Question orbital Elevators and satellites/moons/space debris

Mr Martian

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Okay so first off let me start by apologizing if this post is in the wrong section.

So I have been thinking about the real-world implementation of Orbital Elevators/space elevators and I just don't see how one could be constructed and maintained without it being constantly bombarded by orbiting satellites and space debris, let alone if one was to be constructed on Mars in the more distant future, eventually Phobos would collide with it's "stem". I can't seem to be able to find much information on this issue, let alone think of a solution, so If anyone has any sources/knows anything I would love to hear :cheers:
 

Izack

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During the course of Red Mars (or was it Green Mars?) there is an explanation of how the Martian elevator oscillates North-South in such a pattern as to always avoid Phobos. I'm not sure how feasible that would be in reality (well, if we're going to talk about feasibility, it should be noted that space elevators may not be possible at all) but it stands up well enough in a sci-fi novel.

I'm not sure sure how debris would be avoided. The tether would have a little too much inertia for sudden manoeuvres less than weeks in advance. I suppose debris control would be a much more serious issue in such a future.
 

Urwumpe

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Moving the elevator is possible... Remember, nobody said that a elevator must be at the equator and perfectly vertical - it just makes it easier to build the elevator. The harder you make building the elevator, the more options you get to avoid moons.

Debris on the other hand is a much worse problem. If you can clear the orbit of the big debris though, you can make the space elevator gracefully degrade, so that replacing tethers after some age is possible.
 

martins

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What about having two tethers based north and south of the equator, converging to a common anchor asteroid? That way, the moon could pass between them.

Of course that would induce transversal forces, so may have even higher requirements for the tethers than just incredible tensile strength.

May be interesting to figure out what would happen when one of the tethers breaks.
 

Urwumpe

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May be interesting to figure out what would happen when one of the tethers breaks.

Alone thinking about how a tether n degrees north or south of the equator would look like in its equilibrium is interesting enough for a small simulation project.

Should be pretty curvy because of spherical gravitation and cylindrical rotation.

Hey... I still need something to learn C#... :thumbup:
 

Ravenous

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...so If anyone has any sources/knows anything I would love to hear
Arthur C Clarke's "3001" has a pretty wild version. By then there are equatorial towers, not just elevators. They are joined at the top by a giant ring - most of it unpopulated and it's at zero gravity. All lunar or interplanetary trips launch from there. (All pretty far fetched I know.)

Simply, once that's available, there's no need for satellites at all... :lol:

EDIT: and as for Phobos, demolish it for the building material. (We've done far worse.)
 
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garyw

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Didn't something like this happen in Red Mars as well? They tethered phobos to the elevator and when terrorists destroyed the elevator the force of the planets rotation "released" phobos like something out of space 1999.......

The description of how the tether came down was interesting though because I recall one line that said something like "and the sound didn't stop, the tether just kept falling, and falling" which just emphasised how long this thing was.
 

Hielor

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Maybe laser guns to vaporize any incoming debris or satellites? :p
 

martins

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Actually, come to think of it, my two-tether solution would probably not work, since the tethers would bend into the equatorial plane (the normal component of the gravitational force for each line segment is towards the equatorial plane), so pretty soon the two tethers would be so close together as to make no difference to a single equator-mounted one. Shame, another multi-billion buck patent idea gone bust ... :lol:

I suspect the same will happen for Urwumpe's single off-axis tether idea. At equilibrium, it would also bend into the equatorial plane, so at interesting altitudes the difference to an equatorial one may not be significant. But I'll leave it to your C# code to test this hypothesis.
 

Urwumpe

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I suspect the same will happen for Urwumpe's single off-axis tether idea. At equilibrium, it would also bend into the equatorial plane, so at interesting altitudes the difference to an equatorial one may not be significant. But I'll leave it to your C# code to test this hypothesis.

I suspect the same, but then, I expect some interesting dynamic behavior - the CoG of the elevator should move like an satellite in Earth orbit that is pulled by a constant force (by the lower tether) - the stable solution should be interesting.

But then, I really started learning C# four days ago, give me some time. :thumbup:

What to expect in mathematics:

http://gassend.net/spaceelevator/3rd-conference-notes/OffEquator-Talk.pdf
 
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Dantassii

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I once thought it would be a neat idea to run one of those space elevators from the surface of the moon to the L1 Lagrange Point.

Combine this with a GEO space elevator and a trip from the Earth to the Moon involves 2 elevator rides and a short hop in a space-only vehicle to get you between them.

'course there was also the idea of an underground monorail-like mag-lev train that goes around the equator of the moon to help you get places once you've arrived...

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Astro SG Wise

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I got to agree with you Mr. Martian, I think that Space Elevators are crazy, and even if given enough time, I don't really think they are feasible. Of course, it is possible the physics works out, but mechanically, the building process may not work. That's just me, besides, it feels like is a cheat on the real thing, space flight. Anyway, that just my opinion. ;)
 

fsci123

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You could alter the orbit of Phobos to match a 2:1 resonance with Mars rotation. Or you could eliminate the ideal of a traditional space elevator and use Phobos as an anchor for a hypersonic skyhook that skims the outer Martian atmosphere.
 

PhantomCruiser

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Given enought time (and money) I'm sure nano-construction bots could make buckeyball tubes strong and light enough to make a space elevator. I'm also pretty sure that by the time we reach that tech level, it'd be useless (maybe).

Does make for some pretty good visuals (anyone seen Postcards from the Future?)
 

MattBaker

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Given enought time (and money)

Given enough time everything not violating the laws of physics can be done and I don't think space elevators have a problem with our current understanding of physics? Just with costs, practicality etc.

And given enough time and money even some (some not all, and probably not the spectacular things) stuff currently violating the laws of physics will be done because we're not omniscient and figured out everything about physics.
 

francisdrake

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I imagine each and every satellite orbiting at any inclination, with an orbit altitude below the counterweight, would sooner or later crash into a space elevator. A satellite passes the equator twice per orbit. So, given the satellite's cross section and the target's cross section (elevator cable diameter) we could calculate a mean time between impacts.

Active collision avoidance maneuvers could reduce the likeliness of collisions, but even small debris can do a lot of damage to a cable.
 
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