Space elevator faces reality

Posted: Monday, August 17, 2009 8:46 PM by Alan Boyle

Pat Rawling / NASA

An artist's concept shows a space elevator stretching down from orbit.

Like almost everyone else in the space vision business, the enthusiasts who foresee a "railway to space" are adjusting their high-flying dreams to fit down-to-earth realities.

"We don't have all the questions, let alone all the answers," Michael Laine, head of the LiftPort Group, told an audience of about 50 people on Saturday during the 2009 Space Elevator Conference on Microsoft's campus in Redmond, Wash. (Microsoft is a partner in the msnbc.com joint venture.)

Laine probably knows as well as anyone how few answers are available.

LiftPort's Web site is still counting down toward his goal of putting a real live space elevator into operation by 2031. But Laine's years-long quest to turn the concept into an actual business left him hundreds of thousands of dollars in debt by 2007, with a legal cloud hanging over his head.

Laine put LiftPort into mothballs and lay low for two years, spending part of that time in the International Space University's study program. It's only been in the past few months that he's been able to lift his head above the clouds again. "We went through some difficult times," he wrote last month in a newsletter, "but are beginning to get all those issues settled to the point where LiftPort will rise again (pun intended)."

Laine told me today that his legal troubles are "kind of in a strange point of limbo," and that he's still massively in debt. But he has enough hope for future ventures that he's willing to get back into the space elevator game rather than moving on to more conventional business ventures.

"I'm actually really happy to be back out there," he said.

Still a laughable idea?
The space elevator concept is one of the highest-flying ideas out there: Imagine a super-strong tether swinging out, say, 100,000 miles from Earth's surface, with laser-powered robots shuttling up and down from a ground- or sea-based station to an orbital platform. If such a thing could be built, the idea's proponents say the system could cut the cost of putting cargo into space from $10,000 to $100 per pound.

The idea is at least a century old - and was most famously popularized by science-fiction guru Arthur C. Clarke, who once said the space elevator would succeed "50 years after everyone has stopped laughing."

At last year's Space Elevator Conference, pioneer researcher Bradley Edwards said the first elevator could be built within 15 years, at a cost of $7 billion to $10 billion. The speakers at this year's conference took a far more sober view of the financial and technical resources that would be required. "They're not the rosy numbers that you hear," said Ben Shelef of the Spaceward Foundation, who manages two NASA-backed contests for space elevator technologies.

In a technical paper presented at the conference, Shelef concludes that the conditions required for a working space elevator are "actually very difficult to satisfy" at any price. That's the bad news. The good news is that the technologies needed for a theoretical space elevator project could well lead to payoffs - even if the elevator itself never gets built.

Those technologies fall into three categories:

Super-light, super-strong materials
The biggest piece of the space elevator system would have to be a tether strong enough to stretch for tens of thousands of miles, passing through Earth's rough weather and the radiation-pounded space environment. NASA's $2 million Strong Tether Challenge is aimed at rewarding the breakthrough development of lightweight materials that are twice as strong as the current industry standard.

Ted Semon

After being put to the test, a Japanese-made carbon nanotube tether looks like a stretched piece of videotape.

During this year's conference, a Japanese-American team tried to win the challenge with a tether made out of carbon nanotube strands. The tether looked and felt like the videotape from an old VCR cassette, as described on Ted Semon's Space Elevator Blog.

The nanotube tether didn't match the strength of its industry-standard competitor, known as the "house tether" - and that means NASA's prize has gone unwon for another year. But Shelef said the contest is still fulfilling its goal of promoting materials research that goes "beyond the leading edge."

He said the materials developed for the competition could conceivably be used in super-strong parachutes for NASA's Mars landings, or better carbon composites for spacecraft, airplanes and automobiles.

Power-beaming systems
Another NASA challenge offers $2 million in prizes for beam-powered robots that can scuttle quickly up a fabric ribbon - sort of like the robotic climbers that would make their way up the thousands of miles of a space elevator's tether.

