinder reduces risk and builds confidence.”

- As crews at Kennedy use the SLS booster and core stage pathfinders for the same processes the actual flight hardware will undergo when processed at Kennedy for Artemis I, completed flight hardware for SLS and Orion will also be delivered.

- “NASA’s first Artemis mission flight hardware has progressed into final assembly and integration, moving well beyond the early design and manufacturing stages of development,” said Mark Prill, SLS core stage pathfinder lead. “Flight hardware for both the SLS rocket and the Orion spacecraft will continue to be delivered to Kennedy as NASA prepares for the launch of Artemis I.”

- NASA is working to land the first woman and the next man on the Moon by 2024. SLS, along with Orion and the Gateway in orbit around the Moon, are NASA’s backbone for deep space exploration. SLS is the only rocket that can send Orion, astronauts and supplies to the Moon on a single mission.

• September 19, 2019: NASA finished assembling and joining the main structural components for the largest rocket stage the agency has built since the Saturn V that sent Apollo astronauts to the Moon. Engineers at the agency’s Michoud Assembly Facility in New Orleans connected the last of the five sections of the Space Launch System (SLS) rocket core stage on Sept. 19. The stage will produce 2 million pounds of thrust to send Artemis I, the first flight of SLS and NASA’s Orion spacecraft to the Moon. 21)

- “NASA has achieved a historic first milestone by completing the final join of the core stage structure for NASA’s SLS, the world’s most powerful rocket,” said Julie Bassler, the NASA SLS stages manager. “Now, to complete the stage, NASA will add the four RS-25 engines and complete the final integrated avionics and propulsion functional tests. This is an exciting time as we finish the first-time production of the complex core stage that will provide the power to send the Artemis I mission to the Moon.”

- The last piece added to the stage was the engine section located at the bottom of the 212-foot-tall core stage. To complete the structure, technicians bolted the engine section to the stage’s liquid hydrogen propellant tank, which was recently attached to the other core stage structures. The engine section is one of the most complicated pieces of hardware for the SLS rocket and is the attachment point for the four RS-25 rockets and the two solid rocket boosters that produce a combined 8.8 millions pounds of thrust. The engine section also includes vital systems for mounting, controlling and delivering fuel from the stage’s two liquid propellant tanks to the rocket’s engines. This fall, NASA will work with core stage lead contractor, Boeing, and the RS-25 engine lead contractor, Aerojet Rocketdyne, to attach the four RS-25 engines and connect them to the main propulsion systems inside the engine section.

- “Boeing expects to complete final assembly of the Artemis I core stage in December,” said Jennifer Boland-Masterson, Boeing operations direct at MAF. “After we deliver the stage, NASA will transport it on the agency’s Pegasus barge from Michoud to NASA’s Stennis Space Center near Bay St. Louis, Mississippi, for Green Run testing. Our team here at Michoud will continue work with NASA to build, outfit and assemble the core stage for Artemis II, the first mission that will send astronauts to orbit the Moon. Lessons learned and innovations developed in building the first core stage are making the second one progress much faster.”

- During Green Run testing, engineers will install the core stage into the B-2 Test Stand at Stennis for a series of tests that will build like a crescendo over several months. This will be the first fully fueled test of this brand new rocket stage. Many aspects will be carried out for the first time, such as fueling and pressurizing the stage, and the test series culminates with firing up all four engines to demonstrate that the engines, tanks, fuel lines, valves, pressurization system, and software can all perform together as they will on launch day.

- The SLS team also achieved another recent milestone by completing structural testing for the stage’s liquid hydrogen tank. The testing confirmed that the structural design for the tank on the rocket’s initial configuration, called Block 1, can withstand extreme conditions during launch and flight. Teams at NASA’s Marshall Space Flight Center in Huntsville, Alabama, put a test version of the tank through the paces during 37 separate test cases that exceed what engineers expect the SLS rocket to experience. The final test used 80,000 gallons of liquid nitrogen to simulate the cryogenic conditions, or extreme cold, that the liquid hydrogen tank will experience in flight. Testing will continue later this year to show the tank’s structural design is adequate for future designs of the vehicle as it evolves to a Block IB configuration and missions with even greater forces.

- In addition to providing propellant and power to get the SLS rocket and Orion spacecraft to space, the core stage houses the flight computers and avionics components that control the first 8 minutes of flight. The avionics system, including the flight computers, completed integrated system level qualification testing showing the components all work together to control the rocket in the Software Integration and Test Facility (SITF) at Marshall. The next step is to test the flight software with all the ground system software, Orion and launch control in the Systems Integration Laboratory at Marshall.

- “NASA and our contractor teams are making tremendous progress on every aspect of manufacturing, assembling and testing the complex systems needed to land American astronauts on the lunar surface by 2024,” Bassler said. “I am confident this hard work will result in a rocket that can provide the backbone for deep space transportation to the Moon and ultimately to Mars.”

- NASA is working to land the first woman and the next man on the Moon by 2024. SLS and NASA’s Orion spacecraft, along with the Gateway in orbit around the Moon, and the Human Landing System are the backbone for deep space exploration. SLS is the only rocket that can send Orion, astronauts and supplies to the Moon in a single mission.

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Figure 22: NASA finished assembling the main structural components for the Space Launch System (SLS) rocket core stage on Sept. 19. Engineers at NASA’s Michoud Assembly Facility in New Orleans fully integrated the last piece of the 212-foot-tall (64.6 m) core stage by adding the engine section to the rest of the previously assembled structure. Boeing technicians bolted the engine section to the stage’s liquid hydrogen propellant tank. The engine section is located at the bottom of the 212-foot-tall core stage and is one of the most complicated pieces of hardware for the SLS rocket. It is the attachment point for the four RS-25 rockets and the two solid rocket boosters that produce a combined 8.8 millions pounds of thrust (35585 kNewton) to send Artemis I to space. In addition, the engine section includes vital systems for mounting, controlling and delivering fuel from the stage’s two liquid propellant tanks to the rocket’s engines. This fall, NASA will work with core stage lead contractor, Boeing, and the RS-25 engine lead contractor, Aerojet Rocketdyne, to attach the four RS-25 engines and connect them to the main propulsion systems inside the engine section (image credit: NASA, Steven Seipel)

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Figure 23: The core stage test team recently completed structural testing confirming the stage’s liquid hydrogen tank structural design is good for conditions that will be experienced in the rocket’s initial configuration, called Block 1, during the Artemis I launch. The 149-foot test article was lifted into a test stand at NASA’s Marshall Space Flight Center in Huntsville, Alabama, where engineers put the tank through the paces during 37 separate test cases that simulated the stresses of launch that the SLS rocket experiences during flight. Testing will continue later this year to show the tank’s structural design is adequate for future designs of the vehicle as it evolves to a Block IB configuration and missions with more extreme forces (image credit: NASA, Tyler Martin)

• September 4, 2019: Technicians at NASA’s Michoud Assembly Facility in New Orleans moved the engine section for NASA’s Space Launch System (SLS) rocket to another part of the facility on Sept. 3 to prepare it for joining to the rest of the rocket’s core stage. The engine section, which comprises the lowest portion of the 212-foot-tall stage, is the last major component to be horizontally integrated to the core stage. The flight hardware will be used for Artemis I, the first lunar mission of SLS and NASA’s Orion spacecraft. Crews completed assembly on the engine section on Aug. 29. NASA and Boeing engineers removed the scaffolding surrounding the hardware to use a special tool to properly position the engine section for its attachment to the rest of the stage. The core stage’s two liquid propellant tanks and four RS-25 engines will produce more than 2 million pounds of thrust to send the SLS rocket and Orion on the Artemis lunar missions. The engine section houses the four RS-25 engines and includes vital systems for mounting, controlling and delivering fuel from the propellant tanks to the rocket’s engines. 22)

- NASA is working to land the first woman and the next man on the Moon by 2024. SLS and NASA’s Orion spacecraft, along with the Gateway in orbit around the Moon, are the backbone for deep space exploration. SLS is the only rocket that can send Orion, astronauts and supplies to the Moon in a single mission.

