Transterrestrial Musings

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Not to mention that nanotube-wrapped fuel tanks would reduce the structural mass fraction of a rocket to next to nothing.

Payload fractions would go as high as perhaps 10% even with chemical propulsion, and so the price per payload kg would go down by a factor of ~5. For the Russians they might get down to $400/kg that way... enough to stimulate significant demand. The new demand would create economies of scale, and then the price would fall even more as you suggest Rand.

The extra demand is thought to be all below $1000/kg, so in my view a technological improvement will be needed first to take the price down that far and then kick-start the demand / economy of scale / flight rate cycle.

Posted by Kevin Parkin at August 21, 2005 10:24 AM

In a discussion with Pat Bahn of TGV, I realized that "rockets are a mature technology" has two meanings that are often confused.

People who use it to advance the argument for space elevators (or nuclear-thermal, or laser launch, or...) generally mean that there's not a lot of headroom left between where we are and the limits of Isp in fuels, of temperature resistance in engine materials, of strength/weight in airframe and tank materials, etc.

Rocket builders from Truax and Hunter onward, OTOH, argue that current rocket engineering is *immature* in an economic and learning-curve sense. I.e. it has yet to move very far from its origins (in the bleeding-edge design, high costs, small production runs, and low flight rates of early ICBMs and "NASA classic") towards a competitive, "civilian" framework of costs and operations.

Both groups are right.

Posted by Monte Davis at August 21, 2005 10:44 AM

Yup, you can take the position that the engineering itself is expensive and set to work on attacking the machining end of the problem, which is also technological and economic in nature.

It seems that is to some extent what Elon Musk has been doing, and we will find out soon enough whether or not progress is easy on that front.

Posted by Kevin Parkin at August 21, 2005 10:56 AM

I vote to grow the demand and let the mature fulfillment catch up with the demand.

Posted by Sam Dinkin at August 21, 2005 11:54 AM

The whole discussion is absurd since there are no "real" space elevators to compare with real rockets. And there won't be any in the near term. It's like comparing real rockets to anti-gravity machines or instantaneous teleportation devices or any other fantastical device which may or may not be invented.

Posted by Jardinero1 at August 21, 2005 01:26 PM

No, we're comparing theoretical space elevators with theoretical rockets.

Posted by Rand Simberg at August 21, 2005 01:35 PM

Right. Anti-gravity and instant teleportation are not theoretically possible. We can't build a space elevator yet, but it looks like it could be done with carbon nanotubes and the technology we could have in a few decades.

There are a number of ways to improve rockets, operationally and technologically. No magic required.

Me, I'm interested in advanced tether applications that would precede space elevators. You still need the flight volume to make it interesting, though.

Posted by VR at August 21, 2005 04:32 PM

I've always viewed rocketry and the space elevator as compelemntary technologies. It seems evident that a space elevator would drive demand for rockets and vice-versa.

Posted by Daniel Schmelzer at August 21, 2005 05:44 PM

How long will it take a climber to get from the Pacific to the top? I think I saw an estimate somewhere, and the time was measured in weeks.

I think space elevators will be the commercial freight of space industry, like super-tankers and trains on Earth, while anyone interested in getting there is a reasonable amount of time will be calling Virgin Lunatic (or something like that).

Posted by Brock at August 21, 2005 06:09 PM

I also suspect that by the time the people who've made US rockets ten times more expensive to manufacture than comparable former Soviet rockets are through with the space elevator, it'll not only be expensive, but the attached five-segment solid rocket boosters will also make it very unsafe.

Posted by Phil Fraering at August 21, 2005 07:50 PM

I vote to grow the demand and let the mature fulfillment catch up with the demand.

I concur with Sam. Create demand and let the free market figure out how to supply the supply.

Posted by Bill White at August 21, 2005 07:57 PM

Something you don't seem to take into consideration Rand is that the $200 figure is a yet-to-be-attained end goal cost for rockets and an (equally hypothetical, I admit) starting point cost for an elevator. The claimed ~$10/kg goal for elevators is certainly debatable but I don't think anyone seriously suggests rockets could ever achieve such economy.

Posted by Will Brown at August 21, 2005 09:01 PM

No, we're comparing theoretical space elevators with theoretical rockets.

But we already have rockets. It's not much of a stretch to get a factor of ten to fifty reduction for rocketry just from greatly increasing launch volume as compared to an untested technology.

