Not too late for more Shuttle flights

If you think about it though, any centrifugal device needs to be balanced,
and how do you do that with people in it?
I suspect small scale devices containing animals is al one will see.

Look at what happened to the iss when a rocket firing produced low frequency
vibrations. do you really think a centrifuge would be a viable addition?
a large one that is.


Brian

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"Pat Flannery" wrote in message
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On 3/11/2010 10:49 AM, Jeff Findley wrote:

And I'm sure it wouldn't hurt to be able to return some stuff back also.

It also reduces reliance on the Russians for carrying our crew up.

(Of course one could dream about finally completing and flying the CAM.
:-)

One can dream... I really wish the CAM would fly.

Didn't Jorge Frank state a while back that CAM had vibration issues during
operation that made it unsafe, so that's why it got dumped?
It's too bad, because it was one of the few experiments that could be done
on the ISS that would have yielded really interesting data in regards to
long term habitation of the Moon or Mars.

Pat

On 3/12/2010 1:41 AM, Brian Gaff wrote:
If you think about it though, any centrifugal device needs to be balanced,
and how do you do that with people in it?

I don't think it was large enough to put people into, so tests would
have been limited to animals like smaller monkeys.
I assume they would been in cages, with two cages balanced on opposite
sides of the centrifuge.
You would want them to be able to move around, so as to measure the
effects exercise had on bone and muscle loss in different g environments.
Unfortunately, the small diameter of the centrifuge would mean they
could get very dizzy while moving around as it spun.
To totally eliminate that effect at one g, you need something around the
diameter of the station in 2001.

I suspect small scale devices containing animals is al one will see.

After the demise of the ISS centrifuge module, some private group was
working toward a mini centrifuge module carrying frogs or mice (I forget
which) that could be launched all on its own.

Pat

Pat Flannery writes:

To totally eliminate that effect at one g, you need something around the
diameter of the station in 2001.

Rather than a centrifuge, why not just spin the whole craft? That eliminates
bearings and vibrations (to some degree) and helps spin-stabilize the craft.
Also the entire mass of the spacecraft can offset small shifts in mass inside
the craft, eliminating the need for a high rim mass centrifuge to achieve the
same effect. Also it's not clear you need to spin to 1g when something smaller
might suffice and thereby avoid the coriolis effects on the inner ear at a
higher spin rate.

This of course puts some design constraints on the spacecraft and requires a
fair degree of axial symmetry. There are always trade-offs....

?

Dave

On 3/12/2010 12:16 PM, David Spain wrote:
Pat writes:

To totally eliminate that effect at one g, you need something around the
diameter of the station in 2001.

Rather than a centrifuge, why not just spin the whole craft? That eliminates
bearings and vibrations (to some degree) and helps spin-stabilize the craft.
Also the entire mass of the spacecraft can offset small shifts in mass inside
the craft, eliminating the need for a high rim mass centrifuge to achieve the
same effect. Also it's not clear you need to spin to 1g when something smaller
might suffice and thereby avoid the coriolis effects on the inner ear at a
higher spin rate.

This of course puts some design constraints on the spacecraft and requires a
fair degree of axial symmetry. There are always trade-offs....

Then you've got the docking problem; you need a de-spun docking port,
you have to stop the spinning when you want to dock, or you do the 2001
trick and spin your spacecraft up to the same rotational speed as the
module.
You could put a de-spun section on one end of the module and use that to
hold the docking collar, solar arrays, and communication antennas (this
is done on a lot of communications satellites where the cylindrical
solar-cell-covered body spins for stability, while the antennas remained
pointing at Earth), but now you are spinning a large diameter airtight
seal between the two sections, and that's going to be difficult to
design from both a air leakage and no torque transference point of view.
To keep the centrifuge in balance you could use a vibration sensor that
detects it being off-balance and transfers some sort of fluid from one
side to the other to balance it out.
Another concept would be to not directly attach the centrifuge proper to
the module at its axis points, so that vibrations can't be transferred
from one to the other; it could either spin on a air bearing at either
end like a lot of gyroscopes do, or use a magnetic field to do the same
thing.
I'm really surprised they had such trouble with the ISS centrifuge
module, as this doesn't sound like a insurmountable problem to address
in its design.
One oddball problem would be that the centrifuge would act like a gyro
wheel and try to rotate the station as it orbited around the Earth.
Two counter-spun sections to it might solve that problem by canceling
out the gyroscopic effects.

