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Radiation is the greatest known danger to
explorers in space. The unit of radiation is called “rem”. Scientists have
reason to think that a man can put up with far more radiation than 0.1 rem
without being damaged; the figure of 60 rems has been agreed on. The trouble is
that it is extremely difficult to be sure about radiation damage a person may
feel perfectly well, but the cells of his or her sex organs may be damaged, and
this will not be discovered until the birth of deformed(畸形的)children
or even grandchildren. Missions of the Apollo flights have had to cross belts
of high radiation and, during the outward and return journeys, the Apollo crew
accumulated a large amount of rems. So far, no dangerous amounts of radiation
have been reported, but the Apollo missions have been quite short. We simply do
not know yet how men are going to get on when they spend weeks and months
outside the protection of the atmosphere, working in a space laboratory. Drugs
might help to decrease the damage done by radiation, but no really effective
ones have been found so far.