High Frontier can help Mars Direct

> With regard to "Some plastics may degrade faster than others. The
> plastics we use on Mars don't have to last for all of eternity, they
> only have to last long enough to grow plants. There is no short supply
> of glass on Mars either. I had a plastic greenhouse once and had to
> replace the plastic every year." In the hard solar ultra violet (with
> no ozone layer protection), most plastics will go fast.

I'm sure that UV blockers can be built into the plastics; the
plastics should be able to last a decade or more with careful
design.

> Changing (i.e.
> rebuilding) the greenhouses on Mars several times in a growing season
> is not like replacing the plastic on a terrestrial greenhouse in the off
> season. The ultra violet and loss of the atmosphere while changing the
> plastic on Mars may kill the crops. Remember an open container of ice
> water will boil on Mars. What garden plants can stand that?

None. That's why you don't do that. Incidentally you would have the
same problem on the moon or in an O'Neill habitat.

One easy way is to have the greenhouse double glazed, and you replace
one side at a time. There are better ways thoughs.

I still think Mars is a dopey idea right now; but these aren't
significant problems you're talking about here.

> Sincerely, Jay Huebner
>
> [www.debticated.com]
>

civilization?"