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Why no Artificial Gravity ??

boooeee said:
if the object (or astronaut) is attached to the wall
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Exactly. If it is not attached to the wall then it experiences no force. Therefore, there are huge differences between gravity and a rotating object.

It won't be exact. If he drops an object from his hand, it will fall to the ground a bit quicker than what he would expect under a normal gravitational field. It will also not fall straight down. However, the differences between a normal gravitational field and what the astronaut experiences get smaller and smaller as the radius of the torus increases.
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Exactly. Things will fall differently and move differently. Since realistic spacecraft are not going to be that big, there will be very big differences. So there are big differences between "artificial graivty" and normal gravity and big differences between microgravity and normal gravity. Given that one of these requires no effort whatsoever and one needs huge amounts of technology, which one is more useful?

The only vaguely sensible argument is the one on bone mass. However, as far as I am aware, the actual cause of these problems is not actually known, although the lack of gravity meaning bones are not needed is a good hypothesis. However, it would be madness to actually design hugely complex spacecraft without even knowing if they will solve the only problem that they might actually solve.
 
Cuddles said:
Exactly. If it is not attached to the wall then it experiences no force. Therefore, there are huge differences between gravity and a rotating object.
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If you are not standing on the floor you feel no force either. In both cases it is the normal force that is felt.

You do not start hovering by simply jumping.


Exactly. Things will fall differently and move differently. Since realistic spacecraft are not going to be that big, there will be very big differences. So there are big differences between "artificial graivty" and normal gravity and big differences between microgravity and normal gravity. Given that one of these requires no effort whatsoever and one needs huge amounts of technology, which one is more useful?
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It depends on what the effects are. Keep in mind that nothing moves in a straight line on earth either, it just aproximates it at normal scales.
The only vaguely sensible argument is the one on bone mass. However, as far as I am aware, the actual cause of these problems is not actually known, although the lack of gravity meaning bones are not needed is a good hypothesis. However, it would be madness to actually design hugely complex spacecraft without even knowing if they will solve the only problem that they might actually solve.
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So you think that the bone can detect gravity and not just the dirrect physical forces? Or do you think that corriolis effect would effect bone deposits?
 
Imagine looking out the window from such a rotating space station. Dizzy? :hypnotize
 
ponderingturtle said:
No you can only move you leg so fast so you can not get a relative velocity to the wall of greater than that. It has to do with the mass and how much force the muscles exert and how fast they can contract.

If you can only move your foot at say 45 mph then you will not be able to run faster than 45 mph.
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I wasn't referring to the running part, but the suspended above the surface part, once you're going fast enough. Plus, there's another benefit -- the craft will most likely be only at a fraction of 1G. I'm quite sure that as gravity lessens you will gain the ability to run faster, as your "weight" will require less energy for you to support while running -- energy that can now be used to go faster.
 
Just thinking said:
I wasn't referring to the running part, but the suspended above the surface part, once you're going fast enough. Plus, there's another benefit -- the craft will most likely be only at a fraction of 1G. I'm quite sure that as gravity lessens you will gain the ability to run faster, as your "weight" will require less energy for you to support while running -- energy that can now be used to go faster.
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But you can only move your leg so fast, it does not matter how low gravity is. Reducing friction goes not simply permit higher speeds, think about cars driving on ice, can they go faster than cars on pavement?
 
ponderingturtle said:
If you are not standing on the floor you feel no force either. In both cases it is the normal force that is felt.

You do not start hovering by simply jumping.
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You have missed the point. If you are not in contact with the Earth, gravity still acts on you and pulls you back down. If you are not in contact with a rotating spaceship then there is no force acting on you, in the absence of air at least.
 
Cuddles said:
You have missed the point. If you are not in contact with the Earth, gravity still acts on you and pulls you back down. If you are not in contact with a rotating spaceship then there is no force acting on you, in the absence of air at least.
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That depends on how you define force. Sliding down the gravitational potential is not the same as a mechanical force. You are weightless in much the same manor in both cases.
 
ponderingturtle said:
But you can only move your leg so fast, it does not matter how low gravity is. Reducing friction goes not simply permit higher speeds, think about cars driving on ice, can they go faster than cars on pavement?
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Non-sequitur ... cars on ice have little to no forward friction, a person in low gravity can still obtain good forward friction. The car on ice still has 100% of its weight pressing on the ice -- but doesn't move because the ice prevents any force from being transferred from the tire (car) to the ground. A person can still press quite well sideways to produce forward motion with their foot on a surface with even 50% of their weight -- the coefficient of friction is not reduced.

Anyway ... all one needs to observe are the differences in mobility of astronauts in moon suits both here on Earth and on the Moon to see where they move around faster.
 
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Cuddles said:
You have missed the point. If you are not in contact with the Earth, gravity still acts on you and pulls you back down. If you are not in contact with a rotating spaceship then there is no force acting on you, in the absence of air at least.
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To clarify: If you are standing in a rotating torroidal space station, with no air in it, and jump, you will fall back down. For a large torroid (mile across) it won't practically be different from gravity. You won't "float" simply because your feet aren't touching the torroid. Correct?
 
