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Patch86
Di-Tron Heavy Industries
Atlas Alliance
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Posted - 2008.08.31 10:27:00 -
[1]
In Arthur C. Clarke's 2001: A Space Odyssey, the spaceship Discovery is described as having a big spinning centrifuge, for the crew to live in, which creates simulated gravity. I always imagined that this would be spinning around the long axis of the ship, like a pencil through a hula-hoop (if you know what I mean).
However, in the sequel 2010, the crew of the Leonov find that Discovery's centrifuge bit had stopped spinning, and it's momentum has been transferred to the body of the ship. The ship is described as tumbling end over end, like a big spinny baton.
If the centrifuge was like how I imagined it in 2001, wouldn't that have meant the ship would have ended up spinning along its long axis (like a drill)? Did I picture it wrong in the first book, or am I getting my mental physics wrong instead?
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 Originally by: Micheal Dietrich
You can even get a midget with a camera to sit on the floorboard.
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ReaperOfSly
Gallente
Lyrus Associates
The Star Fraction
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Posted - 2008.08.31 10:38:00 -
[2]
As I see it, there are two possibilities. First, the centrifuge's axis was not parallel to the ship's axis. If I recall, it was contained fully within the body of the ship so it's perfectly possible to do this.
Secondly, the centrifuge's axis was parallel to the ship's axis as you imagined. As it spun down and transferred angular momentum to the ship, the ship would spin like a drill. But it was orbiting Io at the time. This is where it gets a bit fuzzy, because I'm not sure how that would affect the spin of the ship. It's bound to have some effect though?
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Quote:
...bored, skint, no charter, and a ship that looks like an explosion in a girder factory...
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Leonora Webb
Gallente
CompleXion Industries
CompleXion Alliance
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Posted - 2008.08.31 10:42:00 -
[3]
Right, if I remember correctly, the centrifuge spin axis is parallel to the main ship axis. The angular momentum remains constant as long as the centrifuge is spinning at the same rate, as in normal flight, so the main ship body would not start to rotate. When the ship fell in to disuse, the centrifuge started to slow down and thus angular momentum was transferred in to the body of the ship. This indeed made the ship rotate along its main axis like a drill, as you said. So you are correct.
However, this is a rather unstable state, and over time pertubations allow the angular momentum axis to change, to allow the craft to spin end-over-end in a more stable spin-state.
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Patch86
Di-Tron Heavy Industries
Atlas Alliance
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Posted - 2008.08.31 13:03:00 -
[4]
While a good idea, that doesn't really play out with the book.
In 2010, in order to salvage the Discovery, they decide to stop it's tumbling spin. To do so, they repair it's fly-wheel, and transfer the momentum back in to the centrifuge (bringing the ship's main body back to a relative halt).
If the end on end tumble were caused by the instability of it's spin, how would transferring the momentum back to the centrifuge stop it?
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Originally by: Micheal Dietrich
You can even get a midget with a camera to sit on the floorboard.
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Leonora Webb
Gallente
CompleXion Industries
CompleXion Alliance
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Posted - 2008.08.31 13:28:00 -
[5]
Edited by: Leonora Webb on 31/08/2008 13:28:27
Interesting. It's not so straighforward though, the centrifuge axis could still be perpendicular to the ship axis, but the centrifuge isn't neccesarily aligned with the end-over-end spin axis. This can produce a resulting torque in a perpendicular direction! It's rather like a spinning top rotating slowly while it's leaning over.
Or you could be right, the centrifuge axis is aligned in just the right direction. Or maybe it's rotatable! Who knows...
Pretty complex situation really, I'm sure Arthur Clarke thought it out, but I doubt we have all the information available to hand.
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ReaperOfSly
Gallente
Lyrus Associates
The Star Fraction
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Posted - 2008.08.31 14:50:00 -
[6]
Well once the centrifuge has been spun up again, it would essentially have two axes of rotation which is an unstable state. The main one along the axis of the ship, and the secondary one which causes the ship to tumble.
Thus, spinning up the centrifuge generates a force on the main body of the ship which causes it to slow down its rotation.
Think of a bicycle wheel. When it's spinning, you need to exert a great deal of force to get it to turn over. The same principle applies here.
__________________________
Quote:
...bored, skint, no charter, and a ship that looks like an explosion in a girder factory...
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Akita T
Caldari Navy Volunteer Task Force
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Posted - 2008.08.31 15:16:00 -
[7]
Edited by: Akita T on 31/08/2008 15:19:56
Official Name: USSC Discovery One
USSA "Registration Number": XD-1
Overall Length: 140.1 m
Overall Beam: 16.7 m
Overall Draft: 17 m
Command Module Diameter: 16.5 m
Reactor Module Length: 32.2 m
Reactor Module Draft: 8.8 m
Mass: 5,440 tonnes
Living Module: Centrifuge, Magnetic-Drive type. 11.6 m. diameter. Rotation Rate 3 RPM.
