by Earlier this year, NASA announced that the Artemis 2 crew moon swingby, an exercise run to prepare for the 2026 Artemis 3 mission, which will land astronauts near the moon’s south pole, was delayed until September 2025.
One reason cited for the 10-month delay was to get to the bottom of the reentry heat shield data from Artemis 1which sent an uncrewed Orion capsule to lunar orbit and back.
Engineers are analyzing data from that shakeout cruise, which was launched by NASA Spatial Address System megarocket on November 16, 2022.
Artemis 1’s 25-day mission ended on December 11, 2022, with the Orion capsule splashing down by parachute in the Pacific Ocean off Baja California.
Related: Top 10 images from NASA’s Artemis 1 lunar mission
Blistering reentry
Orion’s heat shield took the 25,000 mph (40,000 kph) reentry speed that day, protecting the capsule ably. But soon after, NASA and contractors began to wrestle with the discovery that Orion’s ablative heat shield They behaved differently than predicted.
Some areas of expected burned material were screened in a way that computer modeling and ground testing did not predict. Also, there was a bit more freeing of the charred material during re-entry than expected.
Orion’s heat shield features the same ablative material, called Avcoat, used during the Program Apollo in the late 1960s and early 1970s. However, the construction process for the heat shield was changed from the Apollo era method.
Vintage Apollo
Although Avcoat is vintage Apollo, the production process for the Orion thermal protection system has been changed in the 21st century.
According to Lockheed Martin, the leading firm Orion heat shield development process, “instead of workers filling 300,000 honeycomb cells one by one with ablative material, then heat curing the material and machining it to the correct shape, the Avcoat team now makes blocks – just less than 200 – which are pre-machined to fit into position and bonded in place to the heat shield’s carbon fiber skin,” the aerospace firm said A website explains.
This process allows Avcoat to be applied in just a quarter of the previous time and also saves money, according to the company.
Basic reason
A post-flight inspection of the Artemis 1 Orion heat shield revealed an unexpected loss of red layer pieces from the spacecraft. NASA is laser focused, quite literally, on understanding the root cause of red loss phenomena, as well as Avcoat cracking.
“We designed and implemented a building block ground test approach using agency and external test facilities,” NASA’s Orion program office told Space.com.
The initial test series began in the summer of 2023 and wrapped up in a final test series in December 2023. “We expect to establish a root cause this spring,” NASA’s office said.
Simulation test
Those Orion heat shield tests involved the Laser Hardened Materials Evaluation Laboratory, a unique facility operated by UES, a BlueHalo company in Dayton, Ohio, and managed by the Air Force Research Laboratory. This laboratory performs thermal simulation testing, equipped with high-power lasers.
Testing was also done at the Arc Jet Complex at NASA Ames Research Center in California’s Silicon Valley. Thermal shielding material is arc jet tested with plasma mimicking the intense heat generated during the Orion capsule’s submerged atmospheric reentry.
For its part, Lockheed Martin teamed up with NASA to organize a core team of engineers to investigate and understand the cause of the red loss and what needed to be done to prevent similar occurrences on future flights, said Blaine Brown, Orion Spacecraft Mechanical Systems. A director at the company.
“Over the past year, the Lockheed Martin team, along with NASA, has been very busy producing test items and supporting re-entry environmental tests in various NASA and industry test rooms,” Brown told Space.com.
These tests have provided the investigative team with a wealth of information, Brown said. “Lockheed Martin is also providing analytical expertise to demonstrate acceptable thermal margins to support flight rationale for the Artemis 2 mission.”
Related: NASA’s Artemis Program: Everything you need
Hiccups heat shield
Last year, the Orion program office at NASA Johnson Space Center in Houston responded to Space.com’s request for comment about heat shield hiccups.
“We expect the material to rise to 5,000 degrees Fahrenheit [2,760 degrees Celsius] the spacecraft turns on re-entry through The Earth’s Atmosphereand see the material flowing through a chemical reaction, but we did not expect the small pieces that came out, compared to being isolated,” said the NASA office.
A healthy margin of virgin Avcoat remained, and temperature data inside the cabin remained at expected levels, so if the crew were on board they would not be in danger, the program office statement explained.
NASA said a dedicated investigation includes planned testing, detailed analysis, extensive sampling of the heat shield, and a review of data from sensors to determine what the Orion capsule experienced on reentry.
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Avcoat changes?
Is it possible that the Avcoat will need changes?
“It is still too early in our testing and analysis to come up with any suggestions or solutions that might address the additional freedom of character,” NASA’s office responded in its 2023 message.
It is possible that the Artemis 1 heat shield phenomenon could just be a fundamental part of this heat shield, the office said at the time.
In addition, it could be what NASA would expect in the return of the capsule from the moon“but we will let you know the details,” said the Orion project office, adding that “our teams want the confidence that we have the best possible heat shield to fly people in the future.”
