Solid Propellant Pulsed Plasma Propulsion System Design

Abstract

Fundamental definitions, a few semiempirical correlations of experimental data, and two design constraints of solid propellant-pulsed plasma thrusters are used to illustrate the design analysis of such an electric propulsion system. The semiempirical relations presented have been generated from thruster data covering impulse bits extending from 2.7 dyne-sec (6/i Ib-sec) to 31 mN-sec (7 mlb-sec) and a specific impulse up to 5100 sec. They are descriptive to within about 8%. Basic ConsiderationsA PULSED plasma thruster utilizes the rapid discharge of energy E from an energy storage capacitor to accelerate a small quantity of mass of plasma to a high discharge velocity. J The ejection of this mass produces an impulse bit 7. If the thruster is operated at a fixed pulse frequency/, an equivalent steady state thrust Tis generated T=fl(1) where any consistent metric or engineering units can be used. The corresponding equivalent steady electric power P delivered to the thruster nozzle by the capacitor is then P=fE(2)If a power conditioner of efficiency rj p is used to charge the capacitor the required bus power will beThe relationship between the propellant mass m consumed per thruster discharge and its equivalent steady flow rate m is rh=fm The specific impulse I sp is thereforewith ing denoting the weight flow rate of propellant. The thrust efficiency 17 1 isIf the power conditioner is included, the system efficiency r? 5 becomesA given pulsed plasma thruster is unique because its thrust is varied at constant specific impulse and efficiency. Variable thrust is realized by merely varying the pulse rate. The electric power requirements are then directly proportional to the pulse frequency.

Recent Advances in MEMS-Based Microthrusters

“…Guman et al [93], relatively early, presented the design of a solid propellant pulsed plasma microthruster to meet specific mission requirements. The solid propellant pulsed plasma microthruster utilized poly-tetrafluoro ethylene (PTFE) as propellant, which has some advantages, such as simple structure, high reliability, and low electrical power for its operation.…”

Effect of power on PPT discharge current

“…The PPT discharge current curves are analyzed to provide an estimate of impulse bit, I bit . The I bit is related to the discharge current via equation (1) and is determined by integrating the discharge current curve (Guman, 1976;Pottinger and Scharlemann, 2007):…”

Discharge Frequency Modulation of Pulsed Plasma Thruster

“…The frequency of discharge is important from the thrust-generation point of view. 17 A method was suggested for pulse modulation by Dubey et al 16 by varying the initial supply voltage and capacitance. However, varying the initial supply voltage and capacitance involves complexities such as the use of a capacitor bank and a high-voltage power supply.…”