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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& 9Nk¥ Aneutronic Fusion Propulsion Introduction Space exploration is limited by existing propulsion technology. Up to now, chemical rockets have been used to reach low-Earth orbit, the Moon, and the outer regions of the solar system. Chemical rockets can use either solid or liquid fuel. Regardless of the type of fuel, their design is similar to that shown in Figure 1. Oxygen is combined with hydrogen or a hydrocarbon fuel in a combustion chamber where high temperatures and pressures cause the exhaust to be ejected through a supersonic nozzle to provide thrust to the rocket. The momentum of the fuel ejected through the nozzle provides the force or thrust that accelerates the rocket forward. There are many variations of chemical rockets, but they all suffer from the need to carry copious amounts of fuel. Other methods have been proposed to decrease the need to carry such a significant mass of fuel into space. Ion drives, for example, are used to provide the very low thrust required to maintain satellites in Earth orbit. The "fuel" that they carry is xenon gas accelerated by electric fields. Nuclear fission propulsion has been proposed for space missions, and therma l nuclear fission reactor rockets were constructed and tested at the Nevada Test Site through Project Rover between 1956 and 1971. 1 I n these rockets, a nuclear reactor provides heat to liquid hydrogen through nuclear fission and ejects the hydrogen gas through a Laval nozzle to generate thrust. While these rockets must still carry hydrogen fuel as a propellant, these rockets can provide more than twice the performance of chemical rockets by using heat through fission rather than reactive chemicals. The results of the 72 reactor tests conducted under Project Rover were very promising and culminated in the successful 12-minute test of the Phoebus-2A NERVA (Nuclear Engine for Rocket Vehicle App lication) reactor that generated over 4 gigawatts of thermal power. One problem associated with nuclear fission rockets is radioactive contaminants. These contaminants in the exhaust make this technology impossible to use in launching payloads from Earth. Additionally, for appl ications in space, radiation protection must be provided for the crew by adding heavy shielding materials or by locating the crew as far as possible from the reactor propulsion system. Nuclear fusion, as opposed to fission, provides another potential propulsion technology. In a fusion propulsion system, isotopes of light elements are fused together under extreme conditions to form heavier elements, releasing large amounts of thermal energy. This thermal energy can be used to heat liquid hydrogen to high temperatures and expand it through a Laval nozzle to provide thrust in a manner similar to that shown in Figure 1. Typically, isotopes of hydrogen and helium would be used in fusion propulsion systems. Deuterium is an isotope of hydrogen and can be separated from the hydrogen in water. Fusion reactions are difficult to initiate due to the high temperatu res and pressures requ ired. Thermonuclear bombs, for example, combine a fusion device with a nuclear fission bomb to provide the high temperatures required to initiate the fusion reaction. Regardless of the conditions required to induce nuclear fusion, the energy release is large. From propulsion standpoint, an advantage of fusion over fission is that for a given amount of thrust, the fusion reaction requ ires less fuel than either fission or chemical propulsion systems. Fusion reactors using deuterium or tritium fuels are easiest to initiate; however, they generate significant amounts of neutron radiation. This is a hazard for the crew on a UNCLASSIFIED/fF9A 9FFI&I:.l.k W&li 9Nk¥ V
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Official release, from the pursue collection. The PDF is mirrored here; the original link is above. 50 pages are in the text index: search them above, or from the library's search.