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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.

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MAGNETO- INERTIAL CONFINEMENT
This method of confinement is an adaptation of the inertial confinement system (ICF)
described above, but also uses some of the methods developed for magnetic
confinement in an attempt to lower the fusion ignition requirements for implosion
velocity and power density. 9 This concept uses a strong magnetic field within a
conducting shell (a magnetic flux conserver). The inertial fusion target plasma lies
within the conducting shell. As the shell is imploded, the magnetic intensity increases
dramatically, constraining and heating the plasma and facilitating fusion. This concept is
being pursued in the United States by the Office of Fusion Energy Sciences of the
Department of Energy. Currently there are two classes: High-gain magneto-inertial
fusion (MIF) and low-to-intermediate-gain magneto-inertial fusion.
High-Gain MIF
The heating power directed into a hot spot for fusion ignition must be greater than the
rate of heat energy loss, and this implies that a high implosion velocity is needed for
high-yield fusion. However, a higher implosion velocity actually lowers the efficiency of
fusion, since less of the cold fuel is assembled (the higher velocity increases the
breakdown of density barriers or growth rate of the Rayleigh-Taylor instability). As
described above, lasers are typically used for direct implosion of the fuel pellet but, to
date, this is not very efficient and the cost per unit energy is high. With a magnetized
target, however, the implosion velocity need not be so high to initiate fusion ignition,
thus lowering the input energy cost without sacrificing efficiency.
Low-to-Intermediate MIF
For low-yield fusion, electromagnetic pulsed power can be substituted for lasers or
particle beams to compress the target. A lower implosion velocity implies that a larger
shell can be used, leading to longer burn duration and a much lower density target. It is
thought that by using an imposed magnetic field, a solid or liquid shell (liner) and a
gaseous target can be used, rather than the usual cryogen ic solid fuel pellets. Such is
the case for the Magnetized Target Fusion experiment being performed at LANL (shown
in Figure 6).
A sim ilar pulsed compression of a fusion fuel gas can be achieved without a target by
instead using Dense Plasma Focus (DPF) having annular electrodes (shown in Figure 7).
In this case a capacitor bank is discharged into the electrodes driving a nanosecond to
microsecond pulse that will heat the plasma created to ignition temperatures. This by
far is the simplest and least elaborate magnetic confinement concept to achieve
aneutronic fusion ignition.
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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.