This article says it might be possible.

A Hoist to the Heavens

Very interesting and it is a new paradigm to conquer to space. The article is worth to be read and I seems that it is between the fiction science and reality unless some technical leaders says that this project is feasible. Carl Sagan has already dreamed of it.

Rodolfo

Alas, materials technology just isn't up to it yet. The only materials we've ever come up with that would be strong and flexible enough to use to build a space elevator can currently only be produced in strands measured in microns, and no one has a really good idea of how to practically put them together into larger structures.

When (if ever) the materials technology is up to it, it's a good idea, though.

-the other Doug

A-a-a-a-ges ago there was a special issue of the JBIS which had a long look at elevators. There are actually a whole range of smaller alternatives using arcs and rotating structures, all of which have considerable bearing on airless worlds. On Earth, I'm not so sure - weather, terrorism and criminal stupidity all militate against a Sword of Damocles tens of thousands of miles long!

I read an article over the past few days that spoke about an advance in manufacturing Carbon nano tubes on a large scale.

This is just one further step in perhaps producing the materials needed for the space elevator idea.


New Scientist had it too but I can't find it at the moment.
http://msnbc.msn.com/id/8976160/

Also, about a year ago, another group was making single-molecule nanotubes up to a foot long. Not the perfect tubes, but ...

Although conceptually simple and fascinating, the space elevator raises many issues, some already discussed above.


-the strand would have to withstand heavy horizontal forces when hoisting a vehicule, westwards when ascending, eastward when descending.

-The hoisted vehicule would need a week to travel all the height, if it travels at speeds comparable to railways.

-On the other hand the vehicule would need to travel very fast, to preserve passengers from radiation belts.

-Thus it would need a very large source of power, comparable to a rocket. So we could really save energy if there is a way to recover the energy of descending vehicles. Otherwise the overall energy is not better than with rockets.

-The strand will need to be electrically insulating, otherwise it would create a gigantic short circuit beteween the ground and the ionosphere, with unpredictable consequences. (A very predictable one would be that the strand would burn in a flash)

-For this reason we cannot use a trolley along the strand, to electrically feed the ascending vehicle (or to recover the energy of the descending vehicle).

-We can no more use an ancilary cable pulling the vehicle along the strand. Such a cable would rub against the main cable, or twist around it (with forces multiplied by the 60 000kms length) and move at hypersonic speed into the atmosphere.

-The strand would wear is space, from micrometeorites impacts or orbital objects impacts. This would appear, not much as a loss of resistance with time, but as a global loss of reliability.

-Massive use of this system would result into lenghening the day-night period.


So the idea of the space elevator is not so simple... I do not say that there are no solutions for the above problems, but what I think I reserve it for a future fiction story to be published.

More information about Carbon Nanotube Sheets, click here.
Now, it is already useful for some space applicacions:
Due to strength normalized to weight is important for many applications, especially in space and aerospace, and this property of the nanotube sheets already exceeds that of the strongest steel sheets and the Mylar and Kapton sheets used for ultralight air vehicles and proposed for solar sails for space applications, according to the researchers.

Rodolfo

A hot air or gas baloon for a venusian lander could use carbon fabrics too. (Perhaps even not nanotubes) as no plastic will do.

Hey, it seems that they really advanced, from lab protos to useable products. Not yet strong enough for the space elevator, but already superior to any other.

Good to hear from your comments since I am just starting to learn this new technology. However, there is still lots of doubts about this feasibility. The good thing is that there are many man who are dreaming and working to achieve it.

Rodolfo

The good thing also is that NASA isn't just brushing this off as some science fiction dream. The author received a grant from NASA's Institute for Advanced Concepts so to me this is a good sign. When this happens is anybody's guess but I think we're moving in the right direction.

I still am not able to figure it out on how the rope is kept tight and upward.

Anything in the space, in the exosphere zone, has nil gravity. How can the geostationary keep the cable outwards?

