SpaceX Starship: how a staggering explosion sent “SN4" plans up in flames

A SpaceX Starship prototype exploded last week during a test, but amid the company's other achievements and broader global events, the news slipped under the radar.

On May 29, hours before SpaceX would send its first humans into space, the "SN4" prototype went up in flames in dramatic fashion. The explosion took place at the Boca Chica facility in Texas, where it's developing a rocket that can send humans to Mars and beyond. The dramatic explosion of "SN4" ended hopes that it would be the first prototype to complete a small "hop" launch.

"Unfortunately what we thought was going to be a minor test of a quick disconnect ended up being a big problem," CEO Elon Musk told Reuters reporter Joey Roulette on Sunday, after leaving the Kennedy Space Center's press site.

The comments led to analysis from Teslarati that the explosion was caused by the ground support equipment, where the "quick disconnect" refers to a propellant connection. These systems need to be able to disconnect and reconnect to the Starship when needed. This suggests the test failed when the quick disconnect system could not completely reconnect.

The event was captured by Tim Dodd, a YouTuber that goes by the name "Everyday Astronaut":

SpaceX was expected to do great things with "SN4." The firm was expected to use the full-size prototype to finally complete a "hop test." Musk stated in April that the prototype would be "physically ready" for a hop test in a few weeks, and that it would fly 150 meters or 500 feet into the air. On May 6, Musk announced the ship's single Raptor engine had completed a static test fire, a critical step toward the jump.

The feat would have meant SpaceX had reached the same height as it did with the "Starhopper." This miniaturized version of the ship, measuring around 60 feet tall rather than around 400 feet, flew to 150 meters in August 2019. The ship was affectionately dubbed by Musk as "R2D2's dad."

A successful launch for "SN4" would have cleared the way for SpaceX to focus on more ambitious tests, like a 20-kilometer jump. That would have enabled the team to focus on planning for next stages, like sending Japanese billionaire Yusaky Maezawa around the moon by 2023. SpaceX plans to let the Starship take over Falcon 9 and Falcon Heavy satellite launches, while also supporting bolder missions like a base on the moon and a city on Mars.

An "SN4" jump would have enabled SpaceX to continue onto its next stage of the project. On Friday, that plan went up in flames.

Slipping under the radar – The event would have been the biggest news in SpaceX's week if it weren't for the fact that there was so much else going on. Space.com reported the explosion took place at around 2:49 p.m. Eastern time on Friday. Around 24 hours later and 1,030 miles away, SpaceX wiped away any chance of the explosion becoming its news story of the week.

At 3:22 p.m. Eastern time on Saturday, a Falcon 9 launched from the Kennedy Space Center in Florida carrying NASA astronauts Bob Behnken and Doug Hurley. The mission marked the end of a six-year journey from NASA choosing SpaceX and Boeing to develop a capsule that could send its astronauts into space. This was the first time SpaceX had launched a human, and the first time in nearly a decade American astronauts had entered space from the United States.

Further events around the world left little chance of "SN4" making any headlines. The coronavirus pandemic continued to spread around the world. The killing of George Floyd by a Minneapolis officer sparked widespread protests against police brutality and the endemic racism within police forces.

The conversation around far more pressing issues meant that not only did "SN4" receive little coverage, but SpaceX coverage, on the whole, was minimized. By the following week, the stories that did receive coverage found a mixed response. Footage of the NASA astronauts ringing the Nasdaq's opening bell on Tuesday, the same day as activists encouraged people to mark "Blackout Tuesday," was criticized by Twitter users as "tone deaf."

Although an important moment for the project, the Starship explosion wasn't even the biggest story at SpaceX this week.

The community responds – Within the SpaceX community, there was discussion about the shock of the explosion. Reddit user "DiskOperatingSystem_" wrote that their "jaw is on the floor," while user "rustybeancake" shared a fun comment template to be used at times like these:

“That’s a shame [currentSN#] has RUD’d, but [part] has no doubt been redesigned anyway, and I’m sure [SN#+1] will be along in a matter of days! I have a good feeling [SN#+1] is the one that will make the hop, no doubt in just a couple of weeks!”

RUD, of course, refers to Rapid Unscheduled Disassembly.

What comes next – The onus could fall to "SN5" or "SN6," under construction in the firm's vertical assembly building. Teslarati estimates that each prototype costs under $10 million to make, a small sum in the grander scheme. CNBC reported that SpaceX was able to raise $346 million in its most recent funding round.

A new hop test could be around the corner. Hans Koenigsmann, the firm's vice president for build and flight reliability, claimed in an interview with Spiegel that the first hop tests could occur in the coming weeks. An orbital flight, he said, could still occur by the end of the year.

Don't rule out a few more RUDs along the way.

The Starship’s journey, summarized

• November 2018 – BFR, first announced in September 2017, gets renamed to Starship.
• December 2018 – Musk confirms the new ship has switched to stainless steel.
• January 2019 – Shortened “Starhopper” prototype unveiled and Musk explains the switch to steel.
• February 2019 – Raptor engine beats a long-standing rocket record.
• April 2019 – Starhopper completes a tethered “hop.”
• July 2019 – Starhopper launches 20 meters (67 feet).
• August 2019 – Starhopper launches 150 meters (500 feet)
• September 2019 – Starship Mk.1 full-size prototype unveiled.
• May 2020 – Starship SN4 full-size prototype completes a static test fire.