Discussion on:

Going up? Take an elevator ride to space

What happens if someone flies a plane (intentionally or unintentionally) into these tubes? What if this happens while a load is on its way into space? It seems like terrorists could have a field day with something like this.

One way to handle a terrorist cutting it would be to have a way to cut loose portions of the counterweight. If you can keep its center of gravity geosynchronous after it has been cut, it will happily continue to orbit there.

It depends on where on the elevator the terrorists hit. The elevator has to go from earth surface to some distance past geosynchonous orbit to keep the cable tight. A break near earth would cause the whole thing to fly out from centrifugall force, a break towards the middle and the outer sections flys away and the lower section collapses like a series of meteroids smashing into earth. There are several sci-fi stories based on a space elevator; the one I think of for this problem with space elevators is Kim Stanley Robinson's Mars series "Red Mars", "Green Mars" and "Blue Mars" about terraforming Mars.

I don't see a plane strike doing any damage to this material. Much like a bullet can't penetrate a silk cloth because the silk is too light and too strong. Carbon Nanotube fibre is 100 times stronger than silk.
This fibre can support a car with a thread that is too small to see! In those early tests, they quickly realized accidental contact with that tight thread caused horrible wounds! You could hit it with a baseball bat and cleave the bat!
A plane hitting this cable would just receive a large dent and then take the cable with it.. The plane would severely loose speed and, after about 200 meters, would spin off. This is also the reason the cable would be located mid ocean with closed air space and a defended support platform.

Amazing. This is what you think about? Looks like the terrorists won.

"What if" is the excuse for doing nothing. What if I go out to get in my car and a tree falls on me? I should not go out; I should stay inside. What if there is a gas leak in my house and it explodes? I should not stay inside; I should go out. I'm so confused ... I am locked in a set of 'what if' tragedies and disasters .... Oh, there is no escape .... what to do, what to do .............

The engineer in me asks what happens when the elevator gets stuck between the two end points? How do you fix it with people on board and imagine the wait time for the repair crew?

As one Engineer to another, this isn't an elevator cab which is either a cable suspended or a hydraulic lifted cab. The plan for a space elevator has always been to have several cables, with an electric current in conductors inside the cables creating an electric field, then using magnets in the cars to run up the cable as a linear motor. Presumably, the cars would draw power from other wires in the cable too.

What I wonder about is the limiting of the car to 200 KPH. This would make sense in the atmosphere. Vibrations would be induced in the cables by winds. Once above the atmosphere, there is no reason to limit the cars speed. It could then accelerate up to any reasonable speed. It would of course have to decelerate at the top too. But, speeds of up to 5000 KPH would appear reasonable once you are more than say 150 KM above ground level. It would be a comfortable trip if you kept the acceleration down to around 12 M/S^2. Changeover would be uncomfortable, as the room would seem to flip from right side up to upside down, but a simple gimbals system would make that easier to take. A quick back of the envelope calculation would give a total trip time of only a few hours. Less than the time for a subsonic transatlantic trip.

The thing would be a power hog. Existing conductors are not up to the task of the power levels that would be needed. You would probably want to power the system from both space and from the ground. The electrical coordination required would be quite interesting.

The existing nano tube fiber systems are not near the strength required for the systems yet. Nano tube fibers to date are not very long. They are also quite flammable. Yes, they will cut steel or even titanium. No need to worry about the fictional terrorists cutting the cable with an aircraft. It would take a laser. But, the cable would burn very well.

Current tether materials are more plastics with the carbon nano tubes embedded. This has the advantage of both binding the little things, and protecting them from the oxygen. This approach has yielded tethers of over a kilometer in length. But, the strength is only a little better than steel. Much work remains to be done on tether materials.

The Space Elevator will need something that can be responsive to vibration dampeners in the atmosphere, resistant to impacts from orbital debris, as well as resistant to UV radiation and cosmic rays. It would also have to have better bonding of the carbon nano tubes into the matrix, and be able to increase the amount of nano tubes in the matrix. It's an interesting materials problem.

Progress is being made though. The sort of material needed will be useful for many construction projects here on Earth too. It will be a wonderful tension member. It can provide great compression strengthening too by having a non compressible material inside a wrapping of this material. Tether wrapped concrete columns would enable mile high buildings to be much lighter. It would enable much longer bridge spans. It would also enable structures that are not currently possible.

