by Amanda Kooser

SAN FRANCISCO (CNET) — “Space is hard” is a phrase we hear a lot and SpaceX knows exactly why.

Elon Musk’s company has witnessed a parade of Starship spacecraft prototypes fall victim to the hazards of testing. The latest is SN4, or “Serial Number 4,” which exploded at SpaceX’s Texas facility on Friday.

The Starship prototype is unrelated to the SpaceX Crew Dragon spacecraft, which is still scheduled to launch two NASA astronauts to the International Space Station this weekend.

A team of dedicated SpaceX watchers had been following the testing. “RIP Starship SN4,” tweeted the space specialists from news site NASASpaceFlight.com, who were monitoring the event.

The fiery loss of SN4 looked spectacular, but it’s just business as usual during SpaceX’s rapid prototyping phase for the next-generation spacecraft Musk hopes will carry humans to the moon and (eventually) Mars. The previous prototype, SN3, crumpled during a pressure test in April.

SN4 was trying out a Raptor engine in anticipation of a short test hop similar to what a Starship “hopper” prototype achieved in 2019. SpaceX is working toward an orbital test flight that would send a Starship into space.

NASASpaceflight.com ran a livestream of the proceedings, giving us a detailed look at the explosive event. You can check out the video and subsequent analysis:

The cause of the explosion isn’t known yet. SN4 seemed to have made it through a short test firing of the Raptor engine prior to the anomaly. SpaceX didn’t immediately respond to a request for comment.

Musk and SpaceX are willing to accept the loss of prototypes in exchange for moving the testing process along at a fast clip. The next Starship, SN5, is already well under way in construction. It will soon step up for testing as SpaceX hopes to get off the ground with an actual hop.

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