Synopsis: Build orbiting rings above the Equator at different altitudes, from Low Earth Orbit to beyond Geosynchronous Orbit. Each ring has a special design that lets part of it be stationary relative to the Earth's surface. Connect the stationary parts to each other, and to the ground, with elevator segments. Can be built with existing materials/technology. Very expensive, though....
Background and Details: Building a ring around the Earth has been suggested many times for many reasons, over the years. Physicists would like the biggest possible atom-smasher, for example. A fusion reactor that big might not only be able to "burn" ordinary protium-hydrogen, it could supply all of Earth's electrical power needs until we run out of hydrogen -- we might need that reactor, of course, just to power the neighboring atom smasher! A global network of evacuated tunnels would increase transportation efficiency and dissociate it from the weather -- and some of those tunnels would likely be world-girdling rings. In Space, an orbiting tubular ring, the tube itself being maybe a mile in diameter, could be a habitat (see "topopolis" link). Even a useless and unlikely thing that just hangs there in the sky to be stared at, in gravitational balance, has been suggested elsewhere around here. :)
The particular type of basic Ring that I wish to describe begins with a simple length of steel cable around the Earth, maybe a meter in thickness (like a suspension bridge cable). When in actual orbit (the first Ring being as low as we can manage, perhaps 100 kilometers above the Earth), there are essentially no stresses on this cable. Once completely constructed, we can increase the orbital velocity of this cable, but it will tend to stay in the same orbit as before, simply because it cannot enlarge (much) to encompass a higher orbit. We will be wanting tension on this cable, but we don't want to overdo it.
Before spinning up the cable, we continue the construction process of this basic Ring. Surrounding this cable (therefore also a ring around the Earth) is a sheath containing superconducting magnets. The sheath and the cable at all times are prevented from contacting each other by magnetic forces (on Earth we'd call it "magnetic levitation", but here everything is already levitating in Zero-G!). Attached to the sheath, on the interior or Earth-facing side of the Ring, would be constructed something like a truss, which will give the sheath strength against compressive forces. On the other side of the Ring, we place special shielding, to protect the Ring from micrometeor damage.
When completed, we use Action and Reaction of magnetic forces between the cable in the sheath to speed up the orbital velocity of the cable, while slowing the orbital velocity of the sheath. There is a "multiplication by mass" effect in this, such that the more mass in the cable, compared to the sheath, the less the cable has to be speeded, to match the slowing of the sheath. NOTE that we will actually need to put several parallel cables in the sheath, and that we might not speed up all of them! As the sheath slows, we begin to drop vertical hanging lines toward the surface of the Earth's Equator. Steel cable IS strong enough for 100-kilometer lengths, although it will have to be several times thicker at the Ring than at the ground (we could use other stuff, of course, like Kevlar). When the sheath slows to zero relative velocity and the lines are attached all around the Earth, we will be ensuring that the Ring stays at a constant altitude. The "centrifugal force" of the cable inside the sheath, over and above its prior orbital velocity, will keep this Ring hanging in the sky. The tensile strength of the cable will of course now be doing what we designed it for.
Some of the hanging lines can now be used as elevator cables, for easy access to Space at 100 kilometers of altitude. Others are needed to supply power to the Ring, for operating the elevators, and other things. One of those other things involves the Law of Conservation of Angular Momentum, which will have certain effects as we move mass from the surface of the Earth up to the Ring. LCAM specifies a tendency for the cable-sheath to change its "orbital speed", as mass is moved onto it from the Earth -- and we must compensate for that by adjusting the speed of the cables inside the sheath. This is particularly why extra Ring-cables are going to be needed. There is a limit to how fast we can make a single speeding cable go. NOTE: I haven't examined this part of the idea in a lot of detail yet; there is a possibility that the speeding cable has to be slowed down -- and there is a limit to that, too, of course! Possibly a Ring-cable specifically dedicated to contra-rotation may handle it... Perhaps at some point plain ordinary rocket engines may be needed, to deal with the effects of LCAM. Do note, however, that generally What Goes Up Also Goes Down, so some overall balance will be possible, between cable-speed and LCAM.
The trouble with building just one Ring of this type is that when you take the elevator up, you are just standing there at some high altitude above the Earth. You are most definitely NOT in orbit! You are still standing in the Earth's gravity, and your weight will probably be unnoticably less than normal. Still, it is a useful place to be, for local weather observation, local communications antennae, and other local stuff (you can't study or broadcast to half the Earth from only 100km up). The Ring itself might be a good place to put some fiber-optics lines, for global communications (fibers going up and down the vertical connecting lines, of course). Even a certain amount of astronomy can be done on this Ring, since most of the atmosphere is below the Ring. Not to mention the penultimate skydiving experience, of course! (The ultimate involves shedding orbital velocity while falling. Orbital velocity is not a factor here.)