The Power Beaming Challenge's bar has been raised every year over the past three years. To win any money in this year's contest, a team would have to send its climber up a kilometer-long (0.6-mile-long) tether stretched between the ground and a hovering helicopter, at an average rate of at least 2 meters (6.6 feet) per second.

"Think about Batman shooting his little dart arrow and going up," Shelef said. "He's going about 2 meters per second."

EADS

Europe's EADS group has tested laser-powered rover prototypes.

Three teams - the Kansas City Space Pirates, Seattle-based LaserMotive and the University of Saskatchewan Space Design Team - have devised laser-powered systems to meet the challenge. They're all likely to go for the gold during a contest tentatively planned for October at NASA's Dryden Research Center in California's Mojave Desert.

"This is like military-grade stuff," Shelef said. "They're doing work on the level of military contracts."

Even if robotic climbers are never beamed up an actual space elevator, the resulting technology could be used to power rovers operating in the icy, sunless depths of craters at the moon's south pole, Shelef said. He didn't mention the potential military applications, but if you watch video of the laser-beam tests, you could easily imagine infrared laser systems capable of tracking or disrupting aerial targets.

High-flying platforms
Another piece of the space elevator puzzle involves building aerial platforms that would serve as way stations for those robotic climbers. In the past, LiftPort's Laine has focused on balloon-lofted platforms that could serve as weather monitoring stations or telecommunications relays - and he said he's hoping to revive the balloon venture, perhaps as part of a military research program.

Others are working to build different kinds of platforms for spreading the space elevator gospel: academic programs that would back research into elevator-centric engineering issues, for example, or a peer-reviewed journal that would publish such research. The talk at this year's conference was that Canada's McGill University would soon be raising its research profile.

"We need to partner with everyone we can," said Semon, who does his part as the president of the recently formed International Space Elevator Consortium as well as a leading blogger following the field.

Should NASA be offering millions of dollars to support technologies for a space elevator that may never be built, at the same time that it's apparently falling billions of dollars short in its drive to re-energize space exploration? Shelef and his colleagues are under no illusion that they'll come up with the next giant leap into space anytime soon. For now, they're content with the small steps being encouraged by NASA's prize program.

"At this budget level, it can't hurt," Shelef told me. "It can only give you a good answer."

Update for 10:15 p.m. ET: Personal Spaceflight's Jeff Foust, who attended the weekend space elevator conference, passes along word that Armadillo Aerospace plans to take aim at NASA's $1 million top prize in the Northrop Grumman Lunar Lander Challenge during Labor Day weekend. The timing for the prize attempt is mentioned on The Space Fellowship's Armadillo discussion forum. Armadillo won a $350,000 prize last year for a less ambitious flight.

More about the space elevator concept:

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Comments

I wonder if it's such a stupid idea to suggest not trying to do the whole tether in one go, but rather to have some form of support along its length with large helium balloons to balance out at least part of its weight? Wouldn't even a slightly heavier strand material work if the weight were partially counterbalanced by lift?

John Burkitt, Nashville, TN (Sent Monday, August 17, 2009 9:35 PM)

Why is everyone so intent on a space elevator for the Earth? Why not use it for the Moon? Lift/lower materials without the penalty of its gravity well. With 1/6 the gravity and no atmosphere, the physical/mechanical requirements are greatly reduced. A moon base thus endowed would be very practical -- the presence of gravity to make life easier for humans, raw materials for structures and no need for "water deposits" to make fuel -- just mine a few NEOs for volatiles and lower the stuff to the surface. And, if you mine He3 for Earth-based fusion, just lift the “bottles” up the elevator and drop them back into the Earth. All pretty “now-tech” stuff.

Jon, Honolulu (Sent Monday, August 17, 2009 9:48 PM)

Great concept that should generate many great spin-offs...

