Artificial gravity

[chad_tukes]

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yeah, centrifuge---not only would it make my head spin right round right round, but it also would make me vomit for a week.

[rodsky]

yeah, centrifuge---not only would it make my head spin right round right round, but it also would make me vomit for a week.

Inside a cetrifuge on earth, say, a carnival ride, you will indeed vomit if you're prone to vertigo, because there is a disparity between what you feel (i.e. the tug of gravity on your side, and the tug of the sideward force) and what you see (the horizon in an incorrect position).

However, in space, there is no up nor down, thus the sensation of "forced orientation" from the proper orientation (i.e. earth's horizon) is not felt, thereby not inducing vertigo--what you feel to be down will always be down--no disorientation...which means, it won't make your head spin, nor will it make you vomit.

To illustrate this further...

...you are now sitting in a chair, reading this post, yet you don't know you're going around and around at 1,600 kilometers per hour, because the earth is rotating like a top, on its axis. Furthermore, the earth is going around the Sun at a speed of 29.8 kilometers per second, which translates to 107,280 kilometers per hour! Pero my question is, can you feel this motion? And are you getting sick and want to vomit now, because of this motion?

So if you're in a centrifugal capsule that creates artificial gravity on a large spacecraft enroute to say, Mars, you won't feel a thing--the only thing you will feel, is the comfortable tug of force on your feet (what you interpret as "gravity") that makes all things in your room stay down and not float away.

-RODION

[KASAAC]

I've heard of this artificial gravity na sa discovery channel

[rodsky]

hmm, lets see..

force of gravity exerted to me F = gm (g=9.81 m/s^2), my mass m=63.5kg, therefore F=623kg m/s^2.

Also, F=G(m1)/r *m, where m1=mass of object, r=distance of object to my body(say 1 meter), G=grav constant 6.6742x10^-11, m=my mass, solving for m1.. therefore m1=220,498,867,775.47 kg. This mass needs to be directly under you and say in a 1m by 1m square. so lets say thickness of this plate is 0.5m, therefore volume is 0.5 m^3, so the density of this gravity plate on the floor of your ship should be (D=m/V) like 440x10^9 kg/m^3 to have at least one gravity like earth on your ship. its like forcing 440,000,000 liters of water into a 1 liter bottle.. hmmmm.

Earth's gravity - Wikipedia, the free encyclopedia

Is my calc correct?

You calculation is correct. However, there is a flaw in the reasoning that, given such density, you can actually build a ship that can house the floor. This is what's going to happen...

a) First, due to the fact that the floor has a density of 40x10^9 kg/m^3, it means it exerts a pull, not only to you and your crew, but the entire ship. Now, you have to assume that the ship itself is made of material that can withstand the bizarre stress involved with having an object (i.e. your floorplate) exert a 1G pull on it FROM all sorts of CRAZY ANGLES, and not only one direction (because the ship effectively wraps around the floorplate). To withstand such forces, then the metal used on the ship itself would have to be very dense, to prevent from buckling under the extreme stresses caused by the floorplate. Which would mean the ship would be tremendously heavy...

b) And speaking of heavy, I forgot to mention that, if you have an object with the same density as the earth, then it would also "weigh" the same as the earth, which gives you a problem--how do you "push" a spacecraft weighing as much as the earth across space? You would need an insane amount of thrust, which would mean an impossibly huge engine.

c) And supposing that indeed, you managed to build this spacecraft, with it's colossal engine working, and being able to push the thing across space...since the 1G is being exerted by the ship as it passes through a system, it could potentially cause a lot of problems because its gravitational influence could affect the orbits of nearby planets, asteroids, and comets. The residents of a nearby planet certainly wouldn't allow you to enter the system

-RODION

[neoraising]

You calculation is correct. However, there is a flaw in the reasoning that, given such density, you can actually build a ship that can house the floor. This is what's going to happen...

