VI.A.l: THE PROBLEM 6 .Al APPENDIX VI.A RADIATION SHIELDING The space environment has long been recognized as potentially hazardous to humans due to high energy charged particle radiation (> 102 MeV). Outside planetary magnetospheres this is due both to an isotropic background radiation of low intensity (generally called the galactic cosmic ray background) and occasional high level radiation from the Sun associated with solar flares. So far during man's exploration of space he has not stayed exposed long enough to show any ill effects due to radiation. The Apollo astronauts saw occasional flashes of light in their eyes on the way to the Moon that have been attributed to the galactic background, but it was not a serious effect at their dose. Unfortunately, the radiation dose rates are generally greater than the biological replacement rate of the damage, so, to a good approximation, the integrated dose goes linearly with time. For a long mission, such as a manned Mars mission or a space manufacturing facility, interplanetary charged particle radiation from the galactic background and solar-flare-associated charged particle events is considered a serious hazard to be shielded against. Basically the problem is that the solar charged particle events by themselves are enough to kill a person in one or two events. They can be shielded against, using bulk mass, but this shielding and the shielding provided by any vehicle structure increases the dose received from the galactic background radiation due to production of secondary particles. Alternatives to mass shielding consist of various "active" shield schemes which use the fact that the incident particles are charged to deflect them with magnetic and/or electrostatic fields. VI.A.2: THE RADIATION ENVIRONMENT The charged particle environment outside planetary magnetospheres can be broken up into a solar component and a "galactic" component.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==