Mars and Island One

Hi Selvaraj!

> The problem I feel boils down to whether or not there will be
> some kind of agricultural activity in space. If any
> agricultural activity is planned to support even say 20
> people, very large space habs will be required.

Not necessarily. As a rule-of-thumb: current intensive agriculture
results in food yields of up to 10 million food-calories per hectare. So
your population of twenty could survive on a couple of hectares of
agricultural land (and probably /much/ less if it was maximised for
efficiency). The worst-case therefore is an area 140m by 140m...a field
that takes about two minutes to walk across. While that's certainly big
by current standards for orbital habitats, it really is nothing much.
More on that area later.

> With the
> available resources - during the next 50 years let us say -
> will it be easier to set up such habs on Moon and Mars or
> have free floating complexes? My suspicion is, it will be
> easier to set up such habs on Moon or Mars.

I disagree. Firstly, in the short term (<25 years), agriculture will not
be a goal of any nations' space effort. There will be experiments,
certainly, and no doubt cute shots of plants growing in Martian and
Lunar regolith (suitably processed and nutrified, of course) but while
food is mostly water, and dried food masses very little, Earth will
undoubtably be the source for 99% of food eaten in space.

That said, once the orbital materials' infrastructure takes off (>25
years), and rotating habitats are constructed - presumably in LEO first,
and possibly as part of the holiday market - then greenery will follow,
but more for psychological and aesthetic purposes than for food
production.

> And since there
> is more likelihood of obtaining water freely on Mars, are the
> Mars enthusiasts right after all?

No, I don't think they are. Martian soil is acidic, poisonous and
lacking in nutrients. The water is extremely salt-laiden. The dust is
pervasive and magnetic. Farming on Mars requires you to not just dome
over any old crater and break out the space-shovel, but to create a
completely self-contained environment, into which all your soil, all
your water, all your atmosphere will require extensive processing and
control. There's really no benefit there, apart from the gravity...on
which point:

> Free floating
> structures will require radii of about a mile to achieve
> significant g levels.

No...Mars' gravity and psychologically acceptable rates of spin (<3rpm)
is attained in a habitat with a radius of 38m.

(Slightly interestingly, an 80m diameter habitat for this 1-Mars
gravity, 80m long, contains two hectares of floor space: the agriculture
necessary for your twenty-person outpost. Perhaps by 2030 or so major
universities might be working together and conducting LEO experiments in
such places...)

> Are O'Neil type structures too
> futuristic for the immediate future?

Oh yes, but I believe that the point Gerard was making was that they
were acheivable, without magic or unforeseen technologies, back in the
seventies - /if/ the political mindset and will was present.

> Perhaps they are the
> butterflies that will emerge after the egg, caterpillar and
> pupa stages!!!

I suspect so. Speaking personally, I see the large O'Neill habitats more
as morally-better, productive and optimistic targets for the vast monies
currently wasted on arms and our species' atavistic attitudes. But there
you go! ;-)

Regards!

Andy G