I've heard it often discussed that one of the biggest problems with long-term space travel is the lack of gravity and the effect it has on the human body. One proposed solution would be a spinning spacecraft, since the centrifugal force generated would simulate gravity. It's easy to imagine why this would work if you've ever been on one of those spinning rides at a fair or theme park, but I have a question: Imagine you are on such a spinning spacecraft, in a weightless environment, and are able to stand on your feet thanks to the imitation gravity. You're holding a ball just in front of your face. You release your grip on the ball. With no gravity but only centrifugal force at work, does the ball "fall" to your feet, or does it float in front of you?
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I would say the ball is accelerated twords your feet by the same force accelerating your body, holding it to the walls of the ship. Centrifugal force would have to be applied to all objects in the craft.
However, if you placed the ball in the exact center of the ship, it should just float there. But if you move it even a micron, Centrifugal force will eventually overcome it and it will be accelerated to the wall. I see it as a small wiggle, followed by a ever increasing spiral pushing it to the walls of the ship.
Of course I may be wrong, but if I understand the phenomena correctly, then I think this is a logical explanation. (think of a merry-go-round. Put a ball in the center and spin it, it will be deflected to the side, unless the ball is dead center and the pushing force is applied evenly) Otherwise, the people would only have gravity if they were already touching the walls of the ship, and then, only in their feet. The slightest jump would propel them until the "fell" onto another wall of the ship. Since there would now be no "pushing" force to hold them down. The "pushing" force is the needed part of gravity for long term survival. If only our feet are feeling gravity, then the rest of our bodies would still be vulnerable to the dangers of long term exposure to a non-gravity environment, hense the centrifugal force is would now be useless.
Star
However, if you placed the ball in the exact center of the ship, it should just float there. But if you move it even a micron, Centrifugal force will eventually overcome it and it will be accelerated to the wall. I see it as a small wiggle, followed by a ever increasing spiral pushing it to the walls of the ship.
Of course I may be wrong, but if I understand the phenomena correctly, then I think this is a logical explanation. (think of a merry-go-round. Put a ball in the center and spin it, it will be deflected to the side, unless the ball is dead center and the pushing force is applied evenly) Otherwise, the people would only have gravity if they were already touching the walls of the ship, and then, only in their feet. The slightest jump would propel them until the "fell" onto another wall of the ship. Since there would now be no "pushing" force to hold them down. The "pushing" force is the needed part of gravity for long term survival. If only our feet are feeling gravity, then the rest of our bodies would still be vulnerable to the dangers of long term exposure to a non-gravity environment, hense the centrifugal force is would now be useless.
Star
I think you're wrong there Fallingstar. Imagine the ball has it's eyes closed. It isn't aware that the walls are spinning, so it would just float.
The merry ground analogy fails because there is a floor to the merry ground that is spinning as well as the edges, so the ball would move. In the rotating ring, the ball isn't in contact with anything, so is not affected by the spinning walls.
Good thought experiment.
Who's up next?
The merry ground analogy fails because there is a floor to the merry ground that is spinning as well as the edges, so the ball would move. In the rotating ring, the ball isn't in contact with anything, so is not affected by the spinning walls.
Good thought experiment.
Who's up next?
Fallingstar1971":cno34ps2 said:
This is correct
This is not correct. If the ball is in the center of the ship and you nudge it towards the edge of the ship it will travel in a straight line towards side of the ship (I am neglecting any rotational velocity that the air may impart). The ship will continue to spin so the ball will look like it is spiraling relative to the ship but the ball will not accelerate or change course. Centrifugal force is a pseudo force. What is happening is that on the rotating ship your body has a velocity and your body wants to travel in a straight line but you cannot go in a straight line you run into the wall (which would be the floor). So there appears to be gravity because you are constantly 'hitting' the floor as your body trys to move laterally in a straight line. This means that even if you jump in the air you will return to the floor because you still have lateral velocity. If you are in the center of the ship (no velocity) and push towards the wall you will slowly drift in a straight line until you run into the spinning wall, resulting a funny video that can be put on youtube.
Ahhhhhhhhhh....... I see says the blind man.........
Thank you, now I understand the phenomena a bit better.
