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AAWSAP DIRD, Aneutronic Fusion Propulsion II, November 2010

U.S. Department of War · 2010-11-01 · 36 pages · text from the file's own layer

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.

UNCLASSIFIED/ /FOA QFFI@IAL Y!H! f>HL I
In order to facilitate efficient fusion, it is also necessary to constrain the motions of the
charged particles (i.e., confine the plasma) in an attempt to maximize the likelihood of
ion collisions. Therefore, the net energy produced by the fusion process is more
realistically the released energy minus the energy consumed for plasma heating and
confinement. The fusion energy gain factor, usually expressed with the symbol Q, is the
ratio of fusion power produced in a nuclear fusion reactor to the power required to
maintain the plasma temperature; for the Lawson Criterion, breakeven Q = 1. However,
to provide sufficient energy to convert that power to a useful level, a minimum Q >5 is
needed, and for a power plant to generate electricity the Q should be >30.
For the fusion reactions shown in Table 3, the (D, 3He) will produce a few fusion
neutrons which can be minimized by running hot and deuterium-lean; however, the
application may be limited by the availabi lity of 3He. Other reactions to consider will be
the (p, 6Li) and (p, 11B). First, a review the most commonly used plasma confinement
methods is needed.
Table 3: Fusion Ignition Temperatures
]
MAGNETIC CONFINEMENT
Magnetic confinement is an often -u sed method for constraining the motion of the
plasma "fuel," increasing the efficiency of nuclear collisions and the fusion process. The
plasma is composed of charged particles and is, therefore, affected by electric and
magnetic fields. Charged particles spira l along magnetic field lines with electrons
spiraling faster and in smaller radii and in opposite directions than their heavier ion
counterparts . As the magnetic field increases at the ends of a magnetic mirror, the
charged particles will reverse direction along the field lines and thus become trapped. A
chamber can be designed such that an appropriate magnetic field configuration can be
produced that guides and constrains the motion of the plasma (see Figure 2). The
pressures (thermal, kinetic, magnetic) of the plasma "gas" are balanced by the high
pressure of the imposed magnetic field-the plasma is "contained" by the magnetic field.
One obvious advantage of this approach is that the imposed magnetic field prevents (or
at least delays) much of the plasma (at energies of tens of keV or temperatures of
several hundred millions of degrees Kelvin) from coming into contact with the structural
elements of the chamber. The pressures are typically on the order of one bar, and
depending on the design, confinement times can span a few seconds to minutes.
Although magnetic confinement designs are in principle steady-state systems, their
primary difficulty is maintaining the strong damping of the various modes of plasma
instabilities that arise in these systems.
UNCLASSIFIED/ /FOR OFFJCJ0L n&li ONLY
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Official release, from the pursue collection. The PDF is mirrored here; the original link is above. 36 pages are in the text index: search them above, or from the library's search.