/sci/ - Science & Math

>>16046785
>>16046832
The reason for this is mass optimization: Superheavy was spending literal tons of mass on ullage gas and the higher the temperature of the gas, less mass needs to be spent on it for the same ullage pressure. It's a reduction in the order of many tens of tons - remember that they aren't using helium but much heavier O2 and CH4 gas.
High temperature methane gas is simple: there is a pure source of very hot supercritical methane from the regenerative cooling system. Tap that directly and you're good to go.
High temperature oxygen gas is much harder: there is no pure source of high temperature O2 because it is not used for regeneratively cooling the combustion chamber. LOX does regeneratively cool the LOX preburner but it wouldn't be nearly as hot as the methane side. There is simply no source of heat large enough on Raptor that isn't already spoken for by the methane.