Star
Thank you, now I understand the phenomena a bit better.
Star
MeteorWayne":1s0nsaow said:
I think the ball would fall because it has the same velocity that the person holding the ball has.
One interesting outcome of a ship of this type (I think!!) is that the 'gravity' at the floor would be like 10 m/s/s and at the middle of the ship the 'gravity' would be 0 m/s/s. That means (depending on the size of the ship) there could be a relatively large difference in the apparent gravity between your feet and your head. So bending over would be a strange feeling. The velocity of your head would increase as it approached the side of the ship and consequently the pseudo gravity would also increase. I am getting motion sickness just thinking about it.
Interesting. I thought I understood the forces behind this but now that I think it over and read your comments I realize I was slightly off as well. So under my newly expanded understanding, it is the rotational velocity that is creating the 'pseudo force' which gives the impression that the person in question is being pulled to the floor.. If this is true, then this opens up another interesting thought experiment.
Let's say this spinning craft is circular with no overhead obstructions and at least one path around its "floor" that is not obstructed by equipment and such. Assuming it is the rotational velocity that creates the gravity like effect, if a person where to run around the spacecraft in the opposite direction of it's rotation would the 'downward' (outward?) force reduce as their run speed subtracted from the rotational velocity? And if so, could they possibly sprint fast enough to cancel out the crafts rotational speed for themselves and effectivly become weightless while all other objects and people remained firmly fixed to the floor?
origin":2nynl9vs said:
You really would want a large enough ship that you wouldnt have this issue.
If only we were building ships for interstellar travel. We would have more information on ideas like this.
You wouldnt need to do all that running. All you would have to do is make a ladder up a sidewall and climb twords the center. The closer you get the less gravity you have. You would probably be able to devise a way to stop your pseudo gravity from there. Possibly something that would spin with the outer wall that you get onto, and it would than slow down and stop so you are at zero gravity. This does allow a much more useful ship i would belive.
''You release your grip on the ball. With no gravity but only centrifugal force at work, does the ball "fall" to your feet, or does it float in front of you?"
It falls, but not to your feet. It falls away from your fet due to the coriolis effect.
Incidentally, I remember in the old "space colonies" days of the 70's and 80's that the ideal 1-G configuration would describe a 1/2 mile diameter arc rotating once per minute. That's a very large configuration. The assumption, for 1-G, was that anything substantially smaller would have too-pronounced a coriolis effect, and cause motion sickness. I would speculate that that motion sickness and similar adverse effects could be overcome by adaptation, the way sailors get used to it on shipboard.
It falls, but not to your feet. It falls away from your fet due to the coriolis effect.
Incidentally, I remember in the old "space colonies" days of the 70's and 80's that the ideal 1-G configuration would describe a 1/2 mile diameter arc rotating once per minute. That's a very large configuration. The assumption, for 1-G, was that anything substantially smaller would have too-pronounced a coriolis effect, and cause motion sickness. I would speculate that that motion sickness and similar adverse effects could be overcome by adaptation, the way sailors get used to it on shipboard.
rreilly656":106otjt9 said:
Precisely why another configuration was developed, the spinning ring may provide a nice uniform gravity, but it does get large if you want to avoid motion sickness. The alternative is to have a couple modules connected by a long tube. The tube is still that half-mile long, but at least it is only in one axis. The benefit over a pure ring is that you can still put a zero-g module in the middle (or partial-g modules elsewhere along the tube).
I can see someone doing space chicken... fling yourself out of the zero-g module towards the outer module, first person to turn to be upright looses. :roll:
FmK":2p5t5f6l said:
True, I'm with you on your comments however it sounds far more interesting to do it without any ladders and contraptions (if possible).. It's a space travelers version of a "stupid human" trick.. All your space traveling buddies are sitting around at their computers and equipment doign their daily chores while firmly planted to the sidewalls when you suddenly break out in a sprint then push off the floor gracefully and "fly" through the cabin to the amazement of all those around you.
However the landing might be far less graceful on the other side. If you dont line up with a clear landing strip, you may very well end up being smacked by some big bay of equipment moving at a good clip relative to you. :shock:An alternative solution to rotating vehicle elements would be what I'd call a "gravity suit," distinct form the fighter pilot's "G-suit" in that this suit would subject the wearer to moderate resistance for extended periods of time.
