Abstract: A fluid storage and expulsion system having a rigid tank, the tank having two propellant chambers and two independently operable piston assemblies slidable in their propellant chambers for expelling propellant. In a first embodiment, a coaxial fluid storage expulsion system having inner and outer pistons is provided. Accordingly, the inner piston is provided which is slidable in an inner annular space for expelling fluid therein through a second opening. As well, an outer piston is provided which is slidable in an outer annular space for expelling a second fluid through a first opening. In a further embodiment, the pistons and tanks are positioned in series. As such, the rigid tank is provided with forward and aft propellant chambers as well as forward and aft piston assemblies. A piston guide, which extends the length of the rigid tank is positioned concentrically within the tank.