Hamid Chowdhury, New York, NY (Sent Monday, August 17, 2009 9:56 PM)

As many times as I have seen this presented, I have never seen the following issue addressed. The elevator is a stationary object basically in a geostationary orbit. It would remain above a single point of the equator rising thousands of miles. We currently have thousands of other satellites traveling in orbits of various inclinations. But let’s concentrate on those in a polar orbit. The point of a polar orbit is that the earth rotates under the orbital plane of the satellite so that it eventually passes over every point of the earth. Although it depends on its altitude, and it would not happen in a single day, it seems logical that something in a polar orbit would eventually “clear” the entire path at the altitude of its orbit. Does this not mean that every polar orbiting satellite is destined to eventually impact the “stationary” elevator at 17,600 mph or more? We already have satellites running into each other. This sounds like an air traffic control nightmare.

Fritz, Greensboro NC (Sent Monday, August 17, 2009 10:04 PM)

Getting into orbit was never going to be easy. The materials angle is fantastically tricky, but carbon is proving amazingly versatile and there may well be a break-thru in time. But the barrage of high-velocity dust that a space-ribbon would have to face is daunting. Shorter tethers might allow much of what space-elevators are promised to do... maybe.

But then even if the SE proves dubious a break-thru in materials will benefit regular rockets and may well lead to a real space-plane. Look at SKYLON, for example. Super-light, super-strong carbon materials would make it that much easier to make and fly back to Earth - really fly, rather than plummet and fry like the Shuttle or capsules. Eventually space-elevators or rotovators may well be deployed on the Moon or Mars, enable by the break-thrus developed here on Earth.

Adam (Sent Monday, August 17, 2009 10:46 PM)

The space elevator is no less likely today than getting men to the moon was when President Kennedy declared we would do it. If the space elevator is never built it will not be because it is impossible but due to a failure of imagination. Remember that many knowledgeable individuals claimed that cars would never go faster the 50 mph because the human body could not take such violent speeds. The question is not if the space elevator can be built, the question is do we have the will to build it.

John (Sent Monday, August 17, 2009 10:50 PM)

A note on the question about building one for the Moon: The elevator stay up by having the center of the cable/ribbon being at just over escape velocity. Since the Moon rotates only once every 28 days the cable would need to be several times longer than one for Earth.

John (Sent Monday, August 17, 2009 10:55 PM)

My question is why build from the ground up? Technically the carbon fiber nanotubes could be built in space and eventually be lowered to a point predetermined to optimize usage. I do not understand the physics of this but apparently neither does any one else... :)

scott (Sent Monday, August 17, 2009 10:59 PM)

On the subject of impacts, the ribbon proposed for the cable is about a meter wide. Even if perfectly stationary it would not be difficult to place it to avoid almost all currently active satellites. The design of the elevator is that it is attached to a floating platform. The platform would be in regular motion to keep it in the clearest possible orbit.

John (Sent Monday, August 17, 2009 11:00 PM)

Wow, Fritz, that's a good question. Thanks. Does anyone the answer to this?

I like this idea of space elevators, but I wonder if all of the practicalities have been thought out.

David, Columbia, SC (Sent Monday, August 17, 2009 11:13 PM)

Jon.

The lack of atmosphere and gravity on the moon would reduce the cost of a lander carrying cargo from a moon base to orbit.

I think electromagnets attached to large metal rings could be used to create a "space elavator" where a platform could be sent up and down the length by varying magnetic properties between the rings. The magnets would also support the weight and position of the rings as they go up. You would be able to have a stabilizer bar along 4 edges and the "tether" wouldnt nearly need to be as strong as what these contests require.

Best place to build it would be in a mountain perhaps bored out at the top. You would prevent most of your major storm issues, tornados, hurricanes, typhoons, etc.

You could power it with huge solar panels.

I just hope in 2039 were not sitting here complaining about the price of gasoline and how "cool" Miley's 36th birthday was. You never can tell.

America Today Anthony (Sent Monday, August 17, 2009 11:38 PM)

Fritz-

Those questions have been addressed. One of the myriad proposed solutions would be to use multiple tethers for redundancy if one should break or get cut.

