Ah! I kept getting hung up on the location of the spool. That makes much more sense now. There seem to be nine designs so far, but we may add more later. Thanks for the explanation!
-Nydoc

Complete
GEO-constructed: The entire ribbon is constructed and inspected in GEO before being lowered to Earth.
Tape Dispenser: This method requires an existing elevator that is self-lifting. A new ribbon is attached at the base and reeled upward. The old ribbon is cut off from the top and lowered to form a new elevator.

Piecemeal
Strand: A small seed ribbon is lowered from GEO to Earth. Robotic climbers are then used to add more strands, building up the ribbon over time.
Segmented: The ribbon is pieced together with each section designed for a specific altitude. This design allows for easy repair of the ribbon, since replacements for damaged sections can be prebuilt.

Self-Lifting
Confetti: This is the simplest of the self lifting designs. It requires the ribbon to have a "reverse taper", or tensile strength greater than 63GPa. A seed ribbon is lowered from GEO to Earth, and then a slightly wider ribbon is attached at the base. The attached ribbon is reeled upwards, and continues to widen until the desired width is attained. Excess ribbon at the top is cut off and released into space.
Respooled: Similar to the confetti design, except that the excess ribbon is respooled at the top instead of being cut off.
Fold-back: This is also similar to the confetti design. Instead of being cut off, the excess ribbon is attached to a climber which is lowered towards Earth. The folded ribbon can be made into a loop once enough ribbon mass has been lifted.
Hanging Loop: The ribbon is unspooled from GEO, with the end held next to the spool and the ribbon moving towards Earth as a hanging loop (U-shape, both ends and the spool remain at the top). Once the bottom of the loop reaches Earth, it is caught and inserted into a drive and maintenance mechanism resembling a printing press. At the same time the two ends are connected at the top. The spool becomes a pulley and the remainder of the spacecraft becomes the counterweight. New material is added to the ribbon at the bottom as it rotates until the desired ribbon mass has been lifted.
Multi Fold-back: This is a self-lifting design with lower strengh requirements. The ribbon will not need a reverse taper, but will need only to be the same width at top and bottom. A seed ribbon is lowered from GEO to Earth. A ribbon of similar width is then attached at the base. The new ribbon is reeled upwards, while the old ribbon is attached to a climber and reeled down towards earth. Then both ribbons are attached to lift a third, wider ribbon. The proccess continues until the desired ribbon width is attained.

This site has the basic concept for the high voltage tether. I would imagine there would be no theoretical problems in having an adaption that would charge batteries, or convert the energy into a microwave beam. Lots of other great info on that site (including orbiting tether simulation software ;-) ).

Someone could even start designing and building robots now that would attach and trim ribbon hanging from a high altitude balloon. Also, since all the new ribbon would be attached at the same place, we might have a mechanism on that spot of the ribbon that would allow easy attachement. Thoughts?

Ok, I'm expounding on your definition to see if I understand your concept correctly. If I'm still off base, please tell me.
-Nydoc  :-|

Hanging Loop: The seed ribbon is folded in half before being rolled on the spool so that both ends are on the outside of the roll and the spool is between the fold. The spool is unrolled from GEO and descends towards Earth with both ends still attached at the counterweight. Once the spool reaches Earth, it is inserted into a drive mechanism and used as a pulley. At the same time, the two ends are connected at the top to form a loop. The loop begins rotating and new material is added to the ribbon at the bottom until the desired ribbon mass has been lifted.

One process by which the ribbon might be renewed woud be to periodically add an excessively long fold of ribbon just above the space debri altitude (1700km). The ribbon would then be pulled downwards, stretching out the fold. The climber would descend while trimming the edges of the ribbon (maybe the fold would need to be pulled out as the climber is descending). If there needs to be a precise curvature at the base, it could be maintained with a cutting laser. I don't know how you would dispose of the trimmings though. This process would be kind of wasteful, but would ensure that all parts of that stretch of ribbon would be continuously replaced with inspected ribbon. (The process could be done higher up if radiation damage was a problem, but it might be better to replace the entire ribbon at that point.)

