Artificial gravity in spinning space ship conumdrum

Shooting Star

Absolute with respect to what? The mean of the distant matter? Or Absolute Space?

If there's a germ of truth in Mach's Principle, which the scientific community does believe there is, then a massive rotating shell spinning around you should produce a centrifugal force similar to what is produced by you spinning wrt the background of the distant matter.

Even otherwise, spinning near a massive body gives rise to different effects than spinning in a relatively mass free region, and the accelerometer would show different readings.

nuby

http://www.artificial-gravity.com/ (lots of references)

http://spaceflight.nasa.gov/gallery/...2_mission1.mpg (video)

nuby

Does that video prove "artificial gravity" is possible?

Andy Resnick

I'm a little confused- are people wondering if the concept is sound, or if it's practical to actually construct such a device?

Is the concept sound (the science)- yes.
Is the device practical (the engineering)- no.

yuiop

Here is a sort of proof that it is not just an assumption:

Imagine two large disk shaped spaceships traveling alongside each other. Each is spinning around their own axis of symmetry parallel to the direction of motion, but rotating in opposite directions with respect to each other. As they move far away from any massive body, which will stop rotating (as you suggest)? If neither stops rotating how would they account for the lack of "apparent centrifugal force" in both spaceships (as you are suggesting) when it is obvious to any local observer (spinning or not) that at least one of the spaceships IS rotating? If both spaceships stop rotating with respect to each other where has the stored rotational energy gone?

LURCH

Yes, the video proves that generating artificial gravity in space via "centrifugal force" is not only possible, but has been done. That is what kept the astronaut's feet on the "floor." It was obviously not a full G, but it was keeping him "down" on the track.

nuby

When I hear "artificial gravity" I think of something out of 2001: A Space Odyssey.. The rotating space craft, with people walking around inside of it. This is not possible. Real "artificial gravity" is created in a smaller centrifuge, with an astronaut strapped inside of it.. Without the straps (or physical motion of astronauts) there will not be a centrifugal force on the astronauts.

This leads to a few more questions:
Why are the astronauts not experiencing the same affects as they would on say a "gravitron" (carnival ride) or in their training centrifuge? Are they experiencing "real" centrifugal force without centripetal force? Can centripetal force exist without gravity?

TVP45

You'll need to do some research on some of your questions. The only reason anyone cares about artificial gravity is the effect weightlessness has on astronauts. So, the place to look for your answers is at the Johnson Space Center, beginning in the Human Adaptation labs.
http://hacd.jsc.nasa.gov/
You might also look at Krug Life Sciences to see some other work being done there.

yuiop

Why do you think centrifugal force is felt in a small centrifuge but not in a large centrifuge?


The astronaut is running in the video because the space station is not spinning. Running inside the rim of a non spinning station has the same effect as standing in a spinning station.

They would experience the same effects as in a gravitron if the station was spinning, (but it was not). I suspect you have not read or thought about any of the responses posted above.

nuby

You are wrong. Unless the astronauts are physically attached to a spinning "centrifuge", or propelling themselves forward (i.e. previous video) they will not experience any sort of "artficial gravity" at all.

Atomsk

You're right but as soon as they touch down to the rotating "ring" if you will the tangential velocity will propel them in the direction of the ring and then the ring itself will keep changing their velocity (acceleration) to keep the person in an artificial gravity. Artificial meaning it's not real, it just seems like gravity because objects are held to the surface without restraints.

I don't understand what you're getting at. It's the centripetal force that lets the person walk on the inner surface of the ring. Maybe they have to acclimate themselves to it after first touching down but aside from that is your argument that it's not the definition of gravity or that it's not possible. I'm not getting a streamlined thought from your posts.

Shooting Star

Arthur C. Clarke was one of the greatest thinkers of all times. He was the kind of scientist who could envision and extrapolate quite a few steps ahead of the boundaries of accepted science at any time. Nobel laureates walked softly when he was around. I am not even going into his writing skills and writing prowess, which went far, far beyond Science fiction by the way.

The scientific details of his so called SF books are phenomenally accurate. The scenario of both "2001: A Space Odyssey" and "Rendezvous with Rama" comes to mind for the sheer amount of technical analysis of rotating space stations. These were written in times when very few people even imagined such things.

You, a Physics ignoramus or a lunatic without a leash, dare comment in one sentence on a great work by a great man which your brain does not have the logic circuits to process. If the things described in the book were not possible, then Arthur C. Clark would not have written about them. Do you understand?

Arthur C. Clark passed away just a month back, on 19th March, 2008. I feel that somebody near to me is no more.

You evidently are much younger than me, and that is why, though being irked, I have never commented on your writings personally. Your youth does not give you the leeway to affront the brilliant works of a great man. Threads have been locked for much less than have been tolerated from you. I advise you to take some time off and learn basic Physics.

If this mail seems to be rude in any respect, then it is meant to be.

Danger

Maybe it would be more appropriate to refer to the centrifugal effect as 'pseudo-gravity' rather than 'artificial gravity'. The latter implies to me some sort of graviton or gravity wave generation which would induce true gravity, while the former just provides a reasonable approximation thereof.

yuiop

As Danger pointed out the "artificial gravity" is just an aproximation of the real thing. If an astronaut managed to avoid the spinning rim for the whole trip then he could avoid being pulled down. (He is actually in a form of internal orbit). But if there is air inside the space station (as there usually is) then the air will gradually be dragged around into synchronisation with the rim and eventually the astronaut too would be dragged by the air and start to "fall".

If he was standing on the spinning rim and let go of a ball, guess where the ball will go?

A) Hover near his hand.
B) Move in an internal orbit like the astonaut before he touched down.
C) Drop towards his feet and stay on the rim after a couple of bounces.


Hint: It's not A or B ;)

nuby

As long as the astronaut was connected to the rim, the ball would have a curved trajectory toward the ground/rim ..

If the answer is "C" and the ball would drop straight towards his feet. What force would keep the ball adjacent to the floor below?

Shooting Star

There was some fruitful discussion on these things some time ago in this thread. The discussion was all right up to post #33.

TVP45

I think perhaps Nuby is looking for an argument rather than an answer.