However, in a significant breakthrough, the space agency has identified the cause of the heat shield problems on the Orion capsule and believes it can simply change the reentry trajectory to avoid the problem reoccurring.
The news means the subsequent Artemis III mission to return humans to the Moon will also be pushed back until the middle of 2027.
Australia is now a key player in the Artemis program, with NASA tasking the Australian Space Agency with creating a rover that will collect lunar regolith, or moon soil, that will eventually be turned into oxygen to support a permanent human base.
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“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, a NASA deputy associate administrator.
“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.”
NASA said its teams took a methodical approach to identifying the root cause of the char loss issue, including sampling of the Artemis I heat shield, review of imagery 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.
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“Using this manoeuvre, 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 splash down.
“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.
“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 behaviour 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.”
The Artemis launch vehicle consists of the Orion capsule, created by Lockheed and Airbus, and the main Space Launch System rocket manufactured by a consortium including Boeing and Northrop Grumman.
However, there is increasing speculation that incoming president Donald Trump could alter the Artemis mission to use SpaceX’s Starship launch vehicle for blast off instead.
Currently, Starship is scheduled to be reconfigured as a moon lander before returning the astronauts to Earth – effectively meaning two launch vehicles are used rather than one.
Starship has now completed six successful test missions, with Trump watching the last blast-off in person.
Adam Thorn
Adam is a journalist who has worked for more than 40 prestigious media brands in the UK and Australia. Since 2005, his varied career has included stints as a reporter, copy editor, feature writer and editor for publications as diverse as Fleet Street newspaper The Sunday Times, fashion bible Jones, media and marketing website Mumbrella as well as lifestyle magazines such as GQ, Woman’s Weekly, Men’s Health and Loaded. He joined Momentum Media in early 2020 and currently writes for Australian Aviation and World of Aviation.
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