"The centrifuge was a spinning band of deck, mounted inside the crew compartment."
As you can see, there is no reason why the centrifuge's spin axis couldn't have been perpendicular to the ship axis, as it would easily fit either way inside the ship.
Although, one does have to wonder why the designers would pick such a rotation direction... maybe because it would be easier to stabilize when spinning up by applying just a bit of thrust to the appropriate side of the nose, whereas if the spin axis would have been parallel, you'd have to use some (non-existing?) lateral-firing thrusters on the exterior at the middle of the ship ?
Yeah, I guess that would make more sense...
_
SHOPS || Mission rewards revamp || better nanofix
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Nigel Sheldon
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Posted - 2008.08.31 15:39:00 -
[8]
prehaps it happened when it suddenly switched planets from saturn to jupiter 
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Patch86
Di-Tron Heavy Industries
Atlas Alliance
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Posted - 2008.08.31 23:31:00 -
[9]
Originally by: Nigel Sheldon
prehaps it happened when it suddenly switched planets from saturn to jupiter
Heh, the only reason they did that is because Kubrick thought the mock-up of Saturn that the special effects team had made looked naff, and that he didn't think they;d ever pull off a good-looking version of Saturn's rings.
Clarke was very grateful for this when, a few years later, the first pictures of Saturn close-up came back from the Pioneer probe. It turned out that we'd been getting it wrong- the rings were a great many times larger and more impressive than we'd imagined before. Clarke said that if they'd pressed ahead with Saturn, the film would have looked pathetically dated with their rinky-dink interpretation of Saturn. Their attempt at Jupiter, however, looks as awesome now as it did 40 years ago.
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Originally by: Micheal Dietrich
You can even get a midget with a camera to sit on the floorboard.
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Wendat Huron
Stellar Solutions
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Posted - 2008.08.31 23:39:00 -
[10]
I see your question and raise it, would it be possible to sustain any kind of life on a zero gravity planet or would that by definition not be a planet?
These forums are FUBAR, upgrade this decade! |
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Kyrall
A Few Killers
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Posted - 2008.09.01 02:18:00 -
[11]
Originally by: Wendat Huron
I see your question and raise it, would it be possible to sustain any kind of life on a zero gravity planet or would that by definition not be a planet?
Any kind of planet would have gravity, but ignoring that for the moment: I'm sure it'd be possible, but maybe only very basic organisms. You would have trouble getting a full food chain going, as I can't imagine there are many higher organisms that can live independently in zero-g. |
Akita T
Caldari Navy Volunteer Task Force
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Posted - 2008.09.01 09:27:00 -
[12]
Originally by: Wendat Huron
I see your question and raise it, would it be possible to sustain any kind of life on a zero gravity planet or would that by definition not be a planet?
Pluto's equatorial surface gravity is 0.059 g (aprox 1/17 of Earth's gravity).
They're not even considering Pluto a planet anymore on account of being too small ("they" being the IAU), it's now officially classified as a "dwarf planet".
"A dwarf planet, as defined by the International Astronomical Union (IAU), is a celestial body orbiting the Sun that is massive enough to be rounded by its own gravity but which has not cleared its neighbouring region of planetesimals and is not a satellite.
More explicitly, it has to have sufficient mass for its self-gravity to overcome rigid body forces in order to assume a hydrostatic equilibrium and acquire a near-spherical shape.
The term dwarf planet was adopted in 2006 as part of a three-way classification of bodies orbiting the Sun.
This classification states that bodies that are large enough to have cleared the neighbourhood of their orbit are defined as planets, while those that are not massive enough to have acquired a round shape are defined as small solar system bodies.
Dwarf planets come in between and have been called by some astronomers as “something that looks like a planet, but is not a planet.”
Even now there is no uncontested distinction between the term planet and dwarf planet. The definition officially adopted by the IAU in 2006 has been both praised and criticized, and remains disputed by some scientists."
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So, by definition, something with such a small gravity to be considered "micro-gravity" (let alone zero gravity) can't ever hope to have an atmosphere, and "advanced" life without an atmosphere is very unlikely (not completely impossible, just very unlikely compared to life in some atmosphere, and that's unlikely to begin with, so I guess you know where this is going).
Yeah, probably, somewhere, there's a species of sentient beings that live (natively) in space... but chances they exist anywhere close enough for us to encounter are pretty damned (astronomocally, heh) small.
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The TX
Gallente
Pulsar Combat Supplies
Alternative Realities
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Posted - 2008.09.01 10:15:00 -
[13]
*tries to read and understand this thread, brain implod....................
