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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.
UNCLASSIFIED//P91t 9PPH!ltlrt 1!181!! 8Htlf Chapter 4: Summary and Predictions The principal reason for attractiveness of plasma/MHD propulsion concepts is that they could in principle reach beyond the limits of conventional propulsion, power, and aerodynamic technologies. It is thus near or beyond those limits that novel plasma technologies will likely find their application. The principal difficulties or flaws associated with the plasma and MHD technologies are as follows: • Weight and complexity, especially if there is a need for a strong (>1 Tesla) magnetic field in large volumes, and if electron beams are needed for ionization. • For MHD accelerator/thruster, power requirements could be overwhelming. • MHD operation is accompanied not only by the work of ampere forces, but also by irreversibilities and entropy generation due to Joule dissipation. This reduces thrust and Isp of propulsion systems. • In the absence of thermal ionization (i.e., at Mach<12), complexity and power budget associated with nonequilibrium ionization all but make MHD propulsion systems impossible. In contrast, applications to reentry, global-strike hypersonic gliders, and aeroassisted orbital maneuvering look very promising in the near future. The "free" thermal ionization enables MHD devices with very modest B field and the ability of plasma/MHD system to provide L/D far beyond that possible conventionally; together, it makes these applications both feasible and desirable for national defense. However, these types of applications are also likely to attract attention of other nations, including (but not limited to) Russia, China, and Japan, that have proven knowledge and experience required to accomplish such missions and technologies. These nations have the capability to develop such novel technologies within several years and deploying those technologies perhaps within 10 years. The fortunes of MHD propulsion could increase dramatically if high-speed (hypersonic) vehicles begin to carry powerful onboard electricity sources, such as nuclear (fission or fusion) reactors. Since deployment of onboard nuclear power is mostly a political rather than a technological issue, it is difficult to predict if this going to occur and, if yes, when. For spacecraft, the current trend of replacing chemical rockets with electric propulsion systems will continue and probably will become the standard. Electric systems can provide a much wider range of operation (e.g., low-thrust fine positioning/pointing, more frequent or nontraditional maneuvers, and longer times on station) than chemical systems can. The trend to larger spacecraft power levels will further accelerate this trend. Ultimately, the high power levels required (hundreds of kW to multi-megawatts) for certain missions will lead to revisiting the use of nuclear fission reactors in space. 25 UNCLASSIFIED/I Oit 9PPIOil'IIL 1!16li Qtik¥
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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.