As originally stated, this Idea is for multiple Rings at different distances from the Earth, all above the Equator. Due to the force of gravitation diminishing with distance, each additional Ring can be significantly farther away from the Earth than the prior Ring, and the same type of elevator cable as before will still work. Remember, each Ring is self-supporting at its own altitude; vertical cables only need to handle the gravity-induced tensile forces between altitudes, by connecting between Rings. We can reach GeoSynchronous Orbit this way, with enough Rings, without the need for such exotic stuff as carbon nanotubes!
When being elevated to the GeoSynchronous Ring, each intermediate Ring might be thought of as being like a Rung on the Biblical Jacob's Ladder. (From a distance, though, this system of Rings and connectors will resemble a giant spider web, with the Earth at the center -- thus the title of this Idea.) When "standing" at the GeoSynchronous Ring, you are truly in actual orbit around the Earth, in Zero Gee. This is the place for manufacturing facilities, a Ring more than 260,000 km long! Perhaps it should be built as a full-fledged topopolis.... Note that this Ring is actually not the best place for Earthly communication purposes; we value it today because it is the only thing offered to us by Earth's gravitation and rotation. Thanks to speed-of-light delays, one of the intermediate stationary Rings, perhaps only 5000km from the surface, will prove to be superior for Eartly communications purposes. Global weather-watching will be easier at such a level, also.
We will want at least one Ring located beyond the GeoSynchronous orbit. See, in every classical Space Elevator scenario, having the extra distance away from the Earth accomplishes two things: It makes it easier to deal with the Law of Conservation of Angular Momentum, and it offers the chance to use the Earth's rotation as a literal sling, to send vehicles to the rest of the Solar System. So, we will want at least one Ring out there, to acquire those advantages. It will be useful for other things also, of course. For example, interferometry-minded astonomers want the largest "baseline" possible between observation locations -- this means they will want observatories on opposite sides of (not to mention other points on) the biggest Ring they can get. And physicists, of course, will want an atom smasher on it!-- Vernon, Sep 11 2003 Topopolis http://en.wikipedia.org/wiki/TopopolisTotally Tubular! [Vernon, Oct 17 2004, last modified Aug 29 2008] Classic space elevator math http://www.zadar.ne...ace-elevator/#WHICHEverything you never wanted to know, heh [Vernon, Oct 17 2004, last modified Oct 21 2004] More classic space elevator stuff http://www.ian-andr...o.uk/ACCspaceE.htmlEverything not mentioned above :) [Vernon, Oct 17 2004, last modified Oct 21 2004] Vacuum Cleaner Vacuum_20CleanerAs mentioned in an annotation, the space around Earth must be cleaned up before this Idea can be implemented. [Vernon, Jul 14 2005] Kinetic Energy Supported Structures to Geostationary Orbit http://www.kestsgeo.com/I disagree with this guy's design, but he has something vaguely similar. [baconbrain, Aug 20 2006] Funding for giant space ring: Granted.-- DeathNinja, Sep 11 2003 The compressive force on a ring 100 km from the surface, but spinning with a period of 24 hours would be very large. I haven’t done the calculation, but I doubt there are any existing materials strong enough.
Also, the relative velocity between the cable and the ring would be about 60000 km/h or greater (if I did that calculation right).-- AO, Sep 11 2003 You realize this concept is not new, yes? Furthermore, you'll need attitude jets on these rings...-- phoenix, Sep 11 2003 AO, by itself, the sheath may very well not be able to support its own weight against gravity. However, remember it is being held up from the inside, by the centrifugal effect of the spinning cable, and the magnetic interactions between the cable and the sheath. Regarding the speed difference, you are indeed neglecting the "multiplication of mass" thing that I described in the Idea. If the sheath surrounds 6 cables, each of which has the same mass as the sheath, then there will be a 6-to-1 ratio of change of speed, when slowing down the sheath and speeding up the cables. See? Now of course the MINIMUM difference in speed will still be orbital velocity (about 8km per second) of the cables within a stationary sheath (stationary relative to Earth's surface), but this does not matter much. The cables are in a vacuum and are magnetically isolated from the sheath. This is by deliberate design, and fundamental to the workings of this Idea.
