HYPOTHETICAL DARK MATTER/AXION ROCKETS: DARK MATTER IN TERMS OF SPACE PHYSICS PROPULSION

Current proposed photon rocket designs include the Nuclear Photonic Rocket and the Antimatter Photonic Rocket (proposed by Eugen Sanger in the 1950s, as reported by Gulevich et al., 2001). In a Nuclear Photonic Rocket, a nuclear fission reactor is used to directly heat tungsten coils or graphite blocks to white heat at the focus of a parabolic reflector. Using a laser to produce the light beam would provide much better collimation, but this is offset by the reduction in efficiency incurred by powering with a laser rather than black-body radiation (a nuclear fission reactor will generally output at least 5 to 10 times more energy as heat than electricity). Then there is the issue of fuel. It would take at least the current energy output of the entire world (1.73 x 10 watt-hours per year as of 2005, according to the EIA/U.S. Dept. of Energy, 2008) to send a probe to the nearest star. According to Brice N. Cassenti, as quoted by Frisbee (2009), a ramjet would allow for very-high-energy expenditures while avoiding the absurdity of carrying x GW (as of 2008) on board a space craft. Instead, it makes sense to use a ramjet to avoid carrying huge amounts of on-board fuel. So more conversion of matter to energy (via DM candidates, for example) is needed to achieve realistic interstellar travel. To make the prospect of interstellar travel practical, this paper examines the feasibility of improving the thrust of photon-driven ramjet propulsion by using DM rocket propulsion. DM would first be converted to low-mass axions, which would then be converted to photons, hypothetically allowing for greater power and thrust than with currently proposed photon sources. In saying this above, the reader should be aware that axions are a DM candidate, but with insufficient mass to upgrade interstellar propulsion. WIMPs are suggested as a starting point because of their neutral character, as well as their high mass values. The open question the readers and the author need to consider is: would a relatively heavy WIMP, if eventually converted to photons, considerably upgrade the power and thrust of a photon rocket drive, to make interstellar travel a reasonable proposition? Proper analysis of relic conditions, in which both gravitons and DM are to be created could be aided by judicious use of the Li-Baker detector (Li et al., 2008 and Baker et al., 2008). Which DM candidates are viable? Taoso, Bertone and Masiero (2008) provide a ten-point test a new particle has to pass to be considered a viable DM candidate: “(I) Does it match the appropriate relic density? (II) Is it cold? (III) Is it neutral? (IV) Is it consistent with BBN? (V) Does it leave stellar evolution unchanged? (VI) Is it compatible with constraints on self-interactions? (VII) Is it consistent with direct DM searches? (VIII) Is it compatible with gamma-ray constraints? (IX) Is it compatible with other astrophysical bounds? (X) Can it be probed experimentally?” It so happens that WIMPs meet all the above tests. Muramaya (2006) gave a mass value of between 100—300 GeV for WIMPs. Furthermore, DM, such as WIMPs, are not thought to be charged particles, so they do not emit electromagnetic radiation at any frequency and thus appear dark. A second theory involving undetected particles is that some dark matter is made of hypothetical subatomic particles called “axions.” Axions are many times lighter than electrons and have no electric charge. One of the main differences between WIMPs and axions is their mass. Thus, the difference between the two theories (WIMPs or axions) is that dark matter is either made of a large number of light particles (axions) or a smaller number of heavier particles. A way to link the two states of DM is to note, first of all, that if, as Weinberg (2008) notes, axions were the whole of DM, that there would be eV maxion 5 10 ≈ for a total DM mass