[extropy-chat] The other space program
charlie at antipope.org
Sun Aug 15 10:38:14 UTC 2004
On 12 Aug 2004, at 18:48, Adrian Tymes wrote:
> --- Eugen Leitl <eugen at leitl.org> wrote:
>> Who's going to build the microwave
>> stations on the ground to
>> track the craft as it goes around the Earth?
> I generally agree with most of your objections here,
> but this one can easily be solved: solar panels (or
> cells on the craft's skin), or a fleet of microwave
> satellites launched by traditional means.
>> The Dark Sky station is as close to LEO as
>> SpaceshipOne. I.e., not at all.
> *shrugs* Doesn't mean it isn't useful in its own
> right. If they can solve the engineering issues of
> floating serious payload at high altitudes...floating
> cities, anyone?
Sure. Until ...
1. The neighbours on the ground get a bit annoyed about the city
blocking all their sunlight
2. The neighbours on the ground who you've just drifted over point out
that under existing international law they have sovereignty over their
head space, and would you mind implementing their shari'a legal code
(For the sake of point (2) above, assume the neighbours have SAMs or an
3. The higher you float your city, the lower the density of the
surrounding air. Therefore the volume of lift gas you need to displace
your own mass in air also increases. When you're so high that
atmospheric pressure is around 1% of sea level, your aerostat needs to
hold 100 times the volume it encloses at sea level. The kind of
altitude these folks are talking about implies kilometre-plus diameter
gas cells, just to hold up something as massive as a 747. If you want a
floating city, you either have to have gas cells the size of continents
or float it down in the troposphere where the pressure's higher but
there's nasty weather to contend with.
(See http://www.mypage.bluewin.ch/airshipsimon/design.html for a basic
overview of how an aerostat works.)
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