The thing I wonder about is if a space elevator gets built, will it be able to compete with rockets on a marginal cost basis? If there's no volume being handled by rocket, then the answer would probably be yes. The quoted costs don't strike me as being very promising.

Posted by Karl Hallowell at August 21, 2005 09:12 PM

There are just so many unknown costs with a space elevator. A big one is cost and lifespan. Even if the elevator can lift payload to LEO for $50/kg, how many total kg can it load in its lifetime? If its lifetime is 50 years and it costs $500 billion to construct, that's a pretty big amortization.

Also, if you're going to assume that the elevator will have available to it new materials of incredible tensile strength, then you have to assume the rockets have access to the same material. How much weight could you save with that as a construction material? Enough to make SSTO reasonable? Enough to make rockets marginally cheap enough that large demand is created, and rockets start coming off assembly lines in quantity?

Posted by Dan at August 21, 2005 09:18 PM

Dr. Edwards is launching a start up company in Dallas, and has attracted an angel. I'd be surprised if he didn't bang the drum loudly in any forum for space elevators by touting their strengths and not digging into the nuances of the argument.

Whatever. It's important to open space, it's also important not to commit all our eggs to one infrastructure basket. As noted, a rising demand for 'rockets' would benefit a space elevator (yes, assuming they can actually be built) and a working SE would increase the demand for rockets.

Still. Assume an SE can trump any rocket in terms of cost. Once the load gets to the top you'll still need rockets to push things around. It's not as if this assumption means the rocket is headed the way of a hoss 'n buggy - just that the demand will increase for other applications.

But I think that Dr. Edwrards is wrong. There will be a mix of ways and means to get from ground to orbit. And that arena will cease to be exciting and merely be a transportation mode. The action will be further out. This is not a bad thing.

Posted by Brian Dunbar at August 21, 2005 09:49 PM

Here's an idea to ponder.

It takes two weeks to complete a mission, whether that involves expanding the cable out to the counterweight, or putting something in GEO and bringing the car back down.

So, it's going to take a whole year to build the thing after the attachment is made. So, it's not going to catch anybody completely by surprise, and by the time that the first paying customer is lifted, there will be plenty of info and testing on the system. When it does go on line, the two-week turnaround means that payloads will be combined to the greatest extent possible to maximize tonnage per launch.

Also note that the first true payload may very well be the second cable--if you have a fixed turnaround of two weeks per line, it makes a heck of a lot of sense to build multiple lines.

So, to the idea. One way to get around the two-week turnaround is to lift a rocket into LEO/MEO altitudes, and release it there. It would then have to accellerate most of the way to orbital velocity on its own, but would be able to do so with rocket motors optimized for travel in a vacuum, and a couple hundred miles of altitude as a head start. Such a hybrid launch method would have a turnaround of a few days, more dependent on preparations on the ground than on the speed of the climber.

Thoughts?

Posted by Big D at August 21, 2005 11:26 PM

Faster, please...

something a lot of people seem to be bypassing about the recent Space Elevator link :

If this coming article in Science magazine turns out to be as revolutionary as it looks on the outside, NASA's going to rapidly find much of its budget augmented or set aside for the express purpose of developing a space elevator.

Posted by cuddihy at August 21, 2005 11:38 PM

It seems I'm forever reading about revolutionary new things that never seem to reach the market. Are nonotube sheets going to be the same?

As for the space elevator... I can't put my finger on it, but somehow it gives me flashbacks to towering inferno and other disaster movies. I don't know why.

Posted by ken anthony at August 22, 2005 12:05 AM

"The claimed ~$10/kg goal for elevators is certainly debatable but I don't think anyone seriously suggests rockets could ever achieve such economy."

I think it's about as possible as shipping something to opposite side of the world for $10/kg- air freight [by boat it would be easy]. I think it's possible but it might closer to cost than compared price*. But of course this elevator idea, is looking at cost instead of price plus with all the cost infrastructure given for free.

*You might get near this price if no frills, and bulk type rates, etc.