The biggest hurdle to developing the basic system is to be able to reliably produce the long strands of carbon nano tubes for inclusion in the matrix.

The material for the power wiring is another fascinating area for consideration. a room temperature superconductor would be ideal. A material that doesn't super-conduct might be necessary, but I would want a material with lower resistance than copper wire.

All of these details are why Aurthur C Clark said it would take 50 years after people stopped laughing before it was done. they stopped laughing 5 years ago.

but I gave it a big "thumbs down" for being longer than the article itself. Reel it in, Bob.

"What do you think? Is this just another example of trying to create science fiction fantasies in real life? Or would such an elevator have real value?"

The more obvious question: Is this just another example of a company creating free advertising/PR at the expense of the media and their readers - because the media editors aren't bright enough to understand that no serious business attempts to work off a 50 year plan. Most can't meet the goals of a 5 year plan. Way to be used not-so-Smart Planet.

It's been a popular SF idea for years, and you zeroed in on the one problem, material strength. We just don't have anything with the right strength and weight characteristics right now. As for what happens if a plane flies into the elevator, it's hard to imagine the size and strength required. I wouldn't want to be in what was left of the plane, and the beanstalk would be pretty much unscathed. As for the fuel burning, yes, nanotubes are carbon and could cook off, but you won't see a 9-11. There are too many ways to dissipate the heat.

A functional beanstalk would make a lot of things possible and aid in raising the quality of life down on the planet.

But, I would only take such a trip if it would actually go somewhere, like a different plannet or something... Not a spacestation, where everything looks just as boring as the trip...

I don't claim to know everything about nanotubes, but I believe that they are grown. Wouldn't it be possible to just have them grow below the factory and raise it into space?
How quickly can they be made to grow?
It would be a hefty and precise build/grow project.

You could also potentially grow a carbon nanotube and splice it to another, then you could parallelize the process. By simply growing 1000 sections at a time and splicing, you could have the fiber growing at about 1000 times the actual growth rate.

May A. C. Clark RIP, but this idea is impossible. Even diamond filaments wouldn't stand the stress, even if they could be manufactured. Worse, this thing would necessarily have to be constructed in geostationary orbit, and the fibers be shielded from the impact of micrometeoroids and space junk. At several hundred dollars per Kg of payload, the thing would cost more money than has ever existed.

There is little reason to go on about "cost" or "money". At this point in the history of the world, money doesn't exist. What exists is "opportunity" that is printed in the form of what used to be called money. World banks and governments control the expansion on the planet by using "interest rates" as a deterrent to rate of growth. The lower interest rates are at the Fed and other "world banks", the more opportunity there is to do something, because you don't have to pay it back with any great "loss". The world truly is now a socialist economy that is being ran by the bank's dictatorial policies. They try to do the right things, it seems, by managing the rate of growth based on the stock market, population and perceived "inflationary pressures".

But, in the end, all that is really happening, at this point, is the lack of "projects" is limiting the employment on the project, and that is directly related to the "interest rates" at the bank, and our in abilities to have long term views on projects, such as this one, which it wouldn't really matter if we were able to complete. Instead, it would employee 10's of thousands of people with a job to complete, money to be made, and things to keep lots of parts of the world employed doing.

It's time for us to really start understanding that the way we view capitalism and opportunity really has lots of issues with how successful we can be at keeping the world running.

We need large scale projects that aren't "WAR", which is what has been the single largest employer we've had. We need to try space exploration from a different perspective than "jump to orbit and look at the earth". NASA's small vehicle projects, going out to look at lots of different things will be very educational, and hopefully reveal some rather amazing things, right here, close by.

But, with gravity as our barrier, we can't get much "mass" off the planet to go do anything "long term". Instead we have all these 1-2 week outings to orbit, and that's all we do, over and over and over...

How long do you think our societies can survive on "build cars", "build houses", "grow food", "birth another baby", "bury another relative", buy another stereo, get the latest iphone etc?

There is much more in the universe that we could be discovering... We waste an awful lot of time, energy and ohh, that "money" stuff on completely useless things.