Pat

Brian Gaff wrote:
If you think about it though, any centrifugal device needs to be balanced,
and how do you do that with people in it?
I suspect small scale devices containing animals is al one will see.


Shirley they thought about that when they designed the CAM ? Wouldn't
there have been some accelerometers that would control some
counterweight rotation to balance the module ?

Was the CAM originally designed to be attached to a far more massive
station where its effects would have been smaller (due to larger station
mass) and could have been mitigated by the CMGs ?

Pat Flannery writes:
Then you've got the docking problem; you need a de-spun docking port, you
have to stop the spinning when you want to dock, or you do the 2001 trick
and spin your spacecraft up to the same rotational speed as the module.

I'd go with the 2001 trick, but rather than a slot, I'd go with a conical
docking adapter with axial symmetry at the centerline front of the main
spacecraft. Doesn't present any special problem for docking.

You could put a de-spun section on one end of the module and use that to
hold the docking collar, solar arrays, and communication antennas (this is
done on

Nah. Spin the whole thing. If you're using solar arrays, arrange them in
cylindrical shells around the craft with mirrors to direct sunlight into them
as the craft rotates.

a lot of communications satellites where the cylindrical solar-cell-covered
body spins for stability, while the antennas remained pointing at Earth),
but now you are spinning a large diameter airtight seal between the two
sections, and that's going to be difficult to design from both a air leakage
and no torque transference point of view.

For comms, send out a non-spinning co-orbital satellite module that can use
standard wi-fi techniques for comms between the main craft and itself but
since it's not spinning it can have the high gain dishes and be able to
carefully align them back to Earth w/o fancy mechanics to keep it pointed
properly on a spinning spacecraft.

Also provides some failure isolation from the main ship and if you co-orbit a
couple of them, some failure redundancy as well....

To keep the centrifuge in balance you could use a vibration sensor that
detects it being off-balance and transfers some sort of fluid from one side
to the other to balance it out. Another concept would be to not directly
attach the centrifuge proper to the module at its axis points, so that
vibrations can't be transferred from one to the other; it could either spin
on a air bearing at either end like a lot of gyroscopes do, or use a
magnetic field to do the same thing. I'm really surprised they had such
trouble with the ISS centrifuge module, as this doesn't sound like a
insurmountable problem to address in its design.

Not me. I've always considered a spinning centrifuge inside a spacecraft to be
a major mechanical headache/nightmare. You don't want *that* gyro seizing up
on you. No way....

One oddball problem would be that the centrifuge would act like a gyro wheel
and try to rotate the station as it orbited around the Earth. Two
counter-spun sections to it might solve that problem by canceling out the
gyroscopic effects.

Yep. Seen that all over the place. The issue is addressed head on in the book
and movie 2010. In fact it is a major plot element for the first EVA team.

Dave

David Spain writes:
Nah. Spin the whole thing. If you're using solar arrays, arrange them in
cylindrical shells around the craft with mirrors to direct sunlight into them
as the craft rotates.


My preference for a 'cycler'/habitat craft would be to skip the solar cells and
go straight to nuclear-thermal-electric. Why limit ourselves to the inner solar
system?

Dave

David Spain writes:
same effect. Also it's not clear you need to spin to 1g when something
smaller might suffice and thereby avoid the coriolis effects on the inner
ear at a higher spin rate.

BTW, you can get a 1g effect in a 1g environment by providing a circular
running track and have the crew run around the track in the spin-wise
direction to experience a higher g.

They did that in the movie 2001 too, but only those in the know realized what
it was about. Too bad they didn't do the special effects to show what happens
when Bowman runs the OTHER* way... ;-)

Dave

*A very QUICK way to get from one point to another in the centrifuge. In a
less UP TIGHT version of 2001, there'd be all these hand painted signs hung up
by the crew saying ONE WAY --- pointing in the spinward direction....

;-)

On Mar 13, 12:43�pm, David Spain wrote:
David Spain writes:
same effect. Also it's not clear you need to spin to 1g when something
smaller might suffice and thereby avoid the coriolis effects on the inner
ear at a higher spin rate.

BTW, you can get a 1g effect in a 1g environment by providing a circular
running track and have the crew run around the track in the spin-wise
direction to experience a higher g.

