Originally posted by Mexico Firstly I know the practicalities of this are ridiculous. But I asked my physics teacher in school and Never got a satisfactory answer. Then I forgot to ask one of my physics lecturers in college, and then dropped physics for geology anyway.
If one was to build a ring shaped object with a diameter 1 meter longer than the Earths Diameter (Taken as a consta ...[text shortened]... ure about the hovering in the first place, It seems like such a weird Idea in the first place.
First of all, the Earth is not smooth, so it would get stuck on the mountains.
Second, any small bump would disturb the equilibrium; I think it would be an unstable equilibrium, but I don't want to try to prove it.
I've seen this sort of problem before and it turns out that it's going to be so close to the Earth that it might as well be touching anyway.
Originally posted by wolfgang59 Theoretical problems often have practical implications. Someday in the future huge rings may be built surrounding moons and planets!
In reality rings do exist around planets, and do manage to hover there...but they're not all made of one piece.
Originally posted by FabianFnas I don't think so. Unless theyhave a expensive orbit correction devise at the same time. And what is the point of having such a ring?
In the future, polo will be played from saddles hung below the gargantuan Fruit-Eating-Tusked-Wallampoo. The polo stick is replaced by super powered versions of that gravity gun in Half-Life 2. Planets will be used as the ball.
Originally posted by AThousandYoung In the future, polo will be played from saddles hung below the gargantuan Fruit-Eating-Tusked-Wallampoo. The polo stick is replaced by super powered versions of that gravity gun in Half-Life 2. Planets will be used as the ball.
Shortly after posting this i did the math, the difference in diameter would have to be a lot bigger than 1m for it to make any kind of difference.
I can think of many uses for a stable man made torus around the earth. Maybe not right now, but if one could connect it to ground (Again with the ridiculous impracticality and need for several breakthroughs in material sciences) you could cut out the need for the vast quantities of rocket fuel used in space exploration. Also it would end up being pretty god damn big, so could solve our ever increasing population problems.......
And you could build a massive steam powered, garlic Ice cream factory up there............😛
Originally posted by Mexico Shortly after posting this i did the math, the difference in diameter would have to be a lot bigger than 1m for it to make any kind of difference.
I can think of many uses for a stable man made torus around the earth. Maybe not right now, but if one could connect it to ground (Again with the ridiculous impracticality and need for several breakthroughs in mat ...[text shortened]...
And you could build a massive steam powered, garlic Ice cream factory up there............😛
Sounds like you're drifting in the direction of the Space Elevator. It's basically a tethered satellite used to make it easier to get stuff into space.
Yea and very Aurthur C Clarke ish at that. Its not quite what I was getting at, simply stating that if it could be done, there are many many uses for it..... Come on Orbital Zero G Ice Cream Factory.....
However in all practical terms it can't be done, for several reasons, even without topography the earth isn't a sphere, and its gravity isn't consistent everywhere, and the volume of raw materials required would be obscene and it would cost more money than is currently in existence and....... etc etc etc..... It is a rather interesting Idea none the less though...
Originally posted by Mexico Yea and very Aurthur C Clarke ish at that. Its not quite what I was getting at, simply stating that if it could be done, there are many many uses for it..... Come on Orbital Zero G Ice Cream Factory.....
However in all practical terms it can't be done, for several reasons, even without topography the earth isn't a sphere, and its gravity isn't consistent ...[text shortened]... existence and....... etc etc etc..... It is a rather interesting Idea none the less though...
If you make the ring from materials harvested in space, make it bigger, and give it regular stress-relief sections, it could work - especially if you attach it to the Earth so it doesn't have to actually orbit.
Originally posted by AThousandYoung First of all, the Earth is not smooth, so it would get stuck on the mountains.
Second, any small bump would disturb the equilibrium; I think it would be an unstable equilibrium, but I don't want to try to prove it.
I've seen this sort of problem before and it turns out that it's going to be so close to the Earth that it might as well be touching anyway.
