From: Henry Spencer <henry@zoo.toronto.edu>
Newsgroups: sci.space.science,sci.space.tech
Subject: Re: LOX producing on Mars
Date: Sat, 22 Jun 1996 04:21:09 GMT

In article <4qb0d4$rtb@hermes.is.co.za> franks@vironix.co.za (Frank Scrooby) writes:
>Why not do things properly from the start ? This theoritical pre-cursor lander
>is going to be flying to Mars with some kind of orbiter right.

Uh, no, why should it?  That just adds complications.  For one thing, it is
significantly harder to brake into orbit first, and then go down into the
atmosphere, rather than just going straight in.

>Place the orbit in a
>suitable orbit, deploy enormous solar collectors and beam the watts down to
>the lander via microwaves...

Unfortunately, this doesn't work very well.  If you want to supply power
more or less continuously to a single site, you need the equivalent of
geostationary orbit, which is a long way out (not as far out as Earth's,
but still not close).  Some very fundamental physics says that microwave
power transmission over such distances demands huge transmitting and
receiving antennas (as in, kilometers across).  Such systems do not scale
down satisfactorily. 

Laser power transmission would work better, but then you're back to a
system using photovoltaic arrays as the receiver, which fails if they
get covered with dust.  As long as you have to deal with that anyway,
you might as well just make the arrays a bit bigger for solar power.
-- 
If we feared danger, mankind would never           |       Henry Spencer
go to space.                  --Ellison S. Onizuka |   henry@zoo.toronto.edu

From: Henry Spencer <henry@zoo.toronto.edu>
Newsgroups: sci.space.tech
Subject: Mars exports (was Re: How Do I Get Back?)
Date: Thu, 22 Aug 1996 14:07:09 GMT

In article <DwF5qp.CHx@dowco.com> phillips@dowco.com (Daniel Phillips) writes:
>>>...to set up semiconducter fab plants on Mars because it's actually
>>>cheaper than Earth for a .1 micron fab line, due to less seismic
>>>activity and lower atmospheric pressure.
>>I hate to say it, but this doesn't hold up to any sort of inspection.  
>>Low Earth orbit, or at most the Moon, is a far better location...
>
>OK, maybe the low pressure is not a big advantage.  But maybe the 
>low vibration >is<?

The Moon is also almost completely quiet seismically.  It's hard to say
which is quieter -- the data for Mars is not very good -- but the Moon
should be quiet enough for most anything that cares.  And the ultimate
in vibration-free operation is orbit, which is even easier to reach and
has its own unique advantages.

>Maybe Mars is a more hospitable place for people.  There is free
>H2O there, and a gravity closer to Earth's...

Mars definitely wins big on local supplies of volatiles like water.  (The
Moon may have polar ice, but apart from the lingering uncertainty about
that, Mars undoubtedly has more, and its supplies are more accessible.)

How much the higher gravity helps people is an open question.  It's quite
possible that 1/3G is no better than 1/6G.  We simply have no data.

>...Having lots of 
>real people around has got to be an advantage for any 
>manufacturing venture.

Having a few of them around, at least, is certainly an advantage.

>Another way of looking at it is, >assume< that people are going to
>settle on Mars, whatever the reason.  Now they have to do something
>to support themselves.  What?

Semiconductor fabrication probably is not it.  The advantages over Earth
are just too small... and if any of them *does* turn out to be important
for some reason, the Moon (or Earth orbit) will score higher than Mars.

Frankly, it is going to be very difficult for a small colony, far away
from Earth's resources, with scarce manpower and slow and expensive
transport, to compete at any sort of manufacturing.  The transport
problems indicate that any viable exports are going to have to be low-mass
high-value goods.  But low-mass goods generally are high-value because of
difficult manufacturing processes, and unless you can find some huge
environmental advantage, such a process will be more economical carried
out near Earth, where spare parts are close at hand and teleoperation can
substitute for expensive on-the-spot labor to some extent. 

It seems to me that any viable export from Mars is going to have to be
intangible -- a bestselling author would be a major asset to a colony --
or else is going to have to be aimed at off-Earth markets, where the
cost of transport is a problem for the Earthly competition too.
-- 
 ...the truly fundamental discoveries seldom       |       Henry Spencer
occur where we have decided to look.  --B. Forman  |   henry@zoo.toronto.edu

From: Henry Spencer <henry@zoo.toronto.edu>
Newsgroups: sci.space.tech,sci.space.policy
Subject: Re: One Way Missions Re: Mission to Mars in 2015?
Date: Fri, 23 Aug 1996 13:01:30 GMT

In article <4vi13n$p8s@ns.hcsc.com> andyh@hcxio.hdw.csd.harris.com (Andy Haber) writes:
>This assumes that a greenhouse will work perfectly on Mars, which for
>a number of reasons it may not.  Mars soil is nothing like Earth soil...

Actually there are similarities.  And plants will grow in almost anything 
that has adequate nutrient supplies and not too many poisons.

>...Mars air is nothing like Earth air either
>so you need to do something about that too...

Mars air is almost straight carbon dioxide, which is just what plants
want.  (Well, I oversimplify, but this problem is manageable.)  Besides,
the first greenhouse or two would probably be extensions of the life-
support system, not independent entities, and would contain much the same
air the humans are breathing. 