The first crude gravity suit was the "penguin suit" worn by Soviet cosmonauts for short periods of time. That suit would contract the wearer into a fetal position if he/she wasn't counteracting that tendency. Similar resistance contraptions can be found at JumpUSA.com.
What I had in mind would be much more wearer-friendly sophisticated, and unobtrusive, and also a lot more complete in terms of where and how it applied resistance. It would take advantage of recent advances in both micro and nanotechnology, and would be comfortable enough to be worn for extended periods of time -- as in at least several hours a day. It would be an adjunct to regular exercise sessions, rather than a substitute for those sessions. I envision it being well-ventilated, relatively easy to put on and take off, and easy to care for.
The first crude gravity suit was the "penguin suit" worn by Soviet cosmonauts for short periods of time. That suit would contract the wearer into a fetal position if he/she wasn't counteracting that tendency. Similar resistance contraptions can be found at JumpUSA.com.
What I had in mind would be much more wearer-friendly sophisticated, and unobtrusive, and also a lot more complete in terms of where and how it applied resistance. It would take advantage of recent advances in both micro and nanotechnology, and would be comfortable enough to be worn for extended periods of time -- as in at least several hours a day. It would be an adjunct to regular exercise sessions, rather than a substitute for those sessions. I envision it being well-ventilated, relatively easy to put on and take off, and easy to care for.
Imagine a 20 or 30 foot diameter wheel with 4 spokes from the hub to the outside wheel. Remove 3 feet from away from the center meaning the hub and 1 and a half feet of each spoke out from the hub. Now imagine what your looking at is a cross section of the ship, which is also spinning. A person standing on what appears to be a spoke (actually a cross section of "floor") would actually have the floor spinning up toward them. This ship now has 4 floors, with people and objects not falling to the floor, but the floor "falling" toward them. Simmulated gravity. No prob.
In the large space ship idea with no obstacles along the joggers path in the rotation of the spin, I just think that running in the direction of spin would give you the same effect of going over the peek of a roller coaster where you would feel the drop of artificial gravity, or in other words, you would feel like you are running down hill. Of course for a better "workout" one might suggest that you run in the opposite direction which would give you the effect of running uphill.
I remember being on a spinning amusement ride where I was told to aim my head always into the center of the rotation axis to avoid an unbalance between my right and left ear drums motion senses. By the way I am extremely prone to motion sickness. And I was amazed by keeping my head pointing directly towards the center felt perfectly comfortable. Then I experimented and tried to move my head very slightly right or left and I experienced an instantaneous and very severe motion sickness feeling. Returning my head quickly to center instantly eliminated the motion sickness feeling. And keeping my head facing towards center but moving only my eyes to the side did not cause a discomfort feeling.
My guess is that unless the spaceship ship is literally tens of miles in diameter, the human body's balance sense would detect the motion sickness feeling from the Coriolis Acceleration effects. I would guess by just walking around along a "jogging path" tangential to the axis of rotation there would be no feeling of motion discomfort. But simply looking to the right or left one would sense this feeling of discomfort. So picture it.... lying in bed on the space ship with your face pointing to the ceiling would be comfortable, but turn on one's side and you might choke on your own motion sickness vomit while sleeping.... Dangerous!
My guess, is that all the ship occupants would prefer to live in the zero g areas, and only go to the gravity sectors for exercise. Those astronauts in the ISS seem very comfortable. My guess is therefore you would have to force the travellers on some futuristic space ship with artificial gravity to stay in the artificial gravity fields, and then lock off the zero g sections, else people will just not hang out on their own free will in the discomfort zones of the artificial gravity areas.
I remember being on a spinning amusement ride where I was told to aim my head always into the center of the rotation axis to avoid an unbalance between my right and left ear drums motion senses. By the way I am extremely prone to motion sickness. And I was amazed by keeping my head pointing directly towards the center felt perfectly comfortable. Then I experimented and tried to move my head very slightly right or left and I experienced an instantaneous and very severe motion sickness feeling. Returning my head quickly to center instantly eliminated the motion sickness feeling. And keeping my head facing towards center but moving only my eyes to the side did not cause a discomfort feeling.
