This paper describes a new type of piston accumulator which uses a solid propellant gas generator to pressurize hydraulic fluid. It is a self-contained device in that both the power source and hydraulic fluid are packaged together in single accumulator. The device rapidly supplies high pressure and high flowrate hydraulic fluid on-demand much like an airbag system for automobiles. It is particularly suited for emergency applications such as closing of subsea BOP shear rams, closing pipeline valves, etc. A conventional piston accumulator can be easily retrofitted with a gas generator cartridge with only minor cap and piston modifications. Retrofitting a conventional compressed gas accumulator with a gas generator cartridge increases the performance of the accumulator by nearly 10X in terms of usable fluid, reliability, weight, and volumetric footprint. Additionally, the gas generator equipped accumulator requires essentially no maintenance and has a service life of more than 10 years. In DMAS applications it can be used in a "Direct-To-Hydraulics" mode by connecting the accumulators directly to the shear rams without the need for any valves other than a check valve. It also eliminates the hydraulic delay system in the DMAS with an electronic delay between CSR and BSR activation, and does not need a complex control system.