-Nydoc

OK Andreas, the definition has been edited. Could someone add this to the glossary now?

Complete
GEO-constructed: The entire ribbon is constructed and inspected in GEO before being lowered to Earth.
Tape Dispenser: This method requires an existing elevator that is self-lifting. A new ribbon is attached at the base and reeled upward. The old ribbon is cut off from the top and lowered to form a new elevator.

Piecemeal
Strand: A small seed ribbon is lowered from GEO to Earth. Robotic climbers are then used to add more strands, building up the ribbon over time.
Segmented: The ribbon is pieced together with each section designed for a specific altitude. This design allows for easy repair of the ribbon, since replacements for damaged sections can be prebuilt.

Self-Lifting
Confetti: This is the simplest of the self lifting designs. It requires the ribbon to have a "reverse taper", or tensile strength greater than 63GPa. A seed ribbon is lowered from GEO to Earth, and then a slightly wider ribbon is attached at the base. The attached ribbon is reeled upwards, and continues to widen until the desired width is attained. Excess ribbon at the top is cut off and released into space.
Respooled: Similar to the confetti design, except that the excess ribbon is respooled at the top instead of being cut off.
Fold-back: This is also similar to the confetti design. Instead of being cut off, the excess ribbon is attached to a climber which is lowered towards Earth. The folded ribbon can be made into a loop once enough ribbon mass has been lifted.
Hanging Loop: Both ends of the seed ribbon are left attached to the counterweight as it unrolls from the middle with the spool descending towards Earth and the ribbon forming a 'U' shape. Once the spool reaches Earth, it becomes a pulley, and the ends are then attached at the top to form a loop. New material is added to the ribbon at the bottom as it rotates until the desired ribbon mass has been lifted.
Multi Fold-back: This is a self-lifting design with lower strengh requirements. The ribbon will not need a reverse taper, but will need only to be the same width at top and bottom. A seed ribbon is lowered from GEO to Earth. A ribbon of similar width is then attached at the base. The new ribbon is reeled upwards, while the old ribbon is attached to a climber and reeled down towards earth. Then both ribbons are attached to lift a third, wider ribbon. The proccess continues until the desired ribbon width is attained.

I think this is good news for the SE. Eventually comstats will be falling out of LEO and wont be replaced. There will be fewer things for the SE to navigate around. The SE opens up so many new markets I don't think this would damage it's financial prospects. I think an SE would be profitable with zero turists as well.

I think a longer ribbon that can release the top piece of ribbon is a good compromise.
The counterweight would have to increase in mass logarithmically the closer it is to GEO. This doesn't allow for that much play in length when you are limited to 100 tons, but that's not a problem.
As long as the ribbon is within reasonable safety margins the economic benifits of a longer ribbon will rule.

I am classifing Hanging-Loop as Self-Lifting design since the seed has to lift the rest of the mass once it reaches the ground. Here are definitions I came up with. Tell me if you like them and we can add them to the glossary.

Complete
GEO-constructed: The entire ribbon is constructed and inspected in GEO before being lowered to Earth.
Tape Dispenser: This method requires an existing elevator that is self-lifting. A new ribbon is attached at the base and reeled upward. The old ribbon is cut off from the top and lowered to form a new elevator.

Piecemeal
Strand: A small seed ribbon is lowered from GEO to Earth. Robotic climbers are then used to add more strands, building up the ribbon over time.
Segmented: The ribbon is pieced together with each section designed for a specific altitude. This design allows for easy repair of the ribbon, since replacements for damaged sections can be prebuilt.

