NPR Talks Skyhooks

David writes "NPR's Talk of the Nation this past week featured Brad Edwards, President of Carbon Designs Inc., to talk about their plans to develop an elevator that would lift people to an object orbiting in outer space. The project's homepage details their plans and ambitions. The discussion expands on callers' concerns about such problems as commercial airliners running into the super long cable or if it would act as a conduit for lightning."

The next x-prize

[maelstrom]

Here is some money that NASA could "invest" in another x-prize like compitition. Get some innovation back into the space game. Maybe once China starts blasting some people towards Mars the US will get off its ass again.

Re:Cripes

[Rei]

I was thinking the same thing. It's way overhyped. Although, the concerns cited in the summary aren't that major.

Commercial airliners will never get close to it; that's what no fly zones are for. Even if an airplane crashed into it, one solution successfully deals with both airline impacts and lightning: "maypoling" the skyhook as it nears the ground (i.e., splitting it into several cables, of which most, but not all, are needed for stability/strength.) As for lightning itself, most types of CNTs would be the "path of most resistance", barring heavy condensation on the cable. Plus, some sites in the world have very little lightning.

Re:I just have to ask...

[mbrother]

The whole concept requires it to be thin. The key is to have a material strong enough to hold up its own weight, because tens of thousands of miles of stuff adds up. What's more disconcerting to me is that at any real distance, it will be essentially invisible.

skiers know...

[kencurry]

What it's like to get stuck mid-air on a long lift.

God help you if the elevator goes on the fritz in the midst of your ride!

What about space debris?

[d474]

What kind of damage can the ribbon sustain if a small meteorite or space junk impact it? No big deal or total failure?

Really informative video

[drgath159]

http://www.isr.us/video/SE-INTRO_Final-1stream-384 .wmv [www.isr.us]

Covers the basics of the elevator, what it looks like, how it works, etc...

The question of how this thing is powered never popped into my head before, but the video shows that they will use a lazer shot from the base station. Crazy stuff.

Re:Cripes

[mbrother]

Yes. I'm not laughing. That's an informed opinion based on knowing something about material science.
Progress has been fast with CNT materials. The promise (which is a promise not a certainty) is that we'll know if we can make a strong enough material in the next five years based on CNT technology. Investing in this sort of research is a good idea (and we nearly hired someone this year who worked in the area).

NPR talks skyhooks.

[lgroner]

One weakness of the plan, as I see it, is the all or nothing nature of the plan. A less risky plan that could be a stepping stone to a space elevator is to start with a much smaller rotating tether in orbit.

Imagine a thousand mile long tether in orbit with its center of gravity 600 above the earths surface. In addition to orbiting the earth The tether would rotate about its center of gravity at a rotation speed such that its speed relative to the earths surface at its ends closent approch would be zero.

A rocket would have to ascend to 100 miles up and rondezvous with a a tether end that, for the moment, is stationary. It would remain atteached to the tether while the tether rotated 180 degrees about its center of gravity. At tht point the rocket would be 1100 miles above the earth and traveling at about twice orbital velocity. If the rocket detatched at this point would would be well above escape velocity.

Longer tethers would reduce G forces and avoid the need for the first 100 mile step. The ultime version of the tether would have a CG in geosynchronous orbit and aon end on the ground.

Re:Going to the moon

[HiThere]

Remember: Net momentum change up and down must equalize, or the weight changes it's orbit. And you need a heavy weight to provide enough ballast.

That said, there are larger problems, and this is probably an overly ambitious approach. I think that it would be better to start with pinwheels rather than a space elevator. You get about half the advantages, at a considerably reduced construction cost. And one pinwheel serves many locations on the earth. (You may well need to wait several hours for one to come by unless more than one is built...but that's not a real problem.)

A pinwheel is several cables attached to a weight and rotating. The arms reach down into the atmosphere to pick up or release cargo. You fly up to reach them in an airplane, and the cargo is picked up or released. You want this to be high enough to have minimal friction, and you want the speed of rotation to be slow enough to give plenty of time for the transfer.

Again, momentuum change needs to average out to zero. But the pinwheel can loft you to a higher orbit, and catch you on the way back down (helping to equalize momentuum).

Pinwheels could actually be even more flexible than space elevators, as they could act as momentuum transfer devices in a way similar to slingshot orbits, but you could position them for your convenience. (That's long term, however, but they don't always need to be in orbit around a planet, the also work in solar orbit.

And pinwheels don't require the super-strong cables that space elevators require (though it would certainly make them more attractive).

Solution to problems: space fountain

[Oniros]

I thought space elevators with cables were out (due to the tensil strength the cable should have) and space fountain were in (since easier to build, not just buildable on the equator, etc.)

http://en.wikipedia.org/wiki/Space_fountain [wikipedia.org]

Re:Interesting interview

[MrResistor]

There is no such thing as a place in the world that doesn't have lightning. That's just stupid.

Besides, there doesn't need to be lighting for electricity to be an issue. You can generate electricity by moving a conductor through a magnetic field. I would think 62k miles of carbon nanotube ribbon running through the magnetic field of the earth would make a pretty good generator.

IIRC, they already have to deal with this when tethering satalites to the space shuttle. I remember hearing that every material they've tried has some length at which it generates enough power to burn itself up (though that length might be several miles).

better yet

[tjw]

> Put the base in the ocean, and stick a carrier task force there to protect it.

Better yet, put it on Nauru.
http://www.cia.gov/cia/publications/factbook/geos/ nr.html [cia.gov]

With the phosphates gone, the international money laundering (er banking) industry dismantled, and nothing else on the horizon, this could be just what this island nation needs.

Finally something that severe isolation is good for.

Re:Greatest story ever!

[trewornan]

There was a real system called "Skyhook" developed by the military. Basically it was a one man recovery system intended for use by spies, downed pilots, etc. Someone on the ground let up a balloon with a cable attached and harnessed themself to the end. A plane with a special "Y" shaped "cable catcher" on the front would then fly into the cable and eventually the "recoveree" would be winched on board. Apparently they did get it working http://www.cia.gov/csi/studies/95unclass/Leary.htm l [cia.gov]

Re:My standard space elevator comment...

[Goonie]

Well, you might also tell those spiders to lift their game, because spider silk is nowhere near strong enough to build a space elevator. It's about three times the tensile strength of steel. A space elevator needs something more than 100 times stronger than steel to be practical.