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By NASA
3 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA Deputy Administrator Pam Melroy speaks at the Microgravity Science Summit at the Eisenhower Executive Office Building, Monday, Dec. 13, 2024, in Washington.Credit: NASA/Aubrey Gemignani NASA leadership participated in the White House Office of Science and Technology Policy’s Microgravity Science Summit (OSTP) on Dec.16 focused on sharing information with leaders across the U.S. federal government about the benefits of microgravity research. During the summit, NASA Deputy Administrator Pam Melroy, OSTP leadership, and others highlighted the importance of the government coming together to understand the transformative power of microgravity and lay the foundation for the next generation of research and innovation.
“The value of microgravity research has never been clearer. This unique environment offers us the chance to explore fundamental questions and test cutting-edge ideas in ways that simply are not possible under the constraints of Earth’s gravity,” said Melroy. “NASA has long been at the forefront of microgravity research, working in collaboration with a growing network of government partners, international space agencies, commercial partners, and academic institutions. Together, we have established a strong foundation for microgravity science aboard the International Space Station, but our work is far from finished. In fact, it’s only just beginning.”
The theme of the summit, “Building a Coalition for the Next Generation of Microgravity Research,” covered work currently being completed on the International Space Station to bring benefit back to Earth, open space to more people, and allow humans to travel farther into space for exploration. Leaders also heard about NASA’s plan to continue the work into the future on commercial space stations and build on the government’s efforts to maintain a national research capability in orbit.
In 2023, the Biden-Harris Administration released a National Low Earth Orbit Research and Development Strategy to provide an interagency strategy and action plan to enable U.S. government-wide collaboration and support of public-private partnerships to ensure continuity of access and sustainable low Earth orbit research and development activities. The strategy supports the United States Space Priorities Framework with a focus on scientific and technological innovation, economic growth, commercial development, and space-related STEM education and workforce development. The summit also included discussion on the great strides and potential for the future in cancer research, semiconductors, wildland fire management, and in space production applications.
“The key to success will be collaboration,” said Melroy. “What we are doing is building a vision for the future—one where microgravity is not a niche area of study, but an essential part of the scientific toolkit for tackling our biggest challenges, helping to improve our national capabilities and posture. A future where space isn’t just a far-off and mysterious destination—it’s an environment for collaboration, discovery, and progress.”
On Dec. 16, NASA also released its Low Earth Orbit Microgravity strategy outlining the agency’s long-term approach to advance microgravity science, technology, and exploration.
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By NASA
The Artemis II Orion spacecraft is lifted from the Final Assembly and Testing (FAST) Cell and placed in the west altitude chamber inside the Operations and Checkout Building at NASA’S Kennedy Space Center in Florida on June 28, 2024. Inside the altitude chamber, the spacecraft underwent a series of tests simulating deep space vacuum conditions.Photo Credit: NASA / Rad Sinyak After extensive analysis and testing, NASA has identified the technical cause of unexpected char loss across the Artemis I Orion spacecraft’s heat shield.
Engineers determined as Orion was returning from its uncrewed mission around the Moon, gases generated inside the heat shield’s ablative outer material called Avcoat were not able to vent and dissipate as expected. This allowed pressure to build up and cracking to occur, causing some charred material to break off in several locations.
“Our early Artemis flights are a test campaign, and the Artemis I test flight gave us an opportunity to check out our systems in the deep space environment before adding crew on future missions,” said Amit Kshatriya, deputy associate administrator, Moon to Mars Program Office, NASA Headquarters in Washington. “The heat shield investigation helped ensure we fully understand the cause and nature of the issue, as well as the risk we are asking our crews to take when they venture to the Moon.”
Findings
Teams took a methodical approach to understanding and identifying the root cause of the char loss issue, including detailed sampling of the Artemis I heat shield, review of imagery and data from sensors on the spacecraft, and comprehensive ground testing and analysis.
During Artemis I, engineers used the skip guidance entry technique to return Orion to Earth. This technique provides more flexibility by extending the range Orion can fly after the point of reentry to a landing spot in the Pacific Ocean. Using this maneuver, Orion dipped into the upper part of Earth’s atmosphere and used atmospheric drag to slow down. Orion then used the aerodynamic lift of the capsule to skip back out of the atmosphere, then reenter for final descent under parachutes to splashdown.