Self-Lifting
Confetti: This is the simplest of the self lifting designs. It requires the ribbon to have a "reverse taper", or tensile strength greater than 63Gpa. A seed ribbon is lowered from GEO to Earth, and then a slightly wider ribbon is attached at the base. The attached ribbon is reeled upwards, and continues to widen until the desired width is attained. Excess ribbon at the top is cut off and released into space.
Respooled: Similar to the confetti design, the excess ribbon is respooled at the top instead of being cut off.
Fold-back: This is also similar to the confetti design. Instead of being cut off, the excess ribbon is attached to a climber which is lowered towards Earth. The folded ribbon can be made into a loop once enough ribbon mass has been lifted.
Hanging Loop: A seed ribbon is lowered from GEO to Earth. The spool is unrolled from the bottom of the ribbon at 100m/sec. At the same time, the other end is reeled down to Earth at 50m/sec so that both ends will be traveling towards Earth at 50m/sec. When both ends reach the ground, the ribbon will already be in motion. The loop can be completed once enough ribbon mass has been lifted.
Multi Fold-back: This is a self-lifting design with lower strengh requirements. The ribbon will not need a reverse taper, but will need only to be the same width at top and bottom. A seed ribbon is lowered from GEO to Earth. A ribbon of similar width is then attached at the base. The new ribbon is reeled upwards, while the old ribbon is attached to a climber and reeled down towards earth. Then both ribbons are attached to lift a third, wider ribbon. The proccess continues until the desired ribbon width is attained.

You are right about this. I hadn't thought it all the way through. However, side swiping motion will still occur.


I realize this. I only thought of atmosphere and magnetic field as side complaints to the simulation. The biggest problem with it is that it doesn't show a GEO station or a climber.


You are right again. Orbital mechanics is not my strong point. Such an orbit may still be useful: it provides more time to react to the break before other elevators would be immediately at risk. Also, there would be fewer elevators immediately at risk.


Interesting. I would have to like to see math or a simulation of that to be sure it would work. Ultimately we would need failsafes that allow for breaks in any section of the ribbon.

Bob - I don't know if a GEO station needs to be clamped on or not. You bring up a good point, and Mumbles brings up several. I'll have to rethink or scrap the original design. Optimally, a GEO station would be spinning to provide artifical gravity. Maybe bearings could be used?

Recovery of the ribbon should not be the primary goal of a safety device. The primary goal should be protection of other elevators. With or without a safety device, a GEO station would still be part of the final design of the elevator. Any safety device built will at least recognize the existance of a GEO station. Why not take advatage of it if possible?

If the ribbon were to break near the anchor, that end would at first appear to be moving westward. The counterweight would orbit in an elliptical path with a 24 hour rotational period (apparently eastward) once the ribbon breaks, soon dragging the ribbon with it. In either case it could contact with a catch mechanism.


I have seen Blaise's simulations and you are correct about the escape trajectory. There are several things his simulation fails to take into account. If the ribbon were to fail, it is highly likely that a climber would be in transit AND it is likely that we would have a GEO station. It aslo doesn't take into account earth's magnetic field or atmosphere, or show any kind of time frame. I don't know if a spare elevator would be a "better" solution. I think putting both failsafes into place would be optimal. Murphy's law is especially aplicable in space.


When I said that the counterweight would "drop to GEO and stabalize" I meant it would be "accelerated into GEO with the aid of thrusters and then put in a stable orbit in order to salvage it". In this situation, the rings would also have to be rocket upwards to save the lower section. This would be, as you say, "a tricky thing". It is also, as you say, highly likely that the attached ribbon would swing in a pendulum manner. However, if it is disconnected from the anchor and on another plane I don't see how it would be a threat to other elevators.


Again: what is the time frame? The rings would not be designed to constrict, but would rather rely on the ribbon "side swiping" the inside of the structure. Also, my brother's picture is not exactly a scale diagram: the struts would likely be several times longer in relation to the diameter.

As far as beefing up the ribbon, that will be done anyway and we still expect the ribbon to fail at some point. If an SE is at all possible, it will be necessary to have more than one. If one ribbon were to break, it would likely cause all other ribbons to break. Replacing all the ribbons everytime one of them breaks is not a good idea. This is a complicated system, but it will be necessary to have a failsafe that recognizes multiple elevators.

