Earlier this year, NASA announced that it would postpone the manned Artemis 2 mission around the moon to September 2025 as an exercise in preparation for the 2026 Artemis 3 mission, which will Land astronauts near the moon’s south pole.
One of the reasons for the 10-month delay was to gain insight into the re-entry heat shield data Artemis 1which will deliver the unmanned Orion capsule into lunar orbit and back.
Engineers have been analyzing data from that stunning cruise, which began with the launch of NASA space launch system November 16, 2022 Giant Rocket.
The 25-day Artemis 1 mission ended on December 11, 2022. Orion The capsule splashed down under a parachute in the Pacific Ocean near Baja California.
related: 10 of the best photos from NASA’s Artemis 1 lunar mission
reentry
That day, Orion’s heat shield reached a reentry speed of 25,000 mph (40,000 km/h), cleverly protecting the capsule.But shortly thereafter, NASA and contractors began grappling with the discovery of Orion’s ablative heat shield Wear is different than expected.
Some areas of expected charred material ablated in ways not predicted by computer modeling and ground testing. Additionally, slightly more charred material was released during reentry than expected.
Orion’s heat shield uses the same Apollo program In the late 1960s and early 1970s. However, the heat shield construction process differs from Apollo-era methods.
vintage apollo
While Avcoat is an old-school Apollo, the production process for Orion’s 21st century thermal protection system has changed.
According to Lockheed Martin, the company leads the Orion’s heat shield During the development process, “instead of having workers fill each of the 300,000 honeycomb cells one by one with ablative material, then heat-curing the material and processing it into the proper shape, the team created pre-machined Avcoat blocks (just under 200 of them). to fit their position and bonded to the heat shield’s carbon fiber skin,” the aerospace company’s Website explanation.
According to the company, this process allows Avcoat to be coated in only one-quarter of the previous time and also saves money.
root cause
Post-flight inspection of the Artemis 1 Orion heat shield revealed unexpected loss of charcoal debris on the spacecraft. NASA has literally been working to understand the scorch phenomenon and the root cause of Avcoat cracks.
“We designed and executed a building block ground test approach using agency and external test facilities,” NASA’s Orion Program Office told Space.com.
The initial test series begins in the summer of 2023 and the last test series ends in December 2023.
mock test
Orion heat shield testing involved the Laser Hardening Materials Evaluation Laboratory, a unique facility operated by UES, a BlueHalo company in Dayton, Ohio, and managed by the Air Force Research Laboratory. The laboratory conducts thermal simulation testing and is equipped with high-power lasers.
Testing is also taking place at NASA’s Arc Jet Complex ames research center In Silicon Valley, California. The arc-jet tests were performed on thermally shielded materials, using plasma to simulate the intense heat generated during the Orion capsule’s re-entry into the atmosphere.
Brian Brown of Orion Spacecraft Mechanical Systems said Lockheed Martin, working with NASA, has assembled a core team of engineers to investigate and understand the causes of carbon loss and what steps need to be taken to prevent it on future flights. Similar situation.
“Over the past year, the Lockheed Martin team has been very busy working with NASA to produce test items and support reentry environment testing in various NASA and industrial test chambers,” Brown told Space.com.
Brown said the tests provided the investigative team with a wealth of information. “Lockheed Martin has also been providing analytical expertise to demonstrate acceptable thermal margins to support the program’s flight principles. artemis 2 mission.
related: NASA’s Artemis Program: Everything you need to know
Heat shield hiccups
Last year, NASA’s Orion Program Office johnson space center Houston responded to Space.com’s request for comment on the heat shield issue.
“We expect the material to ablate at 5,000 degrees Fahrenheit [2,760 degrees Celsius] spacecraft encounters during re-entry Earth’s atmosphereand observed the charring of the material through chemical reactions, but we did not expect these small fragments to fall off rather than be ablated,” the NASA office said.
A statement from the program office explained that there was still a significant amount of original Avcoat remaining and temperature data in the cabin remained at expected levels, so the crew were not in danger if they were on board.
NASA said a specialized investigation included planned testing, detailed analysis, extensive sampling of the heat shield and a review of sensor data to assess what the Orion capsule experienced during reentry.
Avcoat changes?
Is it possible that the Avcoat needs to be changed?
NASA’s office responded in a 2023 communique: “Our testing and analysis are too early to produce any potential recommendations or solutions to address the issue of additional carbon release.”
The office said at the time that the Artemis 1 heat shield phenomenon may simply be inherent to the heat shield.
Additionally, this may be NASA’s expectation for the capsule’s return. moon“But we’ll let the data tell us,” the Orion program office said, adding, “Our team wants to believe we have the best heat shield to keep humans flying.”
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Image Source : www.space.com