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Fraser
2004-Nov-18, 06:04 PM
SUMMARY: Science fiction writer Arthur C. Clarke famously predicted that we'd see space elevators 50 years after people stopped laughing at the idea. Jerome Pearson has been thinking about space elevators since the early 1970s, and he's been watching the growing enthusiasm (and fading chuckles) with great interest. But he knows there are significant challenges in engineering and materials that still need to be overcome, so he's suggesting NASA build an elevator on the Moon first. And the agency is taking the idea seriously.

What do you think about this story? Post your comments below.

antoniseb
2004-Nov-18, 06:17 PM
This is a pretty cool story. Building the first space elevator on the moon makes good sense. It gets over the problem that Earth weather, and the combustability of Carbon nanotubes are a real threat to a system that costs many billions of dollars to construct. There is also a great deal less man-made debris in lunar orbit for the elevator to need to avoid. We could probably launch an ion-driven solar powered craft to go around and collect the few bits that are up there, and crash them into the moon before the elevator is built.

Once the cable is strong enough there's be no reason that you couldn't have climbers accelerating up to thousands of miles per hour, perhaps reaching the L1 or L2 platform in a small fraction of a day.

Fraser
2004-Nov-18, 06:36 PM
That was my thinking too. I figured it might be a great way to get astronauts up and down to the lunar base, but Pearson figures it's just too slow. The astronauts would get irradiated. Maybe with some kind of maglev system you could hit 1,000 km/h since there's no friction? That would only take about 60 hours.

antoniseb
2004-Nov-18, 06:55 PM
Originally posted by fraser@Nov 18 2004, 06:36 PM
Maybe with some kind of maglev system you could hit 1,000 km/h since there's no friction? That would only take about 60 hours.
If a maglev system were installed, speeds near 10,000 km/h should be achievable. The difficulty is that the cable would need to support the strain of acceleration, and you'd need two cars doing pretty much the same things at opposite ends of the cable so as to keep the rest of the system balanced.

Once the cable is strong enough, the car could use the magnetic protection mentioned in yesterday's news, and a thick layer of moon dust to keep the passengers relatively free from most radiation.

Guest
2004-Nov-18, 07:12 PM
Let's forget Mars. That was a silly and naive part of the space vision. All cash , time and science should be directed at establishment of a real functional lunar base, where real science can be done and the possibility of a space elevator is also a nice thing to consider

Bert Murray
2004-Nov-18, 09:03 PM
For more discussion on the Space Elevator concept join the NSS Space Elevator Cyber Chapter yahoo group at: http://groups.yahoo.com/group/nsecc/

Regards,
Bert Murray
President of NSS Space Elevator Cyber Chapter

kashi
2004-Nov-18, 10:33 PM
I agree that the moon is a far more sensible focus than Mars for the time being. Having a fully functionaly base there would help reduce the cost of missions to Mars in the future. The elevator idea sounds cool; I'll be following it closely.

gavwvin
2004-Nov-18, 10:49 PM
This is an idea people are taking seriously: http://www.liftport.com/
interesting reading!

George Morrone
2004-Nov-18, 11:29 PM
Just curious: What about accidents? If an Earth based space elevator were built, what if say a scram jet flying at Mach 10 flew into the elevator? Or a satellite? If the elevator were cut 40,000 feet up, what would happen?

mxsxsm
2004-Nov-19, 12:28 AM
The idea of building a space elevator on the moon is brilliant in concept and breathtaking in scope.

The exploration of the moon was more a vanity project than anything else, despite the technological spinoffs that have benefited us, both commercially and militarily.

Had the moon been able to provide the US with some rationale as a military theater of operations, we would no doubt have had a considerable presence on the moon by now, the expense of pure scientific exploration, discovery and exploitation been nearly cost-free.

Perhaps not as expansive or advanced as Clavius Base (ironically, another sort of bold inspiration by the brilliant Arthur C. Clarke) but certainly a dynamic, thriving lunar existence for sure, eventually achieving almost the same sort of everyday, mundane news of regularly scheduled supply and crew change announcements we've come to expect from the Earth orbiting, money draining, white elephant aka the ISS.

I've always resented those members of the US Congress responsible for NASA's measly tiny budget, a mere pittance, for being so short sighted and miserly funding NASA, especially against the backdrop of a multi trillion dollar economy and many billion dollar military procurement costs that are shamelessly wasted.

So the idea of creating a lunar base with the fundamental purpose of saving huge amounts of money by developing the space elevator to bring launching costs down to only a fraction of what it would otherwise mght be is a wonderful, brilliant concept.

