Abstract: System (300, 400) and methods (500) for testing a reaction thruster (100) in a vacuum environment. The methods comprise: disposing the reaction thruster in a vacuum chamber which is at least partially connected to earth ground; removing at least one gas from the vacuum chamber to provide the vacuum environment; operating the reaction thruster so as to create a beam of electrons; and/or electrically isolating the electrons of the beam from at least one electrically conductive surface of the vacuum chamber. The electrical isolation can be achieved by applying an electrical bias voltage to the beam via an electrode. The electrode may comprise a conductive object disposed in the vacuum chamber and/or at least a portion of a vacuum chamber wall. In all cases, the electrode is electrically isolated from a portion of the vacuum chamber that is connected to ground.

Abstract: System (300, 400) and methods (500) for testing a reaction thruster (100) in a vacuum environment. The methods comprise: disposing the reaction thruster in a vacuum chamber which is at least partially connected to earth ground; removing at least one gas from the vacuum chamber to provide the vacuum environment; operating the reaction thruster so as to create a beam of electrons; and/or electrically isolating the electrons of the beam from at least one electrically conductive surface of the vacuum chamber. The electrical isolation can be achieved by applying an electrical bias voltage to the beam via an electrode. The electrode may comprise a conductive object disposed in the vacuum chamber and/or at least a portion of a vacuum chamber wall. In all cases, the electrode is electrically isolated from a portion of the vacuum chamber that is connected to ground.

Abstract: A cloud of small to medium-sized space debris is mitigated by releasing drag-reducing particles into the cloud from a dispenser vehicle, causing the particles to collide or otherwise interact with, and thereby exchange momentum with, the debris particles, reducing the orbiting velocity of the debris to a degree sufficient to cause the debris to de-orbit, or to accelerate the de-orbiting of the debris, to Earth. Certain embodiments also include a shepherd vehicle containing systems for identifying and tracking the debris cloud and for coalescing the debris cloud to increase the particles density in the cloud.

Abstract: A system for uniformly distributing propellant gas in a Hall-effect thruster (10) (HET) includes an anode (42, 42′) and a porous material gas distributor (60, 89) (PMGD). The porous material (120) may be porous metal or porous ceramic. Propellant gas is directed from a supply to the PMGD for distribution into a gas discharge region (16) of the HET (10). The gas flows through the porous material (120) of the PMGD and out of the PMGD's exit surface (71) into the annular gas discharge region (16). The PMGD has an average pore size, pore density and thickness that are optimized to control the flow of the gas at the desired flow rate and distribution uniformity at a relatively short distance downstream from the PMGD. This feature allows HET to be short, significantly decreasing susceptibility to vibration problems encountered during vehicle launch. The PMGD can include a shield (79, 80) for preventing contaminants from traveling upstream from the gas discharge region from adhering to the porous metal.

Abstract: A method and apparatus for using a magnetic field generated by a thruster magnet to control electron current emitted by a cathode assembly. The magnetic field reduces leakage current drawn by an inactive anode by producing a magnetic field in proximity to the inactive anode. This magnetic field increases the impedance to the anode for electron current which is produced in the cathode assembly. This reduction in leakage current reduces the amount of electron current produced by the cathode assembly. This control system can be implemented by connecting all thruster anodes and cathodes in parallel to an anode power supply.

Abstract: A series of long slats, preferably parallel and spaced apart uniformly, extend from a base plate to form a series of cavities between the slats for trapping high energy ions in the exit plume of an ion accelerator. The plume shield is designed to minimize escape of ions and sputtered atoms from the shield. The effectiveness of the shield in trapping and retarding ions and sputtered atoms can be accomplished by biasing the potential of the shield with respect to an adjacent structure and by inducing a magnetic field parallel to a target area of the shield, which can limit electron current to the target area.

Abstract: A specially designed magnetic shunt is provided encircling the anode region and/or annular gas distribution area of an ion accelerator with closed electron drift. The magnetic shunt is constructed to concentrate the magnetic field at the ion exit end, such that the location of maximum magnetic field strength is located downstream from the inner and outer magnetic poles of the accelerator. The specially designed shunt also results in desired curvatures of magnetic field lines upstream of the line of maximum magnetic field strength, to achieve a focusing effect for increasing the life and efficiency of accelerator. The anode of the accelerator can diffuse ionizable gas through a porous plate for an even distribution of the gas in the distribution area.

Abstract: A specially designed magnetic shunt is provided encircling the anode region and/or annular gas distribution area of an ion accelerator with closed electron drift. The magnetic shunt is constructed to concentrate the magnetic field at the ion exit end, such that the location of maximum magnetic field strength is located downstream from the inner and outer magnetic poles of the accelerator. The specially designed shunt also results in desired curvatures of magnetic field lines upstream of the line of maximum magnetic field strength, to achieve a focusing effect for increasing the life and efficiency of accelerator.

Abstract: A radiation type heat dissipator for use in a plasma engine is formed of a refractory metal layer upon which there is deposited a radiation emissive coating made of a high emissivity material such as zirconium diboride. The radiation emissive coating has a surface emissivity coefficient substantially greater than the emissivility coefficient of the refractory metal and thereby enhances the optical radiating efficiency of the heat dissipator.