Using Avcoat material response data from Artemis I, the investigation team was able to replicate the Artemis I entry trajectory environment — a key part of understanding the cause of the issue — inside the arc jet facilities at NASA’s Ames Research Center in California. They observed that during the period between dips into the atmosphere, heating rates decreased, and thermal energy accumulated inside the heat shield’s Avcoat material. This led to the accumulation of gases that are part of the expected ablation process. Because the Avcoat did not have “permeability,” internal pressure built up, and led to cracking and uneven shedding of the outer layer.
After NASA’s Orion spacecraft was recovered at the conclusion of the Artemis I test flight and transported to NASA’s Kennedy Space Center in Florida, its heat shield was removed from the crew module inside the Operations and Checkout Building and rotated for inspection. Credit: NASA Teams performed extensive ground testing to replicate the skip phenomenon before Artemis I. However, they tested at much higher heating rates than the spacecraft experienced in flight. The high heating rates tested on the ground allowed the permeable char to form and ablate as expected, releasing the gas pressure. The less severe heating seen during the actual Artemis I reentry slowed down the process of char formation, while still creating gases in the char layer. Gas pressure built up to the point of cracking the Avcoat and releasing parts of the charred layer. Recent enhancements to the arc jet facility have enabled a more accurate reproduction of the Artemis I measured flight environments, so that this cracking behavior could be demonstrated in ground testing.
While Artemis I was uncrewed, flight data showed that had crew been aboard, they would have been safe. The temperature data from the crew module systems inside the cabin were also well within limits and holding steady in the mid-70s Fahrenheit. Thermal performance of the heat shield exceeded expectations.
Engineers understand both the material phenomenon and the environment the materials interact with during entry. By changing the material or the environment, they can predict how the spacecraft will respond. NASA teams unanimously agreed the agency can develop acceptable flight rationale that will keep crew safe using the current Artemis II heat shield with operational changes to entry.
NASA’s Investigation Process
Soon after NASA engineers discovered the condition on the Artemis I heat shield, the agency began an extensive investigation process, which included a multi-disciplinary team of experts in thermal protection systems, aerothermodynamics, thermal testing and analysis, stress analysis, material test and analysis, and many other related technical areas. NASA’s Engineering and Safety Center was also engaged to provide technical expertise including nondestructive evaluation, thermal and structural analysis, fault tree analysis, and other testing support.
“We took our heat shield investigation process extremely seriously with crew safety as the driving force behind the investigation,” said Howard Hu, manager, Orion Program, NASA’s Johnson Space Center in Houston. “The process was extensive. We gave the team the time needed to investigate every possible cause, and they worked tirelessly to ensure we understood the phenomenon and the necessary steps to mitigate this issue for future missions.”
The Artemis I heat shield was heavily instrumented for flight with pressure sensors, strain gauges, and thermocouples at varying ablative material depths. Data from these instruments augmented analysis of physical samples, allowing the team to validate computer models, create environmental reconstructions, provide internal temperature profiles, and give insight into the timing of the char loss.
Approximately 200 Avcoat samples were removed from the Artemis I heat shield at NASA’s Marshall Space Flight Center in Alabama for analysis and inspection. The team performed non-destructive evaluation to “see” inside the heat shield.
One of the most important findings from examining these samples was that local areas of permeable Avcoat, which had been identified prior to the flight, did not experience cracking or char loss. Since these areas were permeable at the start of the entry, the gases produced by ablation were able to adequately vent, eliminating the pressure build up, cracking, and char loss.
