ot: scifi to real life? centrifugal force in space?
Mistara
Posts: 38,675
does anyone know if anyone has tested in real life if a spinning space station would make gravity for people living on it?
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No test needed. That is simple physics. However, it does not "make gravity", but the centripetal/centrifugal force can simulate with it with the right geometry. It is the same principal that keeps people on a roller-coaster from falling out in a loop.
Ciao
TD
That said, actually building something like that in space (i.e. big enough and rotating at the right speed and not flying apart) is an entire different problem. But that's engineering, not physics...
TD
No test needed. That is simple physics. However, it does not "make gravity", but the centripetal/centrifugal force can simulate with it with the right geometry. It is the same principal that keeps people on a roller-coaster from falling out in a loop.
Ciao
TD
but, iz still just a theory if they don't actually test it in space?
what if a greater mass of celestial body goes by, will it pull the space station into it's orbit?
does a yoyo work on the real space station? that would be kewl to see.
i read an article they brought bees to the space station, the bees couldn't fly.
The people at NASA were/are big fans of 'Babylon 5' because they had the physics more or less right. Some of its people even got in touch with Straczynski or some of the special effects people and were avidly curious to know how they managed to work out the correct rotation of the station and Earthforce destroyers, because, by their own calculations, they had got them right. :)
i'm a big fan of the 1st season Bab5. "### tons of spinning metal , all alone , in the night"
there was something with the colors of the jump gates, comin and goin,
you can test this theory at Adventure Land or you could read this article
http://en.wikipedia.org/wiki/Rotating_wheel_space_station
It's very possible, and unlike the roller coater the theory behind it was not proposed by methed out tattoed carneys.
See also http://en.wikipedia.org/wiki/Micro-g_environment for more info. The movie 2001 also had it right. In a rotating space station, you have to be out at the rim to get the full effect of simulated gravity. If you "climb" to the core of the station, you would be back in a microgravity environment. It's been proven that prolonged exposure to microgravity is bad for muscle tone and bone density.
Should work OK, although the arm action will probably need to be relearned. I'd like to see someone try that untethered. The really fun thing with that scenario is that, if the yoyo is heavy enough, it would spin in place while the astronaut goes up and down... ;-)
Edit: back to the original question, I'm sure I've read of centrifuges being used for a variety of experiments in space stations for many years. Exactly the same principle, it's just a bit smaller. There were plans to put a module with an astronaut-sized centrifuge on ISS, but that project was cancelled.
This is a fun discussion! On a spinning space station, if you were out at the rim, a yoyo should work normally. It might act a little differently at less than 1.0g though. It should work in micro-g as well, but it would be like any direction is down. Standard tricks like walking the dog and rocking the cradle would not work without enough local gravity.
Here's another fun one. Get a Helium balloon and tie it to something inside your car. As you go around a corner, the balloon leans to the INSIDE of the turn, not the outside. The balloon acts as if it had negative gravity acting on it because of the buoyancy of the Helium.
Even more fun: Get two wheeled chairs on a large hard surface like a lobby. Get a length of rope. Two people hold on to the ends of the rope while spinning around each other using their feet to go as fast as possible. Then you stop pushing with your feet and pull on the rope to pull yourselves toward the center. You will go faster and faster until you both fall out of your chairs. These are the kind of things serious Physics students at Caltech do... :lol:
The guy who writes for Wired's Dot-Physics feature recently did the maths on rotational simulation of 'gravity'. It's a good article if you're interested in seeing how the calculations work.
Incidentally, while I don't think anyone has yet built a spacecraft or space-station that exploits this effect, generating 'gravity' by rotation has been tested. NASA uses large centrifuges to train astronauts, spinning them at very high speed to simulate the intense G-forces of a rocket launch.
Does a yo-yo work on a spinning space station?
Let's be clear, we're talking about a doughnut shaped classic space station like in the movie "2001" where people walk around on the inside of the outer rim. The real International Space Station is only a hollow tube. Floating in the middle of a hollow tube spinning around you would not have any gravitational effect whatsoever!
But assuming the classical doughnut space station, I would say yes a yo-yo would work just fine. However, it might exhibit some strange behavior if the radius of the spin is short. I haven't worked out the mathematics but if you are standing on the "floor" and flip a yo-yo downward toward your feet the yo-yo might drift to one side slightly if the radius of the space station is not much longer than your height or the rate of spin is large. I suspect that if such a "drift" occurs it would be less noticeable if your space station were much larger or the spin rate slower. Let's say a radius of 100 feet instead of 10 feet. And certainly with a space station radius of 1000 feet the yo-yo behavior would be almost normal because at that radius the spin rate would need not be very large to create a force equal to normal Earth gravity.
