[ExI] High power orbital greenhouses

[Samantha Atkins]

On 03/02/2011 11:08 AM, Adrian Tymes wrote:
> On Wed, Mar 2, 2011 at 4:40 AM, Eugen Leitl<eugen at leitl.org>  wrote:
>> On Tue, Mar 01, 2011 at 08:22:22PM -0800, spike wrote:
>>> Oy that's a lot of people.  I am surprised this old planet can feed all of
>>> us.
>> It can't, actually. Not with today's technology. Not on the long run.
> So we improve the technology over time, just like we've always done.
>
> To rip a thought experiment from the game SMAC: suppose you had a
> kilometer-long orbital greenhouse, with a vast array of solar panels to
> provide all the power you'd need.

There is no way this would be viable economically per unit mass of 
foodstuffs compared to on the ground oldschool or hydroponics.  At the 
point it remotely is you move much of the population off planet (as you 
would then have the means and infrastructure) anyway.    If you posit 
magic tech we don't have to make it work then you can posit slightly 
different (and not so far away) magic tech to synthesise foodstuffs out 
of raw elements right on earth.


>   (If you need a number, then
> extrapolating near-future photovoltaic panels to square kilometer sizes,
> assume a few gigawatt-hours per day, distributed among the entire
> greenhouse.  More is possible.)  How would it work?  What types of
> mass inputs and outputs could you have?  Would capturing a comet
> for local water ice help?

Not without magic allowing the shipping of these panels to space or fab 
planets in space plus the necessary space construction and maintenance 
capability.  We are a very long ways from doing that.  Especially in 
space robotics and general space infrastructure.

> Most importantly, could you entirely replace the energy contribution
> from fossil fuels with electricity (and locally converted forms thereof,
> such as light from electric lamps)?
>

Today? No.  In the next decade?  Not likely unless there is a very very 
large solar breakthrough on earth.  From space? Not for at least two 
decades if then.

- samantha