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At around 7:15 pm local time, SpaceX Starship’s SN8 prototype fired one or more Raptor engines for the third time ever, taking spectators by surprise – only a dress rehearsal was expected. An hour later, CEO Elon Musk revealed that SpaceX had indeed lost control of the rocket.
Unfortunately for SpaceX, this isn’t the first incident where a fire has led to the loss of control of Starship. In May 2020, starship serial number 4 (SN4), the first full-scale prototype to have a Raptor installed, successfully completed its third static fire test. Moments later, a vent line adjacent to the engine section caught fire, burning for a minute or two. Eventually, possibly due to the destruction of cables or pipes, SpaceX apparently lost control of SN4 and had to wait two full days for the cryogenic propellant to evaporate and evaporate before teams could approach the rocket to inspect, repair and retake the control.
Now, most likely, the Starship SN8 has suffered a similar, but not identical, failure, cutting off some level of control. Elon Musk spoke on Twitter about an hour after the Raptor rocket’s third static fire, revealing that SpaceX had lost control of Starship’s pneumatics, referring to the hydraulic systems needed to operate most of the rocket’s valves. For SN8, this meant nothing more than bad news.
When cryogenic liquids (and all things in general) heat up, they expand, taking up more volume. To counter that endless process of heating, boiling and turning the cryogenic propellant into gas, the fresh propellant is charged almost continuously as the hotter gas is discharged, thus maintaining safe tank pressures. If the ability to vent those gases is lost, the ability to maintain safe pressures ensues.
As Musk noted above, the Starship SN8 fortunately – and unexpectedly – had one or more burst discs installed, referring to single-use mechanical valves designed to open (i.e., burst) above a specific pressure. The SN8’s nose blast disc did just that, bursting to create an outlet for the pressure that builds up inside the rocket and thus preventing the small nose-based liquid oxygen reservoir (LOx) from exploding.
Unfortunately, the harbinger of Starship’s loss of control is a far less positive story. According to Musk, one of the running Raptor SN8 engines may have suffered significant failure, melting one or more critical engine components. It is unclear exactly how a seemingly contained engine failure evolved into a total loss of the spaceship’s hydraulics, but it is certain that redundancy will be added and updated designs implemented to ensure that a similar failure does not recur.
Notably, both the unofficial live streams of LabPadre and NASASpaceflight.com clearly showed Starship quite literally. dripping molten metal for more than two minutes after the static fire. Whatever the cause of that extremely hot fire, anything that can continuously melt metal for minutes will almost certainly have devastated the stern of the Starship SN8 and the Raptor engines installed inside it. It’s nothing short of a miracle that the SN8’s main LOx tank wasn’t hacked either.
Ultimately, the SN8 will likely need extensive repairs and one, two, or even three replacement engines before it can safely restart testing and proceed towards its 15km (~ 9.5 mi) launch debut. Additionally, SpaceX’s lack of valve control likely means the company will have to wait at least 24+ hours before workers can safely return to the launch pad and begin those inspections and repairs.
To update: The roadblock was removed at around 11pm local time and SpaceX workers appear to have already returned to the pad, meaning the SN8 spaceship has been completely dismantled and is safe to approach. Inspections and repairs will likely begin as soon as possible.
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