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Fink Angel
Caldari
The Merry Men
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Posted - 2008.09.01 20:05:00 -
[14]
Originally by: The TX
*tries to read and understand this thread, brain implod....................
If you really want your brain to implode, Centrifugal force does not really exist as such. It's a "pseudo force".
http://www.physicsforums.com/library.php?do=view_item&itemid=84
Anyway back to my usual level, is it too late to jump in with a "rings around Uranus" gag? |
ReaperOfSly
Gallente
Lyrus Associates
The Star Fraction
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Posted - 2008.09.01 20:31:00 -
[15]
Originally by: Fink Angel
Originally by: The TX
*tries to read and understand this thread, brain implod....................
If you really want your brain to implode, Centrifugal force does not really exist as such. It's a "pseudo force".
A laughable claim, Mister Bond, perpetuated by over-zealous teachers of science. Simply construct Newton's laws in a rotating system and you will see a centrifugal force term appear as plain as day.
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Fink Angel
Caldari
The Merry Men
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Posted - 2008.09.01 20:32:00 -
[16]
Originally by: ReaperOfSly
A laughable claim, Mister Bond, perpetuated by over-zealous teachers of science. Simply construct Newton's laws in a rotating system and you will see a centrifugal force term appear as plain as day.
I don't really understand it, I just posted to appear all knowledgable like! 
I'm more of a "nob gag" kinda guy! |
Akita T
Caldari Navy Volunteer Task Force
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Posted - 2008.09.01 21:38:00 -
[17]
Originally by: ReaperOfSly
A laughable claim, Mister Bond, perpetuated by over-zealous teachers of science. Simply construct Newton's laws in a rotating system and you will see a centrifugal force term appear as plain as day.
Come on, do you really expect me to do coordinate substitution in my head while strapped to a centrifuge ?
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ReaperOfSly
Gallente
Lyrus Associates
The Star Fraction
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Posted - 2008.09.01 21:55:00 -
[18]
Originally by: Akita T
Originally by: ReaperOfSly
A laughable claim, Mister Bond, perpetuated by over-zealous teachers of science. Simply construct Newton's laws in a rotating system and you will see a centrifugal force term appear as plain as day.
Come on, do you really expect me to do coordinate substitution in my head while strapped to a centrifuge ?
No, Mister Bond, I expect you to die. |
Imperator Jora'h
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Posted - 2008.09.02 00:05:00 -
[19]
The Discovery's centrifuge is perpendicular to the main axis of the ship (see here or just look at a pic of the ship and you realize it has to be so).
As for its spin when the centrifuge stops haven't any of you ever played with a gyroscope? The torque is perpendicular to the spin. How about riding a bike (your wheels act like a gyro and stabilize you from tipping over, perpendicular to your direction of travel). So if you stop the centrifuge in Discovery it would transfer its momentum and spin it long ways as we see in the movie.
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Akita T
Caldari Navy Volunteer Task Force
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Posted - 2008.09.02 00:50:00 -
[20]
IF the centrifuge is the way it's shown in the picture you just posted, then spinning it up/down would cause the main body of the ship to rotate along the "long" axis like a screwdriver, NOT tumble over like a thrown stick.
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Akita T
Caldari Navy Volunteer Task Force
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Posted - 2008.09.02 01:27:00 -
[21]
Ok, found the relevant book sections...
Originally by: 2001
The equatorial region of the pressure sphere - the slice, as it were, from Capricorn to Cancer - enclosed a slowly rotating drum, thirty-five feet in diameter. As it made one revolution every ten seconds, this carrousel or centrifuge produced an artificial gravity equal to that of the Moon. This was enough to prevent the physical atrophy which would result from the complete absence of weight, and it also allowed the routine functions of living to be carried out under normal - or nearly normal - conditions.
[...]
The spin of the carrousel could be stopped if necessary; when this happened, its angular momentum had to be stored in a flywheel, and switched back again when rotation was restarted. But normally it was left running at constant speed, for it was easy enough to enter the big, slowly turning drum by going hand-over-hand along a pole through the zero-gee region at its center. Transferring to the moving section was as easy and automatic, after a little experience, as stepping onto a moving escalator.
Originally by: 2010
We'll all have to move quickly; not only is time running out, but Discovery seems to be in very bad shape. We could hardly believe our eyes when we saw how its spotless white hull had turned a sickly yellow.
Io's to blame, of course. The ship's spiralled down to within three thousand kilometres, and every few days one of the volcanoes blasts a few megatons of sulphur up into the sky.
