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\F2\CSTANFORD ARTIFICIAL INTELLIGENCE LABORATORY
\CDEPARTMENT OF COMPUTER SCIENCE
\CSTANFORD UNIVERSITY
\CSTANFORD, CALIFORNIA 94305
\F0



							17 October 1974



\J
	O'Neill envisages the colonization of interplanetary space
as the result of a government plan for relieving overpopulation and
for providing a nice earthlike environment.  This is not the only possible scenario,
and, to my mind, not the most likely one.
In this note, I would like to explore the following alternative:
	
	1. Instead of or as well as \F1official\F0 colonization, there are
unofficial colonies by groups intent on getting beyond the control of
the present national governments.
There are many possible motivations for this.  Some come
from the the worldwide trend to increasing bureaucracy and regulation
whether in the name of preserving the environment, increasing equality,
or preserving morality.  Many social thinkers believe that increasing
regulation of life styles is needed to deal with the various crises of
society.  This increases the probability that some groups will want to
escape.
Another motivation for space colonization is to ensure that a nuclear war
wouldn't destroy the whole of humanity.

	2. Instead of trying to create an earthlike environment and paying an
enormous price for it, they settle for the most austere colonies consistent
with survival.

	If the Shuttle is developed and if the projected cost of $300 per
pound transferred to low earth orbit is realized, the it may be that the
cost of launching a space colony will be within the means of non-governmental
organizations or even of very wealthy individuals.  Consider what
an austere space colony involves compared with O'Neill's luxurious plan:


	1. The use of centrifugal force to provide gravity is given up,
and the colonists must adapt to weightlessness.  The evidence from Skylab
is that this is possible, but exercise may be necessary to preserve health
and the possibility of readapting to earth may have to be given up.

	2. An earth-normal atmosphere is given up in favor of the lowest
pressure of pure oxygen that can be tolerated - five pounds per square inch
has been used throughout the American space program.

	The amount of matter required per person is then the sum of three
terms:

	The first is proportional to the volume of air wanted to move around
in.  If we accept O'Neill's estimate of 150,000 pounds per square inch for
the strength of steel, we get that the mass of steel required to contain
the air is about half the mass of the air contained at 300K independent
of the pressure of the air or the volume of the spherical container used.
If we allow 100 kg of oxygen per person, this gives a volume of 300 cubic
meters per person, i.e. a large roomful, and 50 kg of steel will be
required to contain it.  

	The amount of food required per person in a steady state depends on
how fast it can be recycled.  If the people eat chickens which eat
chlorella, less than another hundred kg per person are required.

	Finally, there has to be tools and machinery which we arbitrarily
estimate at 200 kg per person.

	Adding in the weight of the people themselves estimated at 75 kg,
we must transport 525 kg per person to orbit at a cost of $660 per kg, giving
a fare of roughly $350,000 per emigrant.

	Thus a colony of 1000 could be launched for less than half a billion
dollars, a sum within the means of a few individuals and also raisable
by a determined organization.

	All this assumes that the government would rent the Shuttle launches
and that enough people sufficiently valued the freedom from the government.
Perhaps these two conditions are incompatible.\.

							Sincerely yours,



							John McCarthy
							Director, Artificial Intelligence Laboratory
							Professor of Computer Science