Space Propulsion Observation and Testing (SPOT) Lab

The University of Alabama has the ability to design, build and test space vehicles and space propulsion systems. Current efforts are focusing on a “Low Earth Orbit Rendezvous” mission with long term aspiration of “Near Earth Asteroid Prospecting.” Supporting lab capabilities include Earth magnetic field simulation, three degrees of freedom attitude control testing, thermal/vacuum space environment simulation, and space propulsion testing (1000 W, 2m x 3m vacuum chamber, 10-6 torr). The SPOT lab has state-of-the-art plasma diagnostics to analyze ion and magnetoplasmadynamic thrusters as well as any plasma interactions with the spacecraft.

The Earth magnetic field is simulated using a Helmholtz cage.  The configuration being employed has three coils in each of the three axes.  Available power supplies produce up to 1.0 Gauss (4x Earth magnetic field strength). The three degrees of freedom attitude control system will be installed inside the Helmholz cage.  This system employs a zero-g satellite research, spherical bearing.  The spherical bearing allows for highly precise optical alignment (0.01 mm) with +/- 45 degrees of rotation.

The thermal/vacuum space environment simulator maintains pressures below 1.3 mPa (10-5 torr) and can achieve and maintain temperatures between -100 °C and 200 °C (liquid nitrogen shroud and 1000W solar simulation lamps).  This cylindrical vacuum chamber (2m x 3m) provides ample space for spacecraft hardware and instrumentation. (high vacuum pump:  Varian HS-20 Diffusion pump).

space propulsion testing

Space propulsion testing is carried out both the environment simulator and the smaller 2m x 2.5m vacuum chamber (capable of 0.13 mPa, 10-6 torr).  The smaller chamber is dedicated to propulsion system testing.  The pumping capacity is currently capable of testing ion propulsion systems up to 100 Watts comfortably.  The limiting factor is the pumping capability of the Leybold Turbovac MagLev 1500C. 


Available power supplies include several Matsusada models (two (2) RK20-40 (20V,40A), two RK60-13.5 (60V,13.5A), one REK650-5.5) and a Spellman high voltage power supply capable of 3300 V at 400 mA.

Material testing of spacecraft materials/plasma interactions is being conducted using an ion source in a self-contained vacuum system.  The system is capable of controlling three separate mass flow streams simultaneously while producing plasma energies from 1.0 to 10 eV, typical of the types and energy levels experienced by spacecraft on orbit.

To characterize propulsion performance and ensure proper space-like conditions are being simulated, three proven plasma diagnostics are available in the SPOT lab: the Faraday probe, ExB (Wien) probe and the Electrostatic Analyzer (ESA).  The Faraday probe measures current density.  The ExB probe is designed to distinguish between ion mass, charge states, and energy levels.  The Electrostatic analyzer (ESA) captures ion energy, usually expressed as energy per unit charge. The ExB (Wien) probe has provided plasma energy state allocations for our Hall Effect Thruster.  We have even combined the ExB and ESA to measure energy state per mass directly. These instruments have a dedicated power supply and data acquisition, Kiethly 6517B.

Additionally, the SPOT now has a state-of-the-art laser induced fluorescence and absorption diagnostic for measuring particle velocimetry. The technique uses the frequency (Doppler) shift between the laser induced fluorescence traces (compared with a static reference) to determine axial and radial velocity of the particles.  Ion velocities are expected to be 15,000 to 20,000 m/s.  This diagnostic is currently providing results with predicted uncertainties of 2.5%.  The research effort currently is to increase the fidelity of this diagnostic technique.