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This Defense Intelligence Reference Document was prepared by the Defense Intelligence Agency's Defense Warning Office in fiscal year 2010 as part of the Advanced Aerospace Weapons System Applications program. It reviews how air flows around objects at subsonic, supersonic and hypersonic speeds, covering shock waves, wakes and ionization. It then compares ways to detect and track hypersonic vehicles, including radar, optical, infrared, LIDAR, infrasound and seismic methods. The report makes four recommendations, among them building a database of aircraft wake signatures and developing novel detectors.
From the source:Release of 2026-09-18 Incident: 11/20/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD surveys how hypersonic vehicles may be detected and tracked by exploiting the physical effects they create in flight, especially shock waves, ionized gas, hot surfaces, and turbulent atmospheric wakes. The report reviews a broad set of detection methods, including radar, infrared sensing, optical imaging, LIDAR, passive radio reflection, infrasound, and seismic techniques, and argues that the most effective systems will likely combine multiple sensor types, because each captures different features of a high-speed vehicle’s passage through the atmosphere. It presents radar and infrared sensing as the strongest existing tools for operational detection, while giving particular attention to wake-based methods such as LIDAR and passive radio techniques for improving tracking, identification, and discrimination of future hypersonic aircraft. The paper identifies hypersonic vehicles as an evolving surveillance problem in which future progress will depend on better multi-sensor integration, improved wake characterization, and novel signature-exploitation techniques.
“Pacific Ocean”4 pages
UNCLASSIFIED/fFOR. QFFIEl.t.L: Uii QD:I! X Infrasound stations, or observatories, could also be used to monitor the acoustic signature of meteors or supersonic aircraft based on their shock waves or the disturbances caused by their turbulent wake. Some meteors, for example, produce subsonic sound from 1 to 5 Hz for several min utes during their flight through the atmosphere. This data could be developed to identify the speed, altitude, and type of object moving through the atmosphere. Seismic When a son ic boom is generated by a meteor or an aircraft, the sound waves pass through the atmosphere at the speed of sound in air at about 343 m/s. Infrasound stations pick up the pressure variations caused by the shock wave many minutes after the event occurred, depending upon the distance between the superson ic object and the station. When a Mach cone generated by a shockwave strikes the ground as shown in Figure 18, the pressure pulse is propagated into the ground and travels as a high-speed N-wave at a velocity far exceeding the speed of sound in air. Ground-based vibrations caused by sonic booms have been detected by seismic sensors originally designed to detect earthquakes as documented by Cates and Sturtevant. 27 Caltech and the U.S.G.S. operate 200 seismographic stations throughout Southern California as part of the TERRAscope seismic network. The network employs detectors that can sense ground vibration between 1 and 20 Hz. The network was actua lly used to detect the sonic boom and pressure vibration induced by the flight of supersonic aircraft and reentry vehicles. On 9 December 1993, the network successfully detected the flight of an SR-71 flying over Edwards Air Force Base at a maximum speed of Mach 3.2. On 30 January 1992, the network was also used to detect the reentry of the space shuttle Discovery, STS-42, over the Pacific Ocean and landing at Edwards Air Force Base. Another Discovery landing on the west coast was monitored by 66 seismic stations in Washington and Oregon. The shuttle was monitored by th is seismic network for 500 km of its trajectory through the atmosphere. The seism ic data from these stations showed the hyperbolic shape of the Mach cone as it impacted the surface of the earth. The angle of the Mach cone showed that the shuttle was traveling at Mach 14, corresponding to an altitude of 55 km. One interesting investigation that involved the use of these seismic arrays involved mysterious sonic booms heard over Southern Cal ifornia in 1991 and 1992. By using data from the TERRAscope array, the source of these disturbances was traced to two F-4 Phantom aircraft flying over Edwards Air Force Base at speeds near Mach 1. Since the TERRAscope array is designed to detect seismic activity, including earthquakes and volcanoes, the detection of meteors and supersonic aircraft generate unwanted data. Caltech has been adding atmospheric pressure transducers to its seismic network to detect and remove airborne signals from the seismic data. Conversely, by combining the infrasound network data operated by the Los Alamos National Laboratory with data from seismic arrays, data from explosions, volcanic eruptions, and other terrestrial sources can be eliminated from infrasound data to better detect the presence of meteors, reentry vehicles, and supersonic aircraft. UNCLASSIFIED//EQA: QlililEl.t.L: W&&: O,.L'l 27
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Official release, from the pursue 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.