Earth-Space Web

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!