A test block of Avcoat undergoes heat pulse testing inside an arc jet test chamber at NASA’s Ames Research Center in California. The test article, configured with both permeable (upper) and non-permeable (lower) Avcoat sections for comparison, helped to confirm understanding of the root cause of the loss of charred Avcoat material that engineers saw on the Orion spacecraft after the Artemis I test flight beyond the Moon.Credit: NASA
Engineers performed eight separate post-flight thermal test campaigns to support the root cause analysis, completing 121 individual tests. These tests took place in facilities with unique capabilities across the country, including the Aerodynamic Heating Facility at the Arc-Jet Complex at Ames to test convective heating profiles with various test gases; the Laser Hardened Materials Evaluation Laboratory at Wright‐Patterson Air Force Base in Ohio to test radiative heating profiles and provide real-time radiography; as well as the Interaction Heating Facility at Ames to test combined convective and radiative heating profiles in the air at full-block scale.
Aerothermal experts also completed two hypersonic wind tunnel test campaigns at NASA’s Langley Research Center in Virginia and CUBRC aerodynamic test facilities in Buffalo, New York, to test a variety of char loss configurations and enhance and validate analytical models. Permeability testing was also performed at Kratos in Alabama, the University of Kentucky, and Ames to help further characterize the Avcoat’s elemental volume and porosity. The Advanced Light Source test facility, a U.S. Department of Energy scientific user facility at Lawrence Berkeley National Laboratory, was also used by engineers to examine the heating behavior of the Avcoat at a microstructure level.
In the spring of 2024, NASA stood up an independent review team to conduct an extensive review of the agency’s investigation process, findings, and results. The independent review was led by Paul Hill, a former NASA leader who served as the lead space shuttle flight director for Return to Flight after the Columbia accident, led NASA’s Mission Operations Directorate, and is a current member of the agency’s Aerospace Safety Advisory Panel. The review occurred over a three-month period to assess the heat shield’s post-flight condition, entry environment data, ablator thermal response, and NASA’s investigation progress. The review team agreed with NASA’s findings on the technical cause of the physical behavior of the heat shield.
Heat Shield Advancements
Knowing that permeability of Avcoat is a key parameter to avoid or minimize char loss, NASA has the right information to assure crew safety and improve performance of future Artemis heat shields. Throughout its history, NASA has learned from each of its flights and incorporated improvements into hardware and operations. The data gathered throughout the Artemis I test flight has provided engineers with invaluable information to inform future designs and refinements. Lunar return flight performance data and a robust ground test qualification program improved after the Artemis I flight experience are supporting production enhancements for Orion’s heat shield. Future heat shields for Orion’s return from Artemis lunar landing missions are being produced to achieve uniformity and consistent permeability. The qualification program is currently being completed along with the production of more permeable Avcoat blocks at NASA’s Michoud Assembly Facility in New Orleans.
For more information about NASA’s Artemis campaign, visit:
https://www.nasa.gov/artemis
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By NASA
NASA Lewis Research Center’s DC-9 commences one of its microgravity-producing parabolas in the fall of 1994. It was the center’s largest aircraft since the B-29 Superfortress in the 1940s.Credit: NASA/Quentin Schwinn
A bell rings and a strobe light flashes as a pilot pulls the nose of the DC-9 aircraft up sharply. The blood quickly drains from researchers’ heads as they are pulled to the cabin floor by a force twice that of normal gravity. Once the acceleration slows to the desired level, and the NASA aircraft crests over its arc, the flight test director declares, “We’re over the top!”
The pressure drops as the aircraft plummets forward in freefall. For the next 20 to 25 seconds, everybody and everything not tied down begins to float. The researchers quickly tend to their experiments before the bell rings again as the pilot brings the aircraft back to level flight and normal Earth gravity.
By flying in a series of up-and-down parabolas, aircraft can simulate weightlessness. Flights like this in the DC-9, conducted by NASA’s Lewis Research Center (today, NASA Glenn) in the 1990s, provided scientists with a unique way to study the behavior of fluids, combustion, and materials in a microgravity environment.
Researchers conduct experiments in simulated weightlessness during a flight aboard the DC-9. The aircraft sometimes flew up to 40 parabolas in a single mission.Credit: NASA/Quentin Schwinn Beginnings
In the 1960s, NASA Lewis used a North American AJ-2 to fly parabolas to study the behavior of liquid propellants in low-gravity conditions. The center subsequently expanded its microgravity research to include combustion and materials testing.
