Satgen239  Radiation and Satellites Part 3  by GM4IHJ          23 Oct 93
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Satgens 237 and 238 discussed radiation problems in near earth space.
Briefly mentioned was Galactic Cosmic Radiation (GCR) which generally
features heavier particles (iron nuclei) , than does the lightweight
radiation of Hydrogen particles from the Sun. Heavy particles can do a
great deal of damage. It had been hoped originally that all particles
might behave like bullets - producing a hole but not much damage beyond
that. This has not proved to be the case. Russian studies have clearly
shown that heavy GCR particles act like bombs causing wide spread damage
over an area much greater than their individual diameter.
This makes GCR very dangerous to anything it hits and worse still there is
the further complication that it is difficult to provide any sort of
adequate protective screening from GCR. Whereas Hydrogen nuclei can be
stopped by sheet metal, GCR can crash through metres of aluminium or
water. Not only does any protection have to be very thick and therefore
very heavy but it cannot afford complete protection because while the
screening may stop the original particle , the GCR hit will produce
hundreds of daughter particles , many of which will hit like a cloud of
shrapnel.
The GCR problem is therefore very serious. Fixed small electronics can be
partially protected by small local shields but a human being who wants to
move about cannot carry a personal aluminium shield nearly a metre thick.
Nor can the whole space craft be shielded in this otherwise redundant
heavy material. Please note that this need for shielding also applies to
anything on the surface of Moons or planets which do not have natural
atmospheric and magnetic shielding.
It has been suggested that we may be able to build strong local magnetic
shielding, but this is an unknown quantity, since we are not sure what
happens to human beings or electronics which are in very strong magnetic
fields perhaps for years. Quite recenly a Russian Cosmos experiment
discovered that a sizable amount of GCR actual gets "magnetically bottled"
in the earth's Inner Van Allen Radiation Belt. Located around the earth
between 60N and 60S latitudes this GCR ring is roughly 8000 kms above the
earth's surface. An area definitely to be avoided.
Unfortunately GCR is not the end of the situation. Local generators of
radiation exist in several planetary systems. The nearest to us is Jupiter
where the inner Moons of that planet are bathed in a strong radiation
field, of which the principal component originates in Sulphur emitted by
Jupiters volcanic moon Io. All around Io's orbit a belt of highly ionised
sulphur makes the general area very dangerous indeed. No doubt similar
problems lurk unseen around other planets in our near neighbourhood. 
So clearly the rule must be " When beyond the Earth's atmosphere and
magnetic field, those who ignore their radiation counters do not survive
for long ". Space is dangerous and radiation is the major danger.
73 de GM4IHJ @ GB7SAN