The worst concern I can think of is meteoroids. At least one of those Rings should be devoted to power plants, radars, computational power, and defenses against everything that might cause damage to this Earth-Space Web.
phoenix, this idea is NOT like Niven's Ringworld. Also, attitude jets are only needed when a Ring like this is NOT firmly attached at multiple points to the ground, as I specifically described here. The Earth's gravity is sufficient to prevent Northward or Southward drifting of the Ring, away from the Equator, and the vertical connecting elevator/power/communications cables keep the Earth in the center of the Ring.-- Vernon, Sep 11 2003 A cable moving at 8 km/s in a strong magnetic field is going to experience eddy currents (assuming the cable is conductive) which will cause severe heating and loss of energy.-- AO, Sep 11 2003 // eddy currents //
Is he anything like Eddy Money?-- DeathNinja, Sep 11 2003 I like it.-- RobertKidney, Sep 11 2003 AO, there is this problem that when someone tries to provide sufficient detail to show that an idea is workable, some nitpicker comes along and talks about some perfectly solvable problem as if it is a problem that nobody will address in the actual design stages of the Idea. I submit that you are making the unwarranted assumption that the magnetic "levitation" fields of this Ring are alone supposed to be directly affecting the tension cables. It doesn't have to be that way. After all, care in the design of maglev trains has meant that eddy currents exist only where wanted (in the linear induction motor, mostly). So, here, in Space, linear induction motots can be used to change the mutual orbital speeds of cables and sheath, but only when the power to those motors is on! A superconductive coating (high-temperature) on the tension cables can provide the means to "levitate" the cables, while preventing eddy currents within the cables. OK?-- Vernon, Sep 11 2003 Fuck Niven, if your ring is stationary relative to the planet it'll fall.-- phoenix, Sep 11 2003 BUT it will rise on the other side, and wobble and stuff, thereby breaking the record for World's Largest Hula-Hoop®.-- thumbwax, Sep 12 2003 phoenix, think about the centrifugal effect of the speeding cables located INSIDE the stationary sheath. They are moving at MORE than orbital speed! AND, the overall Ring can only fall by becoming a smaller-diameter circle! This is prevented by those interior cables!
thumbwax, no, sorry, all those attachment lines are there to prevent such hula-ing.-- Vernon, Sep 12 2003 Vernon, I don’t mean to shoot down the idea, but I am concerned with your assertion that the Earth-Space Web is possible with existing materials and technologies. I don’t think it is because of the very high speeds and forces involved in the device. It is probably true that these problems can be overcome in the design phase, but that would be future technology, not existing technology.
Besides that, I think it’s a good idea.-- AO, Sep 12 2003 AO, no new principles or materials are needed. OK, I might have exaggerated a bit about "existing technology"; if we were using existing Space Shuttles to transport to orbit the material for that first Ring, we'd be at that project for a ridiculously long time. Still it COULD be done that way.... Regarding your concern about the forces and speeds: While the speeds are extreme, the forces are not really. Consider a ten-meter length of the stationary sheath; it has how much mass trying to fall to the ground? Its weight is being supported by ten-meter lengths of several massive super-orbital cables, and I'm sure you will agree it has much less weight than an existing ten-meter maglev car on its supports. So, the only concern is the speeds, and again I think that to OK to imagine these things. Check out the technology invested in "synchrotrons", which casually keep near-light-speed particles under control. So, I think a mere 10-20km/sec (estimated) is quite handle-able, in a maglev sort of way. The neat thing about superconductors is that they represent a kind of dynamically stable continuous perfection. Just what we need to sheathe those speeding cables!
For the really nit-picky person, there is a failure-point for this Idea that does need to be defined. Consider a suspension-bridge cable that is looped into a circle, and has a Radius of 6400km (a bit larger than the Earth). If this circle is spun up like a flywheel until its rim is moving at 10km/sec, well, the circumference of this flywheel is about 40,200km, and so is doing one whole rotation in a little more than an hour (67minutes). Is the cable strong enough not to break? At what speed (or RPM if you prefer) will it break? Thanks! That breaking speed, plus 8km/sec of orbital speed, will be the maximum possible speed for a steel Ring-cable, and certainly its value needs to be known (and it will be different for different-Radius Rings).
