GPIM AF-M315E Propulsion System
The NASA Space Technology mission Directorate's (STMD) Green Propellant Infusion Mission (GPIM) Technology Demonstration Mission (TDM) will demonstrate an operational AF-M315E green propellant propulsion system. Aerojet-Rocketdyne is responsible for the development of the propulsion system payload. This paper statuses the propulsion system module development, including thruster design and system design; Initial test results for the 1N engineering model thruster are presented. The culmination of this program will be high-performance, green AF-M315E propulsion system technology at TRL 7+, with components demonstrated to TRL 9, ready for direct infusion to a wide range of applications for the space user community.
Space Propulsion Technology for Small Spacecraft
As small satellites become more popular and capable, strategies to provide in-space propulsion increase in importance. Applications range from orbital changes and maintenance, attitude control and desaturation of reaction wheels to drag compensation and de-orbit at spacecraft end-of-life. Space propulsion can be enabled by chemical or electric means, each having different performance and scalability properties. The purpose of this review is to describe the working principles of space propulsion technologies proposed so far for small spacecraft. Given the size, mass, power, and operational constraints of small satellites, not all types of propulsion can be used and very few have seen actual implementation in space. Emphasis is given in those strategies that have the potential of miniaturization to be used in all classes of vehicles, down to the popular 1-L, 1-kg CubeSats and smaller.
Effect of Duty Cycle on Catalytic Thruster Degradation
T is generally known within the industry that the life of hydrazine catalytic thrusters is dependent on the way they are operated. Total impulse, number of pulses, pulse width and frequency, operating temperature, and the operating environment all contribute to thruster wear and degradation. This duty cycle dependence has become increasingly evident in the application of these thrusters to three-axis stabilization of spacecraft; differences have been observed in the rate of performance degradation and in the type of anomalies experienced. It has become clear, for example, that demonstration of great capability in one application does not necessarily imply a similar capability under a different type of use. These findings have significance with regard to the goal of producing standardized thrusters that will satisfy the requirements of a variety of missions and thus minimize costs for thruster development and qualification. This paper addresses the effects of duty cycle on performance of 5-lbf (22-N) thrusters used for three-axis stabilization. Some aspects of anomalous thruster behavior and duty cycle effects have been discussed in the literature,1>2 but there has not been a broad treatment of the subject. Also, understandably, thruster manufacturers are reluctant to discuss problems that may have been encountered in the course of development testing or flight applications. For this study, the information available includes flight and groundtest data involving a number of different designs and mission duty cycles. The intent of this paper is to demonstrate the influence of duty cycle on thruster degradation, and to show how various phenomena are related to the way the thruster is used. Finally, cases will be presented which show that a thruster design chosen for a specific application may be at a distinct disadvantage when evaluated for different requirements. It should be recognized at the outset that it is not possible to cover all the observed anomalies and that different designs may respond differently to the same duty cycle. However, it is hoped that this discussion will reveal something of the sensitivity of hydrazine thrusters to the way they are used, since this can be an important consideration in spacecraft design.