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  • threelonmusketeers@sh.itjust.worksMEnglish
    1·
    2 months ago

    I posted this over in the SpaceX community, but I guess I’ll post it here too:

    TL;DW:

    Zack draws an allegory of a parasitic relationship between the Superheavy booster (host) and the Raptor 2 engines (parasite dependent on the host, but inflicting detrimental effects).

    Overview of what is known of the current autogenous pressurization system:

    • Raptor 2 uses methane in its regenerative cooling system, which provides a clean source of gaseous methane which is used to pressurize the methane tank.
    • There is no equivalent clean source of gaseous oxygen on Raptor 2, so the easiest option is use dirty “oxygen rich” exhaust from the preburner. This exhaust is mostly oxygen, but contaminated with water and carbon dioxide.

    Water ice floats on liquid oxygen, but CO2 ice sinks in liquid oxygen, settling on the bottom of the LOX tank and clogging the engine inlets.

    Proposed failure mode of IFT-2: Roll and flip maveuvers caused the CO2 “snow” to collect on one side of the bottom of the LOX tank and overload the filters on that side.

    Upgrades to B10 LOX filteration system prior to IFT-3: Two filters (likely mesh) each stretching across the entire cross-section of the LOX tank.

    Proposed failure modes for IFT-3:

    • The roll and flip maneuvers allowed ice to make it past the filters via gaps between the stringers at the edge of the tank.
    • The roll and flip maneuvers caused shift in ice distribution on the filter which lead to a structural failure of the filter itself.

    Upgrades prior to IFT-4: Optimized staging and boostback trajectory to minimize unnecessary roll maneuvers. Result: First successful splashdown of Superheavy.

    Other notes:

    • Even if the design of the filters has been perfected, the presence of ice likely precludes rapid reusabilty. While the CO2 ice would sublimate and could be vented, the water would need to be drained/pumped out between flights.
    • All of these issues would be addressed if Raptor 3 includes an oxygen heat exchanger, which could provide a clean source of gaseous oxygen to pressurise the tank.

    The full video has way more details than I could summarize here; definitely worth a watch!