Some guy named Andreas said much the same thing  at www.spacesolarpower.wordpress.com Does anyone know if a one degree error in optimum phase lock still produces a tight beam from phased arrays? Can we hope to have a means to keep most of a million of these plus or minus one degree? If so, My guess is way to go!   Neil

Weaving does have some advantages, but it does not increase the strength per kilogram. Long runs between high tension towers are typically solid copper wire. Search for Hoytether which is something like a fishnet.
The rocking back and forth method does allow using tapered ribbon, and suitable CNT = carbon nano tubes may be available soon. There may, however, be some surprises when we try to do the rocking method very large scale. There seems to be some disagreement about the behavior of stretch transients, and the degree of dampening = energy loss which will occur.
Ribbon heating may not be a problem as CNT can tolerate very high temperatures. Hot ribbon will cool efficiently by radiation. Epoxy or other binders will deteriorate at a few hundred degrees c. The laser beam used to power the climber may accidentally heat the ribbon and cause heat damage to the binders.   Neil

I don't know of any problem with a hydrogen helium mixture. Perhaps mostly helium at liftoff; then use hydrogen as the top off gas. Both are bad about leakage. At present, supply exceeds demand, so helium is cheap. Huge balloons would quickly make helium in short supply. It could cost 100 times the price of hydrogen. Hydrogen production can be scalled up, but doubling the helium production, would involve extracting it, where it is only a few parts per million, and in small quantities, where the other gas in the mixture is also costly to purify. Dumping unneeded gas of most kinds in the atmosphere will soon incur the wrath of environmentalists.  Neil

If the 180 gigawatthours is correct, for the stored energy, then we used about 360 gwh to accellerate the ribbon from zero to 8 kilometers per second in 100 hours. If the windage loss is 1% per hour, we need 3.6 gigawatts = the output of a large nuclear plant, 24/7 just to make up the windage loss. Oscilations are likely in a one peice iron ribbon, which will likely also heat the ribbon about 3.6 gigawatts per hour. I think this is one reason one meter segments, slotted together were proposed. The pay load is going to slow the ribbon locally, stretching the ribbon ahead of the pay load. The ribbon will bunch up behind the pay load. In a sence the mass of the ribbon behaves like a pay load in the up tower, stretching near the top and bunching up near the bottom. In the down tower the ribbon will accellerate, stretching at the top and bunching up at the bottom. The electric bill will be enormous unless the ribbon is in a vacuum shieth in Earth's atmosphere.
True we can convert perhaps 2% of the kenetic energy in the loop during the peak demand period, but the loop will begin to sag putting extra stress on the towers, as the ribbon slows. Has anyone devised a plan to manufacture a one peice iron ribbon loop about 4160 kilometers long?  Neil

Hi clone einstein: Wecome to www.liftport.com
That is mostly correct. A few parts have me confused. Are you constructing a separate lunar elevator that passes though L1? This SE can be about 60,000 kilometers long with presently available materials. With CNT with great specs 300,000 kilometers might be optimum. The space elevator anchored at earth can be 100,000 kilometers long or more, so the ends pass each other closely when the moon is closest to earth. The moon's orbit is not circular, so the ends would sometimes be about 50,000 kilometers apart, unless the ribbons overlap about 50,000 kilometers when the moon is closest. Overlap could mean tangle, which would be bad as the speed difference is high.
 The radius to the tip of the Earth SE might be 106,000 kilometers; so the circumfrence is 666,000 kilometers divide by 24 = 28,000 kilometers per hour =  almost that fast with respect to the tip of the lunar elevator, I think. This is almost as much delta v as required to lift off from Earth, for the moon. Perhaps you had something else in mind? If the moon pay load drops off the end of the Earth SE it is less than a day travel time to the moon, even allowing time to decelerate to a soft landing.  Neil

Lofstrom and Space Elevator are both large extensions of present technology. Many of the details cannot be theorly tested small or medium scale. If Lofstrom can put ten million tons per year in low earth orbit at $3000 per ton, the cost jumps to about a $10,000 dollars per ton if there are costomers for only a million tons per year, which is to say the fixed expenses are almost a ten billion dollars per year. Is it realistic to think there might be an annual 30 billion dollars available from customers, before Lofstrom was very deeply in debt?
If Lofstrom delivers 20 ten ton packages to orbit; doesn't the customer have an enormous cost assembling 20 modules in orbit or worse, enroute to Neptune? The third or fourth Space Elevator may be able to deliver 200 tons as a single package en route to anywhere. Sorry if my arithmetic is bad, but Space Elevator matches the customer demands better initially even though Lofstrom is better the second century of operation, assuming a Lofstrom has a life of a century, and the World Space economy does not stagnate. Can either system tolerate a ten times overload, if the craft provides 90% of the thrust? Can the Shuttle (or equivalent) accelerate the Lofstrum loop by decellerating the shuttle prior to re-entry into Earth's atmosphere = regenerative breaking?
The reason Andreas is thinking a 50 kilometer tower at each end is: the early Lofstrum may be able to levitate the loop, but levitating the vacuum shield the first 50 kilometers may prove impractical. We can likely do without the vacuum shield above 50 kilometers altitude.   Neil