Another tangential issue that's been addressed, and I haven't seen any answers, is should one tether break, how would we deal with the tether as it falls to Earth.

MrPex, Sacramento, CA (Sent Monday, August 17, 2009 11:49 PM)

Even though the physics support this idea, there are other realities I have not seen addressed. You can only "get off" at a geo orbit (22,000 miles). If the elevator went 100 mph (a feat in itself), the trip would take 220 hours (9+ days) one way. So for multiple people taking this trip, this "elevator" is not just a small room to stand in, it has to be a complete hotel (rooms, beds, food, sewer system, etc) capable of support for weeks without external supplies. This "tether", regardless of super light materials, is a structure big enough to carry something the size of a building or railroad cars and a structure long enough to wrap around the earth. It takes 5 years to build the largest bridges (1+ miles); this is a 22,000 mile bridge. I guess if we start now, we'll have plenty of time to work out the bugs as we go.

Dennis, Houston, TX (Sent Monday, August 17, 2009 11:59 PM)

A polar sattelite would not pose a significant problem as the tehter could simply be adjusted by moving the floating base or with the use of adjustable gyroscopes

Dylan, Calgary,Alberta (Sent Tuesday, August 18, 2009 12:14 AM)

Just a note on the physics. A space elevator has the space end at geosynchronous orbit (22,000 miles) so it can stay above the same point on the earth. The earth end must be on the equator. This is the same orbit where TV satelites sit and where our TV dishes point to.
The moon is 250,000 miles and does not stay above the same spot on the earth, so anything attached to the earth and moon would immediately start to wrap around the earth.

Dennis, Houston, TX (Sent Tuesday, August 18, 2009 12:14 AM)

What happen if an Earthquake or Hurricane hits this thing? I highly doubt this would ever work... It comes at a very high risk factor...I would even say higher risk than taking a ride into orbit on the Shuttle... And what happens if the base on Earth Brakes or is ripped off?

Sorry, I don't find this at all practical... However, I find the research into it practical for it may improve and advance current technologies for various applications..

Will (Sent Tuesday, August 18, 2009 12:25 AM)

Alan's story reminds me of the whole sci-fi becomes sci-fact trend.
As you all know we are facing some issues right here on the home planet.
Here's a thought...
As sci-fi become sci-fact, so does Hippie Gibberish become sci-fact in today's version of The Climate Crisis.
The space travel sci-fi that is reaching fruition as sci-fact today became part of the public consciousness in the late 1950s.
Fifty years in the pipeline, and we still get artist conceptions...much like PopSci of the 50s...the pics are cooler, but...you get the idea...same ol', same ol'.
Hippie Gibberish began about ten years after the concept of Man in Space entered our minds as potential reality.
That gives us a decade to mull over this Anthropogenic CO2 scam.
A decade during which Sir Richard Branson and Algore will make bazillions.
Algore is the Hippie Gibberish guy.
Branson's the sci-fi/sci-fact guy.
Both are betting that the fifty years to fruition trend will continue.
What a mess, eh?
Feel better about Man in Space and The Climate Crisis.
Have a look at this...
http://lynnkid.blogspot.com
It presents a doable solution to many of today's issues...including space junk as mentioned by one commenter to this posting.
Remember this...even the earliest space pioneers realized that guided missiles ( rockets ) were of little, or no use in Space...Rockets are not SpaceCraft...never will be.
Long range, manned vessels will require a self-sustaining fuel source...solar.
Gaia Two also addresses this issue.
Forge Ahead!
Enjoy!

steve smyth (Sent Tuesday, August 18, 2009 12:37 AM)

Can't wait until the high powered laser hits the tethering helicopter. Wouldn't want to be that pilot.

Brian (Sent Tuesday, August 18, 2009 1:10 AM)

The big problem is that each satellite and piece of space junk passes over the equator twice every orbit. Most of these objects, and there are thousands, are below the altitude of the top end of the projected elevator "shaft". I believe that the average object would make ten to sixteen equator crossings per day as the earth turns below.
A collision with any object that we currently can track would likely be lethal to the elevator tether.