Oh, one more thing in favor of this Idea. That same weight of the stationary sheath will count as a kind of "extra strength" for the speeding cables. The cables are trying to break by expanding under the influence of the centrifugal effect, but that expansion is being countered by the weight of sheath, which wants to fall to Earth. So, in addition to the intial 8km/sec that the cables can speed at for free (orbital velocity), there is some additional speed they can safely have, simply because of the weight they are fighting. Perhaps this aspect will turn out to be so perfect a match that we can make the sheath as massive as we like, and we can always safely speed up the cables to hold it off the ground...(within the limits of the maglev fields, of course!).-- Vernon, Sep 12 2003 I'm thinking of a commuter spacecraft towed by one of these cables like a San Fran cable car.-- FarmerJohn, Sep 12 2003 FarmerJohn, that may sound nice, but be careful. I have described two completely different sets of cables in this Idea, and any confusion of the two needs to be avoided. The primary cables are hidden away inside the structure of a Ring, and only interact with the Ring-sheath, partly to ensure that the entire sheath is evenly supported by those primary cables. Meanwhile, the secondary cables are stationary and attach the sheath to the surface of the Earth (or stretch across Space from one stationary Ring-sheath to the next). Elevators using these cables might better be called "cog trains".-- Vernon, Sep 12 2003 ...and in the darkness, bind them.-- 2 fries shy of a happy meal, Sep 12 2003 [Vernon] a big plus for the synopsis, but then a minus for the idea, because I'm buggered if I can see the advantages over a conventional space elevator (apart from the atom smasher for physicists - and everyone knows that physicists are the most useless, limp-wristed, mullet-endowed, corduroy-wearing cheese eaters on the planet, so why the heck (swearword altered for pre-watershed reading) should we help them?)...
Cancels to a neutral vote-- suctionpad, Sep 12 2003 Okay, and magnetic force is going to hold this moving cable in check?-- phoenix, Sep 12 2003 suctionpad, yes, I know that this is a somewhat off-the-wall idea, mostly because of its vast scale, but then this place is the HalfBakery. Still, consider that EVERY Ring in the overall structure is geostationary with respect to Earth, and this has value of its own (communications facilities described in several places). Consider retirement homes on some of the Rings, where distance has diminished Earth's gravity to half (or some other fraction) of the normal value, for example. You can be sure that the longer the idea exists, the more uses for such Rings will be found!
phoenix, yes, I'm pretty sure that our existing superconducting magnet technology is up to this task. Note the amount of weight (force) between cable and sheath, as described in prior annotation to AO. The heaviest loads will be that of the droplines between Rings and ground, and each Ring CAN have enough super-orbital cables to carry those loads.-- Vernon, Sep 13 2003 This sort of thing has been discussed on space-oriented newsgroups forever.
Take a look.-- bdh, Jul 14 2005 Some of the problems I remember people talking about: -low frequency vibrations can develop in the rings, so you need it connected to the ground with many towers at odd spacings. -rings are gravitationally unstable without towers maintaining its position -space junk breaks the ring
On the plus side, you can use just one ring in LEO instead of GEO, ride on it magnetically and let drag accelerate you to orbital velocity.
I think this ends up being another bad version of the Lofstrom Launch Loop.-- bdh, Jul 14 2005 [bdh], the Idea describes many drop-cables connecting the lowest high-altitude ring to the Earth's surface (and between any other ring and its neighbors), and so that should qualify as means to dampen those vibrations, as well as maintain the relationship of the rings to each other. In appearance, the overall Earth-Space Web would resemble an ordinary orb-spider's web. Yes, space junk as currently present in orbit would all have to be cleaned up, before this could be built. I think I have a "vacuum cleaner" Idea around here somewhere for that.
Regarding using the super-orbital cables similarly to the launch loop, that WOULD be a bad idea. Simpler to just directly climb the ring-connecting cables. (I did describe using an outer-most ring, beyond geosync orbit, as a means of putting Earth's rotation to work as a space-ship slinger.)-- Vernon, Jul 14 2005 Well, the Launch Loops is orders of magnitude cheaper, but your version is more halfbakery-compliant. :-P-- bdh, Jul 14 2005 I worked up something similar to this idea from scratch, based on some misunderstanding annotations to the Zero Gravity Monorail. I have some differences from the posted design.
This idea uses super-orbital-speed cables as the "centrifugal mass". There is an annotation somewhere about the possible tension on the cables, which should have revealed an error in the design. Any tension on the interior cables is a waste. I propose a fluid as the centrifugal mass, whether as discrete "cars" on a maglev track, or as particles in a particle accelerator. Bits of the mass could be slowed down and sped up to counter local loads, and to transfer energy from one side of the ring to the other. No tension is possible, so all the energy goes to holding up the structure. Plus, in a catastrophe, the particles go out, instead of leaving a cable to saw the planet.
I also think that only one ring is needed. A maglev car on its top side could serve as a catapult, and launch loads to any velocity, which is to say altitude, including enough fuel to shape the orbit into a round one.
I'll write up the other, more trivial, differences sometime. For now, this idea is feasible, and inspirational. [+]-- baconbrain, Aug 19 2006 random, halfbakery