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The centrifuge of USS Discovery

Garuda

Forum Supporter
On almost every weekday I go for a run in the forest after work, and while doing that, it's a good time to think about different things. Recently I came to think about the scene in 2001 where Frank Poole is running around the centrifuge (a really good scene, that one). I wondered how many g:s is actually experienced in Discovery's centrifuge, and what happens when Poole runs in there? What if he changes direction?

I took out the DVD and did some timing. From the access tunnel scenes, I measured one rotation to last for 20 seconds. Poole runs one "lap" in 23 seconds. From the blueprints kindly displayed on this forum (not official, I know, but good enough for this) I measured the diameter of the centrifuge to be 10.5 meters. That means that the perimeter of the cylinder is moving at 1.65 m/s.

My high school physics being a bit rusty, I asked a relative for help and got that the g experienced in a rotating cylinder is g=v^2/r (r being the radius and v the perimeter speed).

If you're not bored enough to have stopped reading by now, that means that Dave and Frank experience about 0.52 g in the centrifuge, or about half Earth gravity. Comfortable. But if Poole is running with the rotation (as he seems to be doing, and I don't mean on the set!) he's experiencing about 1.8 g, or almost double Earth gravity. That's quite a difference! And lastly, if he would run just a little bit faster, and against the rotation, he would become weightless and probably start floating around the space inside the centrifuge...

Just some thoughts. I really wouldn't mind to try that for real... :wtf:
 

DX-SFX

Alphans
But if Poole is running with the rotation (as he seems to be doing, and I don't mean on the set!) he's experiencing about 1.8 g, or almost double Earth gravity. That's quite a difference! And lastly, if he would run just a little bit faster, and against the rotation, he would become weightless and probably start floating around the space inside the centrifuge...

I don't think it makes a difference does it?

Hmmm, an interesting thing to think about.
 
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Garuda

Forum Supporter
On reflection, I think you're right.

The way I see it, if Poole is running against the rotation, and matching it's speed, he's not moving in relation to Dave in the flight deck. So there's not any difference, and they're both weightless. (The speed of Discovery through space can be ignored in this case.)

Ok, now imagine standing in the centrifuge, and bouncing a tennis ball! :twisted:

Yes, that would be interesting, because the ball will follow a straight line through space, but JD standing in the centrifuge is not. So to JD the path of the ball will appear curved, as if a mysterious force is affecting it (this is the coriolis effect, the same one affecting winds and currents on Earth). So throwing a ball to a mate on the other side of the centrifuge is trickier than it seems.
 
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DX-SFX

Alphans
The way I see it, if Poole is running against the rotation, and matching it's speed, he's not moving in realation to Dave in the flight deck. So there's not any difference, and they're both weightless. (The speed of Discovery through space can be ignored in this case.)

That was the conclusion I came to. Funnily enough he could still run around the centrifuge because of it's circular shape in zero gravity if it wasn't turning. They did something similar on the inside surface of Skylab in the seventies. However the bigger the diameter of the circle the harder it is as the runner's inertia and forward direction in a straight line relies on the floor curving up to give his next footstep purchase on the floor in zero g.
 

DX-SFX

Alphans
There is some NASA footage somewhere. The astronaut incorporated some hand stands and somersaults into the display too.
 

cricket

Alphans
Awesome find! I remember seeing this in school more years ago then I want to admit. :D
 
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JMChladek

Alphans
There were indeed some flaws with the centrifuge, but I don't think the gee force was necessarily one of them. Since we don't see Dave in it during Frank's run, it is also possible that HAL could have sped it up for the exercise part, then slowed it down for the leisure part (making it easier for somebody to transition from the hub to the inside).

It has been noted that the centrifuge is a bit on the small side for something like this and there is one other nasty side effect nobody considered called the choreolis effect (sp?). This can have a bad reaction on the inner ear of a person since the spinning astronaut inside has his head spinning at a different rate from his feet. Usually it isn't a problem when one is almost stationary (such as on an exercise bicycle or treadmill). But, if they move and turn their head, the fluid flow in the inner ear becomes turbulent due to the movement of the centrifuge and the differential of the motion rates in different parts of the body and one may have to grab a motion sickness bag at that point due to the disorientation. If the rotational structure is made bigger, then the effect isn't as pronounced. So a giant rotating space station can work (like Babylon 5), but not necessarily a centrifuge hub in a spacecraft.

It is a concern in developing exercise equipment for a Mars mission as we don't know if the crew compartment on a ship will be rotating with a teather to a booster section to keep the crew in some level of Gee force, or if a smaller compartment will during exercise. If it is a smaller compartment, then a crewmember pretty much has to anchor his head in one position while exercising in order to keep his inner ear from going crazy. Only other option might be development of a drug that could desensitize the inner ear to sudden fluid changes like that. Only problem there is it might affect the astronaut's balance in other things.

Its a whole interesting problem when one thinks about it.