Of course fuel cost would significant factor if you were at near these price levels. You would also might need to recover/recycle/reuse parts of launcher. And you need lots of volume and big launchers, like the Saturn V. Let's look at Saturn V:
Stage Number I: Gross Mass: 2,286,217 kg Empty Mass: 135,218 kg. And use Kerosene and Lox. Kerosene is fairly cheap- $.50 per kg and Lox is about .05 per kg. So you have about 1 million in fuel cost. The structure in terms just raw materials has is probably worth $100,000- if you sold as pure scrap. So for fabrication we pay 1/2 million [not including engines]. So let's round the whole cost to 2 million.
Stage Number II: Gross Mass: 490,778 kg. Empty Mass: 39,048 kg And using LH&LOX. Fuel is more costly let say it's cost is 1/2 million. And 1/4 million for structure. So whole cost 1 million.
Stage Number III: Gross Mass: 119,900 kg. Empty Mass: 13,300 kg. So 1/2 million
So, let's say the whole thing fueled and ready go is 4 million. You get 118,000 kg into LEO.
So that's around $40 per kg and probably need to be launching one of these every day.
Ok, so you launch it from Equator, this should increase your payload by small percentage. And you don't need a self destruct mechanism because you aren't near a population. You could recover the first stage, getting $50-100,000 in scrap, and maybe reuse engines, the second stage is probably toast, but the third stage, if you have gas station in orbit it could be reused- it could easily be worth as much as you paid for it on Earth. You perhaps could get say $30 per kg for it's dry weight, so around .4 million dollars. Of if it was desighed to get the second stage rocket into orbit, you could have around 1 million worth reusable hardware

Hmm. Yeah, I guess $10 per kg is too low, more like $30-40 kg for bulk cargo and $50-100 kg for frills/passengers would be around the cheapest chemical rockets could go.

Posted by gbaikie at August 22, 2005 02:17 AM

Space elevators are simply not robust enough. One failure in one elevator could take out the world's entire launch infrastructure, since fragments from that elevator would quickly hit all the other elevators.

Rockets, even if they explode regularly, don't make all the other rockets in the world explode at the same time.

Space elevators also are potential deathtraps for passengers. They leave people in the radiation belts for too long unless the passenger module moves very fast (no mechanically attached climber, then), and if the elevator breaks when the passengers are in a bad range of altitides, the passengers will die even if their module has reentry heat shielding -- the accelerators on such a steep reentry will be fatal. You could add rockets to give a side impulse to go into orbit, but the required delta-V would be large in the worst case, a good fraction of the delta-V from ground to LEO.

Posted by Paul Dietz at August 22, 2005 04:51 AM

One failure in one elevator could take out the world's entire launch infrastructure, since fragments from that elevator would quickly hit all the other elevators.

Yes and no. The situation is not that simple - what is? To give you a snappy comeback (not to be taken so seriously) Columbia burned on re-entry. Nothing happened to all of the other Orbiters but the net effect was the same as your scenario; a single failure - a chunk of foam - took an entire system out of service.

What happens when an SE fails depends on where the failure is, and how prepared the operators are to execute any DR plans. How big are the fragments? Can you wiggle the other ribbons out of the debris path? Looks like it's possible. Is this enough? Dunno.

Study is needed before you can simply dismiss the idea with handwavium.

Posted by Brian Dunbar at August 22, 2005 07:41 AM

One NASA report I read described a failure of a space elevator as catostrophic, even if the elevator was based on a floating platform away from populations. If NASA is terrified of the political ramifications of losing a shuttle and crew how likely is it they'd risk the equivelant of a small floating city? Politics trump technology these days.

Posted by rjschwarz at August 22, 2005 08:59 AM

One NASA report I read described a failure of a space elevator as catostrophic...

We couldn't possibly build a first space elevator massive enough to do catastrophic damage. Put the multi-gigaton cables in SF books (and the version in the 1999 Smitherman report for NASA) out of your mind. Everybody who's doing any serious thinking about SEs today is following Edwards' scenario of about 800 tonnes total for 100,000 km. Think Saran Wrap.

(I was always puzzled by the SF scenario of making the SE from a captured asteroid. If you had the rockets and the rest of the space infrastructure to do that, you wouldn't need a SE.)

Posted by Monte Davis at August 22, 2005 11:26 AM

Unless you're talking tethers you are talking an elevator that goes from the surface up to near earth orbit or beyond. That is a lot of material and if it snaps part of it will come down, not just float in the he air. Imagine 40-60? miles worth of chain with a few train cars attached falling to Earth. Even if the chain is light and of nanotech strength the laws of physics are gonna do some damage to the area where this thing falls.

Posted by rjschwarz at August 22, 2005 11:37 AM

Good point.

