AAWSAP DIRD, Aneutronic Fusion Propulsion II, November 2010

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Chapter 3: Fusion Propulsion
FUSION REACTORS FOR PROPULSION
Controlled nuclear fusion reactors have been seriously studied since the late 1960s
after tokomaks demonstrated a very promising improvement in temperature and
confinement time that had potential to become power-producing reactors. After 15
years, such studies predicted that the size and complexity of a DT (deuterium tritium)­
fueled Tokamak would be prohibitively too large to be considered for aerospace
applications. However, in the early 1990s when it became clear from large tokamak
experimental results that controlled fusion for terrestrial power generation would
require an indeterminate time to develop, a surge of interest in fusion-powered
propulsion grew. All such studies abandoned the use of DT fusion fuels because of the
need for heavy shielding for the 14-MeV neutrons and the requirement for launch safety
and the additional complexity of breeding tritium. Only (D, 3He) (deuterium helium-3)
and (p, 11B) (hydrogen boron) fuels have been considered because of the higher specific
powers achievable for air and space flight.
Field- Reversed Configuration Reactors
(U) The seminal study on fusion propulsion that developed specific design parameters
was performed in 1993. 10 It reviewed previous studies and used a generic cylindrical
fusion plasma model for analyzing the specific power for such a system using (D,3He)
fuel (shown in Figure 8). The estimated gross mass of the 968-MW reactor was 112 Mg
with a corresponding mass of 999 Mg for a DT-fueled system, (lMg=l metric ton).
Optimization of this conceptual design using the FRC plasma confinement using colliding
beams has led to a much more compact configuration of 33 Mg producing 100 MW
(shown in Figure 9). 11 This reactor's plasma confinement chamber has a length of 7
meters and diameter of 0.84 meters. Half of the plasma fusion products and unfused
fuel is circulated through the magnetic separatrix to a direct converter while the other
half is diverted and expelled to provide propulsive thrust.
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Plasma Temperature (keV)
Figure 8. Specific Power as a Function of Plasma Temperature of Fusion Rocke\ 1
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