SpaceX has long marketed Starship as a fully and rapidly reusable rocket designed to deliver thousands of pounds of cargo to Mars and make life multiplanetary. Achieving reusability at scale requires a space vehicle that can tolerate mishaps and faults so that a single failure does not spell a mission-ending catastrophe. The tenth test flight on Tuesday evening demonstrated SpaceX’s focus on building this fault tolerance. In a post-flight update, the company stated the test stressed the limits of the vehicle’s capabilities. Understanding these edges is critical for SpaceX’s plans to eventually use Starship to launch Starlink satellites, commercial payloads, and astronauts.
When the massive Starship rocket lifted off on its tenth test flight, SpaceX did more than achieve new milestones. It purposefully introduced several faults to test the heat shield, propulsion redundancy, and the relighting of its Raptor engine.
The heat shield is among the toughest engineering challenges facing SpaceX. As Elon Musk has acknowledged, a reusable orbital return heat shield is the biggest remaining problem to achieving one hundred percent rocket reusability. The belly of the upper stage, also called Starship, is covered in thousands of hexagonal ceramic and metallic tiles that make up the heat shield. Flight 10 was focused on learning how much damage the Ship can accept and survive when it goes through atmospheric heating. During the test, engineers intentionally removed tiles from some sections and experimented with a new type of actively cooled tile to gather real-world data and refine the designs.
The Space Shuttle Columbia provided an unwelcome lesson on thermal shield vulnerability in 2003. A piece of insulating foam struck the thermal tiles on the left wing of Columbia during liftoff, a critical error that resulted in the loss of the vehicle and its seven astronauts upon reentry. Twenty-two years later, SpaceX is focused on mapping performance even in worst-case scenarios. If post-flight data shows the Ship stayed within anticipated temperature margins, it pushes the company forward toward the eventual goal of landing the stage upright to be refurbished and reused.
Propulsion redundancy was also put to the test. The Super Heavy booster’s landing burn configuration appeared to be a rehearsal for an engine failure. Engineers intentionally disabled one of the three center Raptor engines during the final phase of the burn and used a backup engine in its place. This was a successful rehearsal for an engine-out event.
Finally, SpaceX reported the in-space relight of a Raptor engine, described on the launch broadcast as the second time the company has accomplished this. Reliable engine restarts will be necessary for deep-space missions, propellant transfers, and some payload deployment missions.
NASA’s Artemis program hinges on SpaceX developing a heat shield that survives reentry and a ship that can reliably relight in orbit to deliver astronauts safely to the lunar surface. The agency has awarded SpaceX just over four billion dollars for a version of Starship that can land on the Moon. The first Starship lunar landing is currently scheduled for mid-2027.
NASA calibrates risks differently according to the mission profile, accepting a higher degree of risk on uncrewed service missions and a very low risk for crewed transport. The agency sets quantitative safety targets that must be demonstrated via testing and flight data before it will put astronauts on a new rocket. Those levels do not change for Starship just because it is a larger vehicle, but it does mean there are more potential failure modes.
Viewed together, these experiments indicate that SpaceX is testing with these standards in mind. The company will introduce many more changes with the next version of Starship, called Block 3, including a higher-thrust Raptor engine, upgrades to the flaps on the Ship, and updates to avionics and guidance, navigation, and control systems. The next step is translating Flight 10 data into future hardware upgrades to move closer to routine operations and days when, as envisioned, Starship launches more than twenty-four times in twenty-four hours.