One aspect of carbon nanotube engineering is being overlooked, however. The enormous tensile strength of the material in the space elevator ribbon can be put to use on Earth as well. A material capable of supporting 22,300 miles of its own length while in tension can certainly support much less weight... say, the weight of a suspension bridge a few thousand miles long. That's right -- using this material, it will become possible to build suspension bridges between continents. Imagine a "Golden Gate" bridge between San Francisco and Tokyo via Hawaii, carrying passengers and freight by rail. Picture a "Brooklyn Bridge" stretching from Montauk Point on Long Island to, say, Ireland... with another bridge spanning the Bristol Channel to Great Britain and another across the English Channel to Calais. Consider the economic effect of being able to move people and goods by rail from Brazil to Africa, Africa to India, India to China, China to Australia... in any weather and without digging tunnels. Imagine covering the exposed areas of these intercontinental bridges with solar power cells to provide electricity for sale. The possibilities for economic impact are endless.

Furthermore, in theory the strength of the carbon nanoube material is so high that we could build movable "bridges" to space from any point on Earth as well as from the Galapagos Station. Let's say we have a big industrial project in some environmentally delicate area -- a project requiring a large amount of metals and power. We don't want to build a steel mill or a power plant on site, so we contract with the Space People for access to a bridge. The "bridge" ribbon would be dropped from the Clarke Orbit to any convenient equatorial point, and its loose end then transported to the desired spot on Earth by rail or ship. Once connected to the surface station, we use the ribbon to ship the Space People whatever goods they desire. In return, needed energy and raw materials could flow from orbital power plants, Lunar mines, etc. down the space bridges for use in situ as needed. When the job's done, the elevator could be sold to another client and the Earth end tranported to the next worksite.

Finally, I think it's a mistake to call this concept a "space elevator". In the minds of most people elevators are claustrophobic, stuffy, and cramped. Instead, it should be called what it is -- a railroad. Elevators suck -- but what could be more inspiring and American in spirit than the idea of building a railroad to the new frontier?

"Attention passengers. This is your conductor speaking. Welcome aboard the Thunderbird, nonstop service to space from White Sands via the Pacific & Orbital Railroad. Our destination is Clarke Station, U.S. Geosynchronous Orbit Territory. Please do not open the windows of the coach once the train is in motion. Thank you and have a pleasant trip."

All aboard!

Posted by B-Chan at August 22, 2005 11:49 AM

> If this coming article in Science magazine turns out to be as revolutionary
> as it looks on the outside, NASA's going to rapidly find much of its budget
> augmented or set aside for the express purpose of developing a space elevator.

The article you link to suggests nanoribbons may be useful for heated car windows and flexible TV screens. I see no claims that it's possible to build 24,000-mile cables.

This is a pattern we see over and over again. A researcher gets NASA money to study a far-out technology like scramjets or space elevators. The researcher publishes some viewgraphs claiming his technology will have fantastic advantages. Science writers immediately fall in love with the idea because it includes great viauals that guarantee them a cover story. Soon, there are calls for NASA to put a large amount of money into the new technology.

Meanwhile, practical approaches are ignored and denigrated because they are based a "mature" technology (which, in the eyes of researchers, is a bad thing).

The result is that Burt Rutan built the first new American spacecraft in 25 years, while NASA, without a thousand times as much money, failed to do so.

Posted by Edward Wright at August 22, 2005 11:53 AM

Bruce, I don't see how high tensile-strength materials enable thousand-mile suspension bridges. What do they suspend from? You still have to have piers in compression, and they'd have to be anchored miles deep on the ocean floor, and they'd have to occur fairly often (every few tens of miles) to keep the bridge deck above water, due to curvature of the earth.

Posted by Rand Simberg at August 22, 2005 11:56 AM

That's right -- using this material, it will become possible to build suspension bridges between continents. Imagine a "Golden Gate" bridge between San Francisco and Tokyo via Hawaii, carrying passengers and freight by rail.

Doesn't the Earth curve the wrong way to do this? A straight line drawn from San Francisco to Toyko would pass deep under the Pacific, perhaps beneath the botton of that ocean floor itself.

Okay, there are gadzillions of cool things we can do with carbon nanotubes but trans-oceanic bridges aren't one of them.

