A Space Elevator Draft

[Condottiere]

Has to be strong enough to withstand collisions, especially cultural ones with religious fanatics.

 

[ShawnDriscoll]

I should probably pay a visit to your log-ass thread.

 

[Tenacious-Techhunter]

The draft has seven cables. The "hexes" can move up/down along the six outer cables. They don't touch the cables all that much, like how a maglev train doesn't touch its rails.

You can’t design the cables to never be touched; they have to be designed to be able to withstand the pressure from the emergency brakes being applied without having to be replaced in such an event. You may want to argue that you’ll just secure them in place with electromagnets, but that requires power, and physical emergency brakes do not; the conclusion, from a safety standpoint, is you require physical emergency brakes, which means you require maintaining contact with the cable. It should also be noted that magnetic levitation can induce resonant vibration that has to be carefully engineered out, which may not last over the lifetime of the system’s various units, and may even affect the stability of the whole system.

 

[ShawnDriscoll]

The draft has seven cables. The "hexes" can move up/down along the six outer cables. They don't touch the cables all that much, like how a maglev train doesn't touch its rails.

You can’t design the cables to never be touched; they have to be designed to be able to withstand the pressure from the emergency brakes being applied without having to be replaced in such an event. You may want to argue that you’ll just secure them in place with electromagnets, but that requires power, and physical emergency brakes do not; the conclusion, from a safety standpoint, is you require physical emergency brakes, which means you require maintaining contact with the cable. It should also be noted that magnetic levitation can induce resonant vibration that has to be carefully engineered out, which may not last over the lifetime of the system’s various units, and may even affect the stability of the whole system.

Who said "never"? Anyway, there will always be resonant vibration, which you seem to hand-wave away with your "engineered out" laziness. And there will always be the expanding of metal in different temperatures, which you failed to mention.

 

[Tenacious-Techhunter]

I’m not the one handwaving it out, you’re the one handwaving it out. Magnetic levitation systems have a much bigger resonance problem than a mechanical system. Given the broad operating conditions required, over which the resonance would have to be carefully excluded, they may be a suboptimal solution for a Space Elevator.

 

[alex_greene]

Gentlemen, that is enough. I'm getting tired of seeing the same names starting to crop up in reports on an almost daily basis.

You do not sell Traveller or Mongoose Publishing well to newcomers. It is unprofessional of Traveller fans to behave in such a manner. I don't care for the image of the crusty old grognard; that's something that should now be left behind in the Eighties, along with the rest of the first generation of Traveller players, of whom I include myself.

Reports have been made, and admins' attention has been called. Is it really worth courting warnings, temporary or even permabans? Settle back in your corners, and stop this. Or admins with more clout than me will.

 

[phavoc]

There have been some who cannot get into their head that science <> engineering (or theory vs. applied). To wit, using the miracle materials of the future doesn't preclude you from building a semi-rigid structure that can move as necessary. Or, from your illustration, you could easily have a cable at each corner of the hexagon that has a lateral brace (or another cable) connecting it to the other cables. This would provide even more support against wind shear. Engineers take what scientists create and discover and build actual things from it - and often they come up with uses and issues the scientists did not.

This is not a matter of “engineering vs. science”; at some point, this thing needs to attach to the face of the planet, composed of purely natural materials. A rigid structure would just become some massive lever arm that wedges the planet’s crust open. So it simply has to be flexible, on account of the purely natural limitations of the planet itself. Better materials don’t change the underlying physical principles that constrain this design.

I took 'semi-rigid structure' to mean something like six cables bound by the hexagons to keep them from crashing into each other, which seems to me like it would act (on the large scale) a lot like a single (non-rigid) cable.

You took it correctly. It would be a very interestimg bit of engineering to make a rigid tower 22k miles tall. Making it semi rigid would allow it to accommodate high winds and other torsional forces. It still might need some sort of thrusters to provide counter energy, or at least that's been postulated. As far as i can tell from reading there isn't a consensus on the exact engineering.

Oddest idea I've seen yet was the Canadian company that got a patent on an inflatable 12 mile tall space elevator. It's not quite in the league of the standard designs with a terminus at geosynchronous orbit. Some call for continuing higher up to provide additional energy for orbital transfers.

 

[Condottiere]

The design has to be pretty convincing in order to insure it.