You state up front (and I'll give you credit for that; many people
wouldn't have) that you have not "calculated on" the question of
whether or not something like Stanford Torus could be made to work.
You then state with utter authority, like you were Saint Paul or
something, that neither has anybody else. You didn't bother to look
into it and see that, actually, a ten week NASA/AMES study group did
get around to crunching a few numbers. You just stated your
uncalculated objections and assumed that your guesses trump anything
anybody else has ever done, and of course nobody else has "calculated
on" this, or they'd understand what you don't need calculations to know.

This is why I used the word "arrogant." You have such confidence in
your initial reaction that you neither do the math nor look to see if
anybody else has. You don't bother to FIND OUT if you are right,
because OF COURSE you are, and anybody who disagrees obviously didn't
bother to check things out, or else they'd know what you don't need to
check things out to know. You seem awfully sure that you are smarter
than everybody else, even everybody else put together, and are
terribly offended when this attitude rubs people the wrong way.

In the interests of full disclosure, I haven't "calculated on" a lot
of this stuff myself, but instead rely on those who have.

Another point which might be made is that, like all good scientific
work, this was published and thus was subject to peer review. There
were many scientists and engineers who, because of their philosophical
make-up, were inclined to oppose the conclusions. But the only
objections ever raised were philosophical or ethical. Nobody found a
fatal flaw in the basic calculations leading to the conclusion that
ordinary steel, aluminum, and glass were up to the task for habitats a
few miles across.

Regards,

Mike Combs

However, if anyone actually does the math and finds
that these materials are indeed inadequate, or does
the research and the math and finds that such a
construction would be economically impossible (even
when using space-based resources such as lunar
materials or near earth asteroids), then please do
share these results with us.

Ed Minchau

--- "Combs, Mike" wrote:

From: Ed Minchau

> However, if anyone actually does the math and finds
> that these materials are indeed inadequate, or does
> the research and the math and finds that such a
> construction would be economically impossible (even
> when using space-based resources such as lunar
> materials or near earth asteroids), then please do
> share these results with us.

And it's not like nobody has ever had the motivation. Robert Zubrin
would very dearly love for everybody to just shut the hell up about
orbital habitats. But even he doesn't try to argue that materials are
inadequate to the task of building such. He just tosses out
generalities about how mind-bogglingly complex the O'Neill plan is, and
tries to prove that as an economic foundation, SPS is a non-starter.

Regards,

Mike Combs

--- In spacesettlers@yahoogroups.com, "Combs, Mike"
>
> From: Ed Minchau
>
> > However, if anyone actually does the math and finds
> > that these materials are indeed inadequate, or does
> > the research and the math and finds that such a
> > construction would be economically impossible (even
> > when using space-based resources such as lunar
> > materials or near earth asteroids), then please do
> > share these results with us.
>

Hi Mike,

I find this thread interesting from the viewpoint that I always
like to revert to - circa 1908. At that time most educated people
would scoff at the idea that in just 60 years there would be people
on the moon. Likewise, they would consider completely ridiculous the
idea that nearly everyone in the "developed" countries would have
their own personal computers - although at that time it would be hard
for anyone to explain what a computer (as we know it) is or what it
does.

I suspect that we can't even imagine the technology that our great
grandchildren will be taking for granted 60 years from now. That's
one reason I think science fiction writers are great, because most of
them have very fertile imaginations. They may have gotten the details
wrong, or the time frame, but science fiction writers of the past
have been - if anything, too conservative in their fantasies.

So I say we should let our imaginations fly. If some doctoral
student 100 years from now does a thesis on early twenty first
century attitudes about the use of Space, and his research brings him
to an archive of this discussion group - I think he'll chuckle to
himself about how quaint our ideas were.

Chris

Lets actually do some back of the envelope calculations shall we.

Firstly:

Stress (tension) on a rotating hoop (for simplicity, the place of
maximum stress is a loop at the outer edges).

stress(tension = (material density)x (angular velocity)^2 x (radius)^2

Anyone who questions the above formula can look it up.

Now: radial acceleration (artifical gravity due to rotation) is as
follows:
acc = (tangential velocity)^2 / (radius)

now tangential velocity = angular velocity X radius

Now after we do all the subtitution we get:

stress = density x acc x radius

Now stress for steel is 200MPa
density = 8000 kg/m^3
and the desired acceleration is 9.8 m/s^2 or for this calculation 10.
2x10^8 = 8x10^3 x 10 x radius

rearranging and solving we get
radius = 2500 m.

So a rotating pressure vessel will contain 100KPa of air, and lets
add a safety factor of 100 % so that stress is now 100 MPa.

This gives a radius of 1200 m.

Bill

--- In spacesettlers@yahoogroups.com, "Xenophile"

--- In spacesettlers, "Bill" wrote:

> This gives a radius of 1200 m.
>
> Bill

Which is bigger than Stanford Torus (800 m radius), even bigger than
the one I'm using in my never-finished sitcom (1000 m radius).