Nevertheless, I'm sorry to say, being so sorely disappointed and let down not only by the myopic budgetary bean counters in Congress, the calcified, lumbering behemoth that is the NASA bureaucracy with its abject lack of courage and imagination, but also by the same Space Shuttle/ISS corporate contractors that always promise so much and deliver so very little, I can not be very optimistic.

Guest
2004-Nov-19, 12:34 AM
If the elevator were cut at 400,000 feet, the lower part, made of relatively thin cable, will fall to the ground; the rest of the elevator will fall upwards until it reaches a new, slightly different orbit.
Not so good if there is an elevator car on the falling portion.

Actually there are plenty of problems with the space elevator and terrorism; I myself don't expect them to be built until the problem of terrorism has decreased a great deal-

this seems like an unobtainable goal to our minds today, but our planet has the potential to develop into a peaceful place in the future (with luck, good judgement and responsibilty).

Incidentally I don't think we really need a space elevator for Lunar traffic; the gravity of that world is low enough for take off and landings to be accomplished with little problem. But it would be a good place for a proof-of-concept showpiece.

GOURDHEAD
2004-Nov-19, 01:17 PM
Jerome Pearson has been thinking about space elevators since the early 1970s, and he's been watching the growing enthusiasm (and fading chuckles) with great interest. But he knows there are significant challenges in engineering and materials that still need to be overcome, so he's suggesting NASA build an elevator on the Moon first. And the agency is taking the idea seriously.
If I understand what is meant by space elevator, its center of gravity must be at an altitude above the object it is orbiting that causes its orbital period to equal the period of rotation of the object it is orbiting. For a space elevator for the moon, that altitude is the distance of the Earth from the moon which places the counterbalancing mass even further away. We could shorten this distance by speeding up the moon's rotation, but that adds expense. We could choose the orbit for the center of mass for the space elevator such that its plane had an angular separation from the plane of the moon's orbit about the earth thus causing the elevator's "far end" to be as near the earth as it could be without crashing into the earth. This would cause the moon end to move longitudinally along paths near the moon's surface. With this arrangement we would have a "highway" between the earth and moon. We may have to put the elevator on the side of the moon opposite the earth to manage gravitational effects of the earth.

If I understand this correctly, it is not very promising. Can I be right about the altitude of the center of mass of an object with orbit synchronous with the moon's rotation?

eburacum45
2004-Nov-19, 03:22 PM
For a single planet system the elevator has to reach to synchronous orbit, yes. But in the Earth Moon system it can also reach to the L1 point, where the gravity of the Earth and Moon balance out. It can also reach to the L2 point, where the gravity of the Earth and Moon work together to make a stable location; this is directly behind the Moon as seen from Earth.

In fact the L1 point is not a point, but varies slightly as the Moon travels in its orbit; but not too much to make this concept impossible.

However to get to the L1 point is nearly as difficult as getting to the Moon; and a mass driver would work fine for lunar launches, so there isn't much point in this except as a test bed for other, more robust elevators.

John L
2004-Nov-19, 08:19 PM
The value of a Lunar Space Elevator over a Lunar Mass Driver is that the entire Lunar Space Elevator could be launched and installed in one or two space shots, while a Mass Driver would be a major undertaking requiring extensive manned or robotic assembly on the Lunar Surface of major structures and power supply systems. The cost savings in the short run or enormous.

John L
2004-Nov-19, 09:57 PM
Originally posted by Guest@Nov 18 2004, 07:34 PM
Incidentally I don't think we really need a space elevator for Lunar traffic; the gravity of that world is low enough for take off and landings to be accomplished with little problem. But it would be a good place for a proof-of-concept showpiece.
Moving small payloads off the lunar surface is easy, but if you want to move millions of tons of lunar dust, ore, processed metals, solar cells for space based power generation, or any other high volume projects, then the space elevator is the most efficient system to do this. The first elevator, deployed from space, could be used to build a larger capacity, more robust system manufactured on the lunar surface. That is the current plan for the Earth based elevator systems and would work just as well on the Moon, Mars, or any other terrestrial body in our solar system.

The best part is the propellantless nature. Ride to the geosynchronous point (or the L1 point for the lunar system) and let go and you'd just float next to the cable. Ride out further and let go and the orbital motion of the cable would provide thrust to the object being released, like a sling. Have the cable extended several thousand kilomters past the L1 point, ride out to the appropriate distance, and let go, and you could have sufficient momentum to drop into a stable low Earth orbit without using any fuel at all. That would be much cheaper than sending fleets of small rockets to lift material through chemical propulsion off of the lunar surface.

