The present invention includes an apparatus and method for volumetric and gravimetric storage of reactants and waste comprising: one or more reactant or fuel storage bladders; and one or more waste storage bladders, wherein the reactant or fuel storage bladders and the waste storage bladders form a stack of bladders, and the stack of bladders are interleaved between the reactant or fuel storage bladders and the waste storage bladders, such that both a volumetric and a gravimetric balance is maintained as reactant or fuel are used and the waste bladder is filled.