• August 30, 2019: The Space Launch System (SLS) rocket engine section, the lowest portion of the massive core stage for NASA’s rocket, is assembled and ready to be mated to the rest of the rocket’s core stage. The engine section, shown on the right beside the rest of the assembled stage, was covered with scaffolding used for assembly and checkout. On Aug. 29, NASA and Boeing technicians at NASA’s Michoud Assembly Facility in New Orleans completed assembly and functional testing on the engine section for Artemis I, the first flight of SLS and NASA’s Orion spacecraft. Now, technicians are removing the scaffolding structures and moving the engine section to another part of the facility to prepare it for integration with the rest of the core stage. Once the engine section is joined to the rest of the core stage, the main structure of the stage will be complete. 23)

- In September, the team will begin the complicated task of connecting the four RS-25 engines to the main propulsion systems inside the engine section. The engine section is one of the most complex and intricate parts of the rocket that will help power the Artemis missions to the Moon. In addition to its miles of cabling and hundreds of sensors, it is a crucial attachment point for the four RS-25 engines and two solid rocket boosters that produce a combined 8.8 million pounds of thrust at liftoff and flight.

• July 26, 2019: NASA Administrator Jim Bridenstine announced on July 25 the agency will conduct a “Green Run” core stage test for the Space Launch System rocket ahead of the upcoming Artemis 1 lunar mission. 24)

- The first eight minutes of every Artemis mission with NASA’s Space Launch System (SLS) rocket will begin with core stage and solid rocket boosters producing 8.8 million pounds of thrust to launch the agency’s Orion spacecraft to the Moon. NASA will test the rocket’s 212-foot tall core stage- the tallest rocket stage the agency has ever built- with a “Green Run” test on Earth before launch day to help ensure mission success and pave the way for future Artemis missions carrying crew to the Moon. Missions at the Moon will be a stepping stone to prepare for human exploration of Mars.

- During the Green Run testing, engineers will install the core stage that will send Orion to the Moon in the B-2 Test Stand at NASA’s Stennis Space Center near Bay St. Louis, Mississippi for a series of tests that will build like a crescendo over several months. The term “green” refers to the new hardware that will work together to power the stage, and “run” refers to operating all the components together simultaneously for the first time. Many aspects will be carried out for the first time, such as fueling and pressurizing the stage, and the test series culminates with firing up all four RS-25 engines to demonstrate that the engines, tanks, fuel lines, valves, pressurization system, and software can all perform together just as they will on launch day.

- “The SLS core stage is an engineering feat that includes not only the largest rocket propellant tanks ever built but also sophisticated avionics and main propulsion systems,” said Lisa Bates, SLS deputy stages manager. “While the rocket is designed to evolve over time for different mission objectives, the core stage design will remain basically the same. The Green Run acceptance test gives NASA the confidence needed to know the new core stage will perform again and again as it is intended.”

- The SLS core stage includes state-of-the-art avionics, miles of cables and propulsion systems and two huge liquid propellant tanks that collectively hold 733,000 gallons of liquid oxygen and liquid hydrogen to power the four RS-25 engines. Together, they will produce more than 2 million pounds of thrust to help send Artemis 1 beyond Earth’s orbit to the Moon.

- The test program for the core stage at Stennis will begin with installing the stage into the test stand. Then, engineers will turn the components on one by one through a series of initial tests and functional checks designed to identify any issues. Those tests and checks will culminate in an eight-minute-long test fire, mimicking the full duration of the stage’s first flight with ignition, ascent and engine shutdown. The results of this test also will provide important data that will confirm how the system reacts as the fuel is depleted from the propellant tanks.

- “With Green Run, we verify each individual component operates well within the core stage system,” said Bates. “It’s more than testing. It’s the first time the stage will come to life and be fully operational from the avionics in the top of the core stage to the engines at the bottom.”

- The test series is a collaborative effort between a number of NASA field centers, programs and contractors. The entire stage was built and manufactured at NASA’s Michoud Assembly Facility in New Orleans. The structural test articles, also built at Michoud, were shipped to NASA’s Marshall Space Flight Center in Huntsville, Alabama, for structural testing. The work done by Marshall’s test teams certifies the structural integrity of the rocket’s core stage, while Green Run shows that the integrated stage operates correctly. The Stennis teams renovated the historic B-2 Test Stand used to test stages for multiple programs including the Saturn V and the space shuttle propulsion system in the 1970s.

- “Green Run is a historic moment for NASA and Stennis for a number of reasons,” said Dr. Richard Gilbrech, Director, Stennis Space Center. “For the first time in NASA’s history, a launch vehicle will use flight hardware for its first test, and the Stennis test stands will once again test the core stage for Moon missions.”

- Historically, other NASA rockets built to carry astronauts have used main propulsion test articles to test the integrated engines and main propulsion system. The SLS program is performing the stage testing with flight hardware. Once the validation of the stage is complete, the entire stage will be checked out, refurbished as needed, and then shipped to NASA’s Kennedy Space Center in Florida for the Artemis 1 launch. The next time the core stage engines roar to life will be on the launchpad at Kennedy.

- NASA is working to land the first woman and next man on the Moon by 2024. SLS and Orion, along with the Gateway in orbit around the Moon, are NASA’s backbone for deep space exploration. SLS is the only rocket that can send Orion, astronauts and supplies to the Moon on a single mission.

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Figure 24: The “Green Run” test of the core stage for NASA’s Space Launch System (SLS) will be conducted at the B-2 Test Stand at NASA’s Stennis Space Flight Center near Bay St. Louis, Mississippi. The historic test stand has been used to test stages for multiple programs, including the Saturn V and the space shuttle. The test stand was renovated to accommodate the SLS rocket’s core stage, which is the largest stage NASA has ever built (image credit: NASA)

• June 28, 2019: Aerojet Rocketdyne recently delivered four RS-25 engines to NASA’s Michoud Assembly Facility (MAF) for integration with the core stage of NASA’s Space Launch System (SLS) in anticipation of the rocket’s first flight on the Artemis 1 mission. 25)

- The RS-25 engine, an advanced version of the Space Shuttle Main Engine, has a strong legacy of safely and reliably powering human spaceflight. All four of the RS-25 engines that will fly on the first SLS flight also flew during the Space Shuttle Program; they have since been updated with new controllers and adapted for the unique operating environment of SLS.

- The engines will be operated at a higher power level than was used during the shuttle flights, providing SLS with additional thrust (Figure 26).

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Figure 25: Photo of the four RS-25 engines prior to shipment (image credit: Aerojet Rocketdyne)

- In addition to the RS-25 engines, Aerojet Rocketdyne is also providing the RL10 engine that will power the SLS upper stage, known as the Interim Cryogenic Propulsion Stage (ICPS), as well as the composite overwrapped pressure vessels and reaction control system thrusters. The ICPS is complete and ready for integration with the rest of the SLS rocket components at Kennedy Space Center.

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Figure 26: An infographic about the first four engines and their flight history (image credit: Aerojet Rocketdyne)

- Earlier this year, Aerojet Rocketdyne delivered the jettison motor, which is part of the Launch Abort System that will ensure crew safety in the event of a launch or pad anomaly. Additionally, Aerojet Rocketdyne has assisted in refurbishing the main engine for the service module, and delivered the reaction control system engines for the Orion crew module and eight auxiliary engines for Orion’s European Service Module, which will ride atop the SLS.