The missing element in your "analysis" is the fact that WHATEVER we manufacture, it must be done using actual RESOURCES mined, grown, or put together by us, here on Earth.

Money IS a collective fantasy, true; and its also true that various tricks can generate more money and "economic activity" out of simple traded information.

BUT...

To DO anything with that money, we still need resources.

So while we are blithely using (up) the resources of the planet, in order to send some few privileged humans out into the solar system, the REST OF US, here on the formerly pristine planet that gave us birth, will be sinking deeper and deeper into a stew of that project's waste products.

How much is it worth, to follow our immature dreams? No one actually COUNTS in a dream -- not beyond three, anyway. By the time a thousand people have gone up the beanstalk to a "better" life in space or on other planets, the bill that comes due for that collective endeavor will have cost the rest of us litterally trilliooo,ooo,ooo,ooons of dollars, and probably millions of lives, in the final analysis.

And without the indefinite continuation of such a benighted policy, the effort will still evaporate into stardust, when the support is withdrawn.

No, money is a way of counting things, and comparing their value.

Thinking that we can spend an infinite amount of money wastes a lot of resources. Everything you or I do is trading some value (mostly our time and talents) for something someone else did. What we are doing is not making money something you don't have to worry about, it's really just changing the way we track it. (we have gone from valuable metals to paper and now to bits.) It doesn't change the reality of what we are tracking, however. If you want to say that it does, you are just making your money (and mine probably) become worthless.

It doesn't matter if you want to take the money spent on arms and use it to buy food. That doesn't change the amount of food there is, it also doesn't change the value of the unused metal. It does though, deprive the metal workers now producing tanks of a means of supplying their families with what they need. Ever try to eat a tank? It isn't very nutritious.

I do like the idea of settling space. I don't however delude myself that we can just spend without paying off or paying back the sources of the money.

Yes, the resources expended in a small war would be enough to pay for a colony on the Moon with a population similar to that of Wyoming. But it would still be an expense that would ultimately have to be either paid, or have the sponsoring society harmed to that amount.

Money may be 'imaginary', but it represents real work and real resources.

Don't be misled. Every Cent must be accounted for, or you are harming someone.

I like this long view and the not war part now if we can just get everyone to cooperate.

Starman35, this has been studied by physicsists and chemists as well as astronomers. At the ground, the tether would be a ribbon around a meter wide, and only a couple of millimeters thick, except for where the power and communications cables are installed. It would taper up in thickness to the station, then taper off after the station. If Carbon Nano tubes (pure) are used, it would be around 30 Meters across at the station. If Diamond were used, it would have to be thicker, around 150 Meters across at the station. If Tungston Steel were used, it would have to be around 2 Meters across at the ground end, and taper up to around 5 KM across at the station.

There are ranges of size needed that are dependent on the tensile strength of the material used. Even spider silk has been considered. The problem there is that the strength of the silk requires water in the bonds. It would have to be encapsulated. Spider silk is about 10 X stronger than steel in tension. That's better than we get with current tether materials, but less than the carbon nano tubes are capable of.

It probably won't be possible to build until after we already have colonies in space. It's much easier to build it in place and then lower it to the ground.

So it is possible, will be profitable, but not in your lifetime. It's long range research at this point. But, research has spinoffs.

There will be whole new industries in the next 20 years or so from this effort.

This is a new take on "Stairway to Heaven"...if one would desire to leave planet earth, why on "earth" do it in a tube that takes a week to get wherever it's going and BTW...what is the destination again?

The waiting room, of course, the official name for which will probably be Earth Terminus 1 or some such. I wouldn't speculate on what it would receive for a nickname...

Once you achieve earth orbit you are halfway to anywhere in the solar system in terms of delta V. Imagine cutting the first two stages off the giant Saturn V rockets we used to send our astronauts to the moon. We could also use rotating beanstalks orbiting the moon and just barely touching down at the surface to transport people and materials to and from the lunar surface. Rotating beanstalks located
throughout the solar system could convert speeds of vehicles simply by docking at the middle point and then traveling out to the end before casting off with a -much- higher speed. Or slow them down by reversing the process. We could fly around the solar system like in a pin ball machine. Beanstalks would not work on Venus because the length of the day and the rotational velocity is unsuitable. Think of transporting millions of tons of material up and down the stalk with zero pollution and no energy drain from earth as all the solar power we could ever use could be coming down on superconducting cables from orbiting solar power stations and from the electrical differences between earth and the other end of the cable. There are incredible fortunes to be made in space, things and new processes we can't even begin to imagine. I just hope we have the guts and intellect to get in on it and not to leave it to the Chinese and Japanese to exploit. And they certainly -will- do it whether we participate or not.

