Re: pressure containment: not a major issue?
- From: Joe Strout <joe@xxxxxxxxxx>
- Date: Mon, 17 Jul 2006 19:59:57 -0600
In article <45b25$44bc2256$927a2cf9$12453@xxxxxxxx>,
"Jeff Findley" <jeff.findley@xxxxxxxxxxxxxx> wrote:
Since your habitat is pressurized internally, buckling shouldn't be a
problem, at least for any sane pressure vessel geometry I can think of.
Well, you still have to balance pressure containment against other
design goals, like rotational stability. For example, a cylinder with
flat endcaps is only stable if already quite short (length = 1.3 *
radius). Add spherical endcaps, and it's unstable at ANY length,
assuming you intended it to spin about its long axis.
(This is easy to see: a sphere has identical moments of inertia on all
axes; stretch it out a bit along one axis, and that now becomes the
minimum moment of inertia; the object's lowest-energy state will be
rotating around a perpendicular axis, i.e. tumbling end-over-end.)
In addition to stability, there are cost issues -- for example, in some
designs, a hemispherical roof may be best in terms of containing
pressure, but a flat roof may take a lot less mass. A minimum-cost
design would require a detailed analysis, I think.
Unfortunately, this analysis has to take into account pressure
containment; I was quite confused this morning when thinking that issue
could be safely ignored.
Best,
- Joe
.
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- From: Joe Strout
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