So, when the introduction of the space shuttle in the early 1980s led to an increase in microgravity research, NASA Lewis was poised to be a leader in the agency’s microgravity science efforts. To help scientists test experiments on Earth before they flew for extended durations on the shuttle, Lewis engineers modified a Learjet aircraft to fly microgravity test flights with a single strapped-down experiment and researcher.
The DC-9 flight crew in May 1996. Each flight required two pilots, a flight engineer, and test directors. The flight crews participated in pre- and post-flight mission briefings and contributed to program planning, cost analysis, and the writing of technical reports.Credit: NASA/Quentin Schwinn Bigger And Better
In 1990, NASA officials decided that Lewis needed a larger aircraft to accommodate more experiments, including free-floating tests. Officials determined the McDonnell Douglas DC-9 would be the most economical option and decided to assume responsibility for a DC-9 being leased by the U.S. Department of Energy.
In the fall of 1993, 50 potential users of the aircraft visited the center to discuss the modifications that would be necessary to perform their research. In October 1994, the DC-9 arrived at Lewis in its normal passenger configuration. Over the next three months, Lewis technicians removed nearly all the seats; bolstered the floor and ceiling; and installed new power, communications, and guidance systems. A 6.5-by-11-foot cargo door was also installed to allow for the transfer of large equipment.
The DC-9 was the final element making NASA Lewis the nation’s premier microgravity institution. The center’s Space Experiments Division had been recently expanded, the 2.2-Second Drop Tower and the Zero Gravity Facility had been upgraded, and the Space Experiments Laboratory had recently been constructed to centralize microgravity activities.
NASA Lewis researchers aboard the DC-9 train the STS-83 astronauts on experiments for the Microgravity Science Laboratory (MSL-1).Credit: NASA/Quentin Schwinn Conducting the Flights
Lewis researchers partnered with industry and universities to design and test experiments that could fly on the space shuttle or the future space station. The DC-9 could accommodate up to eight experiments and 20 research personnel on each flight.
The experiments involved space acceleration measurements, capillary pump loops, bubble behavior, thin film liquid rupture, materials flammability, and flame spread. It was a highly interactive experience, with researchers accompanying their tests to gain additional information through direct observation. The researchers were often so focused on their work that they hardly noticed the levitation of their bodies.
The DC-9 flew every other week to allow time for installation of experiments and aircraft maintenance. The flights, which were based out of Cleveland Hopkins International Airport, were flown in restricted air space over northern Michigan. The aircraft sometimes flew up to 40 parabolas in a single mission.
Seth Lichter, professor at Northwestern University, conducts a thin film rupture experiment aboard the DC-9 in April 1997.Credit: NASA/Quentin Schwinn A Lasting Legacy
When the aircraft’s lease expired in the late 1990s, NASA returned the DC-9 to its owner. From May 18, 1995, to July 11, 1997, the Lewis microgravity flight team had used the DC-9 to fly over 400 hours, perform 70-plus trajectories, and conduct 73 research projects, helping scientists conduct hands-on microgravity research on Earth as well as test and prepare experiments designed to fly in space. The aircraft served as a unique and important tool, overall contributing to the body of knowledge around microgravity science and the center’s expertise in this research area.
NASA Glenn’s microgravity work continues. The center has supported experiments on the International Space Station that could improve crew health as well as spacecraft fire safety, propulsion, and propellants. Glenn is also home to two microgravity drop towers, including the Zero Gravity Research Facility, NASA’s premier ground-based microgravity research lab.
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By NASA
Sandra Connelly, deputy associate administrator for NASA’s Science Mission Directorate, left, Lori Glaze, acting deputy associate administrator for NASA’s Exploration Systems Development Mission Directorate, Robyn Gatens, director of the International Space Station at NASA Headquarters, and Carrie Olsen, manager of the Next Gen STEM project for NASA’s Office of STEM Engagement, discuss key takeaways at the conclusion of NASA’s LEO Microgravity Strategy Industry and Academia Workshop, Friday, Sept. 13, 2024, at Convene in Washington. NASA’s LEO Microgravity Strategy effort aims to develop and document an objectives-based approach toward the next generation of human presence in low Earth orbit to advance microgravity science, technology, and exploration.NASA/Joel Kowsky As part of NASA’s effort to advance microgravity science, technology, and exploration in low Earth orbit (LEO), the agency conducted two stakeholder workshops in London and Washington to solicit feedback from the international community, including NASA’s international partners, American industry, and academia on Sept. 6 and Sept. 13, respectively.