John L
2004-Nov-19, 10:10 PM
Originally posted by mxsxsm@Nov 18 2004, 07:28 PM
I've always resented those members of the US Congress responsible for NASA's measly, tiny budget, a mere pittance, for being so short sighted and miserly funding NASA, especially against the backdrop of a multi trillion dollar economy and many billion dollar military procurement costs that are shamelessly wasted.
I have to disagree with you here. It was NASA that has funded the real world research into this project and has been doing so since the first scientist pointed out the carbon-nanotubes theoretically met the specifications needed to build a Space Elevator. Until their invention, the material needed to make the cable had always been called unobtainium because no one thought it would ever be found. Groups like the NIAC mentioned in the article were NASA funded, and the people that started Liftport (see link in a post above) both worked on those projects and continue to recieve NASA and US university support to develop this technology into a working real world system.

As for NASA's budget, it is only 1% of the national annual budget of the US, but that is more than $10,000,000,000 a year. As for military expenditures, the US spends annually more than all of the other countries in the world combined, but for that we have a military that can face any other force on Earth without worry of losing. Worth the price IMO. I, too, would love to see NASA's budget at least double, and projects like cheap orbital access be extensively researched, or prizes like the X-Prize funded to help speed our access to space, but we've got 280,000,000 people that break themselves down into almost as many groups who each have priorities for spending the US's tax dollars; not all of which agree that cheap and easy access to space should be our first priority.

Guest
2004-Nov-19, 10:19 PM
Hmm. I like the idea; but I can see a use for the L2 elevator too.
Material could be released from the L2 elevator into the solar system at large- it could be a highway to the solar system.

In particular I am interested in a solar collection swarm in the Earth/Sun L1 position, or perhaps in a ring outside the orbit of the Moon; this solar power ring could be made using Lunar silicon.
Building an elevator to Earth/Moon L2 could make this a fair bit cheaper.

eburacum45
2004-Nov-19, 10:21 PM
logs in to claim previous post.

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Greg
2004-Nov-20, 02:48 AM
I am glad people are taking this idea seriously now. Considering that it is possible to create an elevator on the moon, then by all means it makes perfect senses to perfect the technology and engineering there before we consider doing it on Earth. It also means we all may live to see such a thing happen, and that is quite exciting.

Guest_hank
2004-Nov-20, 09:40 PM
The problem in Earth orbit appears to be electrical potential differences -- remember the big surprise when the ifrst attempt to extend a llong cable from a Shuttle in Earth orbit ended prematurely because the cable shorted out electrically. Given how much more we're learning about sprites, elves and the other electrical surprises in the upper atmosphere, I've wondered if any earth-grounded space elevator could work.

A lunar one sounds more promising -- but I suspect comparable surprises would be likely.

John L
2004-Nov-22, 03:04 PM
Guest_Hank,

Carbon nanotubes shouldn't have that problem, but that's being tested for, too. The bigger problem actually is atmic oxygen. Molecular oxygen itself reacts chemically with a lot of materials significantly weakening them, but atomic oxygen could completely corrode most cable materials in short order. It will be the combination of carbon nanotubes and some type of epoxy resin that will make the cable work.

eburacum45,

I hope that warning wasn't directed at me. I only referenced Liftport because they've done a lot of the work in this field, and have great resources to explain the system. I'm an accountant in Texas, not any type of engineer in Washington state. If that's considered advertising, then I'm guilty, but I didn't see it that way.

eburacum45
2004-Nov-22, 06:25 PM
No, don't worry; that message was put there by the mods because I, not you, was a naughty boy.

anyway;
Electrical differences might acually be an advantage at some future date; properly set up a space elevator could generate electricity; not a bad thing in the post-oil economy.

However you would need hypothetical superconductors within the tether- someting not yet available in real life.

Bob Munck
2005-Apr-05, 10:18 PM
One tiny correction: the article says that Earth and Lunar SEs don't work the same way, but in fact the two possible Lunar SEs also don't work the same way as each other either.

An Earth SE is held in tension by Earth's gravity pulling down and centrifugal force -- caused by the revolution of the Earth -- pulling up.

A Lunar L1 SE is held in tension by the Moon's gravity pulling down and Earth's gravity pulling up.

A Lunar L2 SE is held in tension by the Moon's gravity pulling down and centrifugal force -- caused by the revolution of the Moon around the Earth -- pulling up.

Note that none of them are "in orbit" in any strict sense, although an Earth SE with zero tension on the anchor point would be in geosynchronous orbit. That won't happen, though anchor tension will be very small when a climber has just started up.