They did that in the movie 2001 too, but only those in the know realized what
it was about. Too bad they didn't do the special effects to show what happens
when Bowman runs the OTHER* way... �;-)

Dave

*A very QUICK way to get from one point to another in the centrifuge. �In a
less UP TIGHT version of 2001, there'd be all these hand painted signs hung up
by the crew saying ONE WAY --- pointing in the spinward direction....

;-)

didnt the crew spin skylab once? i forget the details

Pat Flannery writes:
On 3/13/2010 9:21 AM, David Spain wrote:

For comms, send out a non-spinning co-orbital satellite module that can use
standard wi-fi techniques for comms between the main craft and itself but
since it's not spinning it can have the high gain dishes and be able to
carefully align them back to Earth w/o fancy mechanics to keep it pointed
properly on a spinning spacecraft.

Also provides some failure isolation from the main ship and if you co-orbit
a couple of them, some failure redundancy as well....

This seems awfully involved compared to just installing a vibration damper
system on the centrifuge...


I disagree. It's something on the complexity of a couple of comm sats next to
the cycler, that should be NBD. Besides Earth/Cycler comms, although
important, by necessity cannot be critical.

A vibration damper, and a highly reliable bearing for a centrifuge on a cycler
is going to be key and probably requires some expensive development work as
well.

To keep the centrifuge in balance you could use a vibration sensor that
detects it being off-balance and transfers some sort of fluid from one
side to the other to balance it out. Another concept would be to not
directly attach the centrifuge proper to the module at its axis points, so
that vibrations can't be transferred from one to the other; it could
either spin on a air bearing at either end like a lot of gyroscopes do, or
use a magnetic field to do the same thing. I'm really surprised they had
such trouble with the ISS centrifuge module, as this doesn't sound like a
insurmountable problem to address in its design.

All this is LESS complex than a comm sat? If I had a preference I'd go with a
magnetic bearing, based on PERMANENT magnets. But I'd rather just avoid the
whole problem altogether. If I put the liquid consumables along the outer rim
of a spun cycler I can get vibration and (with plumbing) mass balance damping
that way too, plus extra radiation shielding. The tradeoff is the puncture
problem.

Not me. I've always considered a spinning centrifuge inside a spacecraft to
be a major mechanical headache/nightmare. You don't want *that* gyro
seizing up on you. No way....

Now the visiting crew is going to get stuck to the inside walls of the
module on boarding it from the centrifugal force, throwing it off-balance,
and as its diameter is so small, they will get vertigo as they move around
inside of it.

Again we're back to spacecraft design trade-offs. You make your spacecraft
look like a (very) scaled down version of the 2001 space station, where
habitation is out on the rim, you won't have to spin so fast to get to say .1g
or perhaps .5g... (I know, handwave alert, this is a sci.space... posting not
an AIAA paper). Yes, that makes it more expensive, so maybe a larger cylinder
like a spun Bigelow module would be cheaper. Just thinking out loud...


One oddball problem would be that the centrifuge would act like a gyro
wheel and try to rotate the station as it orbited around the Earth. Two
counter-spun sections to it might solve that problem by canceling out the
gyroscopic effects.

Yep. Seen that all over the place. The issue is addressed head on in the
book and movie 2010. In fact it is a major plot element for the first EVA
team.

This can be solved by how you align the centrifuge; if it's aligned with one
end bearing facing towards Earth, and the other towards space, it will act
like a gyro as it orbits; but if it's aligned at a ninety degree angle to
the direction of the orbit so that it appears to be "rolling" along the
orbital path like a tire rolling in a circle around the Earth, then the
problem is alleviated, as the spin axis stays in the same direction during
the whole orbit.

Good points. But for a cycler that may not really matter if always stays out
of a planetary orbit after injection.

For a spinning cycler you'll have to spin around the thrust axis/CG if you
want gravity while under low acceleration propulsion. For a cycler that enters
planetary orbit once in orbit you can align it so that it's rolling along the
orbital path as well, but only when any 'lander' is not docking/un-docking.

Surprisingly, that's not how the centrifuge module was to be mounted on the
ISS, and it would have ended up with its rotational axis pointing towards
Earth. Here, NASA's Intelligent Systems Division works on balancing the
centrifuge: http://ti.arc.nasa.gov/projects/ssrl/centrifuge.html You can see
the movable weights to keep everything balanced in this illustration:
http://iss.jaxa.jp/iss/pict/cr.jpg

I guess it just goes to show you can't think of everything.... This is easier
to engineer than a co-orbiting comm sat???

Dave