NOVELTY - A first volatile liquid rocket propellant (24) contained in a first reservoir, having a liquid volume (20), has a volatility sufficient, under operating conditions, to pressure feed the first propellant and a second less volatile liquid rocket propellant (44) to the rocket engine (42) without the need for a separate feed mechanism. The second propellant being contained in a second reservoir (12) which is in pressure communication with the first reservoir and the propellants being fed through conduits (38) (40) and (46).    USE - In feeding liquid propellants to a rocket engine under pressure.    ADVANTAGE - The pressurizing vapor is a vapor in equilibrium with one the propellants so that the need to carry a separate pressurizing gas to pressurize the propellants, as is common in prior art systems, is eliminated. This eliminates the need for a pressurizing gas tank and associated equipment necessary for the pressurizing gas to pressurize the propellants (stored gas systems) or the need for a propellant reservoir with a very large ullage space (blowdown systems). The pressurized fuel system self throttles the rocket engine by providing a gradually reducing propellant flow. The system may be shut off and reactivated reliably and repeatedly. Any number of propellants may be supplied under pressure as long as the propellants are in pressure communication with at least one pressurizing propellant that has a volatility such that its vapor pressure, under operating conditions, is sufficient to pressurize the propellants to a required predetermined pressure.    DETAILED DESCRIPTION - INDEPENDENT claims are also included for; (a) a method of providing liquid propellants to a rocket engine including removing vapor from the ullage space (30) through a vapor/liquid separator (28) for use in cold gas thrusters, applying pressure to an inert fluid interposed between the first propellant vapor and the second propellant, using a pump (43) to assist feeding one or both propellants and electrically heating the first propellant to cause vaporization; and (b) a method of transferring liquid propellant from a donor tank to a receiving tank under zero gravity conditions. The first propellant being selected from ethane, ammonia, nitrous oxide, propane and light hydrocarbons containing dissolved ethane, ethylene or methane. The second propellant being selected from hydrogen peroxide, nitric acid, nitrogen tetroxide, perchloryl fluoride.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of an embodiment using a common container.    common container (10)    second reservoir (12)    circumferential crimping (13)    first reservoir liquid volume (20)    first volatile liquid rocket propellant (24)    vapor/liquid separator (28)    ullage space (30)    (40)(46) outlet conduits (38)    rocket engine (42)    pump (43)    second volatile liquid rocket propellant (44)