|
It
has all happened before. The architects of ships have often made
errors, and travellers have died from them. Time after time in the
19th century, mariners failed to reach the North Polar regions
because their ships, although seemingly of brilliant design, were
unsuited for the ferocious environments they would meet.
In
1844 the British Admiralty put Sir John Franklin in charge of
three of the new propeller-driven steamships, believing that these
at last gave them the means of break the ice to penetrate the
North-West Passage.
The propellers could be pulled clear of the ice if necessary, and
– a then unheard-of luxury – a system of hot-water pipes warmed
the cabins. But none of these preparations did any good. All three
ships were crushed by the ice, and none of the officers or crew
returned to civilisation.
Some thirty years later, another determined effort to get through
the ice was made by the energetic owner of the New York Herald,
James Gordon Bennett.
At
the cost of the then huge sum of $100,000, he had a polar
exploration ship, the Jeannette, built with extraordinary
defences. Its bow was bolstered by 10 feet of solid oak and pine.
Its sides were thickened by planking to a depth of more than 20
inches. And solid oak beams, 12 by 14 inches, were laid
athwartships to withstand any conceivable pressure.
When the Jeannette cleared San Francisco bay on July 8,
1879, its crew was as optimistic as Sir John Franklin's men had
been. But the splendid carpentry proved to be of no use. Soon
after entering the ice, the bow buckled and the seams opened. The
ship tilted crazily and had to be abandoned.
And these problems have never really been solved. Even with the
current melting of ice, the best way to the North Pole is still
either by flying or by submarine.
As
in a trip into deep space, these were voyages that nobody knew –
of knows – in advance how to survive.
A
manned spaceship on its way to Mars obviously has to be covered
with some substance that will repel cosmic rays. But what
substance? There are several candidates.
The obvious one is lead. This heavy metal will absorb almost any
radiation, but it is just too heavy. To coat the inhabited parts
of a spaceship with lead would make the vessel so much harder to
propel that it would make the voyage intolerably expensive.
Another solution is to cover the crew quarters with a layer of
water, since water absorbs radiation. But water is difficult to
control. Such a plan is complicated and could easily go wrong.
A
more sure solution is a covering of some kind of plastic. Plastic
is much lighter than metals such as aluminium, and the number of
possible plastics, like the possible number of compounds of
carbon, is immeasurably huge.
At
all events, if a catastrophe is to be avoided, the problems of
protecting the crew from radiation must be fundamental to the
ship's design, not put on at the end as an afterthought. Unlike
the polar mariners of two centuries ago, Mars voyagers must be
truly prepared for danger. |