a) First, due to the fact that the floor has a density of 40x10^9 kg/m^3, it means it exerts a pull, not only to you and your crew, but the entire ship. Now, you have to assume that the ship itself is made of material that can withstand the bizarre stress involved with having an object (i.e. your floorplate) exert a 1G pull on it FROM all sorts of CRAZY ANGLES, and not only one direction (because the ship effectively wraps around the floorplate). To withstand such forces, then the metal used on the ship itself would have to be very dense, to prevent from buckling under the extreme stresses caused by the floorplate. Which would mean the ship would be tremendously heavy...

b) And speaking of heavy, I forgot to mention that, if you have an object with the same density as the earth, then it would also "weigh" the same as the earth, which gives you a problem--how do you "push" a spacecraft weighing as much as the earth across space? You would need an insane amount of thrust, which would mean an impossibly huge engine.

c) And supposing that indeed, you managed to build this spacecraft, with it's colossal engine working, and being able to push the thing across space...since the 1G is being exerted by the ship as it passes through a system, it could potentially cause a lot of problems because its gravitational influence could affect the orbits of nearby planets, asteroids, and comets. The residents of a nearby planet certainly wouldn't allow you to enter the system

-RODION

as for the material,carbon nanotechnology is a good start..its structurally strong but it is light..and if you're talking about long distance space travel, i assume traveling at the speed of light?..coz the gravity inside the spacecraft would be VERY big to counteract with earth-based materials..i think the answer to that lies in the Large Hadron Collider..hehe

[rodsky]

as for the material,carbon nanotechnology is a good start..its structurally strong but it is light..and if you're talking about long distance space travel, i assume traveling at the speed of light?..coz the gravity inside the spacecraft would be VERY big to counteract with earth-based materials..i think the answer to that lies in the Large Hadron Collider..hehe

Good observations, but it has nothing to do with the previous discussion on the density of the floorplate. If however, you raised the point of carbon nanotechnology as a substitute for the material of the floorplate/ship hull, it would still be a null suggestion, because the density of the said material HAS TO BE the same, to attain the 1G force, and the arguments I presented earlier will still be in effect.

-RODION

[randzg]

You calculation is correct. However, there is a flaw in the reasoning that, given such density, you can actually build a ship that can house the floor. This is what's going to happen...

a) First, due to the fact that the floor has a density of 40x10^9 kg/m^3, it means it exerts a pull, not only to you and your crew, but the entire ship. Now, you have to assume that the ship itself is made of material that can withstand the bizarre stress involved with having an object (i.e. your floorplate) exert a 1G pull on it FROM all sorts of CRAZY ANGLES, and not only one direction (because the ship effectively wraps around the floorplate). To withstand such forces, then the metal used on the ship itself would have to be very dense, to prevent from buckling under the extreme stresses caused by the floorplate. Which would mean the ship would be tremendously heavy...

b) And speaking of heavy, I forgot to mention that, if you have an object with the same density as the earth, then it would also "weigh" the same as the earth, which gives you a problem--how do you "push" a spacecraft weighing as much as the earth across space? You would need an insane amount of thrust, which would mean an impossibly huge engine.

c) And supposing that indeed, you managed to build this spacecraft, with it's colossal engine working, and being able to push the thing across space...since the 1G is being exerted by the ship as it passes through a system, it could potentially cause a lot of problems because its gravitational influence could affect the orbits of nearby planets, asteroids, and comets. The residents of a nearby planet certainly wouldn't allow you to enter the system

-RODION

Thank you rodsky for enlightening me on this. I now see some of the flaws of my assumptions. But I'll try to put in some other ideas and i'll try to correct these flaws:

a. Indeed these "gravity plates" (shall we call it that for now?) will be exerting gravity all over the ship, but if it is, structural engineers can design the ship to withstand these forces, they've been designing 1G forces on earth for years. And it might actually be beneficial to the structure of the ship because space has vacuum pressure-so this tends to pull out the structure of the ship while the gravity tends to pull it back in, the net pressure (vacuum pressure minus gravity pressure) should be lesser than one without the other force. So in effect we might have a lighter ship?

b. Also this gravity plate does not have the density of the earth because the r distance is only 1.0 meters in my assumption (i assumed human to be like 2 meters tall for faster calcs), and not the radius of the earth (r is the centroid distance of the object). Go like another 3 meters away from the plate and gravity might be reduce like half or more? Indeed momentum equations depends on mass of these objects to move. So i guess thats gonna be a problem - but it can move, only slower.

c. Well, the equation suggests that if i move like 3 meters away from the plates that reduces the gravity by half already. So i dont think it is gonna have a gravity cone like a planet but a size of the star ship enterprise or a millenium falcon.

