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This Defense Intelligence Reference Document, dated 1 November 2010, was produced by the Defense Intelligence Agency under its Advanced Aerospace Weapon System Applications (AAWSA) Program. It surveys propulsion technologies that include chemical, ion, and nuclear fission rockets, fusion schemes, aneutronic fusion, and antimatter propulsion. It also covers radiation shielding and speculates on research needs over the next 30 years for missions from low Earth orbit to Mars, Jupiter, Saturn, and Alpha Centauri. The document concludes that aneutronic fusion promises to be an important mechanism for future space propulsion.
UNCLASSIFIED/ ,SFIHl 8FFHil.t.k Wfili IH.k\f Ion Drives Ion thruster electrical propulsion provides a convenient and efficient method of generating thrust. A gas that is easily ionized, such as xenon, is carried onboard as a propellant. The voltage difference between an electrode and a metal screen accelerates xenon ions toward the screen and out the back of the spacecraft, generating thrust. The specific impulse of this kind of drive is about 3,000 seconds. It is relatively common for satellites to use ion drives, generating minute forces measured in millinewtons, to maintain orbit. Solar energy and radioactive decay are possible sources of electric power for satellites in Earth orbit. In deep space, fusion or fission reactors could provide electrical power. However, once the xenon propellant has been expended, the ion drive is no longer useful. Ion drives include the VASIMR (Variable Specific Impulse Magnetoplasma Rocket) designed by the Ad Astra Rocket Company in Webster, Texas. This system uses two RF radiowave antennae to couple energy into an ionized gas that is used for propulsion in space. While ion drives are often used to help maintain orbit for satellites circling the Earth, the VASIMR technology has been proposed for use in moving payloads throughout the solar system. The specific impulse for this technology is cited as 5,000 seconds compared to ~3,300 seconds for typical ion drives. 5 Photonic Propulsion Photons of visible light, infrared radiation, or x-rays can produce thrust through momentum transfer, where the momentum of each photon is given by p = h/A (h = Planck's constant, A = radiation wavelength). Photonic propulsion has been explored by Y. K. Bae Corporation (http://www.ykbcorp.com) who holds a patent on a photonic laser thruster. These drives generate no contaminants and require a source of electricity to produce photons. Their photonic laser thruster (PLT) uses an active resonant optical cavity formed between two mirrors on a pair of spacecraft to generate thrust. Photonic drives would be viable on fusion or fission-powered spacecraft if their power output were used to generate electrical power that could provide light. RADIATION SHIELDING Radiation shielding will be important for astronauts traveling to the Moon, to the other planets, and to other star systems. Radioactive particles and cosmic rays left over from the big bang, radiation from supernovae, x-ray emissions from black holes, and a constant flux of energetic protons from our own sun all contribute to the radiation dose received by humans in space. Radiation levels are typically measured in sieverts (Sv), expressing the amount of energy deposited in human tissue from radiation. One sievert is equivalent to 1 joule of energy absorbed for every kilogram of tissue. 6 , 7 An older unit, the rem (Roentgen equivalent, man) is still in common use: 1 rem = 0.01 Sv. Sieverts are now the international standard unit. 6 UNCLASSIFIED/;CFQA: QFFIQI0k WEliii Qllk>f
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Report, from the dia 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.