Where can I get some of the stuff you're smoking? Get back to your bong, hippie.

Space elevator from earth, I don't think it is a good idea. You right, Terrorist could have a lot of fun with it but there is a lot of space junk also that could hit it. I thought we check out this idea years ago? and the cost of making it safe was too high.

Yes, we did check it out years ago. The results were that it is a good idea, but that it isn't feasible yet. it is within the known strength of materials, but is too hard for us at the level of technology available then. Our ability is getting closer to what it would take, but it's still a project for the future. First go around it was considered not doable for a Century. The, not for a half century. Now, it seems to be something to consider seriously in around 20 years.

I think that the time to seriously consider doing it will be in 10 to 15 years. Meanwhile, the research should consider.

This report is someone who is pushing for the research.

Yes it would be a great leap for the pioneering of space as our chemical rocketry leaves much to be desired in restrictions of cargo. I believe that yes in 50 years if we are still the dominant species here and manage not to blow this world up man has the capability to do these things that are in the realm of sc-fi. But personally until we can get along with nations and individuals of our own species we shouldn't be allowed to screw up space as we have screwed up our own planet/spaceship Earth. The world is driven by greed it seems and until we can address these issues, yes do the science and invention but do not implement it until we are all on the same page morally and for the right reasons. I am sure that we are not alone in this vast Universe and we should get our own house in order before we even think about spreading out of our own backyard. As for the comment about planes and terror and such the math dictates that this elevator would have to be located on the equator but I would have it be in a location that is as remote as possible to quell any action of this kind.

Not all locations on the Equator are equal. There are two preferred locations because the Earth is not a perfect sphere.

I just saw a video where a guy proposed a 20-mile-high tower. He said it was do-able with just steel. He claimed it would increase payloads by some big %. (I forget the exact number. Something like 50%. Or maybe it was 2x. [Big difference!] Sorry, I can't find it again.)

My point is, what could we build NOW to decrease cost of putting stuff into orbit? Is there any call for it? How many satellites do we need?

I'm no physicist but my intuition tells me that any increase in potential energy you get by riding the space elevator into geosynchronous orbit must be offset by a reduction in potential energy at the other end (i.e., the space station). So how does it stay in orbit? Isn't the space elevator just a variant of the perpetual-motion machine?

There is a tail on the space elevator that extends beyond geosynchronous orbit that keeps it taut. Any mass beyond geosynchronous orbit that is orbiting at geosynchronous speed will pull outward on the cable.

So the space station AND the tail get pulled down. You still have to conserve energy. However, if the tail had an ion engine, powered by solar panels, that would do it. (The mass for the ion engine would have to come up the space elevator, and replacement solar panels every now and then, but that's OK.)

You are right, you still have to conserve energy. I like your idea of an ion engine. But the total mass of the elevator system means any individual load on it has a miniscule effect. I think it's also possible that the elevator could generate its own electricity by just being a conductor passing through the magnetic fields out there.

No, raising the loads requires energy. That is supplied by a large orbital power station. There is not loss or gain of momentum that is not included in the calculations. There is even an acceleration on the cable from the Earths magnetic field that will have to be taken into account.

That is all taken care of in the overall totals.

Long term, the total energy up and down will balance. If not, the planet would either be slowed down or sped up. But, it might take a million years to be able to measure it.

by the way, the Moon is slowing down the Earth anyway. Earth is also speeding up the Moon too. Someday (in about 5 Billion Years) the Earth will fling the Moon off into space.

Meanwhile, the Sun is slowly changing the earths orbital speed too. (Geological change is rapid in comparison to how fast the Solar Orbit is changing.)

Space is complicated.

