AAWSAP DIRD, Aneutronic Fusion Propulsion II, November 2010

This Defense Intelligence Reference Document, dated 1 November 2010, was prepared by the Defense Intelligence Agency's Defense Warning Office under the Advanced Aerospace Weapons System Applications program. It reviews fusion plasma physics, confinement methods and propulsion concepts that use aneutronic fusion fuels such as hydrogen and boron-11. It concludes that pulsed DPF or IEC thrusters may replace satellite ion thrusters in the near term. It also finds that aneutronic fusion propulsion will not be practical beyond the solar system without breakthrough propulsion physics.

From the source: Release of 2026-09-18 Incident: 11/1/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD revisits aneutronic fusion propulsion in a more systems-oriented manner, arguing that fusion concepts using low-neutron fuels such as proton-boron or helium-3 could become attractive for space propulsion because they reduce shielding burdens and may support direct conversion of charged-particle energy into thrust or onboard power. The report reviews the relevant fusion plasma physics and focuses on several candidate confinement approaches, then connects those concepts to possible applications in near-space, orbital, and interplanetary propulsion. It presents the most plausible nearer-term use as very high-power electric or plasma propulsion for satellites and deep-space missions rather than atmospheric flight or interstellar travel, while emphasizing that major obstacles remain in ignition, sustained confinement, system mass, power handling, fuel storage, launch integration, and end-to-end engineering.

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Chapter 2: Fusion Plasma Physics
At the most basic level, nuclear fusion occurs by forcing atomic nuclei close enough so
that the attractive strong force (which binds nuclei together) overwhelms the very
powerful electromagnetic repulsion force. Under such circumstances the nuclei fuse
together to form a single nucleus, creating an atom of a different element (along with
byproducts such as radiation and neutrons). Because the strong force dominates over
such short-length scales ( ~10- 15 meter, the diameter of a medium -sized nucleus), the
fusion of heavier nuclei are inherently more unstable, with smaller binding energ ies. For
light nuclei, the binding energies of the individual nuclei are significantly smaller than
that of the fused nucleus; it is the released energy of the fusion process (in the form of
high -energy photons or kinetic energy of nuclear products such as neutrons) that is
sought as an energy source. Table 1 shows Fusion reactions including the relevant
aneutronic fusion reactions.
Table 1: Principal Fusion Reactions
E (M e V)Main , ,rro/1 d I i 11 ue/
+T-a:+ n 17 .5
T +p
{
+ 3 H c + n
+y
T + T - a:+_ n
d1 •a,1 ed fu i II fuel
+ ~, C--+ + p
p+ L i-+ a,+ H
r>+7 i- 0"
r>+ II - 30'
To fuse a sufficient number of nuclei within a span of time for practical use, it is
generally necessary to heat an ensemble of atoms to the very high energies shown in
Table 1. These energies (temperatures) are high enough that electrons are stripped
from their associated nuclei, producing a plasma of free electrons and ions. The fusion
reaction cross sections (cr), the probability of interaction for these reactions in barns =
10-28 m2, is shown in Figure 1. For the maximum reaction rate temperature, the ratio of
the total amount of energy (kinetic plus radiation) released in the fusion reaction
relative to the bremsstrahlung radiation released is shown in Table 2.
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