Then mi first tought to solve this case is that this is due to the centripetal force originated by the Earth's rotation. This will satisfy the Newton's Third Law of Motion, Isn't it? The total weight mass to put there is 600 TM is to compensate the weight that the rope and elevator might weight? The first geostationary at 36K Km is utilized to stabilize the inertia between two extrems points: on the floor and the other geostationary at 64K Km.

Is that a simple explanation so that the people understand on how the cable, and geostationary along with the 20 TM of space elevator won't fall off do to the Earth's gravity. Please correct me if I am wrong

Rodolfo

Rodolfo:

As I understand it, the principle behind space elevators is fairly simple.

Although the ends (or indeed any point) of the cable are certainly *not* in orbit, the centre of mass *is* - and at GEO. To make the thing work you need as much above, as below, so as to keep the whole thing balanced. In practice, any cable would have to be actively guided down to earth, while the GEO mass would be sufficiently high as to balance the cable. The structure has to be sufficiently strong as to support it's own weight and that of the payload, hence the need for exotic materials. If things go badly wrong, then the thing falls - this is *not* a good idea!

You *don't* need the whole shooting match to get many of the benefits - as I mentioned before, arcs and rotating columns will also work, especially in airless environments. What you probably *do* need, however, is an active space-based industrial infrastructure, which to my mind implies exploitation of NEO objects for mass and materials.

Bob Shaw

Bob: Now I understand it.

It is obvious that the cable must be very exoctic to witshtand a weight of over than 600 TM. I have not seen any rope able to hold up an weight of almost Boeing 777-200 airplanes. I haven't heard of the others funny things such as arcs and rotating columns. Well, with the time, I will discover them.

Anyway, thank you for your input.

Rodolfo

More information about Elevator Space, Click here.



Looks not so far About the time of Mars exploration.

Rodolfo

For information about other means of achieving orbit (and much more), check this page, under 'papers', starting with 'Dynamic Compression Members', continuing with the three 'Orbital Ring Systems and Jacob's Ladders' papers and finishing with 'Supramundane Planets' through to 'How to Move a Planet'. I remember reading these papers in the JBIS and being quite impressed with them -- I particularly liked 'Supramundane Planets'.

Bill

Bill:

I hadn't realised that the UK Independence Party (Isle of Wight Branch) (Gilbert and Sullivan Section) had such an influence on speculative space technology!

Now, as for Bob Forward...

Bob Shaw

Some new articles:

Trading Rockets for Space Elevators

Space Program: Looking Up

There are several NASA prizes being offered for some of the basics of Space Elevator technology. I expect that such a device can be built eventually, but I think that we will need to develop special nano-factories which are capable of forming many simultaneous long threads of carbon nanotube, and then weaving them together to make the heavy duty ribbon required for the task.

This is plausible in the relatively distant future, but is not based on anything we currently are designing today. My guess is that the first space elevator will be built toward the end of this century.

Some more news from Space.com:

Space Elevator Gets FAA Lift

The LiftPort Group, the space elevator companies, announced September 9 that it has received a waiver from the Federal Aviation Administration (FAA) to use airspace to conduct preliminary tests of its high altitude robotic “lifters.”

The lifters are early prototypes of the technology that the company is developing for use in its commercial space elevator to ferry cargo back and forth into space.

The tests, which are planned for early fall, will simulate a working space elevator by launching a model elevator “ribbon” attached to moored balloon initially up to a mile high. The robotic lifters will then be tested in their ability to climb up and down the free-hanging ribbon, marking the first-ever test of this technology in the development of the space elevator concept.

According to Michael Laine, president of the LiftPort Group in Bremerton, Washington, the FAA go-ahead is a “critical step” in the ultimate developing of the group’s LiftPort Space Elevator concept.

First and a new progress...now elevator has reached up to 300 meters of height...

