SpaceX found unexpected 'erosion' to its spaceship's heat shield after its first NASA astronaut mission, so it revamped the system

• SpaceX discovered unexpected erosion on its Crew Dragon spaceship's heat shield after its first astronaut mission.
• A SpaceX executive said the crew members — NASA astronauts Bob Behnken and Doug Hurley — were never in danger.
• But as a precaution, SpaceX has updated the heat shield ahead of its next crewed launch in October.

SpaceX discovered unexpected damage to part of its Crew Dragon space capsule after the vessel carried its first astronauts this summer, officials said on Tuesday.

The Demo-2 mission flew NASA astronauts Bob Behnken and Doug Hurley to the International Space Station on May 30. The two men stayed there for two months, then weathered a fiery fall through Earth's atmosphere to splash down in the Gulf of Mexico on August 2.

But after the company recovered and studied the toasted space capsule up-close, examiners spotted something unusual: deep erosion on Crew Dragon's heat shield.

That thermal protection system is a collection of heat-resistant tiles that line the spaceship's vulnerable underbelly. It protects Crew Dragon by deflecting and absorbing heat that can reach 3,500 degrees Fahrenheit while the space capsule plummets through the atmosphere and creates superheated plasma on its return to Earth.

SpaceX expected to find some wear and tear, but not quite this much.

"We found, on a tile, a little bit more erosion than we wanted to see," Hans Koenigsmann, SpaceX's vice president of build and flight reliability, told reporters during a briefing on Tuesday.

Koenigsmann said the affected part of the heat shield is close to "tensions ties" that connect the Crew Dragon to its large cylindrical trunk. (The trunk helps propel the spacecraft in orbit but is thrown away before the spaceship begins reentry.) One of four areas surrounding those tension ties got deeply worn away by searing-hot plasma as Behnken and Hurley returned to Earth.

Still, the spaceship and its crew safely returned home despite the unexpected problem.

"At all times the astronauts were safe and the vehicle was working perfectly," Koenigsmann said.

NASA and SpaceX revamped the heat shield for the next astronaut mission

Before Behnken and Hurley returned to Earth, Elon Musk, SpaceX's CEO and chief designer, said reentry was the part of the mission that he worried most about.

NASA surveyed the heat shield for damage ahead of that return flight, while the Crew Dragon capsule was still docked to the space station. During its two months attached to the orbiting laboratory, small bits of space debris could have damaged the ship's heat shield. The inspection relied on a robotic arm on the space station and some onboard cameras but did not turn up any problems.

It was only after Behnken and Hurley were safely back on Earth that SpaceX discovered the weak spot in its heat shield.

But these are the types of issues Behnken and Hurley's flight was meant to find and iron out.

Whereas theirs was considered a demo mission, the Crew Dragon is next set to carry a crew on its first routine mission, called Crew-1. NASA astronauts Mike Hopkins, Victor Glover, and Shannon Walker, and Japanese astronaut Soichi Noguchi are scheduled to launch aboard the Crew Dragon on October 31.

NASA and SpaceX have already reinforced the vulnerable part of the heat shield ahead of that flight, Koenigsmann said.

"We've gone in and changed out a lot of the materials to better materials," Steve Stich, the program manager for NASA's Commercial Crew Program, which oversees the SpaceX astronaut missions, told reporters on Tuesday. "We've made the area in between these tiles better."

NASA tested five samples of the new tile in a simulated environment that mimics reentry — a wind tunnel at its Ames Research Center in California.

"I'm confident that we fixed this particular problem very well," Koenigsmann said. "Everything has been tested and is ready to go for the next mission."

It's unclear why the excessive heat-shield erosion didn't show up on the prior demo mission, an uncrewed test flight in which Crew Dragon launched, docked to the space station, and returned to Earth with no human passengers. Koenigsmann speculated that the capsule may not have experienced the problem because it was lighter and had a slightly different trajectory on that mission.

"At the end of the day, it's great that we found it on this ride," he said. "This was not an unsafe situation at all. This is something that we observed and and then, basically, changed to make sure that nothing nothing bad will ever happen."