Moon to Earth tether

Huh?

I think I saw something about this in my inc. or Entrepreneur magazine earlier this summer. Something like a red ribbon elevator.

Didn't understand it at all. All I could focus on is the rotation of the earth and the moon orbit... Earth become a big ball of yarn/ red ribbon.

Will check back to see if I can grasp the concept from further posts.

Simple tethers are quickly cut by micrometeoroids. The lifetime of a simple, one-strand tether in space is in the order of five hours for a length of ten km. Several systems have been proposed to correct this. The U.S. Naval Research Lab has successfully flown a long-term tether that used very fluffy yarn. This is reported to remain uncut several years after deployment. Another proposal is to use a tape or cloth. Dr. Robert Hoyt patented an engineered circular net, such that a cut strand's strains would be redistributed automatically around the severed strand. This is called a Hoytether. Hoytethers have theoretical lifetimes of tens of years. In low Earth orbit, a tether could be wiggled to dodge known pieces of space junk.

Beanstalks and rotovators are currently limited by the strengths of available materials. Although ultra-high strength plastic fibers (Kevlar and Spectra) permit rotovators to pluck masses from the surface of the Moon and Mars, a rotovator from these materials cannot lift from the surface of the Earth. In theory, very high flying, very supersonic aircraft could deliver a payload to a rotovator that dipped into Earth's upper atmosphere briefly at predictable locations throughout the tropic (and temperate) zone of Earth.

Tethers have many modes of vibration, and these can build to cause stresses so high that the tether breaks. Oscillations (also called vibrations or mechanical transients) can be sensed by radio beacons on the tether, or inertial and tension sensors on the end-points.

Mechanical tether-handling equipment is often surprisingly heavy, with complex controls to damp vibrations. The one ton climber proposed by Dr. Walter Edwards may detect and suppress most vibrations by changing speed and direction. The climber can also repair or augment a tether by spinning more strands.

Over a few tens of days, electrodynamic tethers in Earth orbit can build vibrations in many modes, as their orbit interacts with irregularities in magnetic and gravitational fields. Electrodynamic tethers can be stabilized by reducing their current when it would feed the oscillations, and increasing it when it opposes oscillations.

Several conductive tethers have failed from unexpected current surges. Unexpected electrostatic discharges have cut tethers, damaged electronics, and welded tether handling machinery. Disposal of waste heat is difficult in a vacuum, so over-heating may cause tether failures or damage.

An electrically conductive tether can act as an antenna for EMP (electromagnetic pulse) -- a strong, but brief pulse of radio energy.

It may be that the Earth's magnetic field is not as homogeneous as some engineers have believed.

Hi Tryagain: You have been studying tethers. My guess is; all of what you posted is correct. A 380,000 km tether may need 200 climbers that will be very busy if damage from micrometeorites occurs several times per hour. Can the 20 ton elevator cargo climber pass climbers laying thread in both directions by squeezing only one meter of a ribbon 1.3 meters wide, or some such?
If damage occurs at five hour intervals on a ten kilometer tether, repaired spots will average one meter apart after 50,000 hours. That will make a bad vibration ride if the elevator travels a hundred meters per second. Neil

Nice topic Neil. I have a passing interest in which way the Tether debate is going. There are many types of Tether, such as:

A tidal stabilized tether is called a "skyhook" since it appears to be "hooked onto the sky".
They are also called "hypersonic tethers" because the tip nearest the earth travels about Mach-12 in typical designs. Longer tethers would travel more slowly. At the limit of zero ground speed, it would be re-classified as a beanstalk).

An aircraft or sub-orbital vehicle transports cargo to one end of the skyhook.

Skyhook designs typically require climbers to transport the cargo to the other end (like a beanstalk).

A beanstalk (more formally a space elevator) is a rotovator powered by the spin of a planet. For example, on Earth, a beanstalk would go from the equator to geosynchronous orbit.

A beanstalk does not need to be charged as a rotavator does, because it gets the required energy directly from its planet's angular momentum. The disadvantage is that it is much longer, and for many planets, a beanstalk cannot be constructed from known materials. An Earth beanstalk would be at the limit of current known material strength.

Beanstalks also have much larger amounts of potential energy than a rotavator, and if heavy parts should fail, they might cause multiple impact events as heavy parts hit the earth at orbital speeds. Most anticipated cable designs would burn up before hitting the ground.

A lot of work still to do methinks.