• June 27, 2019: The last of four structural test articles for NASA’s Space Launch System (SLS) was loaded onto NASA’s Pegasus barge Wednesday, June 26, 2019, at NASA’s Michoud Assembly Facility in New Orleans. The barge will deliver the liquid oxygen (LOX) tank structural test article from Michoud to NASA’s Marshall Space Flight Center in Huntsville, Alabama, for critical structural testing. The liquid oxygen tank is one of two propellant tanks in the rocket’s core stage that will produce more than 2 million pounds of thrust (8896 kN) to help send Artemis 1, the first flight of NASA’s Orion spacecraft and SLS, to the Moon. The nearly 70-foot-long test article is structurally identical to the flight version, which will hold 196,000 gallons of liquid oxygen super cooled to minus 297 degrees Fahrenheit (-182ºC). 26)

- NASA is working to land the first woman and next man on the Moon by 2024. SLS is part of NASA’s backbone for deep space exploration, along with Orion and the Gateway in orbit around the Moon. SLS is the only rocket that can send Orion, astronauts and supplies to the Moon on a single mission.

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Figure 27: Last Test Article for NASA's SLS Rocket departs MAF (Michoud Assembly Facility), image credit: NASA, Jude Guidry

• April 16, 2019: The boat-tail structure, a fairing-like cover designed to protect the bottom end of the core stage and the RS-25 engines, has been joined to one of the most complicated and intricate parts of NASA’s Space Launch System, the engine section. The engine section comprises the lowest portion of the massive core stage of the deep space rocket. It houses four RS-25 engines that will produce 2 million pounds of thrust to send the rocket and NASA’s Orion spacecraft on lunar missions. 27)

- NASA is charged to get American astronauts to the Moon by 2024. Our backbone for deep space exploration is SLS, the Orion spacecraft, which will launch from NASA’s Kennedy Space Center in Florida on missions to the Gateway in lunar orbit for missions to the surface of the Moon. The agency will launch SLS and Orion on their first integrated test flight around the Moon in 2020.

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Figure 28: Technicians moved the engine section and boat-tail for final assembly to a climate-controlled area of NASA’s Michoud Assembly Facility in New Orleans. Engineers will use the new tool and an internal access kit to finish assembly. The tool, seen here in the blue frame around the bottom of the engine section, allows more people to work on engine section tasks at the same time — accelerating the pace of production and reducing engine section integration and assembly time. This tool, along with other production and processing improvements, will help enable the core stage to be completed this year. The liquid oxygen tank structural test article as well as the liquid hydrogen tank flight hardware for the first mission of SLS are located just behind the engine section (image credit: NASA)

• April 15, 2019: America’s powerful new deep space rocket, NASA’s SLS (Space Launch System), will face harsh conditions and extreme temperatures in flight when launching NASA’s Orion spacecraft and potential cargo to lunar orbit, and for that, it’ll need strong protection. 28)

- Technicians and engineers have qualified 3D printing to aid in the application of the thermal protection system to the smaller, more intricate parts of the rocket. Spray-on foam or traditional insulation is applied to both large and small components of SLS; it protects the rocket from heat during launch and keeps the propellant within the large tanks cold.

- However, small hardware or cramped areas like the internal ducts of the engine section require technicians to either manually spray the foam on or apply a foam casting using, in some cases, a 3D printed mold. During the process, the foam, which is mixed and poured into the mold, expands to perfectly fit the part. This decreases overall processing time by reducing the need for complex and tedious post-process trimming.

- NASA and Boeing engineers performed extensive development and qualification pour foam testing early in the program. Using this data, the team developed a refined process that reduced the amount of time required to certify individual 3D printed molds and allowed the team to spend more time focusing on the critical requirements that must be met for each flight foam application. This streamlined the process, from 3D printing to pour application, and allowed for quicker processing times.

- NASA is charged to get American astronauts to the Moon by 2024. Our backbone for deep space exploration is SLS and Orion, which will launch from NASA’s Kennedy Space Center in Florida to the Gateway in lunar orbit. From there, astronauts will ultimately use a proposed human lunar landing system for missions to the surface of the Moon.

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Figure 29: A Space Launch System (SLS) rocket model is prepped for wind tunnel testing by Courtney Winski, aerospace engineer, at the Unitary Plan Wind Tunnel at NASA's Langley Research Center in Hampton, Virginia. The pink pressure-sensitive paint on the 0.8 percent scale model emits a bright crimson glow when reacting with oxygen in the presence of high-pressure airflows. This test allows engineers to understand changing pressures exerted on the rocket during a launch (image credit: NASA)

• April 4, 2019: NASA is a step closer to returning astronauts to the Moon in the next five years following a successful engine test on Thursday at NASA’s SSC (Stennis Space Center) near Bay St. Louis, Mississippi. The latest “hot fire” was the culmination of four-plus years of testing for the RS-25 engines that will send the first four Space Launch System (SLS) rockets into space. 29)

- “This completes four years of focused work by an exceptional Stennis test team,” Stennis Director Rick Gilbrech said. “It represents yet another chapter in Stennis’ long history of testing leadership and excellence in support of this nation’s space exploration efforts. Everyone involved should feel proud of their work and contributions.”

- Thursday’s hot fire on Stennis’ A-1 Test Stand completed:

a) Acceptance testing of all 16 former space shuttle main engines that will help launch the first four SLS missions. NASA has contracted with Aerojet Rocketdyne to build new RS-25 engines for additional SLS missions, and work already is underway to do so in the company’s factory in Canoga Park, California.

b) Developmental and flightworthy testing for new controllers (plus one spare) to be used by the heritage RS-25 engines for the first four missions.

c) A 51-month test series that demonstrated RS-25 engines can perform at the higher power level needed to launch the super heavy-lift SLS rocket.

- “Engines are now a ‘go’ for missions to send astronauts forward to the Moon to learn and prepare for missions to Mars,” said Johnny Heflin, deputy manager of the SLS Liquid Engines Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “We’re ready to provide the power to explore the Moon and beyond.”

- The RS-25 rocket engine test era began Jan. 9, 2015, with a 500-second – more than 8 minute – hot fire of RS-25 developmental engine No. 0525 on the A-1 Test Stand at Stennis. NASA tested the first SLS flight engine on March 10, 2016. Altogether, the agency has conducted 32 developmental and flight engine tests for a total of 14,754 seconds – more than four hours – of cumulative hot fire – all on the A-1 stand at Stennis.

- Having launched 135 space shuttle missions, these main engines are considered the most tested engines in the world. When the Space Shuttle Program ended in 2011, NASA still had 16 engines that ultimately were modified for SLS.

- These engines were originally designed to perform at a certain power level, known as 100 percent. Over time, the engines were upgraded to operate at higher and higher power levels, up to 104.5 percent operating power level by the end of the shuttle program. For SLS, that operating level has to be pushed even higher.

- To help accomplish that, and to interface with new rocket avionics systems, NASA designed and tested a new engine controller, which serves as the “brain” of the engine to help monitor engine operation and facilitate communication between the engine and rocket. Early developmental testing at Stennis provided critical information for designing the new controller.

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Figure 30: RS-25 flight engine No. 2062 is lifted onto the A-1 Test Stand at NASA’s Stennis Space Center near Bay St. Louis, Miss. The Aerojet Rocketdyne-built engine was delivered to the stand March 20 and test fired April 4 (image credit: NASA/SSC)

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Figure 31: NASA conducts a test of RS-25 flight engine No. 2062 on April 4 on the A-1 Test Stand at Stennis Space Center near Bay St. Louis, Miss. The test marked a major milestone in NASA’s march forward to Moon missions. All 16 RS-25 engines that will help power the first four flights of NASA’s new Space Launch System rocket now have been tested (image credit: NASA/SSC)

- The first new flight engine controller was tested at Stennis in March 2017, with a string of controller hot fires to follow. The April 4 test marked the testing of the 17th engine controller for use on SLS flights, providing enough for all 16 heritage RS-25 engines.

- With development of the new controllers, NASA had to test the new power level as well. First, it was demonstrated that the engine could perform at the needed 111 percent power level. Next, NASA needed to prove a margin of operating safety.

- In February 2018, operators pushed the engine to 113 percent power for a total of 50 seconds. It lengthened that firing time in two subsequent tests, until late this February, when the engine was fired at 113 percent power for 430 seconds of a 510-second test.

- That set the stage for Thursday’s successful test of flight engine No. 2062. When this specific engine fires again, it will help send astronauts aboard Orion around the Moon on a test flight known as Exploration Mission-2.

