I understand that the propellants (e.g. LOX & LH2) are stored in a rocket tank which is pressurized by Helium or a neutral gas, so as to push the propellants towards the tank outlet, to the turbo-pump suction, and feed the engine combustion chamber. In space i.e. in zero gravity, where "up" and "down" have no meaning like on earth, how is it ensured that (only) the propellants are pushed towards the tank outlet? Merely pressurizing the tank does not ensure this, because it may so happen, that the gas under pressure is shrouding / accumulated near the tank outlet, and pushing the propellant to the other end..away from the outlet, and thus starving the combustion chamber.