Bill Smith, Kalama, Washington (Sent Tuesday, August 18, 2009 1:21 AM)

New technologies require monetary investment to bring them to fruition. NASA is to be commended for fostering innovation, even if it fails in its original intent.

Matthew Ota, Lebanon, NH (Sent Tuesday, August 18, 2009 1:25 AM)

Jon in Honolulu, the moon moves around the earth, so you couldn't tether to it. The tether would wrap around the planet till it broke.

Fritz in Greensboro, the end of the tether would be geostationary (remaining over one point) as all the satellites that far out are. It wouldn't impact another geostationary sats. There IS a concern for satellites in LEO (low earth orbit). One ompact by something moving 18k mph would destroy the tether.

Scot, the tether will be lowered from orbit to the surface, but it probably won't be manufactured there. It will be easier to build a small light tether and shoot it into space on a conventional rocket, lower it, and then add/laminate stronger and stronger tethers to the first one.

Chris McCoy (Sent Tuesday, August 18, 2009 1:30 AM)

Hi the idea of the space elevator from Arthur C Clarke may at one time be considered science fiction is now science fact. We are living proof how science fiction is a part of every day life. As Napoleon Hill once said, that all concepts and ideas were once formed in the minds of men, and with enough will and determination will become reality. "What the mind of man can conceive and believe, it can achieve."

Gene Belanger, Medicine Hat, Alberta, Canada. (Sent Tuesday, August 18, 2009 2:06 AM)

When you scratch the Space Elevator you discover an ungainly and clumsy 19th-century concept. The problem is in static support – meaning essentially you hang the rope, and that's it. However, the Third Millenium solution is to mine mind to be found in generation of dynamic lift supporting the device, as independently suggested by dr Hyde (of LLNL, unpublished results) in his Starbridge concept and by me in the Project Synchrodyne (Acta Astronautica 45(1999)143-153). It's the old/new contest of Wright v. Zeppelin, with the winners (well, of the first match) visible all over the skies. Just for comparison, unencumbered by crushing dead weight of the support structure, The Synchrodyne is expected to be able to carry a payload roughly equal to its own mass to GSO and back on daily basis, and at a cost (depending on size and the state of art) in the range of $ 1 to & 100 per ton. Transmitting cheap space-produced electricity with virtually no losses and at the rate of roughly 1kW/kg almost as an afterthought. It's essentially a device which could outsource (in economically viable way) the planet utilities, manufacturing, and agriculture into GSO by the middle of this century, putting the stake through the problems of hunger, global warming, and depletion of resources for good. The main problem – plaguing in fact any dynamic flying machine – remains that of reliability, but recent advances in the field of high temperature superconductors (the last high point is Tc of 242 K!) hold promise of enhancing the availability of the device in dramatic fashion by eliminating the most precarious part of the system, i.e. cryogenic liquid-cooled supermagnets. What a pity that my paper published in peer-reviewed journal of such standing was virtually ignored even by scientific community!

Predrag Raos, Croatia

August 19, 2009

Predrag Raos, Zagreb, Croatia (Sent Tuesday, August 18, 2009 2:09 AM)

To add to John's note on the hypothetical Moon's elevator - the elevator there would also have to face away from the Earth.

Marek, Toronto, ON (Sent Tuesday, August 18, 2009 2:12 AM)

Wouldn't the "ribbon" have its weakest point half-way up? Consequently, wouldn't it have to be able to support "only" half its total weight plus the attached payload? Therefore, if it would be made thicker towards the middle of the overall length, the material wouldn't need to be as strong.

Marek, Toronto, ON (Sent Tuesday, August 18, 2009 2:24 AM)

Space elevators for the near to medium future are a dumb idea. A single massively expensive project more vulnerable than the shuttle program to catastrophic failure. Can anyone even begin to guess how the materials involved will interact with the earths atmospheric charge differentials and magnetic fields. How well will the cable resist degradation from cosmic radiation, micro meteorites, and human sabotage. The hyper accelerated protons and neutrons alone can transmute the atomic composition of materials like it does inside atomic reactors with much weaker radiation.