Point being that our common world experience of "gravity" is essentially an "acceleration". Similarly the force on a yo-yo moving along inside the edge of a spinning space station is also an "acceleration" although the causes of the acceleration are different.
The acceleration on Earth that we call "gravity" is caused by the concentration of mass (the Earth) causing a curvature of space, and objects free to move will "slide down" this curvature of space to as low as they can get.
The acceleration of an object on a spinning space station is caused by a continual change of angular momentum.
However, I don't think gravity is even necessary for a yo-yo to work. The mass of a yo-yo flung in some direction in the absence of gravity will spin normally and when it reaches the end of the string will likely have enough friction with the string loop on its central peg to start winding up the string. The trick would be to keep the yo-yo from bouncing in odd directions without gravity to keep the string taught. It's probably already been tried on the International Space Station. Ask some 3rd grader. It might be possible but would be a learned skill.
Edited to add:
But now that I think about this a little, the force on an object in your hand while you are standing on the inside of the outer rim of a doughnut shaped spinning space station is certainly an acceleration. However, once you let go of the object it will fly off at a particular direction at a constant velocity (acceleration =0) because the spin of the space station is no longer acting on it causing a change in its angular momentum. At the point it is let go, it has a direction and velocity, and in the absence of any other force or object in its way it will continue in that direction at that velocity forever. Unlike an object in Earth's gravity which once free to fall still has the force of gravity working on it and will continue to accelerate and get faster and faster.
As long as the yo-yo is connected to you by a taught string it is still essentially attached to the space station and still getting a change of angular momentum causing an "acceleration" so "yes" a yo-yo should work in that situation.
I thought "I bet Chris Hadfield has done this" and Google'd "Chris Hadfield yoyo".
I didn't find anything with Hadfield, but that search string led to a video of astronaut Don Pettit playing with a yoyo on the ISS.
I thought "I bet Chris Hadfield has done this" and Google'd "Chris Hadfield yoyo".
I didn't find anything with Hadfield, but that search string led to a video of astronaut Don Pettit playing with a yoyo on the ISS.
Cool beans!!
but, iz still just a theory if they don't actually test it in space?
what if a greater mass of celestial body goes by, will it pull the space station into it's orbit?
does a yoyo work on the real space station? that would be kewl to see.
i read an article they brought bees to the space station, the bees couldn't fly.
Hmmm,"is it still just a theory if they don't actually test it in space?"
Well, actually, technically I guess you could say that, but they haven't put a 10 ton weight in space and flung it at the earth at 100 thousand miles an hour, yet they're pretty sure it would wipe out most of Europe in one hell of a blast. Nor have they put a pressure meter at every point at the bottom of the ocean to make sure that the pressures are what they calculate them to be. But, they're pretty damn sure they know within a few fractions of a percentage point what the value will be. Mathematics is our friend. With it we can calculate all sorts of futures with great degrees of certainty. Scientific theories make testable predictions. Some theories are very sound. Mechanics, strength of materials, thermodynamics, gas pressures, planetary gravitation, quantum mechanics are examples of very very sound and accurate theories that mathematics gives us answers accurate down to several decimal points. Whereas weather prediction, market behaviors, and other chaotic process are still rather complex and iffy.
And yes, if the space station were alone in empty space and if a massive enough celestial body passes by the space station at the right speed, distance and direction it could be pulled into it's orbit. But while the space station is orbiting the Earth what's more likely is that such a massive body would have to get so close to the Space Station to snatch it from the Earth that both would be pulled into collision with the body.
But somebody with the time, inclination and mathematical skill could think about this and actually create a set of equations describing the situation. Is there a mass, speed, and direction of body, space station, and Earth at which the space station could be snatched from the Earth? Is there a solution to the equation set, meaning that it is possible? Or is there no solution to the equations, meaning that it is truly impossible?
If a space station is in orbit around the earth, the earth is the biggest thing in the neighborhood. If something was to fly by and rip the station out of orbit, it would have to be around the same mass as the earth, or larger. Such a close encounter would probably rip away half the earth's atmosphere and cause tidal forces that would rip the crust apart. There are potential extinction level events that do not involve getting hit by a rock the size of Manhattan. These are referred to as low probability events. As in, sure, they might happen, but so far, there have only been two huge mass extinctions in around 4.5 billion years. That's not a hit rate I'm particularly worried about. After all, us Mammals survived the last ELE.
