[ExI] Skylon as first stage.

[Keith Henson]

On Thu, Apr 21, 2011 at 9:26 AM, Eugen Leitl <eugen at leitl.org> wrote:
> On Thu, Apr 21, 2011 at 07:41:18AM -0700, Keith Henson wrote:
>> On Thu, Apr 21, 2011 at 2:03 AM, Eugen Leitl <eugen at leitl.org> wrote:
>>
>> snip
>>
>> > On the Moon, you can use linear motor/magnetic levitation launches.
>> > http://www.physorg.com/news91272157.html
>>
>> MagLev is *so* 70s.
>
> Turbines and ICEs are *so* steampunk. But they continue to provide the bulk
> of our power.

Turbines run as high as 60% efficient.  It is unlike that PV will ever
get that good.  Commercial ones already mass as little as 1/10th
kg/kW.

I think they are the best choice for power satellites.

snip
>
> Maglev doesn't yet quite exist apart from test lines
> http://en.wikipedia.org/wiki/Maglev_(transport)
> nevermind more advanced approaches like mass driver,
> or launch loop, or space fountain.

It bothers me that nobody has built a model of a launch loop.  It
shouldn't be that hard, particularly if you built it upside down

> We've got great technology in the pipeline, but the first
> steps in SPS will be quite pedestrian, using technology
> more than 1000 years old: http://en.wikipedia.org/wiki/Rocket#In_antiquity

That's my opinion.  Heating a working fluid (hydrogen) with
concentrated light is something Hero of Alexandria would have
understood 2000 years ago.  "An aeolipile (or aeolipyle, or eolipile),
also known as a Hero engine, is a rocket style[1] jet engine[2]"
http://en.wikipedia.org/wiki/Aeolipile

Keith