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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magnetic mirror
pole regions serve as a
magnetic mirror or bottle
that traps and reflects charged
particles - the particles gain
energy
Figure 2. Illustration of Magnetic Mirror Confinement in Vicinity of Jupiter
A second, related magnetic method is to join the ends of the solenoid together as a
toroid, confining the plasma to a ring. A simple toroidal (i.e., circu lar) field, however,
provides poor confinement because the radial gradient of the magnetic field strength
results in plasma drift. A method to reduce drift and produce a stable plasma
equilibrium is to superpose a poloidal magnetic field with the toroidal field, thus driving
a current through the plasma itself. This provides a path for the plasma moving along
the outer edge of the toro id to migrate to the inner edge and vice versa. This is the
method used in tokamak systems (shown in Figure 3). Another solution has been to
structurally modify the toroid chamber into a figure-eight configuration. This allowed
plasma to spend half of the time on the inner portion of the tube, and half of the time
on the outer portion of the tube. Such systems are called stellarators. This configuration
has eventually evolved back into a (non-axially symmetric) toroidal configuration;
rotating the windings in such a manner produces a stable plasma equilibrium while
eliminating the need for a toroidal magnetic field. The fundamental issue with these
confinement systems is that they require superconducting magnetic coils, pressure
vessels, and neutron-energy-absorbing blankets for a 6-meter major radius by 6-meter
high plasma, an enormous technological undertaking-and that is just for an ignition
demonstration (see Chapter 5) .
Figure 3. a) Tokamak and b) Stellarator Confinement
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