My guess is that unless the spaceship ship is literally tens of miles in diameter, the human body's balance sense would detect the motion sickness feeling from the Coriolis Acceleration effects. I would guess by just walking around along a "jogging path" tangential to the axis of rotation there would be no feeling of motion discomfort. But simply looking to the right or left one would sense this feeling of discomfort. So picture it.... lying in bed on the space ship with your face pointing to the ceiling would be comfortable, but turn on one's side and you might choke on your own motion sickness vomit while sleeping.... Dangerous!
My guess, is that all the ship occupants would prefer to live in the zero g areas, and only go to the gravity sectors for exercise. Those astronauts in the ISS seem very comfortable. My guess is therefore you would have to force the travellers on some futuristic space ship with artificial gravity to stay in the artificial gravity fields, and then lock off the zero g sections, else people will just not hang out on their own free will in the discomfort zones of the artificial gravity areas.
Back in the '70s we had a space station with many of these properties. It was sort of cylindrical and an astronaut could (and sometime did) do laps around the circumference. This space station was called Skylab, and you can probably find videos of in online or at some Air and Space / NASA museums.
Use of the word gravity here simply refers to the apparent effect, not the underlying forces and principles involved. Oddly enough, because of this, most people do not realize how important an atmosphere (any gas/plasma) is in an artificial gravity situation. Imagine this scenario:
A cylindrical craft is launched and begins an interplanetary voyage. If there is a clear area on the inner circumference of the craft, a suited astronaut (before the craft has started rotating) could evacuate the atmosphere, place himself at a stationary point inches from the wall in this area and then have the craft begin rotating. The astronaut would simply remain floating inches from the spinning wall.
The reason for this is simple. This type of artificial gravity relies on the exact same principle as the rocket did to take off and accelerate. Transfer of Momentum. The rotating craft has a certain amount of energy invested in it by the rotational thrusters. In a vacuum (inside and out), there is no medium that can transfer this energy to any other object that is not in direct physical contact with the rotating portions of the craft. No transfer, no movement. Any particle that has energy and can interact with matter can transfer momentum. And a gas, while not the most efficient means, has an big advantage in that it occupies a larger volume at a given density than a solid.. Each gas atom that contacts the spinning wall, picks up momentum. Each gas particle that collides with an energized one transfers a portion of that momentum. The end result is that the craft loses a little momentum to the air, which in turn, is now imparting that momentum to any object it comes in contact with. And since the momentum in any portion of the rotating craft will be towards the closest wall, you will move in that direction faster and faster since the gas will get denser the closer you get (remember, the momentum the gas has will cause it to move towards the wall as well which raises the density) and the more gas particles impacting you, the more momentum, and the faster you move. In a small craft, the density changes would be negligible and your rate of fall would not perceptibly change before you contacted the wall. In a large craft (such as a hollowed out asteroid tens of kilometers across, the pressure changes would be such that there will be an area in the center where pressure drops towards vacuum and apparent gravity to zero (no gas to transfer momentum). Incidentally, a small craft will require more frequent rotational thruster bursts since the amount of energy invested in the craft is negligible, and momentum will be bled off quickly by friction in the internal atmosphere. A large craft has so much mass invested in in the craft itself, that the momentum bleed off will negligible.
Once you've contacted the wall, you will acquire the same momentum it has. In order to leave the wall, you would need to somehow shed this energy in order to get airborne. I suppose if the craft is large enough, you could employ a lift or ladder, but on a small craft, there will not be enough pressure change to create a central vacuum to float in.
Please note that I left out the whole sideways vector responsible for most of the problems people would experience in a small rotating craft to simplify the explanation.
A cylindrical craft is launched and begins an interplanetary voyage. If there is a clear area on the inner circumference of the craft, a suited astronaut (before the craft has started rotating) could evacuate the atmosphere, place himself at a stationary point inches from the wall in this area and then have the craft begin rotating. The astronaut would simply remain floating inches from the spinning wall.