RecoveringYuppy said:
To clarify: If you are standing in a rotating torroidal space station, with no air in it, and jump, you will fall back down. For a large torroid (mile across) it won't practically be different from gravity. You won't "float" simply because your feet aren't touching the torroid. Correct?
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I would think that if you start out standing on a torroid that is already turning then you are sharing its momentum and would retain it upon jumping so then, yes, you would fall back to the "ground".
 
Just thinking said:
Non-sequitur ... cars on ice have little to no forward friction, a person in low gravity can still obtain good forward friction. The car on ice still has 100% of its weight pressing on the ice -- but doesn't move because the ice prevents any force from being transferred from the tire (car) to the ground. A person can still press quite well sideways to produce forward motion with their foot on a surface with even 50% of their weight -- the coefficient of friction is not reduced.

Anyway ... all one needs to observe are the differences in mobility of astronauts in moon suits both here on Earth and on the Moon to see where they move around faster.
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Nonsense a car on ice can get going almost as fast as a car not on ice, it just takes longer. BUt it is not going faster from its reduced drag.

But how much faster where they with out suits on earth vs with suits on the moon? The reduction in weight made moving in the suit easier, sure, but that does not mean it would enhance your speed by itself all that much.
 
OK, ponderingturtle, I believe we've gotten onto some sort of misunderstanding on this issue, and instead of trying to go back and sort it all out, I will simply spell out what I believe to be the case with regards to moving in lower gravity and thinner atmospheres.

1) You can run faster in lower gravity (not Zero-G) than you can normally here on Earth, all other conditions being the same. (I believe the difference will be significant.)

2) You can run faster in a thinner atmosphere than 1-bar given all other conditions being equal. (But not by much -- less drag is why.)

3) The conditions aboard a rotating spacecraft (ring-type) that simulates gravity via rotation will likely have less than 1-G and a thinner atmosphere.

Now ... to address your points:
Nonsense a car on ice can get going almost as fast as a car not on ice, it just takes longer. BUt it is not going faster from its reduced drag.
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I'm not sure what your point is here ... as I am referring to a difference in gravity, not drag (see above -- drag will have a small difference). Also, frictional coefficients will be the same with less gravity, so why are you introducing an argument involving ice?

But how much faster where they with out suits on earth vs with suits on the moon? The reduction in weight made moving in the suit easier, sure, but that does not mean it would enhance your speed by itself all that much.
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Again, a non-sequitur -- It's not about how much faster they can move on Earth without moon suits. Let's compare apples with apples. The astronaut with a moon suit has the same mass here on Earth as on the Moon, and likely the same friction on loose soil on Earth as on the Moon's surface. But where do they move faster? The moon. Now, you must ask yourself, is it because of the lack of an atmosphere? At the velocities they moved, not really. So what is different? Ahhhh ... less gravity!
 
Just thinking said:
OK, ponderingturtle, I believe we've gotten onto some sort of misunderstanding on this issue, and instead of trying to go back and sort it all out, I will simply spell out what I believe to be the case with regards to moving in lower gravity and thinner atmospheres.

1) You can run faster in lower gravity (not Zero-G) than you can normally here on Earth, all other conditions being the same. (I believe the difference will be significant.)

2) You can run faster in a thinner atmosphere than 1-bar given all other conditions being equal. (But not by much -- less drag is why.)

3) The conditions aboard a rotating spacecraft (ring-type) that simulates gravity via rotation will likely have less than 1-G and a thinner atmosphere.

Now ... to address your points:

I'm not sure what your point is here ... as I am referring to a difference in gravity, not drag (see above -- drag will have a small difference). Also, frictional coefficients will be the same with less gravity, so why are you introducing an argument involving ice?



Again, a non-sequitur -- It's not about how much faster they can move on Earth without moon suits. Let's compare apples with apples. The astronaut with a moon suit has the same mass here on Earth as on the Moon, and likely the same friction on loose soil on Earth as on the Moon's surface. But where do they move faster? The moon. Now, you must ask yourself, is it because of the lack of an atmosphere? At the velocities they moved, not really. So what is different? Ahhhh ... less gravity!
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Evidence? What is your evidence that you can move faster in say .5g and even faster in .1g? Yes a given speed might not take the same output of energy, and for some people that might be a limiting factor in speed in 1g so they would go faster, but say for a good sprinter, in say .1g how much faster can they go?
 
I think Just Thinking is right. On the moon you would run faster since a) there's less friction (no air) and b) your muscles are working more efficiently against the weaker gravity.
 
But in running you are travelling perpendicular to the force of gravity, you aren't working against gravity in running.
 
Hmmm, good point, but you have less weight you have to carry, wouldn't that equal less work, thus more efficiency and speed?
 
Skeptic Guy said:
Hmmm, good point, but you have less weight you have to carry, wouldn't that equal less work, thus more efficiency and speed?
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Well legs are not like rocket boosters, so there are issues of how effectively they can get ke into you in such a system.
 
Skeptic Guy said:
Hmmm, good point, but you have less weight you have to carry, wouldn't that equal less work, thus more efficiency and speed?
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A little, since running isn't 100% free of up/down motion, but, in horizontal motion, you are "working against" inertia and friction, not gravity.
 
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