Potential energy is added to the elevator cab from energy sources in orbit or on the ground, no PE is drawn from the elevator itself. This is the point of the elevator, the cab does not need to carry its own energy source and can recover the PE required to climb out of the gravity well when it falls via regenerative braking. Rockets and jets have to carry their own energy sources as well as a reaction mass. Most of a rocket is reaction mass/fuel and the hardware to manage it. In fact if more mass is imported from space than is exported the elevator transport would be a net energy generator.

While we are fanatsizing, laminate supercondutor on the surface of the elevator and plasma coat that with reflective material. The resulting structure should be effectively immune to thermal shock from laser or other sources and provide a handy way to deliver power to the ground.

Locating the elevator in a remote location is daft. That is like locating a major seaport, airport, rail and road terminus (same thing really) in a remote location. The only results are to pollute the remote location to inconvenience all the staff and users who have to relocate to the remote location and add to the construction cost.

A more practical device to start with would be a skyhook.

http://en.wikipedia.org/wiki/Skyhook_%28structure%29

sounds like a semi-permanent addition to earth, if not another piece of space junk. how do you take it down when inevitably it becomes obsolete, or needs repair? if the cable should break --stuff happens-- what happens where and on whom it may fall? what if the space station has to be replaced? do you spool the cable back to earth/sea? what keeps the cable as nicely taut as in the drawing? centrifugal force? who will insure this for, e.g., the aforementioned civil airliner or military jet that crashes into it, or design flaws? isn't japan marked by unsteady geology, of the sort that causes earthquakes?

For a spinning tether, you don't 'take it down', you just cut it in half, and both halves go flying off into space. The timing of the cut will determine where they go. The pieces can be retrieved later for recycling. If you have the reaction mass available, you could also just push on the center and move the tether to any point desired.

For practical use, the tether will need thrust units at both ends, and in the center.

These are not simple machines.

What's incredible is that this article was written and what's more incredible is that I wasted the time to read it.

Obviously this has real value. Once its created, the cost of making more of them drastically reduces as it will cost substantially less with each subsequent one to get the materials into space to construct it.
The cost, once created, versus rockets would be akin to the user experience of the internet via dial-up vs always connected wifi-based broadband.
Not to mention the materials aspect. The prize of $2m towards a material for this goes a long way towards creating a material with other properties as well. On a strength-to-weight ratio, imagine cars stronger and lighter than today's current cars. Their fuel economy (be them petroleum or electric or fusion powered) will drastically increase and thus their fuel costs will go down. Not to mention the materials being carbon based means its in even more abundance than iron for steel (which is essentially infinite).

Its not just the space elevator, its the various things that this also allows for.

I noticed they plan to "Pin" it to the ocean floor. I would think it would be wiser to attach to a more mobile platform in the ocean. We already track "Space Junk". We know their orbits, a mobile platform would allow the whole thing to run a pattern weaving it around the space junk. A no fly zone easily handles basic air traffic on earth. This is tech that is a long way off, but not impossible. Of course, powering the system would be plenty tough. The Cable has to be very light weight or it would fall apart under its own weight, thus the need for Nano-Carbon tubes.

The problem with the 'floating anchor' is that the cable requires tension to avoid resonance problems (like a flapping flag). There will be several hundred tons of upward pull on the ground end of the tether. It's be embarrassing to have your sea anchor go flying off into interplanetary space. There will also be the pulls and pushes caused by the movement of the 'cabs'.

Adding weight to the hold down floating anchor will be much easier than adding cable and counterweight to lift it up. For example, a 100,000 km cable and its counterweight is about 75 times the mass that it can lift from the earth's surface.

You mention the pulls and pushes caused by the movement of the 'cabs'. Putting on too heavy of a cab will actually pull the space elevator down.

I hope they can prove us (doubting Thomases) wrong. I still enjoy a forward thinking article with little scientific evidence over the gloom and doom that seems to pervade the "news". I hope everyone can enjoy a lighthearted moment and see this as it is!

UN-CONVINCED: Theoretically yes, but my skepticism will go away when you are able to span a bridge across oceans whether such a bridge is above the water surface or below the water surface or whether the bridge is used for trains or autos or the elevator type.
Until then it is a futuristic idea for a different century.

in the early 60s JFK set a goal to land a man on the moon and return him safely before the end of the decade...it happened in 1969!

