Re: How to really terraform (part 1)

From: Andrew Usher (k_over_hbarc_at_yahoo.com)
Date: 06/16/04 

Date: 15 Jun 2004 21:16:24 -0700

quibbler <quibbler247@yahoo.com> wrote in message news:<MPG.1b37e2af9f06d3a98986e@news.individual.net>...
> In article <pan.2004.06.14.20.49.36.841598@hotmail.com>,
> khallow@hotmail.com says...
>
> > I wonder though if it'll turn out to be cheaper to build insulated pipes
> > carrying liquid water
>
> One could probably build the pipeline from insulative materials like
> fiberglass. Of course one could use foam insulators and even vacuum
> cavities too, though this would get expensive. A more cost effective
> solution would be to partially bury the pipeline or to pile up large
> dirt/rock berms on top of the pipe. As a coup de grace one could color
> the surface of the berm black to help absorb solar heat during the day.
>
> > The coldest temperatures experienced along the Alaska pipeline were
> > roughly -60C (-79.8F) while the Martian poles routinely reach -140C.
>
> Yes, but the Trans Alaska PipeLine is above ground in many places,
> whereas this could be covered by meters of insulative material. If
> necessary one could build heating elements into the pipeline, inside the
> insulator jackets. For that matter, since water is a polar molecule,
> you could use alternating magnetic fields to heat it in much the same
> way that a microwave oven operates.

A point that hasn't been noted is the energy to heat and melt the ice
at the poles. To heat from -150 F to freezing takes 90 BTU/lb and
melting, 145 BTU/lb.
This gives 235 BTU/lb or 75 Wh/lb. With our 400 billion lb/day, this
is a requirement of 30 TWh/d or 1.25 TW.

This is doable, possibly, with solar energy during the summer.

We would want to switch hemispheres anyway, to improve the temperature
conditions. That is, during the northern summer, pump only from the
north cap, and vice versa. This way solar energy would always be
available for the work.

Do realise, though, that once this plan is in operation, it will be
cloudy much of the time, reducing solar output. This is problematic.
 
> > A final significant point is that petroleum has a high usable energy
> > content. So part of the fluid can be burned to generate heat and energy to
> > keep the fluid warm and pump it onwards. I don't know the energy budget
> > for the pipeline,
>
> Very roughly the estimate was 40,000 cubic feet per second of water.
> I'd estimate that we'd need this to be moving at about 40-50 ft/sec to
> have a reasonably sized pipeline. Given that water is about 60 lb/cu
> ft, were looking at in excess of 120 million foot pounds/second or about
> 160 MW/s continuous, neglecting issues like friction and assuming that
> my back of the envelope calculation isn't otherwise flawed. Assuming
> that inefficiencies and other factors don't drive it up by more than a
> factor of 3 or 4 then it should be the kind of energy that a moderately
> sized nuclear reactor on earth could supply.

Uh, MW/s is not a unit of power - you wanted MW. The energy lost to
friction along the 3,000-mile path would far exceed that to set it in
motion initially, so we need to know the constants of friction. You
would have pumping stations along the way, each with a large solar
array or a nuclear reactor.
 
> > ie, how the infrastructure is powered, but there's some
> > obvious ways to power Earth-based petroleum pipelines that wouldn't apply
> > to water pipelines on Mars.
>
> One means which shouldn't be overlooked is a salinity gradient turbine.
> These devices use osmotic pressure differences between fresh water and
> brine to produce energy. Since the MERs have established that there are
> likely to large salt and brine deposits on mars, salinity gradient
> energy would probably be pretty viable. It would also end up combining
> the water with salts and making them less vulnerable to freezing in the
> process.

I would think Carnot's law would defeat you in this case.

I would like to respond to everyone that's posted about the pipeline
idea here.

The main needs are:

1. Establishing a route for the pipes.

This will involve: a pipe encircling each pole, in order to
effectually acquire ice from the entire cap; a pipe from each pole to
the equator; a set of pipes around the world in the equatorial region,
to disperse the water for evaporation. This last does not need to
cover the whole equator (which is fortunate, as there are some
obstacles of terrain), but only a sufficient length that all can
evaporate without saturation.

The diameters should probably be around 50' and the main lines would
have about 20 ft/sec flow.

2. Power for pumping and heating.

This has been discussed above. Note that if nuclear reactors are
planned, we probably will have to build them on Mars.

3. Evaporation at the equator.

My first thought is to pour the water into a trough alongside the
equatorial pipe, to allow natural evaporation.

The requirement here is 1,000 BTU/lb = 5 TW (using similar
calculations). Solar heating gives, on Mars, about 50 W/ft^2 maximum,
which gives about 300 Wh/d/ft^2. We'd then need 16 billion sq ft area.
The circumference of Mars is 70 million ft, and given that we won't
use all of it due to terrain, about a 300' wide trough is called for.

This needs to be absolutely flat, and well insulated on the bottom so
that all the heating goes into the water.

Again, cloudiness increases this requirement. If we are going to use
nuclear at all, we might as well use it here, rather than solar
heating.

4. Collection of ice at the poles.

This simply requires transportation to one of the plants metling it
and adding to the pipeline. The ice cap certainly contains CO2, and
this should be allowed to escape into the air. 

--
With all that said I wonder whether the trucks would be cheaper, as no
other equipment or power is needed anywhere. All that would be needed
is to establish a factory to produce millions of identical trucks.
If anyone has an idea, why not take a guess at what the cost might be
for either of these approaches.
Andrew Usher

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