That should work, but it would take a lot of energy to compress the hydrogen when we wanted the sky station to decend. Hydrogen is quite safe if the low altitude for the station is 10 kilometers or more = not enough oxygen for a self sustaining fire. I don't think we have built anything nearly this large since the Hindenberg, so we need to start building a 1/10 size pilot model soon or we won't reach full size by 2031, when we hope to build the first 20 ton space elevator. How big does it need to be to be useful with a 200 ton space elevator which we might start building in 2035? I doubt if we can get that much helium by 2035, unless we stop dumping helium into our atmosphere, now. If we don't use a sky station for the first space elevator, we probably will not use a sky station for the 2nd, 3d etc.
How about a free flying sky station which could serve most of the countries of the Northern Hemisphere as it spiraled toward the North pole? Perhaps the attached space elevator would perform poorly after the sky station was over about 45 degrees North latitude? Free flying would perhaps double the pay load of the sky station = the weight of the cables to Earth's surface that we would not need. At 45 degres North latitude the ribbon would be about horizontal at the sky station. It would curve gently toward vertical, passing perhaps 100 kilometers North of the Clark belt, over the equator. That would reduce the number of GEO satellits we need to dodge around. Neil

A M Swallow is correct. The satellite  and desert 1/2 gigawatt are a bit easier to operate and maintain if they use space mature solar panels without mirrors, turbines and generators, but the huge microwave source and huge antenna will be essentually new technology which likely cannot be fully automated until we have a decade of operating experience. This is another good reason to operate the first several SPS in LEO, so that technicians can live on the satellite. The temperature cycling is likely more severe in LEO than in the desert and it will be an 88 minute cycle instead of a 24 hour cycle. LEO is, however, mostly spared the weather and seasonal cycles, and a semipolar orbit allows beaming to most of the countries of Earth every peak demand period with as few as two satellites, I think.   Neil

I did this analysis to indicate that desert solar electricity is only about 1/10th as good as GEO or Solarsychronous SPS = solar power satellite. One half gigawatt is enough power for a large city. Very large cities need several gigawatts. Lets consider 12 square kilometers = 3 kilometers, East and West by 4 kilometers, North and South. There is a solar power tower close to the Southeast and Southwest corners of the property. They are about 200 meters tall. The land slopes up about 2% from South to North, but is otherwise quite flat. More slope would be better, but more is almost always hilly which is bad. You can see ideal sites are rare. Homes and ranches are practical except very close to the two solar power towers, but maximum height of trees and structures is typically 4 meters, but only 2 or 3 meters in a few spots. Exceptions are the 50,000 steerable mirror towers which range from 12 to 20 meters tall, a few of them with a wind turbine above the mirror. The mirrors average 100 square meters and produce an average of 400 watts per square meter in late June at 1 pm in their beam of sunlight. The heat exchangers near the top of the twin towers absorb an average of 2 gigawatts, and delivers 1.9 gigawatt to the steam turbines. Some additional energy comes from steam super heaters also on the tower. Electrical output is 0.5 gigawatts. With good luck the wind turbines and some photovoltaic panels produce 0.01 gigawatts for a total of 0.51 gigawatt put on the grid. Typically the grid accepts a bit less, so some heat energy is stored in the molton sodium-potassium nitrate in the heat exchanger, and a reserve tank. Sometimes this is sufficient to power the Southwest turbine at reduced power until an hour after sunset which is about the end of the peak demand period. Some additional mirrors may be located to the East of the towers to catch the late afternoon sun. While this would produce some evening reserve, it is likely not cost effective as the towers would be on private property.
As you can imagine, 50,000 mirror towers on 12 square kilometers, is near the limit to prevent shading each other in the late afternoon, especially in December when the sun is low in the sky. Shading is rather severe shortly after sunrise, but that is not very important as the wholesale price of electricity is low mid morning, and it does take about two hours to warm the sodium-potassium nitrate to optimum operating temperature each morning/3 hours typically in December. The installation cannot be enlarged except at diminishing returns, as a 4 kilometer beam produces an illuminated spot bigger than the heat exchanger, even if the mirror is minutely concave. A precision concave mirror is much more costly than plain mirrors and a 500 square meter heat exchanger has considerable heat loss in a high wind. I suppose transparent shutters would help on windy days, and the heat exchanger could be a bit larger than 500 square meters.
The start up crew arrives before sunrise, each morning at the SE tower, for the startup procedure. Typically they leave one technician to monitor, then go to the Southwest tower which will be in a poor position to receive energy until late morning. If there are no problems, all but two are off duty by one pm.
Perhaps ten employees, including two trainees, are needed as the towers need to be observed during start up on Saturday, Sunday, sickdays and holidays as well as week days, so payroll is not a trivial expense, even with the systems highly automated. Please embellish, refute and/or comment. Neil

Hi Andreas: Does sliding down from 35,000 kilometers have advantages over dropping from that altitude? Clearly sliding up from 37,000 kilometers gets you higher speed than falling up from 37,000 kilometers.   Neil