A "cable to space" is very ambitions, maybe more so than a moonshot, but what a cool thing to try!

Good luck to you researchers.

In 1960, my friend Yuri Artzutanov wrote an article "V Kosmos na Electrovoze (English: Into Space with the Help of an Electric Locomotive)", where he discussed the concept of the space elevator as an economical, safe and convenient way to access orbit and facilitate space exploration. The idea was popularized in the novel "Fountains of Paradise" by another friend of mine, Sir Arthur C. Clarke.

Yuri developed the idea from works of Konstantin Tsiolkovsky, who in 1895 proposed an idea of building an 'orbital tower'.
Yuri suggested using a geo-synchronous satellite as the base from which to construct the tower. By using a counterweight, a cable would be lowered from geo-synchronous orbit to the surface of Earth while the counterweight was extended from the satellite away from Earth, keeping the center of mass of the cable motionless relative to Earth.

Note that the ideas of the tower and the elevator differ since the tower is a compression structure, while the elevator is an orbiting tension structure, much easier to build and maintain. This was what caught Arthur's interest. Arthur, inventor of the 'Clarke Belt', was the first to publish a method allowing for geo-synchronous satellites. In his article in Wireless World, Arthur offered mathematical proof that such a concept was possible. Many laughed at Arthur, as many now laugh at Yuri.

While Yuri worked out a system that he believed would allow for the construction of the space elevator, Arthur always felt that diamond, or some form of nano-carbon material, would be needed to achieve the necessary weight to strength ratio. We shall see.

My hope being that the Japanese will credit Sir Arthur C. Clarke and Yuri Artzutanov for their visionary contributions.

As Arthur was fond of saying: "The earth is only a cradle, one from which humanity must mature, or someday face extinction."

Robert Bishop
www.novamir.org

Yes. I remember reading about this in Clarke but didn't remember which book. He made his out of diamond mined from Jupiter. He said that the core of Jupiter was diamond.

This is a fascinating project. When the lunar program was announced, we didn't know how we'd do it either - and that was only a ten year window.

The final frontier,to boldly go where no man has gone before.Or as Ralph said"To the moon"Where we can mine helium 3 and solve all of our energy challenges.Then asteroid harvesting ahh the possibilities.

In Kim Stanley Robinson's excellent sci-fi trilogy, Red Mars, Blue Mars, and Green Mars, they build theirs out of a mix of nanotubes and diamond. Larry Niven also has them in his sci-fantasy Rainbow Mars. I think it's totally feasible eventually, although anchoring it to the seabed is a new one on me. Clarke even talked about floating ocean platforms instead of his original idea of land anchors, to move them out of the way of asteroids.

As a retired research worker, I applaud scientific research and the fantastic benefits of the space race, and, I think the Space Elevator will eventually work well.. But, the underlying motive of the space race (Ie. mineral exploitation) is just a taxpayer funded scheme to give incredible wealth to a very few people.
These schemes always add to our long-term debt - which means we demand that 99% of our children will also contribute to today's top 1%.
We are already passing so many bad legacies on to our children - like decimated oil reserves, decimated fish stocks, decimated top-soil, decimated wildlife species, decimated forests, pollution and rising oceans.
What an embarrassing legacy! - Imagine, at the reading of our will.. "To my children, I also bequeath my 20 trillion dollar debt!" (quote from the Vs20 Group)

Well, thank Reagan and the Bush family for that. It's more to do with corporate greed governing US policy than it is with technology research and development. Tech creates jobs; rogue bankers and their political minions destroy economies.

Blaming the US National Debt on one political party or another is just a cop out!

When Clinton left office, the National Debt was around 8 Trillion Dollars. It was around 7 trillion when he entered office. When Bush left Office, the National Debt was 10 Trillion Dollars. It is now around 15 Trillion Dollars, that means that 1/3 of the total National Debt has been run up under the current President.

But, The spending of the government is the domain of Congress. Most of the build up of Debt under Bush was in his last two years. That was under the Democrat dominated congress of Pelosi and Reid. This was also the makeup of congress during the first two years of the Obama Administration.

However, no Congress since the beginning of the great depression has had the discipline to pay off the debt. That includes both Democrat and Republican congresses over more than 80 years.