The reason for this is simple. This type of artificial gravity relies on the exact same principle as the rocket did to take off and accelerate. Transfer of Momentum. The rotating craft has a certain amount of energy invested in it by the rotational thrusters. In a vacuum (inside and out), there is no medium that can transfer this energy to any other object that is not in direct physical contact with the rotating portions of the craft. No transfer, no movement. Any particle that has energy and can interact with matter can transfer momentum. And a gas, while not the most efficient means, has an big advantage in that it occupies a larger volume at a given density than a solid.. Each gas atom that contacts the spinning wall, picks up momentum. Each gas particle that collides with an energized one transfers a portion of that momentum. The end result is that the craft loses a little momentum to the air, which in turn, is now imparting that momentum to any object it comes in contact with. And since the momentum in any portion of the rotating craft will be towards the closest wall, you will move in that direction faster and faster since the gas will get denser the closer you get (remember, the momentum the gas has will cause it to move towards the wall as well which raises the density) and the more gas particles impacting you, the more momentum, and the faster you move. In a small craft, the density changes would be negligible and your rate of fall would not perceptibly change before you contacted the wall. In a large craft (such as a hollowed out asteroid tens of kilometers across, the pressure changes would be such that there will be an area in the center where pressure drops towards vacuum and apparent gravity to zero (no gas to transfer momentum). Incidentally, a small craft will require more frequent rotational thruster bursts since the amount of energy invested in the craft is negligible, and momentum will be bled off quickly by friction in the internal atmosphere. A large craft has so much mass invested in in the craft itself, that the momentum bleed off will negligible.
Once you've contacted the wall, you will acquire the same momentum it has. In order to leave the wall, you would need to somehow shed this energy in order to get airborne. I suppose if the craft is large enough, you could employ a lift or ladder, but on a small craft, there will not be enough pressure change to create a central vacuum to float in.
Please note that I left out the whole sideways vector responsible for most of the problems people would experience in a small rotating craft to simplify the explanation.
One thing I noticed about the running fast and feeling weightless idea, according to the prior post for 1g of gravity, the "cylindrical surface" would have to be 1/2 mile large and traveling at 1 turn per minute. This equates to around 90 mph. That's a heck of a sprint.
There have been a lot of good, thought provoking topics brought up and putting them all together... Imagine, floating inches off the surface as it is wizzing by you at 90. It'd be great till that wayward chair/desk/computer/trashcan/(insert object here) came along, or until the 90 mph air resistance caused you to "fall" to the rapidly moving floor to a much more dramatic and possibly comical end...
Ouch
ooof
ow
eek
errk
etc...
There have been a lot of good, thought provoking topics brought up and putting them all together... Imagine, floating inches off the surface as it is wizzing by you at 90. It'd be great till that wayward chair/desk/computer/trashcan/(insert object here) came along, or until the 90 mph air resistance caused you to "fall" to the rapidly moving floor to a much more dramatic and possibly comical end...
Ouch
ooof
ow
eek
errk
etc...
The thought of rubbing a surface that's moving at 90+ mph is a little nerve-racking.
Something I once heard from a professor when I was in college was that the human body (particularly our bones) require the constant force of gravity in order to stay healthy over long periods of time. He stated that the bone density would decrease similar to someone with osteoporosis. Since pseudo gravity is just an effect, it is not a constant force like that of actual planetary gravitation. I've always thought that astronauts still experience this gravitational force, but it's faked out by the centrifugal motion of being in orbit. Therefore, the current astronauts may lose muscle mass due to the exercise issue, but their bone density remains healthy.
Does anyone know if this is correct and how the human body would react to interstellar-type travel where the nearest gravitational field would be somewhat negligible due to the distance from a large body? I would suspect that even the pseudo gravity from a spinning spacecraft would not help certain physiological conditions (assuming that my above statement is correct).
Something I once heard from a professor when I was in college was that the human body (particularly our bones) require the constant force of gravity in order to stay healthy over long periods of time. He stated that the bone density would decrease similar to someone with osteoporosis. Since pseudo gravity is just an effect, it is not a constant force like that of actual planetary gravitation. I've always thought that astronauts still experience this gravitational force, but it's faked out by the centrifugal motion of being in orbit. Therefore, the current astronauts may lose muscle mass due to the exercise issue, but their bone density remains healthy.
