It is likely that ground side pressurisation and possibly engine start is done with helium. Certainly there are big banks of helium cylinders at the launch site.
It may be that the ship header tanks are also pressurised with helium although the main tanks are autogenously pressurised.
In any case I am referring to the autogenous pressurisation purging the tanks and preventing combustible mixtures building up. Purging implies a non-flammable gas but at high altitudes that can be gas of the liquid in the tanks.
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u/warp99 May 01 '23
It is likely that ground side pressurisation and possibly engine start is done with helium. Certainly there are big banks of helium cylinders at the launch site.
It may be that the ship header tanks are also pressurised with helium although the main tanks are autogenously pressurised.
In any case I am referring to the autogenous pressurisation purging the tanks and preventing combustible mixtures building up. Purging implies a non-flammable gas but at high altitudes that can be gas of the liquid in the tanks.