From Julian White
Chepstow, Gwent
I am a little puzzled about the pessimistic tone of the article regarding the
shielding of Mars missions from stellar and cosmic radiation (This week, 4
January, p 9). This issue has been tackled many times by both the scientific and
science fiction community. Many ideas have been put forward for achieving the
necessary levels of shielding in a minimalistic way.
Two main ones stand out. The first, described 20 years ago by Gerard K.
O’Neill in his book The High Frontier, is to provide the living
quarters with a reasonable amount of shielding, but have a small, heavily
shielded compartment at the centre of the spacecraft to act as a “storm shelter”
where the astronauts go when radiation levels peak. They would also sleep in the
storm shelter to minimise their total exposure throughout the mission.
The second idea is to utilise water as the shielding material (
Nature, vol 330, p 709). Although it is probably not as good as lithium
hydride, it is much better weight-for-weight than aluminium at stopping
high-energy particles. And on a long mission to Mars, water certainly has a few
other uses, reducing the overall cost of the shielding.
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Perhaps the designers of the Mars mission would do well to have a look at the
vast literature on this subject and see whether it would really cost $30
billion to stay within existing dosage limits.
