[extropy-chat] The other space program

[Adrian Tymes]

--- Charlie Stross <charlie at antipope.org> wrote:
> On 12 Aug 2004, at 18:48, Adrian Tymes wrote:
> > floating
> > cities, anyone?
> 
> Sure. Until ...
> 
> 1. The neighbours on the ground get a bit annoyed
> about the city 
> blocking all their sunlight

If the city's not too big and floats high enough,
the sunlight goes around them.  Much like a cloud.

> 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 
> immediately?

There's a maximum altitude that applies to.
Specifically, nations don't get to apply their law to
any satellite (or thing at comparable altitude) that
happens to go overhead.  Still, the station would
presumably do much better simply to avoid those areas
- military issues aside, they wouldn't make for good
customers.  (This being a private venture, they would
presumably seek to make money off of it.)

> 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.

Depends on how large the city is.  This is what I
meant by the "engineering issues" they'd have to
solve.  (And I'm not necessarily saying they are
solvable.  Not saying they aren't, either.)