Originally by: 2010
Walter Curnow knew that as an abstract principle; but he did not really feel it in his bones until he saw the entire hundred-metre length of Discovery turning end-over-end, while Leonov kept at a safe distance. Years ago, friction had braked the spin of Discovery's carousel, thus transferring its angular momentum to the rest of the structure. Now, like a drum-majorette's baton at the height of its trajectory, the abandoned ship was slowly tumbling along its orbit.
Originally by: 2010
'Anything you need?'
'No - Max and I are doing fine. We're going into the carousel now, to check the bearings. I want to get it running as soon as possible.'
'Pardon me, Walter - but is that important? Gravity's convenient, but we've managed without any for quite a while.'
'I'm not after gravity, though it will be useful to have some aboard. If we can get the carousel running again, it will mop up the ship's spin - stop it tumbling. Then we'll be able to couple our airlocks together, and cut out EVAs. That will make work a hundred times easier.'
'Nice idea, Walter - but you're not going to mate my ship to that... windmill. Suppose the bearings seize up and the carousel jams? That would tear us to pieces.'
Originally by: 2010
Very cautiously, with many pauses for checking, power was fed to the carousel motors and the great drum was brought up to speed, reabsorbing the spin it had long ago imparted to the ship. Discovery executed a complex series of precessions, until eventually its end-over-end tumble had almost vanished. The last traces of unwanted rotation were neutralized by the attitude-control jets, until the two ships were floating motionless side by side, the squat, stocky Leonov dwarfed by the long, slender Discovery.
So, you have three options only.
ONE, you interpret "equatorial region of the pressure sphere - the slice" as meaning the "slice" alongside the long axis of the ship (as opposed to the "slice" perpendicular to it), then it all makes sense.
If you go with the picture posted by Imperator Jora'h, then you have two sub-options :
TWO, Arthur C. Clarke just made a big, BIG mistake... no way could that setup work (and it's the most likely option)
or
THREE, the flywheel was rotating perpendicular to the rotation of the centrifuge, which does make SOME sense, but not very much, to be honest... it would be easier to construct, true, but it would make no sense with regards to the quoted 2001 passage.
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Patch86
Di-Tron Heavy Industries
Atlas Alliance
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Posted - 2008.09.04 22:51:00 -
[22]
Originally by: Imperator Jora'h
The Discovery's centrifuge is perpendicular to the main axis of the ship (see here or just look at a pic of the ship and you realize it has to be so).
As for its spin when the centrifuge stops haven't any of you ever played with a gyroscope? The torque is perpendicular to the spin. How about riding a bike (your wheels act like a gyro and stabilize you from tipping over, perpendicular to your direction of travel). So if you stop the centrifuge in Discovery it would transfer its momentum and spin it long ways as we see in the movie.
Could you explain in some smaller words? I feel buoyed by your confidence, but didn't so much understand what you said 
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Originally by: Micheal Dietrich
You can even get a midget with a camera to sit on the floorboard.
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ReaperOfSly
Gallente
Lyrus Associates
The Star Fraction
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Posted - 2008.09.04 23:08:00 -
[23]
Originally by: Akita T
So, you have three options only.
ONE, you interpret "equatorial region of the pressure sphere - the slice" as meaning the "slice" alongside the long axis of the ship (as opposed to the "slice" perpendicular to it), then it all makes sense.
If you go with the picture posted by Imperator Jora'h, then you have two sub-options :
TWO, Arthur C. Clarke just made a big, BIG mistake... no way could that setup work (and it's the most likely option)
or
THREE, the flywheel was rotating perpendicular to the rotation of the centrifuge, which does make SOME sense, but not very much, to be honest... it would be easier to construct, true, but it would make no sense with regards to the quoted 2001 passage.
I think you need to work on your rotational mechanics. Imagine the ship tumbling over like a thrown stick, and that Imp's picture is correct. Spinning up the centrifuge WOULD stop the ship tumbling over. That's because the spinning centrifuge would exert a stabilising force on the main body of the ship, much like a spinning bicycle wheel exerts a stabilising force on the main body of the bike.
__________________________
Quote:
...bored, skint, no charter, and a ship that looks like an explosion in a girder factory...
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Slade Trillgon
Siorai Iontach
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Posted - 2008.09.05 10:21:00 -
[24]
Edited by: Slade Trillgon on 05/09/2008 10:22:23
Originally by: Patch86
looks as awesome now as it did 40 years ago.
Man you know you are aging when you see something like this and go, man that wasn't 40 years ago
Then you pause and think that wow it was  I was not born for a decade later, but
But now that I think about it that movie was way ahead of its time.
LMAO!!!
EDIT: And what a brilliant movie maker Kubrick was!!!
Slade
Originally by: Crumplecorn
NerfBat is now known as the WaveMachine.
DesuSigs
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