AAWSAP DIRD, Aneutronic Fusion Propulsion II, November 2010

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the MeV alpha particles for the (p, 11B) into a direct thrust would increase the l sp
to >5,000 seconds with thrust levels >5 N/kW.
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Plasma Jet
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Figure 13. Design of an IEC Jet Thruster - Experimental Device (left)
INTERPLANETARY
Many of the fusion reactor applications described in Chapter 3 have been specifically
applied to space propulsion. The key reason for the benefits of such systems lies in the
fundamentally different nature of fusion propulsion compared to chemical or nuclear­
thermal propulsion. Fusion propulsion systems pay a mass penalty for carrying their
power source. However, a propellant mass savings results from the high thrust per unit
mass that arises from high exhaust velocity that overcomes the power-source mass
penalty. These potential performance enhancements are shown in Figure 14, wh ich
illustrates fusion propulsion's capabilities for fast transport of humans or efficient
transport of cargo between circular solar orbits for Earth -Mars one-way rendezvous
missions.18
In order to achieve the efficient solar system travel shown in Figure 14, propulsion
systems must achieve specific powers of at least 1 kW/kg at exhaust velocities of ~105­
106 m/s, leading to thrust-to-weight ratios of ~10-3 . The required range of parameters
and a comparison with chemical and nuclear thermal propulsion options appears in
Figure 15. 19 The capability of tuning the exhaust velocity over factors of 10- 100 is a
desirable feature that facil itates energy intensive missions. For the same delivered
payload the fraction of the propellant and nonpayload mass is significantly minimized
for fusion propulsion as compared to the other propulsion options.
UNCLASSIFIED/ /POI\ OPPICIAL U.!I!! er~t'I'
18