First point obviously right, so we're obviously only talking about an ideal case.
Second one - I actually think it would be stable. Imagine a small perturbation to this equilibrium position. You can perturb it in two ways.
- Rotation about the centre - it would still be hovering at the same height. Therefore this is neutral equilibrium.
- Move the centre of the ring away from the centre of the Earth. Then the net effect of gravity would be to pull it back to the centre. So you've got stable equilibrium w.r.t. this perturbation.
This contrasts with the case of a pole standing on it's end mentioned earlier. Here, if there's a perturbation gravity acts to increase the perturbation, so it's unstable.
Originally posted by mtthw First point obviously right, so we're obviously only talking about an ideal case.
Second one - I actually think it would be stable. Imagine a small perturbation to this equilibrium position. You can perturb it in two ways.
- Rotation about the centre - it would still be hovering at the same height. Therefore this is neutral equilibrium.
- Move the ...[text shortened]... ere, if there's a perturbation gravity acts to increase the perturbation, so it's unstable.
That's how I would have looked at it.
Answering the practicality question, there's all kind of practical applications. Orbital tethers, connected to several such uniform rings would provide cheap and fast transportation to various points in orbit, periodic ion engines or standard chemical rockets would allow for cheap and effective orbital correction thus overcoming the differences between the theoretically perfect system and the practical reality, packages placed at various points containing sensors and equipment would allow effectively geosynchronous orbits where we would no longer be limited to them having to be in an equatorial orbital plane. This would improve satellite GPS and imaging resolution, placement of power relay satellites wherever they're needed. The list goes on.
There would be safety concerns regarding a destabilisation of the orbit, but sufficient safety mechanisms could be designed prior to the system being put into place.
Originally posted by agryson That's how I would have looked at it.
Answering the practicality question, there's all kind of practical applications. Orbital tethers, connected to several such uniform rings would provide cheap and fast transportation to various points in orbit, periodic ion engines or standard chemical rockets would allow for cheap and effective orbital correction thus ...[text shortened]... but sufficient safety mechanisms could be designed prior to the system being put into place.
THANK YOU
Non-equatorial geo-synchronous orbits are something we can think of NOW as a benifit (Forget the costs) possibly constucted of light alloy or carbon fibre between 'nodes' (eg comms satellites)
Non-equatorial geo-synchronous orbits are something we can think of NOW as a benifit (Forget the costs) possibly constucted of light alloy or carbon fibre between 'nodes' (eg comms satellites)
Once this technology goes into full-scale development, nano-reinforced fibres can be made as long as desired as opposed to the few centimetres we currently have. At a knock down price too. Woven into ropes, covalently bonded, such materials already have a greater extensional strength than Kevlar (about 800% more as far as I know! Don't trust me on that though, I can't find the reference).
Interesting article cheers.... Nano fibers and the various other directions nanotech is going are generally quite interesting to follow, mainly because nobody has any real Idea as to what this stuff is really capable of. If these fibers can be woven into high tension cables or used as structural reinforcement then its a pretty serious jump in our materials sciences........
Still no orbital garlic Ice cream factory though....
from the structural engineering perspective, materials under gravity, the compression induced by gravity alone within the torus would be quite high
so much so that instability of the cable/chord/tendon - long things tend to be described as such, would virtually collapse laterally almost instantly
now a sphere over a sphere is a different monster, or space frame or structure created that is limited in both vertical and lateral directions so that buckling is either reduced or severely limited
the best and most efficient bridges are those that are of hollow form - box section, but it is difficult to achieve sectional depths much less than 1/60 th of their spans, after which either deflection - usually down, in this instance either up or down when buckling, or laterally ( 1 km would be a very thin strip in this case ) depending on how many cross linking structures are joined
do like the idea, but the stresses induced are scary, if it were strong enough to carry the compression, it would however work, but instability would no doubt win the day, and fatigue or vibration would exact a significant toll
tension structures work so much more efficiently, use helium ballons !
Odd Question, kind of physics related
02 Feb '08 18:33
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