The agency released a draft set of 42 objectives in late August, seeking input from U.S. industry, academia, international communities, NASA employees, and others to ensure its framework for the next generation of human presence in low Earth orbit, set to be finalized this winter, includes ideas and contributions from a range of stakeholders. The objectives span six categories: science, exploration-enabling research and technology development, commercial low Earth orbit infrastructure, operations, international cooperation, and workforce and engagement.
“As we chart the future of human exploration, it’s vital that we harness the insights and expertise of our diverse stakeholders,” said NASA Deputy Administrator Pam Melroy. “These workshops provide an invaluable platform for stakeholders to share their insights, helping us create a strategy that reflects our shared ambitions for the future of space exploration.”
Consultation is a fundamental aspect of NASA’s LEO Microgravity Strategy, emphasizing the importance of collaboration and the integration of diverse perspectives in advancing scientific research and technology development in low Earth orbit. By actively engaging with stakeholders –including scientists, industry partners, and educational institutions –NASA aims to gather valuable insights and align its objectives with the broader goals of the space community.
“Engaging with a wide array of voices allows us to tap into innovative ideas that will enhance our missions,” stated Robyn Gatens, director of the International Space Station and acting director of Commercial Spaceflight. “This collaborative approach not only strengthens our current initiatives but also lays the groundwork for future advancements in space exploration.”
To contribute to NASA’s low Earth orbit microgravity strategy, visit: www.leomicrogravitystrategy.org
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By NASA
A waxing gibbous moon rises over the Indian Ocean as the International Space Station orbited 266 miles above.Credit: NASA As NASA and its partners continue to conduct groundbreaking research aboard the International Space Station, the agency announced Monday it is seeking U.S. industry, academia, international partners, and other stakeholders’ feedback on newly developed goals and objectives that will help guide the next generation of human presence in low Earth orbit.
“From the very beginning, NASA’s flagship human spaceflight programs have built upon each other, expanding our knowledge and experience of humans living and working in space,” said NASA Deputy Administrator Pam Melroy. “As commercial industry is constructing new human-enabled platforms for low Earth orbit, NASA must answer the question: what should our goals and objectives be to advance our future science and exploration missions?”
NASA published draft high-level goals and objectives outlining 42 key points in six main areas: science, exploration-enabling research and technology development, commercial low Earth orbit infrastructure, operations, international cooperation, and workforce and engagement.
“Feedback is essential for shaping our long-term microgravity research and development activities,” said Ken Bowersox, associate administrator, Space Operations Mission Directorate at NASA Headquarters in Washington. “We are committed to refining our objectives with input from both within NASA and external partners, ensuring alignment with industry and international goals. After reviewing feedback, we will finalize our strategy later this year.”
The agency will conduct two invite-only workshops in September to discuss feedback on the draft goals and objectives. The first workshop is with international partners, and the second will engage U.S. industry and academic representatives.
NASA employees also are invited to provide input through internal agency channels. This approach reflects NASA’s commitment to harnessing diverse perspectives to navigate the rapidly evolving low Earth orbit environment.
“Organizations are increasingly recognizing the transformative benefits of space, with both governments and commercial activities leveraging the International Space Station as a testbed,” said Robyn Gatens, International Space Station director and acting director of commercial spaceflight at NASA Headquarters. “By developing a comprehensive strategy, NASA is looking to the next chapter of U.S. human space exploration to help shape the agency’s future in microgravity for the benefit of all.”
Stakeholders may submit comments by close of business on Friday, Sept. 27 to:
https://www.leomicrogravitystrategy.org/
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Amber Jacobson
Headquarters, Washington
202-358-1600
amber.c.jacobson@nasa.gov
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