Re: any limits on mechanical seals?

In article <1152729377.569442.197910@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
wbogen@xxxxxxxxxxxxx wrote:

An interesting idea but not practical, in my opinion; there are far too
many uses for a stationary portion.

Would you list some?

Well, docking is the obvious one. Then there's observation; it's hard
to keep your telescope trained on something when you're whizzing around
at 2 RPM. Also, workers need to travel frequently between the habitat
(where they live) and the big external manufacturing or power facilities
(where they work) -- this could most efficiently be done via transport
tubes, but such tubes need a stationary place to attach.

In addition, the problems presented
by trying to dock (especially more than one ship) on a rotating station
far surpass the problems presented by large rotating seals.

I disagree. A 1km radius colony with 100 meter tethers would have
almost 7km of potential landing pad.

Of *unusable* landing pad. The very idea is ludicrous. Your landing
platforms are whizzing by at over 400 km/hr -- and in circular (rather
than straight!) paths! I'm all for thinking outside the box, but let's
not open our minds so far that our brains fall out. :)

Say it's a continous
strip/belt/runway. A ship would slowly approach the runway

From what direction can you slowly approach such a runway? Any
direction I imagine involves passing through (a) the runway, (b) the
habitat, or (c) the runway supports that are moving at 400 kph. (A) and
(b) violate the laws of physics, and as for (c), you'd quickly end up
adding to the space-debris problem (see other thread).

If you can solve *that* problem, I think you may have something mildly
interesting -- but only "mildly" since it would mean only very
specialized spacecraft can go to/from the habitat. I prefer to allow
pretty much any ordinary spacecraft to visit. But that's probably moot,
since I don't think this problem is solvable anyway.

A poor case, I think. Can you imagine a town where all vehicles have to
park 1 km outside the city limits, and passengers and cargo transferred
in and out of town by some other means? Yes, it's possible, but it's
highly inefficient and expensive compared to letting the ships dock
directly.

It's only 100m from the inside of the colony, not 1 km.

With your impossible landing-strip scenario, yes. I was addressing the
more reasonable proposition of ships matching orbits with the colony a
short but safe (e.g. 1 km) distance away, and then transferring
passengers and cargos using some sort of ferry, such that only one ferry
would dock at the time. More reasonable, but still horribly inefficient.

I'm trying to imagine a town-analogy where vehicles carrying tons of
explosive fuel approach at varying speeds to a town-wall/membrane that,
if breached, could kill thousands quickly. Can't seem to do it but that
does describe the colony situation.

I don't think it does. There would surely be emergency doors at key
places -- including between the dock and the main habitat -- that would
automatically shut in the event of a drop in pressure. And with
structures this large, even blowing a fairly largish hole in the hull
does not result in immediate depressurization -- it could take weeks or
months, depending on the relative sizes of course. That allows plenty
of time for those in the compromised portion to make it into emergency
chambers, or don emergency suits.

Such an accident would probably result in *some* casualties -- those
close to the explosion, just as on Earth -- but I think not as many as
you're imagining.

Best,
- Joe
.

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