OT: Building O'Neill habitats on Earth?

On Jul 4, 2005, at 10:26 AM, Ian Woollard wrote:

> On 7/4/05, Lucio de Souza Coelho wrote:
>>
>> Maybe my intuitive reasoning is wrong, but I think that the pressure
>> distribution in a sphere or cylinder 10 Km across would be completely
>> different in Earth's gravitational field - which is basically uniform
>> close to the surface, very different from the radial "gravitational
>> field" of a habitat. So I don't think that pressure alone could
>> sustain the building, if that is what you are hinting.
>
> Well, pressure halves every 6km on earth, so the pressure at the top
> is only
> 1/3 that at the bottom.

The forces in a colony are completely different. On Earth, every
molecule in the atmosphere feels the pull of Earth's gravity. In the
colony, the attraction between the hull and each molecule in the
atmosphere is negligible. The only force on a given atmospheric
molecule is the other molecules plus a shear force in a layer just
above the hull and around any other rotating hardware, but that force
is around the axis of the rotation, not towards the hull. I the Lucio
is right. The pressure and density will probably be uniform, with the
shear forces causing the atmosphere to rotate around with the hull.
There is no reason that I can think of to believe that the pressure at
the hull will be any different than the center.

>
> So if you run the bottom at 2 bar absolute, the top would still be 1/3
> bar
> above ambient, about 3 tonnes per square meter. So provided you have
> less
> than 3 tonnes of stuff per square meter it stays up. IRC with O'Neil
> cylinders I think the aluminum itself is maybe 3cm thick. That works
> out at
> only 81 kg per square meter.
>
> It's a surreal idea, but it seems to work.
>
> --
> -Ian Woollard
>
> Simplicity is the ultimate sophistication - Leonardo
> "Communism" is deprecated. Please use "Terrorism"
>
The first space tourism business is already profitable! Burt Rutan
spent about $40 million of Paul Allen's money to build SpaceShip One.
This vehicle was piloted into space three times in 2004. The third
flight won the $10 million dollar Ansari X-Prize, writing 'Virgin' on
the vehicle's tail pulled in some more cash, and the flights lead to a
$120 million contract with Virgin Galactic to build the first true
sub-orbital tourist vehicle.

Al Globus
Evolvable Systems Group (http://ic.arc.nasa.gov/projects/esg)
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Views expressed in this email are only my opinions and are not the
position of any organization I'm familiar with.