Defense Intelligence Reference Document Detection And High Resolution Tracking Of Vehicles At Hypersonic

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o Manned military jet fighters - The fastest military jet is the MIG-25 Foxbat at
2,115 mph (M = 3). The fastest U.S. jet is the F-15 at 1,875 mph (Mach 2.6).
Current U.S. efforts are concentrating on unmanned vehicles, such as the X-43A.
o Surveillance aircraft - The SR-71a "Blackbird" achieved 2,056 mph (Mach 3.3) in
1976 using an air-breathing engine. Its rumored replacement, the SR-91 Aurora,
would have been capable of Mach 6. In 2008, the U.S. Air Force entered into an
agreement to design a Mach 6 unmanned "blackswift" aircraft using a scramjet.
o Passenger jets - The current record holder is the Tupolev Tu-144 "charger" at
1,553 mph (Mach 2.15). Reaction Engines Limited has proposed the A2 hypersonic
passenger liner using liquid hydrogen to fuel the aircraft and to cool the wings and
fuselage. This aircraft is expected to achieve Mach 5. In 2000, Russia and the
People's Republic of China entered into a 25-year agreement to develop the
Leninetz AYAKS hypersonic transport plane using kerosene fuel and a variety of
techniques to attain Mach 8 to 10. An MHD (magnetohydrodynamic) engine is
used to further accelerate combustion products produced by the engine. Lasers
and RF generators are employed to disrupt the bow shock, reducing drag and
doubling the velocity of the vehicle.
o Stealth missiles - The USAF Falcon Project planned for building a Mach 6 HTV-3V
"Blackswift" platform but was cancelled in 2008. The NASA X-51 scramjet vehicle
is based on the Falcon scramjet and is scheduled for testing in 2010. This vehicle
is capable of Mach 7+.
DETECTABILITY OF NEW HYPERSONIC AIRCRAFT
While conventional RADAR and optical systems may be able to track existing vehicles, future
aircraft capable of Mach 8 and above are now being designed and tested. New propulsion
technology and drag reduction techniques also offer new ways to detect such aircraft. Based
on a review of hypersonic vehicle detection and tracking, four recommendations are made for
research and technology development over the next 30 years to increase the detectability of
hypersonic objects passing through the Earth's atmosphere.
Recommendation #1 - Build a Database of the Wake Characteristics for
Existing Aircraft
There is considerable information about the aircraft contained within the turbulent wake that
trails it. The wake provides an indication of the vehicle's path and its current bearing. By
analyzing the Strauhal eddy formation, it is possible to ascertain its velocity and hydraulic
diameter. The wake can also provide information on the chemical combustion products that
can be obtained through LIDAR and can indicate the fuel used by the aircraft. Some aircraft,
such as the X-43A and the proposed Reaction Engines Limited A2, use hydrogen as the fuel,
so the absence of carbon molecules in their turbulent wakes could aid in their identification.
Authors Mark Garnet and Aaron Altman from the University of Dayton 29 proposed the
development of a database of turbulent wake data for conventional aircraft to allow their
identification. They point out that, although the aircraft may be designed for stealth, their
wakes cannot be hidden. They presented data on the unique characteristics that can be used
to identify the wakes generated by the F-15, F-16, F-18, and B-52. They also point out the
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