SpaceX Starship wraps up nosecone ‘cryo proof’ and first of several Raptor static fires

While pretty, Starship SN8's firework-like light show is unusual and unlikely to be a good sign. (NASASpaceflight - bocachicagal)

SpaceX has successfully ‘cryoproofed’ the first fully-assembled Starship prototype’s nose-based propellant tank and used that same tank to fire up a Raptor engine, crossing off one of the last major tests before the rocket’s 15-kilometer (~9.5 mile) launch debut.

On November 4th, after a few false-starts, Starship Serial Number 8 (SN8) kicked off its first round of testing after becoming the first prototype to have a nose section permanently installed. On that Wednesday evening, SpaceX most likely put the rocket through a partial cryogenic proof test explicitly focused on SN8’s new nosecone and a small secondary propellant tank situated in its tip. Designed to act as a secondary reservoir for the relatively small amount of propellant Starships need to land, SN8’s two header tanks were likely loaded with cryogenic liquid nitrogen – a safe, nonreactive stand-in for liquid oxygen and methane.

Having proven that Starship SN8’s newly-installed liquid oxygen header tank and associated plumbing is capable of loading, managing, and offloading dozens of tons of cryogenic fluid while navigating a 40-meter-tall (~130 ft) vertical pipe, SpaceX was ready to move onto the next step: a wet dress rehearsal (WDR) and Raptor static fire.

While SpaceX has technically completed eight successful Raptor static fires on four separate prototypes, including the first three-Raptor static fire ever attempted with Starship SN8, the company has never attempted a static fire while solely drawing propellant from header (landing) tanks. All but essential for Starships to be able to reliably reignite their Raptor engines in flight and keep cryogenic landing propellant liquid for hours, days, weeks, and even months, much smaller header tanks make it easier to keep propellant highly pressurized and in the right place to supply Raptors.

After several days of test windows come and gone and an aborted attempt on November 9th, Starship SN8 finally ignited one of its three Raptor engines, feeding the engine with liquid methane and oxygen stored in two separate header tanks. Oddly, a second or two after startup and ignition, Raptor’s usual exhaust plume was joined by a burst of shiny firework-like debris. A relatively normal five seconds later, the Raptor cut off, though the engine appeared to remain partially on fire for another ten or so seconds – also somewhat unusual.

Ultimately, the observed anomaly could be as simple as debris accidentally left in the vicinity of Raptor’s plume or, while less likely, concrete erosion. There’s also a chance that it was pieces of Raptor’s complex turbopumps or preburners, although it’s also unlikely that the engine would have continued running (as it did) if it had lost that much internal hardware.

(Update: Thankfully, NASASpaceflight.com reporter Michael Baylor says that the cloud of debris observed on November 10th “is not a [Raptor performance] concern,” making pad debris the likely source.)

SpaceX has canceled another static fire window on November 11th, leaving the next opportunity for a second (of three) expected static fire between 9am and 9pm CST (UTC-5) on Thursday, November 13th.

Eric Ralph: I write about space, among other things.
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