Figure 32: NASA is going to the Moon and on to Mars, in a measured, sustainable way. Working with U.S. companies and international partners, NASA will push the boundaries of human exploration forward to the Moon. NASA is working to establish a permanent human presence on the Moon within the next decade to uncover new scientific discoveries and lay the foundation for private companies to build a lunar economy (video credit: NASA, Published on 11 March 2019)

• March 19, 2019: NASA and its industry partners continue their steady progress toward launching the nation's newest rocket, NASA's Space Launch System (SLS). Engineers and technicians at NASA's Marshall Space Flight Center in Huntsville, Alabama, are integrating components with the SLS launch vehicle stage adapter, which connects the core stage of the world's most powerful rocket with its interim cryogenic propulsion stage (ICPS) that provides the power to send Orion to the Moon. 30)

- One newly installed piece of hardware — the frangible joint assembly — is designed to break apart, allowing the hardware elements to separate during flight. When a remote command is given, pistons fitted inside the ring assembly push upward, instantaneously separating the upper part of the rocket from the adapter and core stage.

- Frangible joint assemblies are widely used in a variety of crewed and uncrewed spacecraft to efficiently separate fairings or stages during launch and orbital ascent and to execute payload deployment. Once the frangible joint assembly is mated with the launch vehicle stage adapter and its pneumatic actuation system is installed, Marshall SLS workers will ship the hardware to NASA's Kennedy Space Center in Florida, where technicians will "stack" the vehicle for final flight preparation. NASA's Space Launch System and Orion spacecraft will pave the way for human missions to the Moon and Mars and groundbreaking new discoveries.

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Figure 33: NASA teams install key SLS Stage Separation Mechanism. NASA and its industry partners continue their steady progress toward launching the nation's newest rocket, NASA's Space Launch System (SLS). Engineers and technicians at NASA's Marshall Space Flight Center in Huntsville, Alabama, are integrating components with the SLS launch vehicle stage adapter (image credit: NASA)

• March 8, 2019: NASA will soon return humans to the Moon for decades to come, and the system that will transport astronauts from Earth to the Gateway near the Moon is literally coming together. Building on progress in 2018, most of the major manufacturing for the first mission is complete, and this year, teams will focus on final assembly, integration, and testing, as well as early work for future missions. NASA is focused on launching the first mission, Exploration Mission-1 (EM-1), in 2020 to send an Orion spacecraft on the SLS (Space Launch System) rocket from the modernized spaceport at Kennedy Space Center in Florida on an uncrewed test flight before sending crew around the Moon and back on the second mission, Exploration Mission-2 (EM-2) by 2023. 31)

- For the Orion spacecraft that will fly on EM-1, engineers will continue stacking the crew and service modules together at Kennedy and performing tests to ensure the modules operate properly together. In the summer, the stacked modules will fly aboard the agency’s Guppy aircraft to NASA’s Plum Brook Station in Sandusky, Ohio, where together they will undergo thermal vacuum testing as well as electromagnetic interference and compatibility evaluations during a four-month test campaign. When Orion returns from Ohio, it will undergo final checks and processing before final preparations for launch and integration with SLS.

- At the same time, Orion teams are also working on the spacecraft and other critical systems for the second mission that will carry a crew of astronauts around the Moon and back. Engineers will continue outfitting and testing the crew module, including pressuring the capsule to verify its structural integrity, powering it on for the first time to ensure it can route commands properly, and routing electrical and propulsion lines. Teams will also perform welding for the environmental control system and fit it for the outer back shells and heatshield.

- In preparation for the first mission with crew, the agency will also test the spacecraft’s launch abort system this June to demonstrate that it can carry the crew to safety if an emergency were to happen on the way to space. During the three-minute test, called Ascent Abort-2, a booster will carry an Orion test vehicle to an altitude of 31,000 feet at more than 1,000 mph to test the launch abort system when the spacecraft is under the highest aerodynamic loads it will experience during a rapid climb into space.

The Rocket — Space Launch System (SLS)

- Technicians at NASA’s Michoud Assembly Facility in New Orleans are nearly finished with production of the first flight’s core stage, the largest element of the most powerful rocket in the world. Technicians have almost completed outfitting the engine section, the complex bottom section of the core stage. Its sophisticated systems feed propellant to the four RS-25 engines. The section will be joined to the 130-foot-long liquid hydrogen propellant tank to form the stage’s aft section. The aft section will then be connected to the 66-foot forward section, which consists of the forward skirt, liquid oxygen tank, and intertank, in a horizontal configuration to form the full stage.

- The four core stage engines for EM-1 will be delivered to Michoud later this year and installed into the core stage engine section. NASA’s Pegasus barge will move the completed stage to Stennis Space Center near Bay St. Louis, Mississippi, where all four engines will roar to life to test the completed stage.

- The team at Stennis has already completed two engine tests this year, concluding a series of nine tests that began last August. This spring, NASA will mark a major milestone to complete testing of all engines for the first four SLS missions. Aerojet Rocketdyne has already started making the engines for additional flights with the goal of reducing the costs of manufacturing by at least 30 percent using smart manufacturing techniques.

- The last structural test article for the core stage, a full-sized flight-like liquid oxygen tank, will arrive at Marshall Space Flight Center in Huntsville, Alabama, this summer on the Pegasus barge. Engineers will finish up structural testing on the intertank and liquid hydrogen tank and then begin with the liquid oxygen tank to push the hardware to the limits under forces that exceed what the hardware will experience in flight. Testing will also continue for multiple avionics and software systems this year as well.

- Building and moving the 212-foot-tall core stage, the largest rocket stage that NASA has ever built, has been one of the most challenging aspects of SLS construction. NASA is applying this experience to the core stage for the second mission, which is already in production.

- Engineers at Marshall, are putting the finishing touches on the 30-foot-tall launch vehicle stage adapter that will connect the top of the core stage to the interim cryogenic propulsion stage, which was previously delivered to Kennedy. This year, Pegasus will deliver the adapter to Kennedy. The SLS booster team in Utah finished the ten solid rocket motor segments needed for EM-1 earlier this year, and they will also be delivered to Kennedy when needed, where they will join other booster parts.

- For the second SLS flight, building is complete for most of the barrels, domes and other structures needed to build the core stage for EM-2. Nearly all the solid rocket motor sections for the boosters on the second mission are cast and being outfitted. Teams are beginning work on additional parts including the Orion Stage Adapter where other small payloads can be carried, the launch vehicle stage adapter and the interim cryogenic propulsion stage.

Kennedy Space Center — Ground Systems

- At Kennedy, the Exploration Ground Systems team also has a busy year ahead in 2019. The crawler team will finish engine maintenance and crawlerway conditioning, and engineers will complete testing of the mobile launcher in the Vehicle Assembly Building. In the spring, the mobile launcher will roll back out to Pad 39B for its final testing at the pad. NASA plans to award a contract for a second mobile launcher this year, allowing more flexibility for upcoming exploration missions.

- At the pad, engineers will start to install a new liquid hydrogen tank that will be used for EM-2. In firing rooms 1 and 2, final upgrades will be made while the launch team finalizes the new countdown procedures for SLS. Teams across the agency will participate in flight simulations with the launch control center at Kennedy, mission control center at Johnson and the SLS Engineering Support Center at Marshall. By the end of 2019, EGS will begin processing the Orion crew capsule and SLS hardware for launch of EM-1.

• January 31, 2019: NASA and its industry partners have completed manufacture and checkout of 10 motor segments that will power two of the largest solid propellant boosters ever built. The solid rocket fuel will help produce 8.8 million pounds of thrust (35.585 MN) to send NASA's Space Launch System rocket on its first integrated flight with the Orion spacecraft. Technicians at Northrop Grumman in Promontory, Utah, in coordination with SLS program leads at NASA's Marshall Space Flight Center in Huntsville, Alabama, finalized the fabrication of all 10 motor segments and fitted them with key flight instrumentation. 32)

- They'll be shipped to NASA's Kennedy Space Center in Florida, joined with booster forward and aft assemblies, and readied to power the SLS Exploration Mission-1 test flight when it launches from Kennedy. The uncrewed test launch will pave the way for a new era of groundbreaking science and exploration missions beyond low-Earth orbit, carrying crew and cargo to the Moon and on to Mars. Marshall manages the Space Launch System for NASA.

