Colony Wall loading.

Lucio de Souza Coelho wrote:

> From: "victoriatangoman"
> To:
> Sent: Monday, February 25, 2002 1:30 AM
> Subject: [spacesettlers] Re: Colony Wall loading.
>
> [snikt]
>
>>Cool trick if it works. I know that this is frequently cited in the
>>work of space tethers, space elevators, but I'm not convinced that
>>it would work in a habitat. Here's why: the force at work on a
>>planetary body is gravity caused by the mass of the the planet. On a
>>habitat, we're dealing with a pseudo-gravity effected through
>>centrifugal force. I think that would be destabilizing because of
>>the coriolis effect. Isn't there something to that? There really
>>wouldn't be a hanging down (implied that gravity is pulling as a
>>vector towards the surface) rather there would be a combination of
>>vectors to consider in the engineering.
>>
> [snikt]
>
> Coriolis effect operates only over something that is moving outward or
> inward the rotation center. For instance, people in the elevators would
> experience Coriolis forces when going up or down. But static structures,
> like the main bulk of the building, would experience centrifugal force only,
> "downward" and constant. So, you would have the advantage of working with
> tensile rather than compressive structures (as Ian Woollard pointed out) and
> also you would have the advantage of the decrease in "weight" as the
> "height" increases (as was pointed out by yourself).

Roughly correct, but the coriolis also applies to something
that keeps the same distance from center (the classic example
is something thrown so that it stops moving- it goes
into a neat 'orbit'; held there by the 'coriolis force'.)

The equation for the coriolis force is:

FCoriolis = -2 m (w x vr)

Where vr is the motion relative to the the rotating frame
i.e the habitat, and w is the rotation vector (points along the
axis, its length is proportional to the rate of rotation),
and 'x' is the cross product operator if you're familiar with
it; which gives a vector at 90 degrees to both vectors
and the length is the length of both vectors multiplied
together times the cos of the angle between them.

For a building, this can be neglected; it doesn't move
significantly relative to the habitat (bigger habitats
have lower w for a given g force at the rim it turns
out.)

You also have to allow for the centrifugal force as well:

f = m r |w|^2, which acts radially away from the center

Oh yeah, inside a habitat, you would also have air
resistance of course... but that doesn't affect buildings
either.

Anyway, I'm not sure that I want to live in an island 3;
particularly with tall buildings in there. If someone
or something brings down the building, it stands a fair
chance of punching through the rim I would think.

Anyway, I simulated all this many years ago, it was fun.
I really hope I get to see an island 1 someday though.

> Lucio Coelho

--
- Ian Woollard (ian.woollard@...)

"Is a planetary surface the right place for an expanding
technological civilization?"
- Gerard O'Neill