SpaceX's new Starship SN4 prototype exploded before an engine test on Friday, causing an explosive fireball at the company's testing facilities near Boca Chica, Texas. The explosion happened at about 1:49 p.m. CT, a minute after a test of the Raptor rocket engine, reports Space.com. It is not clear what caused the explosion. The accident comes just before Elon Musk's company and NASA launch the Falcon 9 rocket with the Crew Dragon spacecraft, with two NASA astronauts aboard, on Saturday.
The SN4 vehicle exploded after the engine started, Business Insider reporters. A fireball exploded next, burning the remainder of the rocket. Celia Johnson, who is one of the remaining homeowners in Boca Chica, told the outlet she heard the explosions before they were shown on LabPadre, a YouTube channel that live-streams SpaceX activity. "I heard all of my windows rattle, and then I heard something hit the house on the roof, like a big thud," Johnson said. "It was a very loud boom. It's left me feeling stressed and a little deafened."
SpaceX has not commented on the situation. The livestream appears to show there was a fuel leak from the SN4. The ship uses liquid methane and liquid oxygen as fuel in separate, cooled tanks. One of the liquids began leaking, creating vapor clouds. When the vapor expanded it reached a flare stack, Business Insider explained. Usually, the flare stack would burn off evaporating fuel, but this ignited the vapors, causing the ship to explode.
The company has seen several other Starship prototypes explode, but Musk has soldiered on. The Starship MK1 was destroyed during a November 2019 and then the SN was destroyed in February, both in similar pressure tests. The SN2 passed the pressure test in March, but the SN3 collapsed during the test in April. The SN4 was the longest-living version, making it through five tests, until it exploded Friday. An SN5 is already in the works.
SpaceX has a chance to quickly move on from the SN4 setback, since Saturday will hopefully see the launch of its Falcon 9 rocket and the Crew Dragon shuttle with two astronauts aboard. The mission, named Demo-2, will send the astronauts to the International Space Station. It will be SpaceX's first crewed flight and the first crewed flight to launch from the Kennedy Space Center since the NASA space shuttle fleet retired in July 2011. The launch was originally scheduled for Wednesday, but was delayed due to poor weather in Florida.