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Figure 34: NASA completes booster motor segments for first Space Launch System flight (image credit: NASA)

• January 15, 2019: The largest piece of structural test hardware for America’s new deep space rocket, the SLS (Space Launch System), was loaded into Test Stand 4693 at NASA’s Marshall Space Flight Center in Huntsville, Alabama on 14 January 2019. The liquid hydrogen tank is part of the rocket’s core stage that is more than 200 feet tall (61 m) with a diameter of 27.6 feet (8.4 m), and stores cryogenic liquid hydrogen and liquid oxygen that will feed the vehicle’s RS-25 engines. The liquid hydrogen tank test article is structurally identical to the flight version of the tank that will comprise two-thirds of the core stage and hold 537,000 gallons of supercooled liquid hydrogen at minus 423 degrees Fahrenheit (20.4 K). Dozens of hydraulic cylinders in the 215-foot-tall test stand will push and pull the tank, subjecting it to the same stresses and loads it will endure during liftoff and flight. 33)

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Figure 35: Photo of the SLS liquid hydrogen tank test in the test stand at NASA/MSFC in Huntsville, Alabama (image credit: NASA/Tyler Martin)

• December 14, 2018: Technicians at NASA's Michoud Assembly Facility in New Orleans, moved the largest piece of structural test hardware for America's new deep space rocket, the Space Launch System, from the factory to the dock where it was loaded onto NASA's barge Pegasus on 14 December 2018. 34)

- The liquid hydrogen tank test article will make its way up the river to NASA’s Marshall Space Flight Center in Huntsville, Alabama, where dozens of hydraulic cylinders in Test Stand 4693 will push and pull on the giant tank, subjecting it to the same stresses and loads it will endure during liftoff and flight. The test hardware is structurally identical to the flight version of the liquid hydrogen tank that will comprise two-thirds of the core stage and hold 537,000 gallons of liquid hydrogen cooled to minus 423 degrees Fahrenheit (20.4 K).

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Figure 36: Photo of the SLS liquid hydrogen tank test article transport at the Michoud Assembly Facility (image credit: NASA/Steven Seipel)

• December 13, 2018: Northrop Grumman Corporation along with NASA and Lockheed Martin successfully performed a ground firing test of the abort motor for NASA’s Orion spacecraft LAS (Launch Abort System) at Northrop Grumman’s facility in Promontory, Utah (Figure 37). The abort motor is a major part of the LAS, which provides an enhancement in spaceflight safety for astronauts. The completion of this milestone brings Orion one step closer to its first flight atop NASA’s Space Launch System and to enabling humans to explore the moon, Mars and other deep space destinations beyond low-Earth orbit. 35)

- “Our astronauts’ safety is our top priority,” said Steve Sara, director, launch abort motor program, Northrop Grumman. “We never expect the launch abort motor to be used, but just like an ejection seat in a fighter pilot's aircraft, if they need it, it needs to work every time.”

- The mission for Orion’s LAS is to safely jettison the spacecraft and crew out of harm’s way in the event of an emergency on the launch pad or during initial launch ascent. Today’s abort motor test, Qualification Motor-2, was the culmination of a series of component tests conducted over the past few years in preparation for qualification. Data from the test will confirm the motor can activate within milliseconds and will perform as designed under cold temperatures.

- The abort motor, which stands over 17 feet tall and spans three feet in diameter, has a manifold with four exhaust nozzles. With its nozzles pointing skyward, it fired for five seconds; the exhaust plume flames reached approximately 100 feet in height. The high-impulse motor burns three times faster than a typical motor of this size, delivering the thrust needed to pull the crew module to safety. The motor achieved approximately 350,000 pounds of thrust (1556 kN) in one eighth of a second, as expected. More analysis will be performed in the coming weeks, but all initial results indicate a successful test.

- Northrop Grumman’s next major abort motor milestones include the Ascent Abort-2 Flight Test (AA-2) set to take place at Cape Canaveral Air Force Station, Florida, in 2019. Previous large-scale tests of the launch abort motor included a development motor test in 2008, a pad abort test of the complete launch abort system in 2010 and the Qualification Motor-1 static test in 2017.

- For the AA-2 flight test, in addition to the launch abort motor Northrop Grumman will also provide the ATB (Abort Test Booster ), which will launch NASA’s Orion spacecraft and LAS to on a preplanned trajectory to obtain data to be used for LAS performance assessment. The ATB uses the same rocket motor as the first stage of a Minotaur IV rocket.

- Northrop Grumman is responsible for the launch abort motor through a contract to Lockheed Martin, Orion’s prime contractor. The Orion LAS program is managed out of NASA’s Langley Research Center in Virginia. Northrop Grumman produces the abort motor at its Magna, Utah facility and the attitude control motor at its Elkton, Maryland facility. The company also manufactures the composite case for the abort motor at its facility in Clearfield, Utah.

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Figure 37: Today’s test firing of the Northrop Grumman-manufactured launch abort motor in Promontory, Utah, confirmed the motor can activate within milliseconds and will perform as designed under cold temperatures (image credit: Northrop Grumman, NASA)

• August 2018: Upper Stage and Adapters: At the forward section of the rocket, just below the Orion crew vehicle, is the OSA (Orion Stage Adapter), which holds the secondary payload accommodations. For EM-1, the OSA is complete and was delivered to EGS in February 2018. Made of a lightweight aluminum alloy, the OSA measures 5.4 m in diameter by 1.5 m high. A diaphragm just below the mounting brackets prevents launch gases from entering the Orion spacecraft. 36)

- Sitting just below the OSA, the ICPS (Interim Cryogenic Propulsion Stage), a modified Delta Cryogenic Second Stage manufactured by ULA in Decatur, Ala. through a contract with Boeing, supplies in-space propulsion for the Block 1 vehicle. The ICPS will provide the TLI burn to send Orion toward the moon during the EM-1 mission. After entering its disposal trajectory with the OSA attached, the ICPS will release the first seven CubeSats (Figure 38).

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Figure 38: Photo of the ICPS, which will provide in-space propulsion for the first integrated flight of SLS and Orion, is complete (image credit: NASA)

• August 14, 2018: NASA Administrator Jim Bridenstine made his first official visit to NASA’s rocket factory, the Michoud Assembly Facility in New Orleans, Louisiana, on Aug. 13, for tours and briefings on progress building the Space Launch System rocket and Orion spacecraft. 37)

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Figure 39: NASA Administrator Jim Bridenstine speaks with members of the media in front of the massive liquid hydrogen tank, which comprises almost two-thirds of the core stage and holds 537,000 gallons (2032 cm3) of liquid hydrogen cooled to minus 423º Fahrenheit (-252ºC). Innovative processes are part of core stage manufacturing including joining the thickest pieces of aluminum ever with self-reacting friction stir welding. The liquid oxygen tank and liquid hydrogen tanks have the thickest joints ever made with self-reacting friction stir welding (image credit: NASA, Jude Guidry)

- Bridenstine, joined by Jody Singer, acting director of NASA's Marshall Space Flight Center and Keith Hefner, director of Michoud, toured the massive facility where manufacturing and assembly of the largest and most complex parts of SLS and Orion are underway. SLS will send the Orion spacecraft, astronauts and critical hardware on bold exploration missions to the Moon and beyond.

- The tour highlighted the SLS core stage which, flanked by two solid rocket boosters, will provide the thrust to propel the vehicle to deep space. The administrator had the opportunity to view SLS hardware just as engineers are putting the finishing touches on the core stage parts by testing avionics, installing special equipment inside the structures and applying thermal protection systems.