Stop wasting the money, shelve it for a hundred years and let it be built when it will be vastly cheaper and more practicle.

sane (Sent Tuesday, August 18, 2009 3:24 AM)

It seems strange that no-one has mentioned the JET-STREAM.

REX @ Poortland Oregon (Sent Tuesday, August 18, 2009 4:19 AM)

The helium balloons might help, but only at the very lowest altitude. Those thing don't rise forever, after all.

Elevator on the moon might be the first application if there is ever a lot of traffic. Seems a bit quiet there lately.

Moving the base of the ladder enough to avoid passing satellites might work as long as they don't pass by too frequently.

If the cable does get broken by some collision, wouldn't that cause the platform holding the cable up with centrifugal force to launch into space, never to be seen again? This could be a problem.

Al Brown, San Jose, CA (Sent Tuesday, August 18, 2009 5:28 AM)

i think they should spend the money on something a little more realistic, thi sis a waste of time and money, its not logical even though it might seem possible in some peoples minds or even on paper, but in real life, it wont work.

fusseltier (Sent Tuesday, August 18, 2009 7:14 AM)

Typo: the past tense of "lie low" is "lay low", not "laid low".

[ALAN ADDS: You are correct, and the verb has been corrected. Thanks for that!]

Paul, Japan (Sent Tuesday, August 18, 2009 7:25 AM)

Why have a tether from ground to space when we could have a geo-stationary platform beam down an 'energy tether' to power a craft or lifting body up to it where the cargo is unloaded and the craft then de-orbits shuttle like and lands at a space port for re-use. The power can come from laser or microwave and be solar generated in orbit. Perhaps the station could start with an inflatable module 'Bigalow'.
The Bigalow module has already been tested in space.

Harold Ziel (Sent Tuesday, August 18, 2009 8:01 AM)

Fritz/David; The Space Elevator concept calls for a mobile platform on the sea, located NW of South America. That way the tether can be moved around to miss satellites, debris, asteroids, etc.

Doug Fingles, Warner Robins, GA (Sent Tuesday, August 18, 2009 8:20 AM)

Scott; The idea is to "drop" the tether from the midpoint and let it extend out to geostationary orbit at the same time, keeping the system in balance. So you are correct, it is easier to drop a rope than push one... :-)

Doug Fingles, Warner Robins, GA (Sent Tuesday, August 18, 2009 8:22 AM)

John; You are mostly correct. The design of the tether calls for changes in width over the length to compensate for micro-meteorite impacts, radical oxygen degradation, etc. It may be a meter or so wide at the ground, but would be about 3 meters wide as it passes through the upper atmosphere.

Doug Fingles, Warner Robins, GA (Sent Tuesday, August 18, 2009 8:26 AM)

Fritz and David,

The question of avoiding satellite impacts is in my opinion the single greatest challenge building that comes with building the space elevator, with power transmission being the second. Though the required materials do not exist yet, eventually they will, it is the specifics of implementing them in order to avoid all these other problems that is important.

There are a few things that you can do to guard against collisions, the first is the orientation of the cable. The shape of the cable that seems to be the easiest to transmit cargo on is a belt, It will be 1 to 2 meters thick, but only a few nanometers wide. You can orient the thin side towards the highest volume of traffic (speed doesn't matter as much, whether there is a .5km/sec impact or a 5km/sec impact there is going to be a similarly sized hole).

That's just a basic passive precaution, there also need to be active safeguards, there are three types of dangers here.

1. Active satellites with propulsion systems that can make the tiny changes necessary to avoid the space elevator. These guys are avoiding each other and debris all the time, the addition of one more obstacle probably won't even impact their fuel usage much, unless they are in some sort of orbit that frequently passes through the space elevator's region.