Isaac Newton didn't actually have to get hit on the head by an apple to observe that an apple would always fall toward the center of the Earth. The mathematics he applied to observations of the physical world explained things with great accuracy, at least until Einstein came along. Einstein's theory that gravity could bend light rays was controversial until it was actually measured. The observations of gravitational lensing did not happen until after Einstein's death.
In spite of the obvious similarity of the coastlines of Africa and South America, people didn't believe in 'continental drift' or what we now call Plate Tectonics. Eventually, it became accepted after enough evidence was collected. The fossil record has examples of identical extinct animals living in Africa and South America. There are living species of earthworms on both continents that are the same, and earthworms don't migrate!
Isaac Newton's equations are still used to calculate the paths for the vast majority of space flights. The problem with them, however, is that they break down in extreme conditions. You can use his equations to calculate the precise position of all the planets except Mercury, since it is extremely close to the Sun. To figure out Mercury, you need Einsteinian relativity.
However, there's a problem with Einstein as well. His theories work well on the macro-level but don't work at the sub-atomic level. To explain that stuff, you need Quantum Mechanics.
Cheers,
Alex.
blah swing a bucket of water around in a circle vertically and the water stays in it due to the inertia of it wanting to fly off in a straight line
inertia is basically things either move or they don't unless something pushes or attracts them like gravity
that is what your space station is doing spinning, the stuff on the outer ring floor wants to be thrown off but the floor stops it,
We are all just buckets of water being flung around in a circle... :lol:
Not true, I had to stop my car and wait for a herd of earthworms to cross the road last week! I was fascinated by the ants mounted on caterpillars that were driving them using butterfly antennae as whips. It was obviously a forced migration.
Unfortunately in order to see this more clearly I had to pull out my map reading magnifying glass from the glove compartment and during close observation I wiped out half the drovers, and the herd scattered in all directions.
There were joint experiments from many countries called Cosmos 782 and 936
http://lis.arc.nasa.gov/lis/Programs/Cosmos/Cosmos_782/Cosmos_782.html
http://lis.arc.nasa.gov/lis/Programs/Cosmos/Cosmos_936/Cosmos_936.html
No experiments with humans and not with a whole Station (too expensive for something not essential I guess)
There are three main problems with a space station large enough to generate gravity by spinning.
1. Expense. It is stupidly expensive to put enough material in orbit to assemble it in space to create this station. though the expense could be greatly decreased if we had a colony on the moon and the material could be mined, and refined there. (Gravity prevents putting it together on Earth then moving it to orbit, there are no materials strong enough to survive, assembled, the trip to orbit .)
2. Stable orbit, There are only a handful of places where you can put an object where, because of the Earth's Orbit, the Moon's orbit around the Earth, the shape of the Earth, etc. that are inherently stable orbits. They are called Lagrange points, of which points 4 and 5 are really the only useful places for this purpose, and the amount of stuff located at those Lagrange points makes putting a station there inherently dangerous due to impacts.
3. Radiation. Even solving the gravity problem does not solve the issue that you have in space where you are not protected by the Earth's Atmosphere and Magnetic field. Current calculations show a human can survive no more than 5 years, over the course of their life, in such an environment. Unlike putting a colony on the Moon or Mars, you can't bury a space station in orbit.
Agreed that at the present time a "classic" spinning space station is outrageously expensive. Though not impossible. Assembled as modules, first as strings of cylinders (as we are currently doing), then as circles of cylinders then as layers of circles of cylinders.
When and if mining of the moon or asteroids becomes feasible, then huge space structures become much more likely. Though I don't understand why they would have to be placed at the LaGrange points. High orbit of the Earth would just as feasible if by that time we clean up the garbage cloud of old satellites and broken pieces of junk that currently shroud the earth. Also I assume that by the time we could build a huge space station and park it at the LaGrange points that we could also round up the existing satellites at those points and attach them to our new masterpiece or subsume their tasks to eliminate the risk of collision.
Also assuming that we can build huge structures in space I would hope by that time that we could also create strong enough magnetic fields and other shielding (perhaps a reservoir shell of water) to greatly reduce the risk of radiation exposure.
Those are not easy tasks, but if we can solve the more pressing problems of governmental and populace stupidity before we bomb or breed ourselves back into the caves or worse, then they could be accomplished in a hundred years.
Not true, I had to stop my car and wait for a herd of earthworms to cross the road last week! I was fascinated by the ants mounted on caterpillars that were driving them using butterfly antennae as whips. It was obviously a forced migration.