- Bridenstine also viewed Orion's latest milestone, the welding completion of the primary structure of the crew module, or pressure vessel, by engineers at Michoud. The pressure vessel is the primary structure that holds the pressurized atmosphere astronauts will breathe to allow them to work in the harsh environment of deep space. This pressure vessel will carry the first astronauts to missions beyond the Moon on Exploration Mission-2.

- "This is a critical piece of America's architecture for our return to the Moon and ultimately, it's a strategic capability for the United States of America," said Bridenstine. "I cannot overstate how important this capability is to America and how all of the team members who work here are contributing to a capability where countries around the world are seeking to partner with the United States as we return to the surface of the Moon and into orbit around the Moon."

• July 31, 2018: The first major piece of core stage hardware for NASA's SLS (Space Launch System) rocket has been assembled and is ready to be joined with other hardware for Exploration Mission-1. The forward skirt will connect the upper part of the rocket to the core stage and house many of the flight computers, or avionics. 38)

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Figure 40: The first major piece of core stage hardware for NASA's Space Launch System rocket has been assembled and is ready to be joined with other hardware for Exploration Mission-1. The forward skirt will connect the upper part of the rocket to the core stage and house many of the flight computers, or avionics (image credit: NASA, Eric Bordelon)

- The backbone of the world's most powerful rocket, the 212-foot-tall (64.6 m) core stage, will contain the SLS rocket's four RS-25 rocket engines, propellant tanks, flight computers and much more. Though the smallest part of the core stage, the forward skirt will serve two critical roles. It will connect the upper part of the rocket to the core stage and house many of the flight computers, or avionics.

- "Completion of the core stage forward skirt is a major step in NASA's progress to the launch pad," said Deborah Bagdigian, lead manager for the forward skirt at the agency's Marshall Space Flight Center in Huntsville, Alabama. "We're putting into practice the steps and processes needed to assemble the largest rocket stage ever built. With the forward skirt, we are improving and refining how we'll conduct final assembly of the rest of the rocket."

- On July 24, the forward skirt assembly was wrapped up with the installation of all its parts. As part of forward skirt testing, the flight computers came to life for the first time as NASA engineers tested critical avionic systems that will control the rocket’s flight. The construction, assembly and avionics testing occurred at NASA's Michoud Assembly Facility in New Orleans.

- Located throughout the core stage, the avionics are the rocket's "brains," controlling navigation and communication during launch and flight. It is critical that each of the avionics units is installed correctly, work as expected and communicate with each other and other components, including the Orion spacecraft and ground support systems.

- "It was amazing to see the computers come to life for the first time" said Lisa Espy, lead test engineer for SLS core stage avionics. "These are the computers that will control the rocket as it soars off the pad for Exploration Mission-1."

- The forward skirt test series was the first of many that will verify the rocket's avionics will work as expected during launch. The tests show the forward skirt was built correctly, and that all components and wiring on the inside have been put together and connected properly and are sending data over the lines as expected.

- The avionic computers ran "built-in tests" that Espy compares to the internal diagnostic tests performed by an automobile when first started. All of the health and data status reports came back as expected. The tests were a success and did not return any error codes. Such error codes would be similar to a check engine light on a car.

- The successful tests give the team the confidence needed to move forward with avionics installations in the core stage intertank and engine section. With more hardware and more interfaces, the installation in the intertank will be more complex, and the complexity will ramp up even more as the team moves to the engine section, introducing hydraulics and other hardware needed for the rocket's engines.

- Engineers will perform standalone tests on each component as they are completed. Once the forward and aft joins are integrated, they will perform a final integrated function test, testing all the core stage's avionics together.

- The fully integrated core stage and its four RS-25 engines will then be fired up during a final test before launch. At NASA's Kennedy Space Center in Florida, the core stage will be stacked with the upper part of the rocket, including Orion, and joined to the rocket's twin solid rocket boosters, in preparation for EM-1.

• July 10, 2018: Aerojet Rocketdyne recently passed a key milestone in preparation for the Ascent Abort Test (AA-2) next year with the successful casting of the Jettison Motor for the Lockheed Martin-built Orion spacecraft's LAS (Launch Abort System). AA-2 is a full-stress test of NASA's Orion LAS, which includes the Jettison Motor built by Aerojet Rocketdyne. The Orion Jettison Motor is used to separate the LAS from Orion as it makes its way to space and is the only motor on the escape system to activate in all mission scenarios. 39)

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Figure 41: The Jettison Motor built by Aerojet Rocketdyne for the Lockheed Martin-built Orion spacecraft's LAS (Launch Abort System) that will be tested during the Ascent Abort Test (AA-2) next year (image credit: Aerojet Rocketdyne)

- In the unlikely event of an emergency on the launch pad or during ascent, the LAS would activate within milliseconds to whisk Orion and its astronaut crew to safety. Once Orion reaches a safe distance from the rocket, the Orion Jettison Motor would ignite to separate the LAS structure from the spacecraft, which could then deploy its parachutes for a safe landing.

- During the AA-2 test, a solid rocket booster will launch a fully functional LAS and an Orion test vehicle to an altitude of 31,000 feet (~9.5 km) at Mach 1.3 (over 1,000 mph) to test out the functionality of the LAS system prior to flying humans. The Jettison Motor will fire last in the test sequence.

- "Every time our engineers work on products supporting the Orion spacecraft or the Space Launch System rocket, they have astronaut safety front and center of mind," said Aerojet Rocketdyne CEO and President Eileen Drake. "The AA-2 test is a critical step to testing the Launch Abort System and our Jettison Motor and ensuring our astronauts always return home safely to their families."

- The Orion Jettison Motor, which generates 40,000 pounds of thrust (177.928 kN), uses a propellant that is poured into a motor casing, where it cures over a period of several days to form a solid, stable cast that burns in a precisely controlled fashion.

- The AA-2 Jettison Motor casting took place at Aerojet Rocketdyne's motor production facility in Sacramento, California. The completed motor will now be shipped to NASA's Kennedy Space Center for integration with the LAS by Lockheed Martin.

• April 3, 2018: NASA's Super Guppy aircraft prepares to depart the U.S. Army’s Redstone Airfield in Huntsville, Alabama, April 3, with flight hardware for NASA’s Space Launch System – the agency’s new, deep-space rocket that will enable astronauts to begin their journey to explore destinations far into the solar system. The Orion stage adapter, the top of the rocket that connects SLS to Orion is loaded into the Guppy, which will deliver it to NASA’s Kennedy Space Center in Florida for flight preparations. On Exploration Mission-1, the first integrated flight of SLS and the Orion spacecraft, the adapter will carry 13 CubeSats as secondary payloads. SLS will send Orion beyond the Moon, about 280,000 miles from Earth. This is farther from Earth than any spacecraft built for humans has ever traveled. 40)

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Figure 42: SLS flight hardware is being transported in a Super Guppy from Huntsville AL to KSC (Kennedy Space Center) in Florida (image credit: NASA/MSFC, Fred Deaton)

• December 22, 2017: The booster avionics system for the SLS (Space Launch System) rocket completed system-level qualification testing in October 2017. Engineers simulated the booster avionics operations in a systems integration lab at NASA’s Marshall Space Flight Center in Huntsville, Alabama, where all the avionics boxes and electronics were tested. The tests verified the fidelity of the system. Two five-segment rocket boosters, developed by Orbital ATK, will provide 80 percent of the thrust for the first two minutes of flight. The booster avionics, receiving commands from the SLS flight computers in the core stage, provide 80 percent of the control authority for the rocket during the first two minutes of flight. Key interactions confirmed during qualification testing included the ability to initiate booster ignition, control the booster during flight, terminate flight, and triggering core stage separation. 41)

• December 15, 2017: When NASA’s Orion spacecraft hurtles toward Earth’s surface during its return from deep-space missions, the capsule’s system of 11 parachutes will assemble itself in the air and slow the spacecraft from 300 mph to a relatively gentle 20 mph for splashdown in the Pacific Ocean in the span of about 10 minutes. As the astronauts inside descend toward the water on future missions, their lives will be hanging by a series of threads that have been thoroughly ruggedized, tested and validated to ensure the parachute-assisted end of Orion missions are a success. 42)

- Through a series of tests in the Arizona desert, the engineers refining Orion’s parachutes have made the road to certifying them for flights with astronauts look easy, including a successful qualification test Dec. 13 that evaluated a failure case in which only two of the systems three orange and white main parachutes deploy after several other parachutes in the system used to slow and stabilize Orion endure high aerodynamic stresses. But behind the scenes, engineers are working hard to understand and perfect the system that must be able to work across a broad range of potential environmental conditions and bring the crew home.

