Defense Intelligence Reference Document Positron Aerospace Propulsion

UNCLASSIFIED,' fflilll. lilFFllil_.,le lal!il!! 8111!¥
Second, low-energy gamma rays from positron annihilation cannot make residual
radioactivity in surrounding air and containment vessels. In contrast, antiprotons
annihilate into a host of high-energy particles, including rr-mesons and gamma rays that
can induce residual radioactivity in nearby materials.
Finally, low-energy gamma rays from positron annihilation can be readily converted into
useful forms of energy, including heat and electricity required for propulsion systems.
This contrasts with large, complex systems required for conversion of antiproton
annihilation and nuclear fission/fusion energy.
There are two reasons why positrons have yet to be used for aerospace applications.
First, it has not been possible to produce them in the numbers required. However,
recent developments in high-energy physics research are resulting in expanding levels
of positron production. Second, methods for storing positrons for basic research do not
hold enough positrons long enough for propulsion applications. Recent developments in
storage techniques may significantly improve the situation, with lifetimes up to months
and possibly years.
Positron Air-Breathing Propulsion
Aeronautical engines burn a mixture of aviation fuel and oxygen in air to heat a working
fluid. To keep engines small, the combustion rate in the engine needs to be high. 5 At
sea level for a fuel-air mass ratio of 0.068, it is 500,000 kJ/m 3-s. To maintain speed,
the thrust specific fuel consumption (TSFC) for turbojets and turbo-ramjets is in the
range of 0.075 - 0.11 and 0.17 - 0.26 kilogram/hour-Newton (kg/hr-N), respectively.
All aeronautical engines are limited in range and flight duration by the fuel on board.
Because of the aforementioned performance bounds of combustion engines, the
aeronautic industry has worked diligently to increase the range and payload of aircraft
by maximizing the performance of combustion engines and optimizing aerodynamic
design. Beyond this, the only way a combustion-powered aircraft can extend its range
and endurance is by in-flight refueling.
Two projects investigated nuclear power as a way to increase performance. In 1946,
the U.S. Air Force established the Nuclear Energy for Propulsion of Aircraft program.
However, this program was disbanded in 1951 in favor of the joint Atomic Energy
Commission-Air Force Aircraft Nuclear Propulsion program. Implementing nuclear
fission to power an aircraft required two approaches. One was direct cycle, whereby air
was heated by passing it through a nuclear reactor; the other was indirect cycle,
whereby the reactor heated a liquid metal that in turn heated air in a secondary heat
exchanger. The program never produced a prototype and was canceled in 1961.
In 1957, the Pentagon started development of a nuclear ramjet missile (SLAM,
Supersonic Low-Altitude Missile) to fly below Soviet defenses. The Lawrence Livermore
National Laboratory Pluto program successfully tested two engines, Tory-IIA and Tory-
IIC (Figure 2), at the Nevada Test Site. The program was canceled in 1964. 6, 7
2
UNCLASSIFIED//F81it 8FFIIIAI!: 1!181! &••1::Y