Documents / Report
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//FIHl 8FFHil.t.k Wfili IH.k\f ( ' / P,ylo,a / ,, k_* L-wa,No11'e Figure 4. Nuclear Fission Rocket Design. Nuclear fission rockets had numerous problems. The fission of uranium-235 emits about 200 MeV for every nucleus that undergoes fission. Approximately 11% of this energy is in the form of neutrinos and is unrecoverable. Approximately 4.8 MeV shows up as kinetic energy in the two or more neutrons that are created for every fission. At least one neutron must be absorbed by another U-355 nucleus and cause fission in order for a chain reaction to be sustained. Most of the energy goes into the kinetic energy of large fission fragments that are created by the breakup of the U-235 nucleus. Fission products are highly radioactive and may be ejected out with the rocket exhaust. Neutrons pose a radiation hazard to any human close to the rocket when it operates. In the tests of the NERVA series of rockets, on at least one occasion, pieces of radioactive material were ejected over a small region of the Nevada Test Site and had to be manually retrieved. On the positive side, the NERVA rockets created large amounts of thrust, and the energy within the reactor was more than sufficient to send its payload to the desired location in the USSR. This prompted scientists to consider the use of thermal fission reactors for use in space exploration, although the persistent problem of radiation exposure to the crew remained unresolved. Two classical designs were proposed. In one design, a reactor would be constructed as shown in Figure 4, and liquid hydrogen propellant would be passed through the reactor to create a supersonic exhaust and to provide thrust. The hydrogen fuel would be located between the reactor and the crew to serve as a radiation shield for neutrons produced during fission. The spacecraft would be elongated to move the crew as far away as possible from the reactor, taking advantage of the l/r2 attenuation of radiation with distance from a source. 11 UNCLASSIFIED//Flilll. lilFFUilAle lal!i! 8Hl!V
Not linked to a story yet.
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.