>Sunlight on Mars is not
>as strong as on Earth and that may affect plants too...

The sunlight in Toronto in winter can get pretty feeble too, but greenhouses
work fine here.  Plants do fine in somewhat-reduced sunlight.

>Your greenhouse
>needs to be able to deal with the extreems of Mars weather without
>letting the plants freeze...

*This* is definitely an issue.

>And, of course, what are you going to
>do when a sandstorm comes up that persists for months and months?

Nothing much.  The Martian dust storms do not cut off all light from
the surface; they block essentially all *direct* sunlight, but a fair
bit gets through by scattering.  There is still a considerable net
reduction, and this has to be thought about in greenhouse design, but
it's not a fatal problem.

>Not to mention crop failure, blight, and so on...

Reasonable diversity of crops, and some caution to avoid bringing plant
parasites along, should deal with this adequately.

>>  And 100g per person-day is more like it, with some simple recycling.
>
>Assuming your simple recycling system works and will last for 40 years.
>Most things I've got haven't or won't last me 40 years.  You need to think
>about that when the nearest department store is 200 million miles away.

My drinking water comes from a waterworks built about sixty years ago:
it's been repaired, upgraded, and improved since, but it's still there and
still supplies about half of Toronto's drinking water.  Phone companies
routinely specify 40-year lives for switching systems (with a total
allowed downtime of 30 minutes).  The last turn-of-the-century 25Hz
generators at the Niagara Falls power plants were retired only quite
recently.  If you're buying a used lathe, one that's 50 years old is a
better choice than one that's 10 years old.  The crawlers that carry
the shuttle out to the pad were built 30 years ago; it was news when
one of them broke a tread a few months ago.  You're confusing shoddy
consumer goods with industrial gear that is built to last. 
-- 
 ...the truly fundamental discoveries seldom       |       Henry Spencer
occur where we have decided to look.  --B. Forman  |   henry@zoo.toronto.edu

From: Henry Spencer <henry@zoo.toronto.edu>
Newsgroups: sci.space.science,sci.space.tech
Subject: Re: LOX producing on Mars
Date: Mon, 24 Jun 1996 18:56:02 GMT

In article <4qalkv$94d@vixen.cso.uiuc.edu> bromley@students.uiuc.edu (Blair Patric Bromley) writes:
>       - you'll need to get your solar cells to open up to catch the limited
>         sunlight on Mars; one more remote mechanical task to handle that
>         an RTG or thermionic converter shouldn't have as difficult a 
>         problem with

Actually, for a big isotope power setup you'll need to deploy heat radiators.

>         ...if the cells only have
>         to operate for a year, then maybe it will be okay... still,
>         you will have more parts that can breakdown...

Actually, RTGs are moderately complex, and note that our experience with
them is almost all in vacuum, not in a thin CO2 atmosphere with significant
amounts of suspended dust.

>      -  as someone else pointed out, what happens if your panels get
>         covered with dirt / dust?

What happens if the RTG heat radiators get covered similarly?

>      - if you are going to operate a chemical processing plant, you're
>        probably going to want it to operate it continuously with
>        a steady power level...

Actually, no, this isn't necessary.  The whole point of a fuel plant is
that you're putting energy into a form that can be stored.  There's
absolutely no need to run such a plant continuously.  You run it when
there's power, and don't when there isn't.

>        You're also going to need additional power circuitry to 
>        condition, and store the variable solar power.  The landing
>        site is not going to have the same type of sunlight throughout
>        the year, let alone the day you know.

Note that there is a similar problem with RTGs, since their output decays
continuously and will be affected at least slightly by the effectiveness
of the radiators (which will vary with wind, sunlight, etc).
-- 
If we feared danger, mankind would never           |       Henry Spencer
go to space.                  --Ellison S. Onizuka |   henry@zoo.toronto.edu

From: jamesoberg@aol.com (JamesOberg)
Newsgroups: sci.space.policy
Subject: ISS Needed for Mars? WAS Goldin's Revealing Quotes
Date: 29 Dec 1997 03:54:40 GMT

Re what we MUST learn before going to Mars.

We already know how to keep a crewmember's heart and muscles strong enough to
endure ten months of zero-G, and then function well under 0.4 G for an extended
period. The return flight in zero-G (or in spun-up higher G) is also
understood. Reconditioning on Earth will be analogous to reconditioning
bed-rest patients -- space flight has taught us that the bed-rest analogy for
muscle and cardiovascular deconditioning is "good enough". And even at today's
medical care prices, hospital bed rest costs a WHOLE lot less than space
station occupancy.

We don't know enough, PERHAPS, about long term cosmic ray exposure, but then,
space station won't teach us anything about it either (hiding under the van
Allen belts).
We CAN learn about that via ground simulations as well.

Of course, medical professionals on the NASA teat will tell you in public that
they have to stay on the teat for the next two decades before they allow you to
do anything else (ask them to DEFINE exactly WHEN they supposedly will "know
enough"). In private, many of them would LOVE to go to Mars right away.

Just rocking the boat again..... ;-)