Does anyone know if this is correct and how the human body would react to interstellar-type travel where the nearest gravitational field would be somewhat negligible due to the distance from a large body? I would suspect that even the pseudo gravity from a spinning spacecraft would not help certain physiological conditions (assuming that my above statement is correct).
Of course, the real question is missing
Do we have to be earth like?
Seriously, it might be only 1/10 G that will allow man to overcome all of the effects that we see in microG envs.
we will not know until we do some RD via a centrifuge at the ISS.
Of course, I am being such a killjoy, on a good question. Love the posts. It has been decades since I have thought about some of this.
I am now trying to figure out if it is clarifying the effect, or simply a lack of recalling. Both sux.
Do we have to be earth like?
Seriously, it might be only 1/10 G that will allow man to overcome all of the effects that we see in microG envs.
we will not know until we do some RD via a centrifuge at the ISS.
Of course, I am being such a killjoy, on a good question. Love the posts. It has been decades since I have thought about some of this.
I am now trying to figure out if it is clarifying the effect, or simply a lack of recalling. Both sux.
That's what I always say whenever the topic comes up. All the places we are tentatively planning to explore (the Moon and Mars) are all less than 1g as well. I've never been able to find the minimal amount of gravity needed though. By minimal amount I mean the amount it would take to be able to accomplish most tasks in more or less the same way we do them on Earth. Sleeping on the floor, throwing things, being able to run water, etc. Even a tiny amount of gravity would probably be a big convenience.
We also know for sure that humans can live in 0g without any permanent damage for at least 438 days (Valeri Polyakov), so astronauts on a station with even some artificial gravity would be able to stay for years at least.
Check out: http://en.wikipedia.org/wiki/Stanford_torus "The Stanford torus is a proposed design[1] for a space habitat capable of housing 10,000 to 140,000 permanent residents..."
and Space Colonization: http://en.wikipedia.org/wiki/Space_colonization
and Space Colonization: http://en.wikipedia.org/wiki/Space_colonization
I'm not sure how you can neglect the effect of the air. The air will be spinning with the entire craft (unless the craft was just caused to start spinning) and the ball will likewise approach the same rate of rotation. to an outside observer, the ball will move outward in a spiral.
To the original question, the ball starts in the hand of a person standing on the wall ("floor") of the spinning craft, therefor the ball is spinning at the same rate as the craft. It will fall to the "floor". As someone else mentioned, it won't fall straight down because of the Coriolis effect.
It just occurred to me that the Coriolis effect probably also means that the the occupant will lean somewhat in the spin-ward direction, and walking in that direction would feel like going uphill. If I'm right, the ball will roll around the ring forever in the direction opposite the craft's spin. This "virtual slope" could be countered by making the floor actually slope in the opposite direction. Anyone have any thoughts on this?
The ball would simply fall down to the ground, but without acceleration to the ground. Becouse while your spinning, the fall is depending on how fast your spinning and when you then release it, it will have the same spin as you, no gravity to accelirate it in mid air, or no tutching of the metal floor, the ball will fall in one speed down, how fast depends on the spin!
Artifical gravity don't really work the same way as gravity does on objects, and it's really not a force, it's just way things are! =)
Artifical gravity don't really work the same way as gravity does on objects, and it's really not a force, it's just way things are! =)
That is if you have a force that stops the ball from the spin it has as you have as the one that is realesing it, if you just realese it, it wants to go down! Ever heard of a slingshot????MeteorWayne":3a465fm0 said:I think you're wrong there Fallingstar. Imagine the ball has it's eyes closed. It isn't aware that the walls are spinning, so it would just float.
The merry ground analogy fails because there is a floor to the merry ground that is spinning as well as the edges, so the ball would move. In the rotating ring, the ball isn't in contact with anything, so is not affected by the spinning walls.
Good thought experiment.
Who's up next?
Though it wouldnt accelerate! Just fall down with the spin it had! But if you would give it a small push up, it would be floating, becouse you then would give it the energy it needs to not fall.
There is no easy way to explain, the biggest thing here that would help you is that if you use the brain!
You totally right! =)rreilly656":37slhf45 said:
The futher down out in the rotation you go, the heavyer you get, so the ball would have less weight then your feet, and just fall to slow to go down to your feet.
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