Unfortunately in order to see this more clearly I had to pull out my map reading magnifying glass from the glove compartment and during close observation I wiped out half the drovers, and the herd scattered in all directions.
Really amusing, but it doesn't alter the fact that earthworms do not migrate ... across oceans! Let's not get into the African Swallow vs. European Swallow debate from Monty Python! :lol:
the cost of the NASA Nautilus-X proposed project is estimated a 3.7 Billion, which is apparently not a lot of quatloos when you look at the cost of other space projects.
many of the modules are inflatable so it would not necessarily have to be built in space.
http://en.wikipedia.org/wiki/Nautilus-X
Oh snap, look who's in the (proposed) transhab!
http://en.wikipedia.org/wiki/Bigelow_Aerospace#mediaviewer/File:Transhab-cutaway.jpg
Agreed that at the present time a "classic" spinning space station is outrageously expensive. Though not impossible. Assembled as modules, first as strings of cylinders (as we are currently doing), then as circles of cylinders then as layers of circles of cylinders.
When and if mining of the moon or asteroids becomes feasible, then huge space structures become much more likely. Though I don't understand why they would have to be placed at the LaGrange points. High orbit of the Earth would just as feasible if by that time we clean up the garbage cloud of old satellites and broken pieces of junk that currently shroud the earth. Also I assume that by the time we could build a huge space station and park it at the LaGrange points that we could also round up the existing satellites at those points and attach them to our new masterpiece or subsume their tasks to eliminate the risk of collision.
Also assuming that we can build huge structures in space I would hope by that time that we could also create strong enough magnetic fields and other shielding (perhaps a reservoir shell of water) to greatly reduce the risk of radiation exposure.
Those are not easy tasks, but if we can solve the more pressing problems of governmental and populace stupidity before we bomb or breed ourselves back into the caves or worse, then they could be accomplished in a hundred years.The reason it has to be Lagrange 4 or 5 is stability. Moving something that massive and stabilizing the orbit requires lots of fuel. Remember F=MA and M doesn't care if you are in microgravity or not. In theory you could place it in orbit of Lagrange 1-3, but again maintaining orbit is still a rough thing. There are other places you could put it, but it will eventually fall into the atmosphere, and we don't really want that. LOL.
Cheaper, and easier to put the station on the Moon, instead of in orbit.
I thought "I bet Chris Hadfield has done this" and Google'd "Chris Hadfield yoyo".
I didn't find anything with Hadfield, but that search string led to a video of astronaut Don Pettit playing with a yoyo on the ISS.
tee heee
thanks for sharing :lol:
'misplaced priorities' :lol:
'precision ball bearings'
It's nothing to do with existing orbital clutter, the problem is long-term stability. Orbits very close to Earth are fairly stable in the long run, if you're above the majority of the atmosphere — a whole separate problem on its own; the top of the atmosphere moves, mostly depending on solar activity, and it's higher than most people think (ISS needs regular boosts because of atmospheric drag).
Orbits further out from Earth have to allow for the Moon's influence. This can be calculated, but it's no use calculating how much an orbit will shift over time if you don't want it to shift in the first place. Eventually this influence will take the low end of your orbit too close to Earth, causing unwanted aerobraking, followed by rather abrupt lithobraking.
The only real options for long-term stability are the L4 and L5 zones (they're not really points). The other three points are useful for certain purposes, but they're unstable; if you look at the dynamics of how the Earth's and Moon's gravity interacts, the least little drift away from L1, L2 and L3 will actively push you further away. L4 and L5 are different, instead of being pushed away, things are pulled back towards them. The final result is a sort of kidney-shaped wobble around the actual L4 and L5 points.
Incidentally, I use the words "long-term" the way an astronomer or SF fan would; I don't just mean millions of years, I mean a lot more than that. :smirk:
OK, I'm not worried about where you put your space station, but getting it there and keeping it there may be easier than you think.
http://www.space.com/26713-impossible-space-engine-nasa-test.html
If this phenomenon is real and proves to be viable it could be used as position keeping thrusters on a space station, or to reposition a fleet of junk catcher robots around to chase junk and nudge it into quickly decaying orbits. Also imagine long term high speed solar system excursions without needing to carry fuel but able to accelerate all the time as long as you had enough electrical power.
Intriguing. It's been reproduced by others, so it probably isn't another Dean Drive (look it up in Wikipedia, it's a bit of a sad story). Thanks for the link.
orbit must be pretty deep?
i picture orbit like grooves on a 33 vinyl album