Abstract: A fuel cell-based power system comprises a fuel cell configured for continuously receiving a first reactant and a second reactant to produce chemical reactions that generate electrical power, water, and heat, a coolant subsystem configured for circulating a primary coolant in association with the fuel cell, thereby absorbing the generated heat, a tank configured for storing a reactant, and a reactant distribution subsystem configured for conveying the reactant from the tank to an independent system, the fuel cell as the first reactant, and the coolant subsystem as a secondary coolant to remove the absorbed heat from the primary coolant and/or a water accumulator. The secondary coolant may be conveyed to a gas thruster as a gas after the absorbed heat has been removed from the secondary coolant. The reactant may be boil off of a cryogenic liquid or vapor or gas transformed from a cryogenic liquid via a heater.