2. Inactive satellites, satellites without propulsion systems, and large debris. The USAF keeps track of all debris larger than about a baseball. We will know where most of these things are, but they can't move to avoid the space elevator, so it will have to avoid them. Moving the counterweight on the top isn't a good way to accomplish this, it is going to be very massive and very far away. (It needs to be out past Geosynchronous orbit, so more than 36,000 km away, or about the circumference of the earth.) Moving the part of the space elevator in the danger zone (up to about 600 km high) would require moving this heavy object much more, also you'd have to be careful about placing other parts of the elevator in danger.

Instead you would have little stations with small engines spaced out along the elevator, who knows how many you'd need, they may be spaced 50 km apart in the lower earth orbit, but thousands and thousands of km apart out in the empty regions.

3. Smaller debris that you don't know about and can't avoid: This will hit you, period. It is unclear how much of it will hit you how often, maybe it will be too bad for a space elevator and we will have to wait 10-50 years (being more careful about orbital debris) for all their orbits to degrade so we can try again. Hopefully it will be manageable however. You'd try to manage it by making your tether much thicker than it needs to be to carry the weight, so that it could operate damaged for awhile. Every now and then (who knows how frequently, maybe every third day, maybe every third week) you'd have to send up special cars to repair the damage. I am guessing that these cars would move much slower than the normal cars, so the tether would be out of commission during repairs. These cars would also refill the propulsion stations on their way. The repairs could probably be done pretty quickly, no reason that 20 cars couldn't do it at once, as long as you have enough laser beams or whatever else you are using to power the cars. The materials science comes back to play here, how efficiently can the tether be modified on site. If we know enough about carbon nanotubes that the cart can stitch them back together again good as new, great! If not then you'd have to operate it like a normal road, fill in potholes as necessary but eventually you need to scrape it clean and re-asphalt it.

You would also want even more redundancy than a thick cable, you would want multiple cables, so if (when) one of them did break due to an unlucky object hitting at a strange angle (you can imagine a straight on hit on the thin edge would tear through the whole thing) you would still have a functioning space elevator and could repair the broken cable. Also multiple cables means that you can still transport cargo while one is being overhauled.

There are tons of other complexities and challenges when building a space elevator, I could go on for another ten pages (I've done it before) but that should about do it for now. I will say that the challenges are huge, enough so that it will be several decades before one is up and running, but the rewards are also enormous. They won't be for the first couple, but once we get the kinks all worked out the 4th or 5th time we do it... Well 40 years after that everyone will laugh at the idea of doing it any other way.

Michael Dunkel (Sent Tuesday, August 18, 2009 8:50 AM)

The other thing that seems rather difficult about a space elevator is that the material that is sent up must equal, in mass, the material that is sent down. Or, the space elevator will either fall down or break up and float away.

Try slinging a rope around a tree branch and climbing it. Climbing something and pulling it down are the same act - the only difference in behavior is based on which one is bigger. The thingy at the other end of the elevator will have to have a mass large enough to keep from being yanked out of geosynch orbit by everything climbing up it, as well as the tensile strength of the tether having to be strong enough to deal with everything climbing down it.

Byron Raum, Beverly Hills, CA (Sent Tuesday, August 18, 2009 9:38 AM)

Right now, even if somebody had a cable of the right strength and length (they *don't*), the radiation belts around the Earth essentially preclude using this for human transport.

Ian Woollard (Sent Tuesday, August 18, 2009 9:50 AM)

Why all the hooplah:
Just build a larger version of the Anti Gravity Gyroscopic Lunging Device simmular to the one that we have built. The only problem will be getting it back. We hav'nt figured out that part yet. Further testing will continue. Soon it will be ready for the world to see. Sorry big brother, you will not stop us.

breakthrough the clouds (Sent Tuesday, August 18, 2009 9:55 AM)

I've thought putting space elevators on the moon would be a great idea, too. It would certainly be more feasible in the near future and a great place to learn how to make bigger ones, like for Earth's elevator.

don smith (Sent Tuesday, August 18, 2009 9:56 AM)

The whole problem with this is the torodial stresses involved from the ground up i.e. wind shear, orbital momentum, spatial impacts, not to mention the huge probelm dealing with the earth's angular momentum of rotation make this impossible using even the most advanced current technologies. Just ask any industrial engineer about the huge stresses involved in building some of today's new superskyscraper's such as the Burj Dubai. The higher we build, the more intrinsic stresses have to be dealt with. Also, there is no getting around the old gravity problem. You still have to reach escape velocity.

