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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//POR. Offl@IAI:: ~S& Qptk\f e - p r ¢ (r) = </J;,,;,;,,1-2 B(μ r) (1.18)4 Tr r The radiation flux is inversely proportional to the square of the distance from a point source of radiation, such as a nuclear rocket engine. It also decreases through any intervening radiation shielding material. The last term in equation 1.18, B(μr), is called the "buildup factor"; it represents the process of reradiation following atomic collision with shield ing material, thus contributing to the tota l radiation dose. This secondary radiation is a problem for all spacecraft since cosmic radiation impacting the spacecraft structural material can produce a cascade of secondary particles t hat can irradiate the crew . A standard technique to decrease the radiation exposure to the crew on a spacecraft using nuclear fusion as an energy source will be to locate the crew as far away from the engine as possible and place as much liquid hydrogen or other light shielding material between the crew and the engine as designs allow. A simpler solution would be to use nuclear fusion schemes that do not generate neutrons. These are the so -called "aneutronic fusion" propulsion techniques. SUBATOMIC PARTICLE MASS, VELOCITY, AND ENERGY Atoms are composed of a small nucleus containing neutrons and protons, along with electrons orbiting the nucleus in shells. The atomic number (Z) is equivalent to the number of protons or electrons in a stable atom. 8 The atomic mass number (A) is the total number of neutrons and protons in the nucleus. The number of neutrons (N) can be found by subtracting Z from A. Atoms or nuclei are represented by a standard nomenclature based on A and Z. ; Atom Since chem ical properties are governed by how many electrons circle the nucleus, Z defines the element and atoms with the same value of Z, but differing numbers of neutrons are referred to as "isotopes" of the same element. Some common isotopes of hydrogen are shown below: hydrogen I IH deuterium ~H , or :D tritium iH , or ~T Subatomic particles, such as a, /3, and neutrons, have a mass described in atomic mass units (amu). One amu is defined as the mass of one atom of carbon-12, and it roughly represents the mass of one neutron or proton. In terms of amu, the mass of various particles are included in Table 2. Due to relativistic effects, particle mass increases as the velocity of the particle approaches the speed of light, and because of special relativity, the mass of particles listed in the tab le is the "rest" mass corresponding to a particle that is not moving. UNCLASSIFIED/fF&A &FFI&I:.l.k W&& Qptk\f 9
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