AAWSAP DIRD, Aneutronic Fusion Propulsion I, November 2010

This Defense Intelligence Reference Document, prepared in fiscal year 2010 by the Defense Intelligence Agency's Defense Warning Office under the Advanced Aerospace Weapon System Applications (AAWSA) Program, reviews aneutronic fusion as a way to propel spacecraft. It compares chemical, ion, fission, fusion and antimatter propulsion, and it also covers radiation shielding and relativistic rocket calculations. It looks at research needs over the next 30 years for missions from low Earth orbit to Mars, Jupiter and Alpha Centauri.

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 surveys aneutronic fusion as a possible advanced space-propulsion method, focusing on fusion reactions that release most of their energy in charged particles rather than neutrons and therefore offer potential advantages over more neutron-intensive fusion concepts, especially in radiation shielding, direct energy conversion, and thrust generation. The report reviews the underlying rocket physics, compares candidate fusion fuels and ignition conditions, and gives particular attention to proton-boron and related schemes, while also discussing Bussard’s concepts and other fusion projects as representative development paths. It also makes clear that the central obstacle remains ignition and sustained net-energy fusion under practical conditions, and it notes additional problems such as x-ray energy losses from the hot plasma, extreme temperature requirements, and the gap between theoretical specific impulse and what proposed systems had demonstrated experimentally. Overall, the document presents aneutronic fusion propulsion as an attractive long-range concept for deep-space travel, but one whose practical realization still depended on major unresolved advances in fusion engineering.

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it collapses and generates a magnetic pinch for a fraction of a second that has high
enough temperatures to generate fusion in the diffuse gas. The production of neutrons
in D-T fusion can be on the order of 10 13 neutrons. While this production may seem
high, if this pulsed system were fired 10 times in 1 second, and all of the energy of the
electrons and ions could be captured, the energy production would amount to only 280
watts.
MUON-CATALYZED FUSION
Th is method, sensational ized by Steven Jones at the University of Utah in the 1980s,
makes use of the fact that certain material crystal shapes (hexagonal close pack, or
HCP) tend to "hide" atoms of hydrogen in the interstitial space between atomic planes
in the crystal. By diffusing deuterium into the crystal through electrolysis, fusion could
be achieved. The famous scientist Sakarov observed this phenomenon as a way to
account for the presence of He-3 in platinum. Platinum, pa lladium, and titanium are
the materials that were used most often to demonstrate this technique. Initiating
fusion by this method has been very poor.
CAVITATION (BUBBLE) FUSION
In water, vapor bubbles are produced when pressures drop below 2,300 pascals ( ~2%
of atmospheric pressure) through a process called "cavitation." When these cavitation
bubbles collapse, they produce high temperatures and pressures for a short period of
time. Cavitation has been shown to release enough energy to pit sh ip propeller blades.
In add ition, heavy water (D2O) and deuterated acetone have been used to demonstrate
that cavitation can cause particles from fusion. Unfortunately, to date, the performance
of cavitation fusion systems has been low.
ROCKET DESIGN USING FUSION ENERGY
While nuclear fusion releases large amounts of energy for a minimal quantity of fuel,
initiation of the fus ion reaction means that fusion ignition dictates the design of the
system . Possible spacecraft designs include pulsed nuclear explosions with impact
plates or sails; plasma confinement methods that generate charged particles used
directly for propulsion; and confinement methods that heat a propellant, like liquid
hydrogen, to be ejected through a Laval nozzle.
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