The first and annual Space Elevator Competition will be held October 21 at NASA'S Ames Research Center in Silicon Valley, California, USA.



http://www.space.com/businesstechnology/05...vator_test.html

Rodolfo

Stairway to Heaven





It would be interesting to see if the first space elevator flight coincides with the CEV's first launch towards the moon.

A recent interview with Bradley Edwards. Good read.

Space elevator contest gets off the ground
NASA backs $100,000 ‘games’ for robot climbers, super-strong materials

Two Events - Many Approaches

Designed to address the technical as well as "social engineering" issues of the space elevator, these two engineering challenges are intended to generate interest and excitement in academia, the space enthusiast community, and the general public.


1) The Beam Power Challenge tasks designers with building an unmanned machine, weighing 50 to 100 pounds (22 to 45 kilograms), capable of pulling itself up a 4-inch (10-centimeter) wide, 200-foot (61-meter) long ribbon suspended from a crane, and powered only by the energy beamed up from a 10,000-Watt xenon searchlight.

Seven teams vied for the $50,000 first prize, five from across the U.S. and two from Canada.

The winner was a team of students from university Saskatchewan. The highest point was one third of the distance (20 meters). The toy didn't have enough energy to elevate further...


2) In the second event, the Tether Challenge, four teams offered their best formulation for an ultra-light, ultra-strong ribbon material. During one-on-one tug-of-wars, each of the entrants were tested to their breaking points.

The winner was the team from the company: Centaurus Aerospace of Logan, Utah, yielded at 1,260 pounds of (571.5 kilograms) force, giving way to the "house ribbon" which broke at just over 1,300 pounds (589.6 kilograms) of force.


None of team from two events have ever won any price and leaving the $50,000 first prize unclaimed.

More details, visit the following URL:
http://www.space.com/businesstechnology/05..._challenge.html

Rodolfo

Lack of total success on the first year of the contest is not something to despair:

"NASA says it was pleased with the quality of the entries, especially considering the event was only announced in March. "We would have probably been more surprised had someone won – they only had six months to prepare," says Harrington.

Next year, both contests will be repeated but the top prizes will each rise to $200,000."

Hmmm, $200K next year?
Now where did I put that piece of Sinclair monofilament...

I saw that Brian Dunbar posted some information over at the yahoo space-elevator group. It's concerning news of recent testing. The same info can be found at Liftport's site:

Posted on Liftport's site, dateline Feb 13, 2006:

Second Round of Tests

Space elevator tether climbs a mile high

NewScientist.com news service Feb. 15, 2006

*************************

LiftPort Group has built a cable
for a space elevator stretching a
mile into the sky and tethered on
balloons, enabling robots to
scrabble some way up and down the
line.

To make the cable, researchers
sandwiched three carbon-fiber
composite strings between four
sheets of fiberglass tape, creating
a mile-long cable about 5
centimeters wide and...

http://www.kurzweilai.net/email/newsRedire...sID=5306&m=7610

Not so good news in the space elevator world.

The space elevator: going down?

I can't access the article (without paying). Can someone provide an "executive summary" what the issues are?

The problem described is that, while microscopic individual nanotubes have the required theoretical strength to build the space elevator, large clusters of nanotubes don't have, due to the accumulation of small defects.

Why is it so? Two possible reasons:
-the fabrication process is not efficient, but we could improve it and obtain perfect large scale nanotube wires with the same properties than the small scale individual tubes
-there is a thermodynamical reason for this, in this case it is impossible to build large nanotubes structures.

A similar problem happenend with monocrystalline metals used into turboreactors, which have to sustain heavy centrifugal forces at high temperatures. Finding that usual metals break in the joints between crystals, the idea was to build monocrystalline blades. But thermodynamical reasons make that defects appear into metal crystals, so that ususally only microscopic crystals can exist. As far as I know mettalirgists found a fix, but these monocrystalline blades are very difficult to make, and thus very expensive and are used only in this case.

