SpaceX founder Elon Musk also wants Starship to fly to Mars, which will, likewise, require a mastery of in-space refueling. NASA may also soon rely on Starship and other massive commercial rockets to launch astronauts from Earth. The Trump administration has proposed canceling NASA’s Space Launch System rocket after two more flights in favor of lower-cost commercial options.
Before any of this becomes possible, SpaceX must prove it has overcome the setbacks encountered on the two previous test flights. Both flights failed at roughly the same time—approximately eight minutes after liftoff—near the end of the ship’s engine firing. SpaceX investigators, working under the oversight of the Federal Aviation Administration, determined the Starship test flight in January failed after propellant leaks led to fires in the rocket’s aft compartment, or attic. This led to the early shutdown of the rocket’s engines and eventual breakup.
Engineers concluded that the leaks were most likely caused by vibrations during the ship’s climb into space. The vibrations were in resonance with the vehicle’s natural frequency, intensifying the shaking beyond the levels SpaceX predicted. For the next test flight on March 6, SpaceX made changes to the ship’s feed lines routing fuel to its Raptor engines, made adjustments to propellant temperatures, and flew the engines at a new throttle setting.
But that didn’t solve the problem. Once again, Starship’s engines cut off too early, and the rocket broke apart before falling to Earth. SpaceX said “an energetic event” in the aft portion of Starship resulted in the loss of several Raptor engines, followed by a loss of attitude control and a loss of communications with the ship.
The similarities between the two failures suggest a likely design issue with the upgraded “Block 2” version of Starship, which debuted in January and flew again in March. Starship Block 2 is slightly taller than the ship SpaceX used on the rocket’s first six flights, with redesigned flaps, improved batteries and avionics, and notably, a new fuel feed line system for the ship’s Raptor vacuum engines.
SpaceX has not released the results of the investigation into the Flight 8 failure, and the FAA hasn’t yet issued a launch license for Flight 9. Likewise, SpaceX hasn’t released any information on the changes it made to Starship for next week’s flight.
What we do know about the Starship vehicle for Flight 9—designated Ship 35—is that it took a few tries to complete a full-duration test-firing. SpaceX completed a single-engine static fire on April 30, simulating the restart of a Raptor engine in space. Then, on May 1, SpaceX aborted a six-engine test-firing before reaching its planned 60-second duration. Videos captured by media observing the test showed a flash in the engine plume, and at least one piece of debris was seen careening out of the flame trench below the ship.
SpaceX ground crews returned Ship 35 to the production site a couple of miles away, perhaps to replace a damaged engine, before rolling Starship back to the test stand over the weekend for Monday’s successful engine firing.
Now, the ship will head back to the Starbase build site, where technicians will make final preparations for Flight 9. These final tasks may include loading mock-up Starlink broadband satellites into the ship’s payload bay and touchups to the rocket’s heat shield.
These are two elements of Starship that SpaceX engineers are eager to demonstrate on Flight 9, beyond just fixing the problems from the last two missions. Those failures prevented Starship from testing its satellite deployer and an upgraded heat shield designed to better withstand scorching temperatures up to 2,600 degrees Fahrenheit (1,430 degrees Celsius) during reentry.
This story originally appeared on Ars Technica.