The invention relates generally to dual mode bipropellant chemical rocket propulsion systems to be used in aerospace applications for 1) orbit raising, orbit maneuvers and maintenance, attitude control and deorbiting of spacecraft, and/or 2) propellant settling, attitude and roll control of missiles, launchers and space planes. The present invention also relates to a dual mode chemical rocket engine for use in such systems. The engine uses low-hazardous storable liquid propellants and can be operated either in monopropellant mode or in bipropellant mode. The monopropellants used are a low-hazard liquid fuel-rich monopropellant, and a low-hazard liquid oxidizer-rich monopropellant, respectively.

Provided are devices for generating a desired gas or mixture of gases by thermally decomposing a gas-generating composition (e.g. an oxalate salt) using the thermal energy generated by reaction of a heat-generating composition (e.g. a thermite mixture), and methods of making and using such devices. The devices of some embodiments include phase-changing separators, i.e. separators that at least partially melt, vaporize, or sublimate as a result of the thermal energy generated by the heat-generating composition.

Provided are devices for generating a desired gas or mixture of gases by thermally decomposing a gas-generating composition (e.g. an oxalate salt) using the thermal energy generated by reaction of a heat-generating composition (e.g. a thermite mixture), and methods of making and using such devices. The devices of some embodiments include phase-changing separators, i.e. separators that at least partially melt, vaporize, or sublimate as a result of the thermal energy generated by the heat-generating composition.