4000 kilometers at the anchor ship and the counter weight still leaves about 83,000 kilometers that can be tapered. If the cross sectional area is one square centimeter where wound on the winch reels, that is 1/10 millimeter thick ribbon if the ribbon is one meter wide. 10,000 turns increases the winch reel radius by one meter. If the average turn is ten meters = 100,000 meters = 100 kilometers on the reel. AM Swallow is correct the reels get huge, even if the ribbon is only 1/100 millimeter thick, which is very optimistic for a 20 ton payload. Only a modest problem for the anchore ship, but a huge problem at the counter weight. Is there any chance we can make do with only 100 kilometers max on the counterweight reels? If Andreas was thinking reels at the counterweight, he likely figured they would turn only in an emergency. It does appear the synchronization of the up and down ribbons can be fine tuned at the junction of the Y which could be 10,000 kilometers above GEO altitude or at the counter weight. The latter may be a waste of ribbon, but it should work.  Neil

Here is windemut sumary from the ribbon power thread. Andress is calling the grabbers climbers:
- The ribbon is Y shaped, with two ends on Earth, and one end in space, way beyond GEO.
- Contrary to the Y image, the Earth strands are kept very close to each other.
- The two Earth ends are connected around a pulley, or separately attached to two reels.
- The branch point is somewhere beyond GEO, around 50,000 km.
- The space end is attached to a counterweight around 90,000 km, or simply peters out far enough.
- A resonant longitudinal oscillation is induced and maintained in the two branches using the pulley/reels
- Depending on the Q-factor of the oscillator, the pulley/reel velocity is small (10-30 m/s)
    compared to the maximum ribbon velocity (~300 m/s)
- With few sources of friction or dissipation, the Q-factor should be excellent.
- The oscillation is the lowest frequency mode, with Earth and the branch point as nodes.
    (lambda = 100,000 km, roughly 1 swing/hour given typical CNT modulus of 1TPa)
- The two strands swing synchronously in opposite phase.
- The net force at the branch point is thus constant and it remains stationary.
- Both strands pass very close to each other through the center of mass of the climber.
- The climber clamps onto the upwards strand, and lets the downwards strand slide.
- Whenever strands reverse direction (every 30min or so), the climber switches clamps.
- Climbers inch up that way at an average speed of 50-100 m/s, I think.
- Climbers can detach from the ribbon at their destination with a vertical extra velocity
    of their choice up to around 300 m/s up or down by timing their detachment.
- Well before GEO, climbers can unclamp from both strands and coast the rest of the way,
    on those same 300 m/s.
- Strands may be able to withstand occasional collisions with each other.
- Or, they need to be kept apart between ends and climber
     (by Coriolis force, centrifugal force, electrostatic charge, or other means)

I just reread (partly skimed) the 11 pages of this tread. I will attempt to summarize: The 200 kilometers per hour suggested by Edwards is a workable minimum. If much slower it will take too many years to add the strengthening threads. Too many years, not only increases the cost, but means a high probability that the ribbon will be cut by a meteoroid or space junk before it is completed. We can compensate with a stronger starter thread, but this requires a heavy lift rocket which may not be available.
The windemut plan offers some hope of faster than 200 kilometers per hour average and bigger pay loads. It also illiminates or reduces the need for the very powerful, and very narrow beam lasers and the powerful electric motors needed for the Edwards plan, which may be too heavy.
All plans for a space elevator require technical advances which may not occur and unpleasent surprises when we actually start building such very large scale.
I suggest we launch the double ribbon windemut plan, and build some climbers and some grabbers and some hybreds. The lasers will need to be in place on day one of the first grabber. If the grabers work poorly or cause bad problems, we can switch to the hybreds or Edwards climbers. Hybred has the advantage that it can climb while the ribbon is moving upward, and even when neither ribbon is moving upwards at a significant speed. The latter is likely, if the oscilating ribbon is out of sync temporarilly.
Two ribbons also means a back up which can repair the other ribbon should it break, get tangled or be much weakened.   Neil

Liftport ordered a furnace to make CNT about two years ago, but it did not meet the specs of the contract. Perhaps the project is still confused. Hopefully bumping this thread will get the attention of a liftport exective.   Neil

Hi publisher: A M Swallow is usually correct, but my guess is modest station keeping energy would keep the wire loops in orbit. Why would we want a solid ellipse? Slightly eliptical would work almost as well as circular, is my guess. Drawing current from the loop would, however, modify the orbit, perhaps making the project impractical. Another problem is: It is very hot close to the Sun, and the magnetic field may average no stronger than Earth, but with distructive bursts during a CME = corronal mass ejection. Possibly plasma could be used as a conductor instead of wire, which has high resistance at high temperature. Plasma is said to have high conductance. Does anyone know how plasma at best compares with copper?
Another problem is beam spread of microwaves is excessive over 92,000,000 million miles. Does anyone know the thoretical minimum spot size for ultra violet or gamma rays at 92,000,000 miles?   Neil