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This Defense Intelligence Reference Document from the Defense Intelligence Agency, dated 21 November 2010, was produced in FY 2010 under the Advanced Aerospace Weapons System Applications (AAWSA) Program. It reviews propulsion concepts that use plasmas and magnetohydrodynamics. It finds the Ajax MHD energy bypass concept meaningless below Mach 12 but calls a reverse energy bypass with a Virtual Cowl potentially practical. It also predicts that electric propulsion will become standard for spacecraft.
“Jet Propulsion Laboratory”4 pages
UNCLASSIFIED//FOR QFFHiIAk W81!! 8HLZ.S nontrivial) of the coupled physical and chemical processes in those plasmas can potentially lead to their better understanding and help them become practical. ELECTRIC PROPULSION SYSTEMS Electric propulsion thrusters can be divided into three categories: electrothermal, electrostatic, and electromagnetic. First, electrothermal thrusters use electric energy to directly heat the propellant and add enthalpy. The heated gas is then accelerated using a conventional converging-diverging gas-dynamic nozzle. Second, electrostatic thrusters use applied static electric fields to accelerate propellant ions via body forces. Third, electromagnetic thrusters use electromagnetic body forces (ExB) to accelerate a plasma (positive and negative charges). An electric propulsion system consists of a power source (e.g., solar or nuclear), power conditioning electronics, engine/thruster (including inlet for air- breathing systems), and fuel/propellant storage and feed subsystem. Energy can be obtained from sunlight, a nuclear reactor, or chemical sources. In the case of solar electric propulsion (SEP), solar photons are converted into electricity by solar cells. The energy could also be beamed to the vehicle using laser or microwave sources. Beaming the power allows for higher power densities but with the added complications of needing a power station and a means of getting the power to the vehicle (direct illumination or via a relay system). In nuclear electric propulsion (NEP), thermal energy from the nuclear reactor is converted into electricity by either a static or dynamic thermal-to- electric power conversion system. Static systems have the advantage of no moving parts for high reliability, but they have low efficiency; dynamic systems have moving parts (e.g., turbines and generators) and do not scale well for small systems, but they do have higher efficiency. Other onboard energy storage systems such as high-density capacitors, flywheels, or fuel cells could be used. Power conditioning systems are required to convert the power system voltage to the form required by the electric thruster. For example, an SEP power system produces low-voltage DC (typically ~l00V); this would need to be converted (via transformers, etc.) to kilovolt levels for use in an ion thruster. The power- conditioning system is often referred to as the power processing unit (PPU); this is, in turn, part of the vehicle's overall power management and distribution (PMAD) subsystem. Various combinations of thruster and propellant are possible, depending on the specific application. The propellant or working fluid can be either stored on board and used in a rocket mode or collected from the atmosphere in an air-breathing mode. The natural system-level trade between these propellant methods is fuel/propellant mass versus power system mass. Air-breathing systems require less propellant mass but require higher energies to perform similar missions. Although rockets will operate in a space or air environment, their thrust durations are limited by the amount of propellant that can be carried. Key performance parameters determine the relative strengths and weaknesses of different propulsion technologies. The fuel/propellant efficiency is characterized by the specific impulse (Isp) for rockets and by the thrust-specific- fuel-consumption (TSFC) for air-breathing systems. It is a measure of how much 5 UNCLASSIFIED/F8R 8FFIGl1lak W65 ODlk¥
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 32 pages are in the text index: search them above, or from the library's search.