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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.
UNCLASSIFIED//POlt Offl@IAL WS& &NkY COMPARISON OF SPECIFIC IMPULSE FOR VARIOUS ROCKET DESIGNS Chemical Rockets Chemical rockets burn solid or liquid propellant. The exhaust gas exits the rocket through a Laval nozzle and generates thrust. Figure 1 provided the outline of a liquid fueled rocket using liquid hydrogen as the fuel and liquid oxygen (LOX) to combust the fuel. Unlike turbofan and RAM engines, rockets are not airbreathing and must carry their own oxidizer. The Laval nozzle is a principle component of chemical rockets; its design is based on compressible fluid flow theory. 4 In general, the nozzle is made up of contoured convergent-divergent cross sections. Conical cross sections are also sometimes used . Its purpose is to transform pressure energy into kinetic energy. Nuclear fusion rockets may also make use of Laval nozzles by heating up a liquid propellant and ejecting it as a supersonic gas. In subsonic flow, fluid can only be accelerated by decreasing the cross-sectional area of the duct section t hat it is traveling through, as in a Venturi tube. Once the velocity in a fluid reaches the speed of sound (Mach 1), the fluid can continue to accelerate only if it is expanded. The Laval nozzle combines a converging section where the flow is subsonic, a throat where the flow is accelerated to sonic speed (Mach 1), and a diverging cone where the flow is accelerated to supersonic speed. The performance of a rocket is based on its thrust, where T = (dm/dt) x Vexhaust, and by maximizing the exit velocity, the thrust reaches a maximum. The pressure of the combusting gases in the combustion chamber directly affect the amount of thrust that the rocket can achieve. Whether a rocket is propelled by gases from combusting propellant or by gases heated through a nuclear fission or fusion reaction, two equations determine the thrust of the Laval nozzle. The maximum mass flow rate through the nozzle can be computed in terms of the nozzle area (Athroat) the combustion or heated gas pressure (po), and the heated gas temperature (To). ( d mJ = Po ~hroa t (1.15) d t _ 'Tmu1m11m --..Jl. o V - (1.16)exhaust - In these equations, R is the gas constant of the propellant gas and y is a thermodynamic property of the gas called the ratio of specific heats. These equations make it possible to compute the maximum thrust generated by a propellant gas through a Laval nozzle based on the pressure and temperature of the gas in the combustion chamber or heating tank. 5 UNCLASSIFIED/fF&A &FFI&I:.l.k W&li &NkY
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