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This Defense Intelligence Reference Document from the Defense Intelligence Agency, dated 20 November 2010, was one of a series of advanced technology reports produced in FY 2010 under the Advanced Aerospace Weapon System Applications (AAWSA) Program. It reviews the theory of subsonic, supersonic and hypersonic flow. It then compares electromagnetic, optical, and acoustic and seismic methods for detecting and tracking hypersonic objects, and it makes four recommendations for progress over the next 30 years.
“Low Earth orbit”4 pages
UNCLASSIFIED/ /f81il 8ffllltlit '1181! tH•tY Expans,on Fans-~- Bow Shock 1/ M, e_;_J \ Figure 13. Hypersonic Flow Past a Sphere. If the sphere in Figure 13 were traveling through the atmosphere at Mach 3, could we identify the speed of the sphere by the peak wavelength of the infrared radiation that it emits? From compressible aerodynamics relationships, conditions behind the bow shock, in region 2, can be calculated. We find that the peak static temperature would reach 597 Kand the peak wavelength 4.85 microns. Figure 14 shows the expected infrared spectrum. For comparison, the spectrum for Mach 3.5 is also shown. In the figure, the wavelength has units of microns (i.e., 10-6 meter).. As the Mach number increases, the peak temperature also rises while the peak wavelength decreases (shifts to the left). The higher the Mach number, the greater the amount of infrared energy emitted. For Mach 3.5, the peak wavelength is 3.92 microns. The energy difference between a Mach 3 and Mach 3.5 aircraft would be significant enough to detect with an infrared camera or FUR (forward looking infrared) detector. 20 UNCLASSIFIED/ /f81il 8ffllltlit '1181!! 8HL\f
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 46 pages are in the text index: search them above, or from the library's search.