SpaceX Tests Starship Fixes After Back-to-Back Failures

SpaceX fired six Raptor engines on the company's next Starship rocket on Monday, clearing a major hurdle on the path to launch later this month on a high-stakes test flight to get the private rocket program back on track.

Starship ignited its Raptor engines Monday morning on a test stand near SpaceX's Starbase launch facility in South Texas. The engine ran for approximately 60 seconds, and SpaceX confirmed the test firing in a post on X: "Starship completed a long duration six-engine static fire and is undergoing final preparations for the ninth flight test."

SpaceX hasn't officially announced a target launch date, but maritime warnings along Starship's flight path over the Gulf of Mexico suggest the launch might happen as soon as next Wednesday, May 21. The launch window would open at 6:30 pm local time (7:30 pm EDT; 23:30 UTC). If everything goes according to plan, Starship is expected to soar into space and fly halfway around the world, targeting a reentry and controlled splashdown into the Indian Ocean.

After Monday's successful static fire test, SpaceX is in the final stretch of preparations for Starship's ninth full-scale test flight. Last month, SpaceX test-fired the rocket's massive booster stage, known as Super Heavy. The Super Heavy booster assigned to the next Starship launch will become the first that SpaceX will reuse from a previous test flight.

This, alone, is a significant step for the Starship program. SpaceX wants the Super Heavy booster and Starship upper stage to become rapidly reusable, eventually operating more like an airplane than a legacy rocket. The booster slated to launch on Flight 9 made its first flight in January, when it soared to the edge of space, released SpaceX's Starship upper stage, and returned to the launch pad, where it was caught in midair by heavy-duty mechanical arms.

SpaceX will again try to catch the Super Heavy booster on Flight 9.

While reusing the first stage is a noteworthy milestone, the next flight is important for another reason. SpaceX's last two Starship test flights ended prematurely when the rocket's upper stage lost power and spun out of control, dropping debris into the sea near the Bahamas and the Turks and Caicos Islands.

With Flight 9, SpaceX hopes to get the Starship program back on track. The company aimed for as many as 25 Starship test flights this year, but will now likely fall short of that number. Near-term goals beyond Flight 9 include returning Starship from low-Earth orbit to the launch site, with a tower catch similar to the one SpaceX used to recover the Super Heavy booster.

Then, SpaceX will begin flight experiments with an in-space refueling system to transfer super-cold liquid propellants between two Starships in orbit. This is an important milestone for NASA, which has a contract with SpaceX worth more than $4 billion to develop a version of Starship for landing humans on the moon. To do that, SpaceX must launch around 10 Starship refueling tankers—the exact number remains unclear—to gas up the moon-bound Starship lander before it can depart low-Earth orbit.

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.