For those who can recall and/or have the novel handy, what was
the Space Elevator in Arthur C. Clarke's The Fountains of Paradise
made of? Was it something at least based in physical possibility?

Now there's another work that should be made available online.

"...monocrystalline blades are very difficult to make, and thus very expensive and are used only in this case...."

High performance jet engines use superalloy <nickle based, usually> blades that have increasingly complicated internal passages for cooling and reducing blade mass. The state-of-the-art has been directionally solidified ORIENTED single-crystal blades. The molding and casting technology is more than *not trivial*, and the performance requirements keep getting more severe, as is the inspection requirements. The single-crystal technology is widely used and mature, however.

The whole report on the impossibility of nanotube cable being strong enough is probably pure b##s**t, based on off-the-cuff assumptions. In reality, while nanotubes have to be strong enough, what's critical to the design is that the strong-enough tubes have to be long enough that inter-tube friction, gained by relatively weak bonding to the tube and mechanical interweaving of tubes, adds up over millimeters to meters or whatever to enough tensile strength to make cable strong.

probably true.

At least this report is not a STUDY of what could be theoretical/thermodynamical limits into nanotube length. It seems that they just picked samples of state-of-the-art "ropes" and tested them. And they found they had much less strength than individual nanotubes. But this is a known result: we don't know yet to make nanotubes larger than say 1mm. But this don't mean that we cannot do this, and more and more people are working on this. So, with no foreseable theoretical limit, we can hope we will be able to build lengthy nanotubes, which will be very useful for the space elevator, or at least for many earthy purposes, such as much lighter cars or aircrafts, large building beams, super strong fabrics, etc.

And this is not the end. While boron nitride showed harder that carbon diamond, perhaps boron nitride nanotubes, or other compositions, will be even stronger than carbon nanotubes. At least it is worth trying.

Anyway today nanotube fabrication is something very rough: to evaporate carbon and hope it will solidify into nanotubes. Some do, but of course there is a lot of rubbish, and no quality product. It is a bit like throwing bricks at randon in hope they do a wall by themselves. Maybe there will be some more clever process, some catalyser able to build continuous and perfect nanotubes of whatever length we want. Or a nanomachine similar to the biological ones working in cells, but operating at a higher energy required to work with carbon bonds. It would rotate while adding carbon atoms, while being fed in energy by chemicals. As carbon atoms are usually not free alone, the nanomachine would start from things like methane molecules, which can be dissolved into a liquid medium.

The only real limit on nanotubes would be it they show toxic like asbestos. Probably they will be, for the same reason (mechanically breaking cell membranes and chromosomes). In this case, of course, their use could be strictly forbidden or restricted only to very special areas. Like the space elevator...

There is not a specific minimum tensile strength needed to build a space elevator. The space elevator is tapered so it gets thicker as it goes higher. I believe the minimum of 63 GPa is what would be required for an untapered space elevator without a margin of safety. The formula for the taper required (area at geosynchronous orbit/area at sea level)is in this wikipedia article
http://en.wikipedia.org/wiki/Space_elevator
A design with taper of 1.5 for 130 GPa (includes a safety margin of 2) was described here
http://www.isr.us/Downloads/niac_pdf/chapter2.html
If the strength was 30 GPa (same safety margin) then it would require a taper of 1.5 * e^4.33 or ~113, if it had a round cross section it if would have 10x the diameter at geosyncronous orbit.
Theoretically it could even be built using kevlar but the taper would be 10^8, obviously not practical.

"...What is it?"

"The result of two hundred years of solid-state physics. For whatever good that does, it is a continuous pseudo-one dimensional diamond crystal - though it's not actually pure carbon. There are several trace elements in carefully controlled amounts. It can be mass-produced only in the orbiting factories, where there's no gravity to interfere with the growth process."

"Fascinating ... I can appreciate that this may have all sorts of technical applications. It would make a splendid cheese cutter."

Quoted from the book, without permission of Arthur himself.