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C00002 00002	SPACE AS A FRONTIER
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SPACE AS A FRONTIER

	The public  is disappointed  with the  progress of the  space
program,  and  I think  this  disappointment is  justifiable.   Early
rhetoric on the space program compared the exploration of  space with
the discovery of the new world,  although it was entirely vague about
the  nature  of the  comparison.    In part,  the  disappointment was
inevitable for the following reasons:

	1. The  planets  of our  solar system  are  not inhabited  by
intelligent peoples.   In fact,  they almost certainly  don't support
any life at  all.  As  places to live,  they are all  less hospitable
than Antarctica,  and no-one  (not one  person in  the whole  world!)
seems inclined to move to Antarctica. 

	2. Space travel remains extremely expensive, and there are no
plans for  reducing  the cost  to an  extent  that will  permit  even
well-to-do people to include it in their travel plans. 

	In  spite of  these  unpleasant facts,  space  does have  the
potential  of serving as  a frontier,  and this is  very important to
human society. 

	The relevant scientific facts are as follows:

	1. Interplanetary space rather than the planets is reasonably
hospitable  to human  life.   This  is because  structures  can exist
without  support  and  because  solar  energy  can  be  collected  by
structures with a  fixed orientation.   Moreover, people can  live in
weightlessness,  and there is  good reason  to hope that  people will
come to prefer a weightless condition to one with gravity.   The only
shortage is matter.  The cost  of matter in interplanetary space will
depend mainly  on the depth of the gravitational well out of which it
has to be taken.   Therefore, the planets  are not as good  places to
get  matter as  the asteroids.    All the  main elements  seem  to be
available in the asteroid  belts, and elements  wanted only in  trace
quantities can be obtained on earth. 

	2. It  is not immediately  clear what would  ultimately limit
human  population  in  interplanetary space.    The  energy limit  is
easiest to calculate.   This limit would  occur when the space  rafts
carrying people completely englobed the  sun and used all its energy.
If  we imagine  people living  so austerely  that their  major energy
limit was food, say 4000 calories per day, we  get 10\F328\F0 people.
Present  American  levels  of  energy  consumption would  give  10↑26
people.  Almost certainly, we would  run out of some material  before
we ran  out  of energy.   This  depends  on whether  matter could  be
obtained from the larger planets.  In any case, this Malthusian limit
is not  what we  are concerned  with.   Humanity would  probably have
aesthetic reasons to limit its  population long before the Malthusian
limit was reached.