The entire Isp Lab facility is a unique laboratory capable
of evaluating either gaseous or condensable propellant EP systems. The Isp Lab maintains the following specialized facilities:
The Isp Lab has the capability for ground-testing
of gaseous propellant Electric Propulsion (EP) systems with available diagnostics to measure several thruster parameters
such as thrust, specific impulse, electrical efficiency and discharge
oscillation.
The centerpiece of the Xenon/Krypton laboratory is a 2-meter-diameter by 4-meter-long space simulation chamber for ground-testing flight-scale ion propulsion systems.
The chamber is evacuated to ultimate pressure using two 48-inch diameter liquid nitrogen-assisted liquid helium cryogenic vacuum pumps.
With the cryopumps the chamber can achieve a vacuum
better than 1E-6 Torr (equivalent to 0.000000001 atmosphere or comparable
to the space shuttle environment) and remove propellant gas emitted by
the thruster at a speed of 120,000 L/s. The facility also utilizes a mechanical
vacuum pump to back the cryopump.
The facility is equipped with a NASA-Glenn-style inverted pendulum thrust measurement stand (shown to the left), a dedicated gaseous mass flow control system for propellant supply, cooling water, power supplies and a comprehensive computer controlled data acquisition system. With the available diagnostics, thruster parameters such as thrust, specific impulse, electrical efficiency, and discharge oscillation can be readily measured.
The existing laboratory instrumentation is available to the Condensable Propellant Facility as well.
A
second space simulation vacuum chamber facility is dedicated to the study
of advanced propellants. Construction for the condensable propellant facility
began in the summer of 2003 and was completed in 2004. The new ground-test facility is specifically designed to evaluate
EP thrusters operating on condensable propellants such as iodine, cadmium,
bismuth, indium and tin.
The new chamber (shown to the right) utilizes three magnetically levitated turbomolecular pumps with pumping speeds of 2,000 L/s each for a robust, oil-free space environment simulation. The chamber will include a custom designed thruster beam stop to capture and pump the exhausted propellant to allow for large propellant flow rates while still maintaining a space-like environment.
In order to study the potential for contamination and metallization of surrounding components, a remotely controlled diagnostic manipulation system was constructed in the exhaust plume of the thrusters. The system is capable of 1-m by 1.5-m linear translation on two axes as well as rotation for motion control of assets during testing.
Remotely
controlled motion tables are shown to the left. They are installed in
both the Xenon Test Facility and Condensable Propellant Facility and are
capable of rotation and translation on two axes for various plume diagnostics.
The facility is capable of operating thrusters with power levels up to 20 kW and thruster performance measurements will be made possible through instrumentation shared between the Condensable Propellants Facility and the Xenon/Krypton Facility.
A UHV vacuum facility was added to the Isp lab to research liquid metal ion sources and field emission electron sources. The facility was designed in the fall of 2007 and completed in the winter of 2008. The chamber is roughly 0.5-meter-diameter by 0.5-meter-long and is capable of pressures as low as 1E-11 Torr.
The chamber is evacuated using a single 300 l/s magnetically levitated turbomolecular pump that is backed by a 110 l/min dry scroll pump. The tank is also equipped with a 300 l/s ion-sublimation combination pump to reach ultra-high vacuum. With the addition of the titanium sublimation pump (TSP) to the ion pump, higher pumping speeds are possible due to the TSP pump’s ability to handle getterable gases.
An additional component to the UHV facility is a trinocular stereo microscope. The microscope has an optical magnification up to 90x and is equipped with a color digital camera. The camera provides the ability to perform in situ imaging, as well as the ability to record video directly through USB2.0.
The Michigan Tech Aerospace Enterprise maintains a laboratory for fabrication and testing of 30-kg-class nanosatellites. Capabilities include complete CAD/CAM/
CAE machining, PCB fabrication, and clean assembly. Past projects include the design and construction of HuskySat, a spacecraft designed to perform passive L-band radiometry for a NASA-GSFC mission to document soil moisture. Currently the lab is the home for project Oculus, which will achieve high-resolution imaging and characterization of resident space objects
A Field Reversed Configuration (FRC) facility was added to the ISP Lab in December of 2007. This facility will be used to study the formation and translation dynamics of annular FRC plasma. The FRC facility is attached to the back of the Condensable Propellant tank.
The FRC experiment consists of two concentric 4-turn electromagnetic coils, insulated by quartz liners. The coils are powered by a 5.8 kJ capacitor bank, with switching accomplished through optically controlled mercury spark gap switches (ignitrons) capable of passing up to 100 kA of current and withstanding a voltage of 50 kV.
Funding for this facility was provided by the US Air Force Research Laboratory.