- While Orion’s parachutes may look similar to those used during the Apollo-era to the untrained eye, engineers can’t simply take that parachute system and scale it up to accommodate Orion’s much larger size. Through testing and analysis, technicians have developed Orion’s parachutes to be lighter, better understood and more capable than Apollo’s. NASA has also been able to adjust the system as elements of the spacecraft, such as attachment points, have matured.

- “Through our testing, we’ve addressed some known failures that can happen in complex parachute systems to make the system more reliable,” said Koki Machin, chief engineer for the system. “We built upon the strong foundation laid by Apollo engineers and figured out how to manage the stresses on the system during deployment more efficiently, decrease the mass of the parachutes by using high tech fabric materials rather than metal cables for the risers that attach the parachute to the spacecraft, and improve how we pack the parachute into Orion so they deploy more reliably.”

- Orion’s parachute system is also incredibly complex. About 10 miles of Kevlar lines attach the spacecraft to the outer rim of nearly 12,000 square feet (~1110 m2) of parachute canopy material – over four times the average square footage of a house – and must not get tangled during deployment. In addition to the fabric parachutes themselves, there are cannon-like mortars that fire to release different parachutes. Embedded in several parachutes are fuses set to burn at specific times that ignite charges to push blades through bullet proof materials at precise moments, slowly unfurling the parachutes to continue the sequential phases of the deployment sequence. All of these elements must be developed to be reliable for the various angles, wind conditions and speeds in which Orion could land.

- With the analysis capabilities that exist today and the historical data available, engineers have determined that approximately 20-25 tests, rather than the more than 100 performed during the Apollo era, will give them enough opportunities to find areas of weakness in Orion’s parachute system and fix them. After the three remaining final tests next year, the system will be qualified for missions with astronauts.

- “There are things we can model with computers and those we can’t. We have to verify the latter through repeated system tests by dropping a test article out of a military aircraft from miles in altitude and pushing the parachutes to their various limits,” said CJ Johnson, project manager for the parachute system. “Lots of subtle changes can affect parachute performance and the testing we do helps us account for the broad range of possible environments the parachutes will have to operate in.”

- Orion parachute engineers have also provided data and insight from the tests to NASA’s Commercial Crew Program partners. NASA has matured computer modeling of how the system works in various scenarios and helped partner companies understand certain elements of parachute systems, such as seams and joints, for example. In some cases, NASA’s work has provided enough information for the partners to reduce the need for some developmental parachute tests.

- “Orion’s parachute system is an extremely lightweight, delicate collection of pieces that absolutely must act together simultaneously or it will fail,” said Machin. “It alone, among all the equipment on the crew module, must assemble itself in mid-air at a variety of possible velocities and orientations.”

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Figure 43: NASA is testing Orion’s parachutes to qualify the system for missions with astronauts (image credits: U.S. Army)

• November 8, 2017: NASA is providing an update on the first integrated launch of the Space Launch System (SLS) rocket and Orion spacecraft after completing a comprehensive review of the launch schedule. This uncrewed mission, known as Exploration Mission-1 (EM-1) is a critical flight test for the agency’s human deep space exploration goals. EM-1 lays the foundation for the first crewed flight of SLS and Orion, as well as a regular cadence of missions thereafter near the Moon and beyond. 43)

- The review follows an earlier assessment where NASA evaluated the cost, risk and technical factors of adding crew to the mission, but ultimately affirmed the original plan to fly EM-1 uncrewed. NASA initiated this review as a result of the crew study and challenges related to building the core stage of the world’s most powerful rocket for the first time, issues with manufacturing and supplying Orion’s first European service module, and tornado damage at the agency’s Michoud Assembly Facility in New Orleans.

- “While the review of the possible manufacturing and production schedule risks indicate a launch date of June 2020, the agency is managing to December 2019,” said acting NASA Administrator Robert Lightfoot. “Since several of the key risks identified have not been actually realized, we are able to put in place mitigation strategies for those risks to protect the December 2019 date.”

- The majority of work on NASA’s new deep space exploration systems is on track. The agency is using lessons learned from first time builds to drive efficiencies into overall production and operations planning. To address schedule risks identified in the review, NASA established new production performance milestones for the SLS core stage to increase confidence for future hardware builds. NASA and its contractors are supporting ESA’s (European Space Agency) efforts to optimize build plans for schedule flexibility if sub-contractor deliveries for the service module are late.

- NASA’s ability to meet its agency baseline commitments to EM-1 cost, which includes SLS and ground systems, currently remains within original targets. The costs for EM-1 up to a possible June 2020 launch date remain within the 15 percent limit for SLS and are slightly above for ground systems. NASA’s cost commitment for Orion is through Exploration Mission-2. With NASA’s multi-mission approach to deep space exploration, the agency has hardware in production for the first and second missions, and is gearing up for the third flight. When teams complete hardware for one flight, they’re moving on to the next.

- As part of the review, NASA now plans to accelerate a test of Orion’s launch abort system ahead of EM-1, and is targeting April 2019. Known as Ascent-Abort 2, the test will validate the launch abort system’s ability to get crew to safety if needed during ascent. Moving up the test date ahead of EM-1 will reduce risk for the first flight with crew, which remains on track for 2023.

• November 8, 2017: Lift off at the end of the countdown is just the first phase in a launch. Two minutes in, booster separation occurs ­– a critical stage in flight, with little room for error. Engineers at NASA’s Langley Research Center in Hampton, Virginia, are doing their part to support NASA’s new deep space rocket, the SLS (Space Launch System). The rocket will be capable of sending the Orion crew vehicle and other large cargos on bold new missions beyond Earth orbit. To understand the aerodynamic forces as booster separation motors fire and push the solid rocket boosters away from the rocket’s core, Langley engineers are testing a 35-inch SLS model in Block 1B 105-metric ton evolved configuration in the Unitary Plan Wind Tunnel using a distinct pink paint. The pressure-sensitive paint works by reacting with oxygen to fluoresce at differing intensities, which is captured by cameras in the wind tunnel. Researchers use that data to determine the airflow over the model and which areas are seeing the highest pressure. 44)

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Figure 44: Wind tunnel test of the SLS booster separation model in Block 1B (image credit: NASA/LaRC)

• October 19, 2017: NASA engineers conducted a full-duration, 500-second test of RS-25 flight engine E2063 on the A-1 Test Stand at SSC (Stennis Space Center) on Oct. 19, 2017. Once certified, the engine is scheduled to help power NASA’s new Space Launch System rocket on its EM-2 (Exploration Mission-2). The test was part of Founders Day Open House activities at Stennis. 45)

- Engine E2063 is scheduled for use on NASA’s second mission of SLS and Orion, known as EM-2. The first integrated flight test of SLS and Orion, EM-1 (Exploration Mission-1), will be an uncrewed final test of the rocket and its systems. The EM-2 flight will be the first to carry astronauts aboard the Orion spacecraft, marking the return of humans to deep space for the first time in more than 40 years.

