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

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need for computational modeling of hypersonic wakes to predict the characteristic signature
of new, unknown aircraft.
A hypersonic vehicle database of wake characteristics for existing aircraft should be
developed based on optical and Doppler RADAR data. Doppler RADAR provides information
on turbulent intensities and eddy formation within the wake. Computational fluid mechanics
models of hypersonic wakes have been done since the early 1960s, such as the work done by
Zieberg and Bleich. 30 Such modeling work should continue capitalizing on the increasing
computer performance that will be available during the next 30 years.
Recommendation #2 - Exploit the Detectability of Hypersonic Aircraft
Based on the Features That Allow Them To Fly Efficiently at High Speeds
Several new propulsion systems for hypersonic aircraft will be tested over the next 30 years.
These include pulsed detonation engines (PDE) successfully tested in 2008 by the Air Force
Research Laboratory and Innovative Scientific Solutions, Inc. over the Mojave Desert. While
these engines are capable of Mach > 6, they have one characteristic that makes them very
detectable. The pulsed detonation of combustible fuel creates a wake with periodic bulges
referred to as "donuts on a rope." As mentioned earlier, measurements of the turbulent
wake behind hypersonic aircraft can be used for detection, identification, and tracking.
The AYAKS hypersonic transport plane under development in Russia uses an MHD engine,
lasers, and RF generators to decrease aircraft drag. The lasers and RF ionize the air ahead of
the aircraft, creating a plasma to disrupt the bow shock and significantly reduce aerodynamic
drag. Drag reduction allows the aircraft to double its maximum speed. The RF and laser
emissions from this aircraft can possibly be used to detect the aircraft in flight from ground-
based antenna or telescopes or from satellites. The MHD engine also generates
electromagnetic radiation that can possibly be detected.
Every new propulsion or drag reduction system under development will have some
characteristic that may make it more detectable from the ground or from satellite. The
Aerospike engine proposed for the SSTO and under development by Rocketdyne and Garvey
Spacecraft involves the use of a novel virtual Laval nozzle that is external to the engine. The
IR emissions from an Aerospike engine may increase its detectability.
Recommendation #3 - Explore the Detection of Vehicles Designed To Be
Undetectable
Over the next 30 years, hypersonic cruise missiles will have the ability to travel at speeds of
up to Mach 8 decreasing the chances of being detected or defeated by antimissiles. The
unmanned NASA X-51 tested in 2010 is capable of greater than Mach 7 (over 4,000 mph),
for example, and is designed to be launched from a B-52. The DARPA/USAF Falcon Project
has resulted in the testing of the HTV-2 at Mach 6. 7 over the Pacific Ocean, designed as a
hypersonic cruise vehicle.
Efforts to disguise aircraft through the use of novel vehicle shapes and stealth materials can
also increase their detectability in other ways. Golovitichev and Hansson presented a paper
in 199931 that stated the following:
30
"The concentrated energy drag reduction concept has proven to be effective for the
cruise range vehicles, preventing the missile deceleration with the benefit that the
spike "products" could envelope the missile in a film of ionized gas which would be
impervious to RADAR pulses, thereby rendering it electronically "invisible". The infra-
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