Concerning Skylab, if you want to see a little more of the excerpt and some other stuff in space, check out the following website and click on the video link:

http://www.williampogue.com/bill-pogues-bio.html
 

Garuda

Forum Supporter
I didn't mean there are any flaws with the Discovery centrifuge. I think 0.5 g is probably enough for a space flight of a longer duration, especially in combination with exercise. There's is no need to speed up the centrifuge for Frank's exercise, as he is in effect achieving the same result by running. Because of the square relationship between rotation and g:s, by almost doubling his rotational speed, Frank is increasing his weight 4 times! That is most likely more than enough for keeping him fit. (But not if he runs the wrong way, as I wrote above). In fact, if Hal speeds up the rotation of the centrifuge, it would probably be too many g:s for Frank if he is running.

Your're absolutely right that the coriolis effect is strong in a small cylinder like this (I have been thinking that going up the ladder to the axis could be interesting for that reason). I didn't know that the coriolis effect gives motion sickness. Interesting, and like you write a problem on small spacecrafts then. (May this explain why my wife lost her breakfast after we tried the centrifuge at Kennedy Space Center a few months ago? I felt quesy, but managed to keep my stomach under control.

I liked the video. Thanks!
 

JMChladek

Alphans
Your're absolutely right that the coriolis effect is strong in a small cylinder like this (I have been thinking that going up the ladder to the axis could be interesting for that reason). I didn't know that the coriolis effect gives motion sickness. Interesting, and like you write a problem on small spacecrafts then. (May this explain why my wife lost her breakfast after we tried the centrifuge at Kennedy Space Center a few months ago? I felt quesy, but managed to keep my stomach under control.

I liked the video. Thanks!

Going from movement to a stop may have had more to do with it in your wife's case (which would have upset the fluid balance as well) depending on how abruptly the ride came to a stop. Now if your wife had moved her head while the centrifuge at KSC was moving, then she would probably have experienced the coriolis effect on her inner ear. I don't think I would want to dip my head down and bring it back up doing that ride or the results might be a bit messy (and I have a pretty good stomach). But if she kept her head straight (like the warning signs say), then it probably would not have been a problem.

And yes, going up the ladder probably would have a Discovery astronaut upchucking in nothing flat once they get to the top.
 

CR

Alphans
Skylab was huge; it was, after all, a modified third stage of a Saturn V.

A slight diversion, here, but has anyone ever ridden in those 'flight sim' things that tilt and roll while a video plays on a large screen in front of you? The effect is quite interesting, as you feel like you're doing full loops and barrel rolls, even though I don't think the compartment you're strapped in actually goes 360 degrees around. I 'rode' in one years ago at a shopping mall where I used to work, and a nice woman my age (who worked in another section of the mall) accompanied me. I had a blast, she screamed like crazy. Neither one of us got sick, but I think she was a bit queasy after the ride.
 

DX-SFX

Alphans
And yes, going up the ladder probably would have a Discovery astronaut upchucking in nothing flat once they get to the top.

If it's straight ladder pointing directly towards the centre of rotation and it was climbed slowly, I don't think it would be a problem as the centrifugal force would always be acting towards the astronauts feet and any sideways component would be tiny. If his head deviated either side of that line by a lot while climbing it or it was climbed quickly, I can imagine that happening.
 

Garuda

Forum Supporter
And yes, going up the ladder probably would have a Discovery astronaut upchucking in nothing flat once they get to the top.

I not disagreeing, but I think maybe a seasoned astronaut can take it (me, on the other hand...:no: :sick:). But I know little about that, so maybe it's worse than I think. But what I really meant was that the coriolis effect is pushing the astronaut sideways as he climbs, so he needs to keep his grip on the ladder.

A slight diversion, here, but has anyone ever ridden in those 'flight sim' things that tilt and roll while a video plays on a large screen in front of you?

Yes, and it's like you say, it's amazing how the relatively minor movements in combination with the screen tricks the senses completely. The last one I rode in was in Las Vegas, a simulation of a shuttle flight in the Hilton Star Trek Experience. Both I and several other visitors were pale with shaky legs afterwards... (but you should know that I'm a coward that normally avoids any ride worse than a romantic boat ride in amusement parks).

The centrifuge in Kennedy Space Center (Astronaut Hall of Fame) is also a simulation. While rotating it tilts and shows a film from a fighter jet flight in front of you. Which fits in what JMChladek writes about motion sickness above. Seeing the paper bags stowed beside me in the little booth didn't help.

 
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CR

Alphans
I second Dr Kane's sentiment. This is indeed a very interesting thread. I know there are 'Post of the Day' tags that pop up around here, but I think this one could get 'Thread of the Day' if such a thing existed.
 

CR

Alphans
Oh, to answer Garuda's edit question, there is a 'sick' emoticon... :sick: Type colon, the word sick, and another colon. (: sick : but without the spaces)
 
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