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SpaceX reveals why the last two Starships failed as another launch draws near (arstechnica.com)

submitted 7 months ago by llamacoffee@lemmy.world to c/spacex@sh.itjust.works

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[–] threelonmusketeers@sh.itjust.works 5 points 7 months ago (1 children)

SpaceX identified the most probable cause for the May failure as a faulty main fuel tank pressurization system diffuser located on the forward dome of Starship's primary methane tank. The diffuser failed a few minutes after launch, when sensors detected a pressure drop in the main methane tank and a pressure increase in the ship's nose cone just above the tank.

Engineers recreated the diffuser failure on the ground during the investigation, and then redesigned the part to better direct pressurized gas into the main fuel tank. This will also "substantially decrease" strain on the diffuser structure, SpaceX said.

I'm having difficulty visualising what this "diffuser" looks like. Is it part of the autogenous pressurisation system? Do any photos of it exist?

[–] llamacoffee@lemmy.world 2 points 7 months ago (1 children)

Imma have to defer to CSI Starbase for this one 😅

[–] threelonmusketeers@sh.itjust.works 5 points 7 months ago* (last edited 7 months ago) (2 children)

I found some info! It is indeed part of the autogenous pressurisation system.

Diagram from mcrs987:

Photo from megagoose11 / Kevin Randolph:

Someone also dredged up a 189-page PDF on Designing and Optimization of Pressurizing Gas Diffusers in Cryogenic Methane Tanks: A Technical Approach if you're really interested :)

Edit: Also, direct links to the Flight 9 and Ship 36 report (archive) and the Flight 10 webpage (archive).

[–] sleep_deprived@lemmy.dbzer0.com 5 points 7 months ago

Well, I took the plunge. From the thesis:

The diffuser introduces the pressurant gas into the propellant tank as a critical component of the pressurization system in a liquid propulsion engine. Element present in both pressurization systems (self-pressurization and by inert gases), the diffuser makes the pressurant enter the propellant tank at a desired direction and velocity to keep the pressure inside the tank at the design level during the pressurization activities without the engine working (on-ground operations or during coasting phase) and to avoid the creation of zones where the operating pressure falls below a threshold value of NPSH during engine firing.

[–] sleep_deprived@lemmy.dbzer0.com 4 points 7 months ago

Hell yeah, great work. Thanks for reporting back, I was very curious about this too!