Anton Kowalski Wichita,KS (Sent Tuesday, August 18, 2009 10:01 AM)

Great and rewarding undertakings have all been challenges. They took time, effort and a lot of engineering successes and failures to become realities. Even an elevator in a not-so-tall building has benefitted from a lot of trial, error, and achievement leading up to commonplace and acceptably reliable results. From waht I have seen, we have the materials strong enough to make it work so it is physically possible.

Bill Marshall, Denver, CO (Sent Tuesday, August 18, 2009 10:07 AM)

At 2m/s it would take 15 days to reach 100,000 miles. Not exactly what most would consider an elevator ride.

[ALAN ADDS: Yes, the usual scenario doesn't envision taking the full 100,000-mile route. Rather, cargo and passengers would be sent up to the orbital transfer station, at 22,000 miles. The usual scenario calls for a weeklong trip to get to that level, so it's not exactly like an elevator ride at the department store.]

Scott (Sent Tuesday, August 18, 2009 10:25 AM)

STATE THE OBVIOUS: Wouldn't some idiot eventually crash a plane into the tether and wreck the whole thing, bringing the platform into a heap of burning metal toward the Earth?

Matt (Sent Tuesday, August 18, 2009 10:26 AM)

Most interesting article Alan! It sure seems crazy a space elevator, but then going to the moon was deemed crazy before we actually accomplished it. It will be interesting to watch this over the years to see how far they can take this crazy space elevator idea and turn it into a money making reality. It sure would benefit getting mass up in orbit far cheaper so we could do more space stations far more cheaply and faster than we do now with the space shuttle.

The power beaming system will also be interesting to watch and could be a real boon for humanity if they can make it work. It's nice to see research being done without it having to have a military application.

Eric, Salinas, CA (Sent Tuesday, August 18, 2009 10:26 AM)

Attaching a space elevator "Ribbon" to the earth I believe would create a massive grounding rod. How would storm created lightning be handled? Also if you do not ground the "Ribbon" how do you handle static charges being built up on the system???
Just a thought.

GM, Palmerton, Pa (Sent Tuesday, August 18, 2009 10:44 AM)

One brainstorming suggestion is NOT to have the tether anchored to the ground (as I have been envisioning it for the last 15 years since I first heard of the concept) but to have the tether attached to a supported platform on the upper edge of the atmosphere where vehicles could "land" and reach the platform as a winged plane.

This would avoid having lower elevation planes or birds or anything else getting sliced by the cable, or vice versa.

Jym Allyn (Sent Tuesday, August 18, 2009 10:47 AM)

As to a space tether on the moon instead of the earth. I don't think that could work, in that the moon is gravitationally locked with the earth, and therefore doesn't spin about its axis. The centripetal force needed to cause the tether to be in tension is provided by the earth's rotation. No rotation no tether...

Keith, Boynton Beach FL (Sent Tuesday, August 18, 2009 10:47 AM)

Fritz may have a good idea for sweeping up space junk.

Harold Ziel (Sent Tuesday, August 18, 2009 10:49 AM)

"John (Sent Monday, August 17, 2009 11:00 PM)"

Ooops. I need to read ALL of the posts before responding.
Thank you.

Jym Allyn (Sent Tuesday, August 18, 2009 10:49 AM)

With all the money we need to reform health care, why are we even thinking about space elevators?

Michael Furlong, Huntington, NY (Sent Tuesday, August 18, 2009 10:50 AM)

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