Space Environment Facility For Electric Propulsion Systems Research

A facility containing 15- and 25-foot-diameter space-environment tanks and support equipment is described. The facility is designed for testing ion and plasma thrustors, 10 sub -7 spacecraft, and related components at pressures in the 10 torr range. Total pumping capacity in the 10 sub -5 torr range for air has been measured at 250 000 liters per second and for hydrogen at 660 000 liters per second. The pumping systems and 28 000- square- foot liquid-nitrogen- cooled condenser are described. Data are presented on an auxiliary fast pumpdown tank that simulates ambient pressures encountered during a booster launch to 10 sub -6 torr range in approximately 2 minutes. Pertinent information concerning a spin test apparatus and thrustor installation method is also included. An electrical and instrumentation system is described consisting of 2 megawatts of 20-kilovolt direct- current power, a 2000-cable patch board network, a 600-channel thermocouple system, and a 400-channel digital data recorder. An annunciator system is provided to indicate status of operating equipment. Some aspects of safety are considered, including interlocking, personnel protection, and procedures.

The sun tower concept of collecting solar energy in space and beaming it down for commercial use will require very affordable in-space as well as earth-to-orbit transportation. Advanced electric propulsion using a 200 kW power and propulsion system added to the sun tower nodes can provide a factor of two reduction in the required number of launch vehicles when compared to in-space cryogenic chemical systems. In addition, the total time required to launch and deliver the complete sun tower system is of the same order of magnitude using high power electric propulsion or cryogenic chemical propulsion: around one year. Advanced electric propulsion can also be used to minimize the stationkeeping propulsion system mass for this unique space platform. 50 to 100 kW class Hall, ion, magnetoplasmadynamic, and pulsed inductive thrusters are compared. High power Hall thruster technology provides the best mix of launches saved and shortest ground to Geosynchronous Earth Orbital Environment (GEO) delivery time of all the systems, including chemical. More detailed studies comparing launch vehicle costs, transfer operations costs, and propulsion system costs and complexities must be made to down-select a technology. The concept of adding electric propulsion to the sun tower nodes was compared to a concept using re-useable electric propulsion tugs for Low Earth Orbital Environment (LEO) to GEO transfer. While the tug concept would reduce the total number of required propulsion systems, more launchers and notably longer LEO to GEO and complete sun tower ground to GEO times would be required. The tugs would also need more complex, longer life propulsion systems and the ability to dock with sun tower nodes. Oleson, Steve Glenn Research Center NASA/TM-1999-209307, E-11833, NAS 1.15:209307, AIAA Paper 99-2872

This paper provides an overview of NASA s activities in the area of electric propulsion with an emphasis on project directions, recent progress, and a view of future project directions. The goals of the electric propulsion programs are to develop key technologies to enable new and ambitious science missions and to transfer these technologies to industry. Activities include the development of gridded ion thruster technology, Hall thruster technology, pulsed plasma thruster technology, and very high power electric propulsion technology, as well as systems technology that supports practical implementation of these advanced concepts. The performance of clusters of ion and Hall thrusters is being revisited. Mission analyses, based on science requirements and preliminary mission specifications, guide the technology projects and introduce mission planners to new capabilities. Significant in-house activity, with strong industrial/academia participation via contracts and grants, is maintained to address these development efforts. NASA has initiated a program covering nuclear powered spacecraft that includes both reactor and radioisotope power sources. This has provided an impetus to investigate higher power and higher specific impulse thruster systems. NASA continues to work closely with both supplier and user communities to maximize the understanding and acceptance of new technology in a timely and cost-effective manner. NASA s electric propulsion efforts are closely coordinated with Department of Defense and other national programs to assure the most effective use of available resources. Several NASA Centers are actively involved in these electric propulsion activities, including, the Glenn Research Center, Jet Propulsion Laboratory, Johnson Space Center, and Marshall Space Flight Center. Dunning, John W., Jr. and Hamley, John A. and Jankovsky, Robert S. and Oleson, Steven R. Glenn Research Center NASA/TM-2004-213329, AIAA Paper 2004-3328, E-14790