Ax-1 Crew Dragon splashdown
A Crew Dragon spacecraft just before splashdown on the Ax-1 mission in April. NASA says that, contrary to a published report, there was no excessive wear to its heat shield. Credit: Axiom Space

WASHINGTON — SpaceX will replace the heat shield on the next Crew Dragon spacecraft flying to the International Space Station after it failed inspections, but NASA says there is no risk of a similar problem for the spacecraft currently at the station.

In a May 24 statement to reporters, NASA said that a heat shield structure that SpaceX built for the Crew-5 mission to the station, slated to launch in early September, failed an acceptance test earlier this month and will not be used on that spacecraft.

“SpaceX has a rigorous testing process to put every component and system through its paces to ensure safety and reliability,” the agency said in the statement. “The test did its job and found a manufacturing defect.”

Those tests include X-rays of the structure as well as applying physical loads to it to simulate the forces it would experience on reentry and at splashdown, said Steve Stich, NASA commercial crew program manager, during a May 25 briefing after the return of Boeing’s CST-100 on an uncrewed test flight.

“What happened for Crew-5 is that, when we put the heat shield through the landing loads, it did not pass,” he said. “We could tell there was some damage inside the heat shield from that test, so we knew we couldn’t go forward and fly that heat shield.”

NASA said SpaceX will use a different heat shield on that spacecraft, Endurance, that will go through the same tests. The agency said in its statement that it was still planning a September launch of that mission.

The defect does not affect the heat shield on the Crew-4 Crew Dragon spacecraft, Freedom, currently at the ISS. “It does not have the same issues in manufacturing that we saw for Crew-5,” Stich said. “It has been through this testing sequence where we go apply all the loads to it and it has passed all those load cases, so we don’t have any concerns about the heat shield on Crew-4.”

The NASA statement was in response to a published report May 23 that claimed that there had been a leak of hypergolic propellants from thrusters on Crew Dragon that caused significant damage to the heat shield at the end of the Axiom Space’s Ax-1 private astronaut mission to the station, which splashed down April 25. That raised a potential issue with the Crew-4 spacecraft that launched less than two days later.

NASA denied there was any leak or heat shield problem on that mission. “The data associated with Dragon’s recent crew reentries was normal — the system performed as designed without dispute,” the agency stated. “There has not been a hypergol leak during the return of a crewed Dragon mission nor any contamination with the heat shield causing excessive wear.”

NASA added there was a “full engineering review” of the Crew Dragon’s thermal protection system after the Ax-1 splashdown and before the launch of Crew-4. While the heat shield’s composite structure was reused for Crew-4, the thermal protection system material itself is new, the case for all crewed missions.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...