Not too late for more Shuttle flights

David Spain writes:
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.

Well if you're trying to minimize issues around redevous and docking. But you
could certainly 'deal' with it...

Dave

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...

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....

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.


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.
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

Pat

Pat Flannery writes:
On 3/13/2010 9:43 AM, David Spain wrote:

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... ;-)

....and before someone jumps down my throat, yes I know, I AM WRONG!
It was Poole, not Bowman, running around the centrifuge...

The centrifuge in the Discovery was supposed to generate 1/6 g (lunar gravity)
when the astronauts were at rest; I don't know how much higher you could get
that be running around in it like shown in the movie.
But even at 1/6 g the diameter was pretty small for this to work without
getting the astronauts dizzy as they moved around in it.

I'm guessing a bit but it looked to be about 40ft in diameter? Aha wikipedia
says 35.65 ft. (11.6m) at 3 RPM.

http://en.wikipedia.org/wiki/Discovery_One

Here's Pete Conrad running around the the inside circumfrance of the Skylab
station, ala' 2001: http://www.youtube.com/watch?v=Awe6vOXURpY
As can be seen in this video, once the astronauts had been on Skylab long
enough, they were capable of doing pretty wild gymnastics without any space
sickness: http://www.youtube.com/watch?v=oYsKGDJe4zE


*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....


Other than air circulation pushing you along, if you ran against the spin hard
enough to go weightless, you should just end up floating in the air above the
"floor".

Unless you do a few hops and jumps along with it. See above... ;-)

Babylon 5 had a scene in one episode where Sheridan ended up floating in the
weightless middle of the station after the central monorail car he was riding
in was blown up, and as was correctly pointed out in the episode the danger he
was in was what would happen when he floated into the rotating inside hull of
the station, which from his point of view would be going sideways at high
speed.

I'm losing my lunch already....

Dave

Pat Flannery wrote:

Babylon 5 had a scene in one episode where Sheridan ended up floating in
the weightless middle of the station after the central monorail car he
was riding in was blown up, and as was correctly pointed out in the
episode the danger he was in was what would happen when he floated into
the rotating inside hull of the station, which from his point of view
would be going sideways at high speed.

Actually, from Sheridan's point of view, he would remain "weightless"
all the way to the ground were it not for the wind.

It would be the atmosphere, rotating with the structure, which would
gradually accelerate sheridan tangentially to the ground and that would
cause him to drop in altitude, at which point the wind would get
stronger and his acceleration be greater towards the ground.


What I have not seen mentioned in any such movies is the effect of
humans routinely changing from g to 0g environments and back to some
level of g.

If, after having had dinner at the restaurant, you take the elevator to
the centre of the vehicle where it is 0g so you can catch the train to
the other side of the station, how will your stomach react ? And how
will it recat when you then take the elevator back to "ground" level
where the gravity will increase once again ?

On 3/13/2010 9:43 AM, David Spain wrote:

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... ;-)

The centrifuge in the Discovery was supposed to generate 1/6 g (lunar
gravity) when the astronauts were at rest; I don't know how much higher
you could get that be running around in it like shown in the movie.
But even at 1/6 g the diameter was pretty small for this to work without
getting the astronauts dizzy as they moved around in it.
Here's Pete Conrad running around the the inside circumfrance of the
Skylab station, ala' 2001: http://www.youtube.com/watch?v=Awe6vOXURpY
As can be seen in this video, once the astronauts had been on Skylab
long enough, they were capable of doing pretty wild gymnastics without
any space sickness: http://www.youtube.com/watch?v=oYsKGDJe4zE


*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....


Other than air circulation pushing you along, if you ran against the
spin hard enough to go weightless, you should just end up floating in
the air above the "floor".
Babylon 5 had a scene in one episode where Sheridan ended up floating in
the weightless middle of the station after the central monorail car he
was riding in was blown up, and as was correctly pointed out in the
episode the danger he was in was what would happen when he floated into
the rotating inside hull of the station, which from his point of view
would be going sideways at high speed.

Pat

Pat Flannery writes:
On 3/13/2010 1:31 PM, David Spain wrote:
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.

This is for the Buzz Bus? I thought we were discussing the test one on the
ISS and trying out the same experiments in a free-flying module in LEO.

Sorry, mixing too much together. Yes to your first question. No to the ISS
module and yes to the free flyer. But attaching a spinning centrifuge to the
ISS of any sizeable mass scares the hell out of me! Is the plan to keep it
spinning all the time?