What do you think?

[neoraising]

its very hard to make artificial gravity with earth-based materials that i think the answer lies in the other fundamental forces like electromagnetism,strong force and weak force since gravity is the weakest of the four..i think a very powerful electromagnet is doable but it would be very big and it would need a lot of energy..

the one with great hope would be in the strong force and weak force which hold the atom together..that's why i said the answer may lie in the Large Hadron Collider since they always experiment with exotic materials and elementary particles..perhaps they can harness the power of gluons and gravitons?

[rodsky]

Thank you rodsky for enlightening me on this. I now see some of the flaws of my assumptions. But I'll try to put in some other ideas and i'll try to correct these flaws:

a. Indeed these "gravity plates" (shall we call it that for now?) will be exerting gravity all over the ship, but if it is, structural engineers can design the ship to withstand these forces, they've been designing 1G forces on earth for years. And it might actually be beneficial to the structure of the ship because space has vacuum pressure-so this tends to pull out the structure of the ship while the gravity tends to pull it back in, the net pressure (vacuum pressure minus gravity pressure) should be lesser than one without the other force. So in effect we might have a lighter ship?

b. Also this gravity plate does not have the density of the earth because the r distance is only 1.0 meters in my assumption (i assumed human to be like 2 meters tall for faster calcs), and not the radius of the earth (r is the centroid distance of the object). Go like another 3 meters away from the plate and gravity might be reduce like half or more? Indeed momentum equations depends on mass of these objects to move. So i guess thats gonna be a problem - but it can move, only slower.

c. Well, the equation suggests that if i move like 3 meters away from the plates that reduces the gravity by half already. So i dont think it is gonna have a gravity cone like a planet but a size of the star ship enterprise or a millenium falcon.

What do you think?

Very good points. However, I still cannot picture a device that has tremendous density, yet loses its influence at a mere 3-4 meters away.

-RODION

[randzg]

Very good points. However, I still cannot picture a device that has tremendous density, yet loses its influence at a mere 3-4 meters away.

-RODION

Please take a look at my calculation:

1. First, i need to correct a calculation error on the first page. m1 = 1.47x10^11 kg instead of 2.20x10^11 kg. So the actual mass needed is lesser now. sorry about that. All else is correct.

2. Mass of object remains the same, where ever you go. It is only the weight of the object that changes.

3. So from the equation of F=G(m1)/r^2 *m, the only change there if we go up about say, 4 meters, is the r, centroidal distance between 2 bodies and F. So we need to solve for the new F at 4 meters away (r=4.0m).

4. So new F = 6.6742x10^-11 x (1.47x10^11)/(4.0^2) * 63.5 = 38.94 kg m/s^2 or 38.94 Newtons or 8.75 lbs. The original F when you are directly on top of the plate (with r=1.0m) is F=623kg m/s^2 or 623 newtons or about 140 lbs, my actual weight.

Conclusion: basing from the equations, when you go up like just 4 meters, your new weight now is only about 8.75 lbs as compared when you are 1 meter away which is 140 lbs. I cant quite imagine this myself but i computed this about twice now and i am convinced that this computation is correct. Please share your thoughts on this.

So this might actually work. So when you build a ship with gravity plates just distance the decks like 8 meters clear every floor. And directly below the grav plate you'll have another corridor that is a mirror on the other one "above".

But the real question now is... how do you put 220,000,000 liters of water into a 1 liter bottle?