Overview of the Development of the Solar Electric Propulsion Technology Demonstration Mission 12.5-kW Hall Thruster

NASA is developing mission concepts for a solar electric propulsion technology demonstration mission. A number of mission concepts are being evaluated including ambitious missions to near Earth objects. The demonstration of a high-power solar electric propulsion capability is one of the objectives of the candidate missions under consideration. In support of NASA's exploration goals, a number of projects are developing extensible technologies to support NASA's near and long term mission needs. Specifically, the Space Technology Mission Directorate Solar Electric Propulsion Technology Demonstration Mission project is funding the development of a 12.5-kilowatt magnetically shielded Hall thruster system to support future NASA missions. This paper presents the design attributes of the thruster that was collaboratively developed by the NASA Glenn Research Center and the Jet Propulsion Laboratory. The paper provides an overview of the magnetic, plasma, thermal, and structural modeling activities that were carried out in support of the thruster design. The paper also summarizes the results of the functional tests that have been carried out to date. The planned thruster performance, plasma diagnostics (internal and in the plume), thermal, wear, and mechanical tests are outlined

Neptune Orbiters Utilizing Solar and Radioisotope Electric Propulsion

In certain cases, Radioisotope Electric Propulsion (REP), used in conjunction with other propulsion systems, could be used to reduce the trip times for outer planetary orbiter spacecraft. It also has the potential to improve the maneuverability and power capabilities of the spacecraft when the target body is reached as compared with non-electric propulsion spacecraft. Current missions under study baseline aerocapture systems to capture into a science orbit after a Solar Electric Propulsion (SEP) stage is jettisoned. Other options under study would use all REP transfers with small payloads. Compared to the SEP stage/Aerocapture scenario, adding REP to the science spacecraft as well as a chemical capture system can replace the aerocapture system but with a trip time penalty. Eliminating both the SEP stage and the aerocapture system and utilizing a slightly larger launch vehicle, Star 48 upper stage, and a combined REP/Chemical capture system, the trip time can nearly be matched while providing over a kilowatt of science power reused from the REP maneuver. A Neptune Orbiter mission is examined utilizing single propulsion systems and combinations of SEP, REP, and chemical systems to compare concepts

Pulsed Plasma Thruster Systems for Spacecraft Attitude Control

Pulsed Plasma Thrusters (PPTs) are finding renewed user appeal due to the growth in small satellite applications. PPTs are especially well suited to small satellite applications because they are simple, low-mass, and high Isp propulsion systems. The solid Teflon fuel allows for a self-contained, inert and stable propellant system. With a power draw of only 0.1 to 150 W and a very small (50 - 800 µNs) impulse bit, PPT technology makes it possible to consider a revolutionary attitude control system (ACS) concept providing stabilization and pointing accuracies previously obtainable only with reaction wheels, with reduced mass and power requirements. NASA Lewis Research Center (LeRC) and Olin Aerospace Company (OAC) are working together to develop an advanced PPT system with twice the total impulse capability and half the mass of the previous best PPT system. The two key factors to accomplish these goals are: 1 ) significantly improving thrust efficiency - the ratio of thrust power to input electrical power and 2) improving the energy density and life of the energy storage capacitor. Typically, PPTs provide relatively low efficiency, with the LES 8/9 PPT delivering a little more than 7 percent. OAC has tested a matrix of configuration parameters with improvement in the efficiency by a factor of 1.5 to 2.0. To achieve the LeRC goals, the capacitor must be capable of 20 million pulses at an energy level of 40 J, ideally with a mass of no more than 1 kg. LeRC and OAC have embarked upon a two-step process to demonstrate the capacitor technology, with benchtop testing at OAC and integrated PPT/capacitor life testing at LeRC to be conducted in the development phase. The program provides for design, fabrication and qualification of a flight PPT, which is then slated to fly as an orbit raising demonstration aboard the Air Force Phillips Lab MightySat II.1 in early 1999. A second unit, configured for ACS functions, is planned for flight on the NASA New Millennium EO-1 spacecraft in mid-1999. With a light, high performance PPT in development for flight applications, it becomes possible to consider replacement of momentum wheels with PPTs. Typical momentum wheel attitude control systems consume 10\u27s of W power and weigh 0.1 kg per kg of spacecraft weight, including the momentum desaturation devices. Mission analysis to be presented shows the PPT to be very competitive with these systems, with the advantages of lower cost, lower mass, extension of ACS capability to very small (nano) satellites, and simplicity in replacing both the wheels and the desaturation devices

Future-Oriented Research Platform For Orbital Cryogenic Storage Technologies (FROST)

To enable human space missions to mars and beyond, future payload mass needs to increase significantly. Cryogenic propellants with both high specific impulse and with the possibility of fuel production on mars make them an excellent choice for these types of missions. Using cryogenic propellants for missions longer than a few hours has several challenges including the need to minimize liquid losses due to boil-off caused by low storage temperatures and to manage the low-g issues. In this paper, a Future Oriented Research Platform For Orbital Cryogenic Storage Technologies (FROST) is proposed as a possible payload for DLRs own satellite program CompSat (500 kg class) in order to be able to carry out an important and necessary development step. The platform is intended to demonstrate new technologies for long-term storage of cryogenic media and to achieve new scientific knowledge about fluid behavior under reduced gravity. The essential elements of the platform are a super-insulated storage tank, a transparent experiment tank and a transparent transfer line. It is planned to realize the mission together with NASA GRC. In the paper, the results of the system study are presented and the possibilities of the platform are explained