NASA to fly steeper Artemis 2 reentry to fix heat shield issue

NASA modifies Artemis 2 reentry to fix heat shield issue

NASA will fly a modified, steeper reentry trajectory for the upcoming Artemis 2 moon mission to mitigate a heat shield problem discovered after the uncrewed Artemis 1 test flight. The agency and its contractors concluded this approach is the safest path forward for the mission, which will carry four astronauts around the moon as soon as early 2025.

The issue involves the spacecraft’s ablative heat shield material, called Avcoat. During Artemis 1’s high-speed return to Earth in December 2022, post-flight analysis found the material had unexpectedly chipped away in over 100 locations.

The root cause of the char loss

An extensive investigation involving NASA, contractor Lockheed Martin, and an independent review team identified the technical cause. The heat shield did not allow enough of the gases generated inside the Avcoat material to escape during the intense heating of reentry.

This trapped gas caused pressure to build up, leading to cracking and the liberation of charred material. The Artemis 1 mission was still successful, and the interior cabin temperature remained safe, but the phenomenon required a fix before flying crew.

Orion’s heat shield is the largest of its kind ever built for a human-rated spacecraft, measuring 16.5 feet (5 meters) in diameter.

Changes for the crewed Artemis 2 mission

Instead of a major redesign, engineers are adjusting the mission profile and the material itself. For Artemis 2, NASA has shortened the distance Orion will travel in the atmosphere before splashdown.

“This will limit how long Orion spends in the temperature range in which the Artemis 1 heat shield phenomenon occurred,” said NASA Orion public affairs official Kenna Pell. The new trajectory involves a steeper entry and eliminates the “skip” maneuver used on Artemis 1.

Lockheed Martin’s Orion spacecraft mechanical systems director, Blaine Brown, confirmed the team performed extensive testing to reproduce the char loss. The modified trajectory, he said, “will minimize char loss and provide more than adequate margin on thermal performance.”

Material modifications and ongoing challenges

The Avcoat blocks for Artemis 2 and the subsequent Artemis 3 mission use the same base formula flown on Artemis 1. The only change is a slight modification to the material’s density.

“We just slightly modified the density to allow gases in the ablative material to escape during high heating and cool down,” Brown explained. He stated the team supports NASA’s decision to fly the current heat shield on Artemis 2.

However, a recent NASA Office of Inspector General (OIG) report notes this solution is complex and does not fully retire the risk. “It is also complex and contingent on a successful test campaign and does not retire the heat shield risk for Artemis 3,” the report stated.

The OIG also directly linked the heat shield investigation to program delays:

• Additional testing caused “cascading delays to all Artemis missions starting with Artemis 2.”
• Artemis 2 is now targeted for no earlier than September 2025.
• Artemis 3, the first human lunar landing attempt of the program, is now scheduled for 2028.

A critical moment during return

During Artemis 2’s reentry, the crew will experience a communications blackout as superheated plasma builds around the capsule. How the heat shield performs on this new, steeper dive through the atmosphere will be a tense moment for mission controllers.

The agency is betting its modified approach will ensure a safe return for the astronauts. All future work depends on the data gathered from this critical crewed test flight.