Eventually, SpaceX wants to catch ships coming back from space with big mechanical arms on the launch pad, similar to the way SpaceX has shown it can recover the rocket's huge Super Heavy booster. This would allow SpaceX to theoretically stack a freshly flown ship on top of a booster right on the launch pad, then quickly refuel it and launch it again.
There are plenty of things SpaceX must prove before the company is able to do this. But SpaceX has already demonstrated it can handle some of the more obvious problems, such as repeatedly igniting the rocket's Raptor engines. The most definitive test will be SpaceX's success or failure with Starship's heat shield.
"We are confident in making a fully reusable orbital heat shield but it will require many flights, many iterations to figure out where the weak points are in the heat shield, where we need to change the design, either strengthening the tile or changing how big the gap is between tiles, or changing what’s underneath the tile," Musk said in a discussion broadcast on SpaceX's official livestream of Monday's Starship launch countdown.
The heat shield was one of the most vexing problems with NASA's space shuttle program. Thousands of tiles peeled off of the space shuttle Columbia when NASA first flew the orbiter on top of its modified 747 carrier aircraft in 1979. Tile damage was a regular occurrence throughout the shuttle program's 30-year service life, necessitating tile repairs and replacement inside the shuttle's hangar between missions.
"The space shuttle heat shield would come back essentially partially broken and would require many months of refurbishment in order to fly again," Musk said. "What we’re trying to achieve here with Starship is to have a heat shield that can be reflown immediately."
On each Starship flight this year, SpaceX has sought to test the performance of new tile designs, including metallic insulators and heat shield sections with "active cooling" to help dissipate the scorching temperatures of reentry into the atmosphere.
NASA's space shuttle Columbia lost thousands of thermal protection tiles during a 1979 flight on top of the Shuttle Carrier Aircraft, a modified 747 jumbo jet. Credit: NASA
"There are 100 different variables that we could tweak with the heat shield tiles, but the only way to know exactly what we should be adjusting is to fly repeatedly and to be able to examine the ship upon landing," Musk said.
Before SpaceX can test the heat shield repeatedly, Starship must first make it through a single flight from start to finish. It has failed to do this on all three attempts this year, following a year of progress with Starship in 2024. SpaceX guided Starship to a controlled splashdown in the Indian Ocean on several occasions last year.
“We have successfully brought the ship back through the atmosphere and achieved a soft landing multiple times, so we know that this is possible," Musk said. "But we have, in the process, shed many heat shield tiles, so we need to be able to do this without shedding heat shield tiles and do so repeatedly."
SpaceX also must make sure the launch pad's catch arms don't damage Starship's heat shield when it comes in for landing. This will only be attempted after SpaceX officials are comfortable they have solved the heat shield problem during tests over the ocean.
"We need to make sure we don’t scrape the tiles off as we slide along the chopstick arms," said Bill Riley, SpaceX's vice president of Starship engineering.
Charlie Camarda, a former NASA astronaut, engineer, and materials scientist, worked on alternatives to the shuttle's heat shield beginning in the 1970s. One of his first jobs at NASA was to demonstrate the feasibility of a heat shield for the leading edge of the space shuttle's wings that used heat pipes for active cooling.