AAWSAP DIRD, Positron Aerospace Propulsion, March 2010

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THE SOLID-CORE POSITRON ROCKET
Figure 11 depicts a solid-core positron-powered rocket, similar in many regards to the
NERVA nuclear-thermal concept. 29
Attenuating
HX
Inlet Plenum
Turbine &
Exhaust Nozzle
Hot Bleed
Line
Figure 11. Solid-Core Positron Rocket Engine With a Hot-Bleed Configuration (courtesy Positronics
Research LLC)30
The cryogenic hydrogen propellant is supplied from a storage tank through a high­
pressure pump and routed to cool the regenerative nozzle, the casing of the heat
exchanger, and the central positron target tubes. Ps enters the in let plenum to the
attenuator that is heated by gamma rays to high temperature. Hydrogen propellant
passes through the attenuating matrix and is heated and exhausted through a nozzle to
generate thrust.
A small fraction of the hot exit propellant is bled off to a turbine that drives the high­
pressure feed pump. The high-temperature bleed can either be mixed with cold
hydrogen to reduce its temperature or directly fed to the turbine. If it is directly fed to
the turbine, it must be made of materials that can withstand high temperatures. The
bleed flow is exhausted from a turbine exit nozzle to space a~er driving the turbine.
As with the NERVA system, the positron solid-core concept is thermally limited by
materials in the heating chamber. The difference is that the fission system requires a
reactor and complex machinery, whereas the positron system relies on Ps atoms
injected upstream from a storage unit. This has two advantages. First, a reduction in
the engine mass for a given thrust is realized; second, there is greater choice in
materials to be used in the heating chamber.
A thermal-fluids analysis was conducted to predict performance. A specific impulse of
920 seconds is attainable with chamber temperatures at 3,000 Kelvin. The
corresponding thrust and power emulate fission systems. Mars trip burn times are on
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