High Performance Capacitor for Pulsed Plasma Thruster

A high energy density capacitor will be developed utilizing Chemical Vapor Deposited diamond as the dielectric. The energy density of diamond multi-layer stacked or comb structure capacitors can potentially exceed 20 J/g. Even more modest energy densities of 2 J/g significantly exceed the current state-of-the-art capacitors used for Pulsed Plasma Thrusters on spacecraft. The use of high energy density diamond capacitors in PPT systems could reduce the mass of the propulsion system by 30%. Previous measurements of diamond test capacitors indicate breakdown voltages in the 3 to 4 kV/micron range and a dielectric constant of 5.5. The high temperature capability of diamond and its non-dipole crystal structure will allow rapid charge/discharge cycles without damage. During Phase I, a single layer test capacitor 5 cm. in diameter will provide 35 nano-farads of capacitance and 0.16 Joules of energy with an energy density of 0.04 J/g. Phase II will develop a multi-layer capacitor in a stacked configuration to increase the energy density, capacitance, and total energy stored in the capacitor. The Phase II device is expected to have energy density greater than 0.5 J/g, provide 1 micro-farad capacitance, and store 4.5 Joules of energy and reduce PPT system mass by 30%.