NASA’s Artemis II mission sent four astronauts around the Moon and brought them safely back to Earth, laying a foundation for crewed flights to the Moon’s surface.

Additional engineering data analysis of the Orion spacecraft’s heat shield confirmed initial data showing the heat shield performed as expected.

In particular, NASA measured whether the thermal protection system effectively safeguarded the crew and Orion systems as the spacecraft reentered Earth’s atmosphere. This test flight was the first time astronauts flew aboard Orion. 

Orion reached a maximum velocity of 39 times the speed of sound and experienced external temperatures exceeding 4,000 degrees Fahrenheit at its peak, all while the four astronauts inside Orion stayed relatively cool with a cabin temperature in the mid-70 degree Fahrenheit range during their return to Earth from the Moon.  

After NASA’s thorough analysis of Artemis I heat shield findings , informed by extensive arc jet material testing at NASA’s Ames Research Center in California’s Silicon Valley, the agency modified Orion’s reentry trajectory for Artemis II by shortening the maximum downrange distance the spacecraft could fly between when it entered Earth’s atmosphere and splashed down in the Pacific Ocean. Analysis prior to the mission showed that limiting downrange distance would limit how long the spacecraft’s heat shield spent in the temperature range at which the Artemis I heat shield phenomenon occurred.

The spacecraft reentered with precision, entering within only 192 feet of its targeted entry interface, and successfully splashed down only 0.59 miles from the predicted landing site off the coast of San Diego. Initial inspections of the thermal protection system, including diver imagery of the spacecraft’s heat shield taken just after splashdown and further inspections on the recovery ship, found it performed as expected, with a significant reduction in the amount of cracks and char loss as compared to Artemis I.  

Upon the spacecraft’s return to NASA’s Kennedy Space Center in Florida after the Moon mission, thermal protection system experts began additional examination of the heat shield, made of 186 unique blocks of an ablative material called Avcoat. The heat shield was then transported to NASA’s Marshall Space Flight Center in Huntsville, Alabama, where work on sample extraction and internal x-ray scans began in August to provide further engineering insight into the system and behavior of the material.

A thorough post-flight assessment review found that Orion’s aerodynamic and aerothermal performance, including the heat shield and backshell thermal protection system, was in line with engineering predictions based on pre-flight analyses and ground testing. The shorter allowable down range during entry reduced the cracking and char loss experienced on the Artemis II heat shield relative to the Artemis I heat shield by a factor of ten, proving the effectiveness of the trajectory modification. Engineers found only nine spots of char loss of varying sizes on the Artemis II heat shield dish, compared to 103 during Artemis I.