• September 22, 2017: Following a series of issues over the last year with the Core Stage for the first flight of the Space Launch System rocket, the launch dates for both the EM-1 and EM-2 flights are beginning to align, with EM-1 now targeting 'No Earlier Than' 15 December 2019 and EM-2 following on 1 June 2022. Additionally, the EM-3 flight has gained its first notional mission outline, detailing a flight to Near-Rectilinear Halo Orbit to deploy the Hab (Habitat) module for the new Deep Space Gateway. 46)

- The first flight of any new rocket is bound to encounter design and initial production delays. And NASA’s SLS (Space Launch System ) rocket is been no stranger to those sort of anticipated effects. - Following a misalignment in the installation of the main welding machine at the Michoud Assembly Facility (MAF), welding for the certification elements for the new SLS core stage Liquid Hydrogen (LH2) and Liquid Oxygen (LOX) tanks picked up.

- After the initial LH2 qualification tanks were welded, a change to the welding machine’s pin was made – a change that resulted in segment welds on the EM-1 LH2 flight tank being too brittle to meet flight specification requirements.

- This pin change and subsequent issue led to the understanding that the LH2 flight tank for EM-1 was no longer flight worthy and thus could not be used for EM-1.

- A plan was then put in place to restore the welding machine’s previously used pin – the one that welded all the Core Stage test articles that have thus far passed all qualification and acceptance testing – and use the upcoming weld for the EM-2 flight LH2 tank as the new LH2 tank for the EM-1 flight.

- However, less than a week after the EM-1 LH2 flight tank issue became known, a worker at MAF damaged the aft dome section of the qualification article for the Core Stage LOX tank.

- In all, these production issues quickly made the Core Stage’s timeline for EM-1’s then-2018 launch date impossible.

- Earlier this year, NASA acknowledged this and announced that EM-1 was slipping to sometime in 2019 – though that was already understood to be “Q4 2019.”



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20) ”SLS Rocket Pathfinders Prepare Teams for One-of-a-Kind Hardware Prior to Moon Mission,” NASA, 27 September 2019, URL: https://www.nasa.gov/exploration/
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21) ”NASA Joins Last of Five Sections for Space Launch System Rocket Stage,” NASA, 19 September 2019, URL: https://www.nasa.gov/exploration/systems/sls/five-sections-joined-for-sls-rocket-stage.html

22) ”Engine Section for NASA's SLS Rocket Moved for Final Integration,” NASA, 4 September 2019, URL: https://www.nasa.gov/exploration/systems/sls/multimedia/engine-section-moved-for-final-integration.html

23) ”SLS Rocket Engine Section Completed for Artemis I,” NASA, 30 August 2019, URL: https://www.nasa.gov/exploration/systems/sls/multimedia/engine-section-completed-for-artemis-I.html

24) Jennifer Harbaugh,”“Green Run” Test Will Pave the Way for Successful NASA Moon Missions,” NASA, 26 July 2019, URL: https://www.nasa.gov/exploration/
systems/sls/green-run-test-paves-way-for-nasa-moon-missions.html

25) ”SLS Core Stage Receives Four RS-25 Engines for First Flight,” SPaceRef, 28 June 2019, URL: http://spaceref.com/news/viewpr.html?pid=54273

26) Jennifer Harbaugh, ”Last Test Article for NASA’s SLS Rocket Departs Michoud Assembly Facility ,” NASA, 27 June 2019, URL: https://www.nasa.gov/exploration/
systems/sls/multimedia/last-test-article-for-sls-departs-maf.html

27) ”NASA Accelerates Pace of Core Stage Production with New Tool,” NASA, 16 April 2019, URL: https://www.nasa.gov/exploration/systems/sls/new-tool-accelerates-pace-of-core-stage-production.html

28) ”NASA Takes Advantage of Innovative 3-D Printing Process for SLS Rocket,” NASA Image of the day, 15 April 2019; URL: https://www.nasa.gov/exploration/
systems/sls/multimedia/3-d-printing-process-for-sls-rocket.html

29) Valerie Buckingham, LaToya Dean, ”NASA Achieves Rocket Engine Test Milestone Needed for Moon Missions,” NASA Release S19-007, 4 April 2019, URL: https://www.nasa.gov/centers/
stennis/news/NASA-Achieves-Rocket-Engine-Test-Milestone-Needed-for-Moon-Missions

30) ”NASA Teams Install Key Space Launch System Stage Separation Mechanism,” NASA, 19 March 2019, URL: https://www.nasa.gov/exploration/systems/sls/
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31) Kathryn Hambleton, ”NASA’s Deep Space Exploration System is Coming Together,” NASA SLS, 8 March 2019, URL: https://www.nasa.gov/feature/nasa-s-deep-space-exploration-system-is-coming-together

32) Jennifer Harbaugh, ”NASA Completes Booster Motor Segments for First Space Launch System Flight,” NASA, 31 January 2019, URL: https://www.nasa.gov/exploration
/systems/sls/booster-motor-segments-completed-for-first-flight

33) Jennifer Harbaugh, ”SLS Liquid Hydrogen Tank Test Article Loaded into Test Stand,” NASA, 15 January 2019, URL: https://www.nasa.gov/exploration/systems/sls/multimedia
/liquid-hydrogen-tank-test-article-loaded-into-test-stand.html

34) ”Largest piece of SLS rocket test hardware moved for testing,” NASA Space Launch System, 14 December 2018, URL: https://www.nasa.gov/exploration/systems/sls/
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35) ”Static test qualifies crew safety launch abort motor for flight in cold conditions,” Northrop Grumman, 13 December 2018, URL: https://news.northropgrumman.com/news/
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36) Kimberly F. Robinson, Scott F. Spearing, David Hitt, ”NASA’s Space Launch System: Opportunities for Small Satellites to Deep Space Destinations,” Proceedings of the 32nd Annual AIAA/USU Conference on Small Satellites, Logan UT, USA, Aug. 4-9, 2018, paper: SSC18-IX-02, URL: https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=4119&context=smallsat

37) Janet Anderson, Jennifer Harbaugh, ”NASA Administrator Views Progress Building SLS and Orion Hardware,” NASA, 14 August 2018, URL: https://www.nasa.gov/centers/
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38) ”First SLS Core Stage Flight Hardware Complete, Ready for Joining,” NASA, 31 July 2018, URL: https://www.nasa.gov/exploration/systems/sls/first-sls-core-stage-flight-hardware-complete-ready-for-joining

39) ”Orion Jettison Motor Ready for Crew Escape System Test,” Space Daily, 10 July 2018, URL: http://www.spacedaily.com/reports/Orion_Jettison_Motor_Ready_for_Crew_Escape_System_Test_999.html

40) Jennifer Harbaugh, ”NASA's Super Guppy Transports SLS Flight Hardware to Kennedy Space Center,” NASA, 3 April 2018, URL: https://www.nasa.gov/exploration/systems/sls/
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41) ”Space Launch System Solid Rocket Booster Avionics Complete Key Testing,” NASA, 22 Dec. 2017, URL: https://www.nasa.gov/langley/image-feature/
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42) Mark Garcia, ”Orion Parachute Tests Prove Out Complex System for Human Deep Space Missions,” NASA, 15 Dec. 2017, URL: https://www.nasa.gov/feature/
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43) ”NASA Completes Review of First SLS, Orion Deep Space Exploration Mission,” NASA, 8 Nov. 2017, URL: https://www.nasa.gov/feature/nasa-completes-review-of-first-sls-orion-deep-space-exploration-mission

44) ”Space Launch System Booster Separation Tested In Wind Tunnel,” NASA/LaRC, 8 Nov. 2017, URL: https://www.nasa.gov/langley/image-feature/space-launch-system-booster-separation-tested-in-wind-tunnel

45) ”NASA Showcases Flight Engine Test During Stennis Open House,” NASA, Press Release S17-072, 19 Oct. 2017, URL: https://www.nasa.gov/news/2017/
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46) Chris Gebhardt, ”SLS EM-1 & -2 launch dates realign; EM-3 gains notional mission outline,” NASA Spaceflight.COM, Sept. 22, 2017, URL: https://www.nasaspaceflight.com
/2017/09/sls-em-1-em-3-notional-mission-outline/



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 (herb.kramer@gmx.net).

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