When the Artemis II Orion crew capsule returns to Earth on Friday after flying around the moon, it will hit the discernible atmosphere some 75 miles above the Pacific Ocean at a blistering 24,000 mph — fast enough to fly from Los Angeles to New York in about 6 minutes. Within seconds, temperatures across its 16.5-foot-wide heat shield will climb to some 5,000 degrees — half as hot as the visible surface of the sun — as the ship rapidly slows in an electrically charged fireball of atmospheric friction.The four astronauts on board — commander Reid Wiseman, Victor Glover, Christina Koch and Canadian astronaut Jeremy Hansen — are counting on the heat shield to keep them safe, in a comfortable environment, all the way through the peak heating zone to a parachute-assisted splashdown in the Pacific off the coast of California.AdvertisementAdvertisement”We have high confidence in the system, in the heat shield and the parachutes and the recovery systems we put together,” Amit Kshatriya, NASA’s associate administrator, said Thursday. “The engineering supports it, the Artemis I flight data supports it. All of our ground tests support it, our analysis supports it, and tomorrow the crew is going to put their lives behind that confidence.”The Artemis II heat shield during its assembly. The 16.5-foot-wide heat shield is required to protect the Orion capsule and its crew from the 5,000-degree heat of the ship’s high-speed plunge back into the atmosphere. / Credit: NASAThe crew and mission managers are confident, they say, despite major problems with the heat shield that was used during the unpiloted Artemis I test flight in 2022, when the Avcoat material making up the shield developed sub-surface cracks and gas pockets that blew away chunks of the protective barrier’s outer “char” layer.Based on nearly two years of tests and analysis, engineers were surprised to discover the damage was most likely caused by the Avcoat material’s lack of permeability during a specific phase of the reentry when the shield was experiencing lower external temperatures while internal layers were still extremely high, generating gas that could not escape.Agency managers decided to order a different heat shield design for downstream Artemis missions. But the heat shield for the Artemis II flight, identical to the one used with Artemis I, was already installed. Replacing it with a new design would have delayed the mission by 18 months or more.The 16.5-foot-wide heat shield protecting the Orion capsule during an unpiloted test flight in 2022 was seriously damaged during reentry. / Credit: NASAInstead, NASA managers opted to launch Artemis II “as is” based on test data and an exhaustive analysis that indicated the shield would work properly if t …
