Satgen559 Radiation and Humans 4 by GM4IHJ (BID SGEN559) 1999-12-11 A hold up in the delivery of packet radio mail to GM4IHJ, has caused a build up of queries regarding Satgens 546,547 and 548 , all on the subject of Radiation and its effects on Space travellers. So here with apologies for the delay, are some answers to your comments and queries. Measuring Units. First, the old units where the concern was with the amount of radio activity contained in a given radioactive sample, or, the measurement of radiation produced by equipment such as X ray machines. Becquerel :- 1 Bq = one atomic disintegration per second from a radio active substance. Curie :- 1 Ci = 3.7 x 10^10 disintegrations per second Roentgen :- 1R = radiation required to produce 1 electrostatic unit of charge in standard NTP air. Second, the new units which have come into use mostly since 1945, as the need arose to quantify the damage done to human tissue by radiation of all kinds. These units are normalized for various types of radiation , noting that damage from heavy particles such as cosmic rays, is far more severe then damage from Xrays, gamma rays or small particulate radiation such as alpha or beta. Gray :- 1 Gy = 1 joule of energy per kilogram of tissue Rad :- 1 rad = 0.01 Gy Sievert :- 1 Sv = A dose of radiation corrected for relative biological effectiveness RBE ie dose in Gy multiplied by RBE factor for that type of radiation Rem :- 1 rem = 0.01 sieverts It was appreciated after Hiroshima, that there was a need to relate radiation intensity to the damage it did to human tissue . But it was not until the long duration Russian space flights in Salyut 7 and Mir, that medical specialists going into space began to quantify the much more serious effects resulting from heavy particulate damage encountered in space radiation , as opposed to the much lighter weight particle and radiation effects encountered earlier. Russian specialist gradually established that whereas small particles behaved like bullets , causing localised damage. Heavy particles behaved like bombs, causing wide spread damage for some distance around the actual point of impact. It is this latter point which makes encounters with Galactic Cosmic Radiation in space outside the protection of the earths atmosphere and magnetic field, much more severe than exposure to solar radiation. Although the once every ten years or so major outbursts from our Sun, can reach levels of radiation where individual particle damage is irrelevant. What matters there is the over whelming total dose. Hope this answers all queries. Many thanks for all your interest and comments on these satgens. Where possible please use email for queries to gm4ihj@branegan.demon.co.uk Its much more reliable than packet.