Take Care
-Nydoc

A safety device was a topic discussed in another forum. It would involve having 2 rings at GEO which would encompass the ribbon and be connected to each other via struts. If the ribbon were to break it would drift eastward. Mechanisms on the inside of the rings could be designed to catch and secure the ribbon as it drifts.

If the break was below the rings:
-Everything below the break would fall to earth.
-The upper ribbon would be held by the counterweight and the rings, and could be stabalized with rockets to avoid severing other SEs.
-Two-thirds of the ribbon would be salvagable.

If the break was above the rings:
-The counterweight would drop to GEO and stabalize.
-The lower ribbon would be caught by the rings. If the weight of the ribbon was too much for the rings, the ribbon would be purposfully severed at the base. The rings could then be rocketed off of the equatorial plane (north or south) to avoid severing other SEs.
-The entire ribbon would be salvagable.

If the break was at one of the rings, the other ring would secure
the ribbon.

Here is a diagram my brother did up:


Of course some way would have to be found of testing the failsafe mechanisms without risk of losing the entire ribbon. I have no idea how the catch mechanisms or the testing of them would work, but I wouldn't mind hearing suggestions.
-Nydoc

I think I'm finally understanding you now. The letter graphics were a big help. I also agree with you that "Self-Lifting" is more accurate than "Reverse Taper".  My original concept was actually a fourth kind of Self-Lifting design. I'm calling it a Multi Fold-back design. To use the letter graphics again, it would look like this: I -> P -> I -> P -> I -> P -> O. Each successive "I" is twice the width as the last. The process could be much longer, depending on the final payload size desired.

I was unaware if balanced ribbon deployment or LEO elevators were actually rational proceedures. I had just heard those terms bantered around in various forums. Thanks for clearing that up.

It did seem to me that if a self-lifting elevator were possible, the counterweight could begin below GEO. Once the ribbon was attached on earth, both the ribbon and the counterweight could be elevated simultaneously, saving on the cost of the seed ribbon. This _might_ be possible, but would be a headache to figure out.

So, relisting the designs metioned (and adding NASA's GEO-constructed concept from 10 years ago) it would look something like this:

Complete:
  -GEO-constructed
Piecemeal:
  -Strand
  -Segmented
Self-Lifting:
  -Confetti
  -Respooled
  -Fold-back
  -Multi Fold-back
Revolving Loop:
  -Hanging Loop


In retrospect, the Hanging Loop and GEO-constructed designs may be similar enough to be put in the same category. The major difference between the two is that one is a loop and the other is a tapered ribbon. Thoughts?

-Nydoc

Andreas, thank you for the clarification on different types of self-lifting elevators.


I meant the initial deployment, lowered from GEO to Earth. What I had in mind you describe as "folding the ribbon". If a U-shaped ribbon is a more plausible or accurate form of this design, then let's describe it that way.

I am not so concerned with the particulars or merits of individual designs, but want to establishing a common terminology to provide definitions of those designs. This would include definitions of the following:
Piecemeal Designs:
  -Layer/Strand (proposed by Brad Edwards)
  -Frankenstein/Segmented
Reverse-Taper Designs:
  -Confetti
  -Respooled
  -Loop/U-Shaped
As well as descriptions of installation proceedures:
Balanced ribbon deployment
Thrust assisted deployment
GEO deployment
LEO deployment
Self-Lifting

Bootstrap/Reverse-Taper/Self-lifting Design:
An elevator design involving a ribbon with >63Gpa tensile strength. A seed ribbon from GEO would pull up a secondary ribbon from earth. The seed ribbon is lowered and used with the secondary ribbon to pull up a third ribbon. The process continues until the desired width is attained. Such a ribbon could be used in a loop, either spanning to GEO or all the way to the counterweight. Laser power to the climbers would not be needed. It would increase the capacity, simplify raising new ribbons and make damage repair much easier. However, many people do not believe the required ribbon strength is attainable.