If you are going to do it for crew gravity, then spinning up the whole works
is probably the way to go. But a cylindrical shape is probably going to be
of too small of diameter to get rid of the vertigo effects, and the old
classic donut shape is a better choice. IIRC, the diameter has to be around
400' before the different rotation rates between the feet and the head
aren't noticeable.

At what g along the rim? Can you shrink it if you spin it slower and go for
less g? Say 1/6g?

Dave

Pat Flannery wrote:

The thing about both B5 and Island Three is that they are incredibly
wasteful of internal volume due to the vast open space above the "ground".

There may be a lot of unused volume, but is it really wasted ? Wouldn't
such a colomy require a fair amount of spare atmosphere ?

And remember that while a relatively small portion had empty space in
the core, the ends had substandtial structures used for spacecraft
parking. So not all of the core was unused.

And having some "wide open spaces" would probably do a lot of good for
mental health of permanent human inhabitants. One might support living
in a collection of tin cans with one window for 6 months, but for
permanent habitation, the requirements would likely be different.

On 3/13/2010 1:31 PM, David Spain wrote:
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.

This is for the Buzz Bus? I thought we were discussing the test one on
the ISS and trying out the same experiments in a free-flying module in LEO.
If you are going to do it for crew gravity, then spinning up the whole
works is probably the way to go. But a cylindrical shape is probably
going to be of too small of diameter to get rid of the vertigo effects,
and the old classic donut shape is a better choice. IIRC, the diameter
has to be around 400' before the different rotation rates between the
feet and the head aren't noticeable.

Pat

On 3/13/2010 2:35 PM, David Spain wrote:

The centrifuge in the Discovery was supposed to generate 1/6 g (lunar gravity)
when the astronauts were at rest; I don't know how much higher you could get
that be running around in it like shown in the movie.
But even at 1/6 g the diameter was pretty small for this to work without
getting the astronauts dizzy as they moved around in it.

I'm guessing a bit but it looked to be about 40ft in diameter? Aha wikipedia
says 35.65 ft. (11.6m) at 3 RPM.

http://en.wikipedia.org/wiki/Discovery_One

What's odd about the one on the Discovery is that it's not located where
you think it would be in the control sphere; you would expect it to go
around the equator of the sphere dividing it into front and back halves
for maximum diameter on the centrifuge, but it's aft of center.
The rotating set in the movie was indeed 40' in diameter.
It also points out what I always thought was the big problem with 2001;
it's fascinating to look at the thing going around, but it doesn't add
one whit to the storyline (what little there is of it) while being very
hard and expensive to produce (as in $750,000 dollars back when that was
real money) The whole movie is like this spectacular gift box with
sparkly wrapping paper and glittering bows and ribbons all over it...and
nothing much inside, a triumph of packaging over content.

Pat

On 3/13/2010 3:07 PM, John Doe wrote:
That's a good point, and the airflow patterns in something like that
(basically a Island Three Lagrange colony) would be pretty strange
especially as you got near ground level and buildings and what-not
started affecting the airflow around them.
The atmosphere itself has mass which will resist it picking up speed due
to the tidal effect as it gets near the surface, and of course the wind
will have to accelerate the person as they "fall" through it and get
pulled down towards the surface by centrifugal force, so he would
probably hit at an angle while not being fully up to the rotational
speed of the surface.


What I have not seen mentioned in any such movies is the effect of
humans routinely changing from g to 0g environments and back to some
level of g.


For real fun imagine walking around inside of this sometime:
http://dreamsofspace.nfshost.com/gifs/stat1.gif
I assume it's designed like that to rotate for artificial gravity on the
way to and from Venus, but it's going to be fascinating as you slide
into one of the corners of the thing.


If, after having had dinner at the restaurant, you take the elevator to
the centre of the vehicle where it is 0g so you can catch the train to
the other side of the station, how will your stomach react ? And how
will it recat when you then take the elevator back to "ground" level
where the gravity will increase once again ?


I think it would take a lot of getting used to, but if the Skylab
astronauts could do that stuff shown in the YouTube videos with out
barfing all over the place, it's probably possible to do.
The axis tramline on B5 was one way of doing things, but you could have
also just traveled around or down the length of the inner surface to get
point-to-point in the interior.
The thing about both B5 and Island Three is that they are incredibly
wasteful of internal volume due to the vast open space above the "ground".

Pat