Sadly, the current memes in Washington is to just pass the problem on to later generations. That only works as long as you can still get people to buy the bonds. We are approaching the end of that road.

As Van Johnson observed in 'The Pied Piper of Hamlin', "For come what will or come what may, the day will come you have to pay...The Piper!"

That day will soon be here.

A) This story is OLD news and sounds as useless and impractical as it did five years ago.

B) Terrorist target?? Get back into your paranoid bubble, Ted. Why on Earth (pun intended) would they target this elevator, undoubtedly carrying a small number of people due to physical limitations, versus a plane/ train etc? They're trying to kill thousands, not dozens.

if I were a terrorist, I'd prefer destroying infrastructure worth $100,000,000,000 rather than a few worthless enemy civilians. The 9-11 terrorists were after the WTC towers. All those infidels killed were just a "bonus." (Before anyone yells at me: yes, I agree, that's really sick. Sadly, that was their belief.)

It would be intersting to see an engineering analysis to compare different methods of achieving orbit. I am sure it has been done and I have seen stories like this one that talks about the individual method, but have not seen a detailed comparison of the various methods.

For instance, using a system like Virgin Galactic that employs traditional jet propulsion on a lift vehicle to achieve a high altitude, then launching a chemical rocket to complete the distance to orbit.

How about using a system similar to a maglev train or a rail gun that would have a track system running up the side of a mountain and perhaps beyond using a guide tower that would use electric to power a magnetic propulsion drive that could be augmented by ram jet and chemical rockets after the vehicle exits the end of the track.

Either of these systems seem more achievable than the space elevator concept and both seem more efficient than a ground launch rocket system.

My guess is that we are closer to an anti-gravity generator than we are to a space elevator, but I would like to see it succeed if it will allow a greater exploration of space and will allow greater access for the development of space based technology systems such as GPS, and satellite communications.

What physics is there to base an anti-gravity generator on? The physics of the space elevator is well established; carbon nanotubes are strong enough. We just need to learn to make them long enough and bind them together. Will it be easy? No, but the physics allows it. What physics allows an anti-gravity generator?

THEY RUINED THEIR NUCLEAR REACTORS AND MILES OF OCCUPIED LAND AND LIED ABOUT IT TO THEIR PEOPLE AND THE USA. NOW THEY WANT TO GO TO SPACE. WHAT ARE THEY SMOKING OVER THERE.

What people seem to miss is that if Graphite Nano-tubes become a reality it will totally revolutionise the construction industry. Steel will simply be a material of the past. There is plenty of carbon about so we would look at the end of the metal era and eneter a totally new era, probably of fusion of digital with strength (graphene has extraordinary electrical properties as well as enormous strength).

Speaking as an Engineer, yes, this material would enable a lot of things. But, don't expect steel to dissapear. Wood is after all still with us.

Concrete gives excelent strength in compression. Concrete is weak in tension. Steel is strong in both tension and compression. Carbon nano tubes are strong in tension and weak in compression. Yes it will have uses, but the uses will be somewhat limited.

Cost will also be a factor.

First of all if we did come up with a material that could handle this sort of thing, what would be the cost of building it in the first place? Second yes it is probably a lot cheaper then Rockets but might have to look at the cost of building it verses a rocket. But i like the idea and it would be fun to ride in one someday. Thinking of new an innovative idea means we are thinking outside the box, and that is how we move forward.

Thanks
Just an opinion

It's a question of payback. You have to look at the total cost of building and launching the rockets for a given amount of conclusion. You also look at the cost of building and operating the total cost of the elevator. The elevator will have a much longer time to payback than the rockets, but it will only have to be built once. The rockets are not reusable (currently). Payback time is close to 20 years in studies I have seen.

currently, businesses want new construction to have a payback time of 14 years.

So, it's not a business case yet, but the case is improving. Every year it gets closer to being economical.

I only wish I would live long enough to take that elevator ride but before the elevator is built maybe we can span the oceans with nanotube arches that will carry cargo on trains powered with solar powered magnetic drive and ... International trade can become as efficient and fast as international communications has become. Oh the brave new world lay before us a paradise for the young to enjoy..No?