Satgen547 Radiation and Humans 2 by GM4IHJ (BID SGEN547) 1999-09-18 Satgen 546 reported levels of radiation encountered in space flight in general terms. Closer examination of the subject , as in the following examples , reveals that there are no simple answers. Solar storms and the International Space Station ... The greatest danger here are the rare but extremely damaging major storms. Some of these once a decade storms will reach levels of 10 or 20 Sieverts or more, which will be fatal for unprotected astronauts. Some shelter will be possible behind fuel tanks or the thick airlock hatches, provided ISS is aligned so that the protection is between the astronauts and the oncoming solar wind. But if any sort of warning is available and storms above 2 or 3 Sv are anticipated, it will clearly be much better to evacuate all station personnel, if that is possible. What is done, depends on just what sort of advanced warning is available from satellites stationed out on the sunward side of the earth. Typical warning satellites orbiting Lagrangian point 1, about 1 million miles sunward of the earth , cannot be expected to give much more than 30 minutes warning at best. Journeys into Interplanetary Space ... are much more daunting. Evacuation back to earth in the event of a monster solar storm, will simply not be possible. Whilst even in quiet solar conditions on an ordinary day to day transit to Mars, there is constant irradiation from Galactic Cosmic Radiation averaging a dose rate of 0.5 Sv per year. The cumulative effect of which on a Mars expedition using the fuel economic Hohmann half ellipse trajectory around the sun, 259 days outbound, then about 455 days wait on Mars for the right planetary configuration to reappear, then another 259 days homeward bound, is about 1.5 Sv . A possibly debilitating dose, not advised for anyone proposing to raise a family on return to earth. Noting in particular that the high kinetic energy of some Galactic Cosmic radiation particle suggests far more actual damage would accrue on this type of flight than would result from a 1.5 Sv dose inside the earths magnetic field. Of course the astronauts could dig a deep hole as soon as they get to Mars and stay in it for 15 months. But this is not something that has been mentioned by authors trying to encourage colonisation of Mars. Where the lack of protection inside the weak magnetic field would mean that a colonist could get very sick after 5 or 6 years or so on the Martian surface. Interstellar Flight ... provides even more hazards. Noting that outside the heliosphere - the boundary where the solar wind meets the galactic wind, the absence of the solar wind implies that there is now no impediment at all to galactic cosmic radiation. So dose rates will be higher than in the solar system. Several biochemical and engineering solutions for reducing the effects of radiation on human tissue , have been proposed. These will be discussed in Satgen 548.