Posted by Bill White at August 22, 2005 11:57 AM

Okay, Rand's critique is better. :-)

Posted by Bill White at August 22, 2005 11:59 AM

Pshaw! Mere details of engineering. I'm no engineer (obviously) but perhaps the intercontinental bridges I have in mind could be suspended between pylons built on floating platforms similar to deep-sea oil rigs. Or we could borrow an inea from the late Dr. Robert Forward and use the ribbons to build powered-loop type bridges. The ribbon would be electrically charged and shot from a linear-induction projector station along a ballistic curve to the desired destination on the Earth's surface. Once there, the ribbon would enter a receiving station, where it would be reversed, accelerated again, and shot back along a reciprocal curve to the projector station. By doing this, we create a loop of constantly-moving charged ribbon. By accelerating this loop to a velocity higher than the orbital velocity, a net force would be exerted on the loop in a spaceward direction. This net force could then be used to "hang" a physical structure from the ribbon, from which the actual bridge would depend.

In addition to providing fast intercontinental surface transportation, these loop bridges would make an excellent way to store surplus electrical power in the form of kinetic energy. The moving ribbons could be "pumped up" with electricity from power plants during off-peak times, and could "pump" the KE back into the grid via an induction generating system during peak load hours.

Anyway, I'm just a lowly comic book artist and writer -- a dream merchant. I leave it to the Big Brains like you guys to figure out how to turn dreams into reality. Good luck!

Posted by B-Chan at August 22, 2005 12:19 PM

Soon, there are calls for NASA to put a large amount of money into the new technology.

I haven't heard or read any such calls except from a few Slashdot fanboys... although I have seen you bewailing them repeatedly.

The total NASA commitment to date has been for two reports and two prizes (for tether strength and power beaming, both of which have many uses besides an SE). They've put far more than that into one demo contract for CEV wiring using CNTs, and probably more still into CNTs for strong materials.

I'm told the total capitalization of alt.space is maybe 1/30th of NASA's annaal budget; well, total spending on SEs since 2000 by *everyone* is maybe 1.5% of alt.space.

It's just an idea, and will remain so until real CNT materials get a lot stronger. Relax. Get some perspective. It's not going to take your rockets away.

Posted by Monte Davis at August 22, 2005 12:24 PM

"Okay, there are gadzillions of cool things we can do with carbon nanotubes but trans-oceanic bridges aren't one of them."

Mabey they will make it possible to GO UNDERSEA BY RAIL man!

Graphite an glitter, remember?

Posted by Mike Puckett at August 22, 2005 01:09 PM

Finally, I think it's a mistake to call this concept a "space elevator".

Too late by years. The committe to name things met and could not agree on a good name so by default it is, and always will be, a space elevator. You weren't at that meeting?

Consider the economic effect of being able to move people and goods by rail from Brazil to Africa, Africa to India, India to China, China to Australia... in any weather and without digging tunnels.

Practical objections to ocean spanning bridges aside we have largly solved the problem of moving stuff between the continents by using large ships and containers. Think of them as fat trains without rails if you want to.

Posted by Brian Dunbar at August 22, 2005 01:47 PM

Actually, ships are considerably cheaper than trains, per unit of mass x distance.

Ships are amazingly cheap machines. They cost a few dollars per pound of dry mass. If only we could make expendable launch vehicles that cheaply -- the 'Big Dumb Booster' vision.

Posted by Paul Dietz at August 22, 2005 02:25 PM

"Bruce, I don't see how high tensile-strength materials enable thousand-mile suspension bridges. What do they suspend from?"

The piers could float. But there lots of problems, whatever is travelling on the bridge would need to travel at high speed or take days to cross. The simple cost per mile to build bridges thousands of miles long would be prohibitive. Finally what problem does a bridge solve? Using a boat is cheaper, than by rail if you compare them. It would be good if we happenned to have wide canal across America to ship things. Or another way to look it, the Mississippi is used to move cargo- rail hasn't replaced it. Oh, and let's not forget about terrorists. Building a tunnel would probably be better- and you don't need carbon nanotubes. No weather, easier security, etc.

But the important thing is bridges are build all the time, and using these carbon nanotubes as a building material would reduce costs, so there is a billion dollar market waiting for these carbon nanotubes and doesn't require the "demand" of space elevators or intercontinental bridges. There is no excuse for not having them available other than the technical challenge of producing them.

Posted by gbaikie at August 22, 2005 02:40 PM

CNT is going to change a large part of modern life on this world before it's done with us. Anybody who thinks that space elevators are the only application is missing the point.

And yes, CNT isn't strong enough yet to make a space elevator. The math says it's possible, but the engineering to economically build and connect multi-centimeter strands isn't here yet. I for one am rather optomistic that space elevators are doable, and a Good Thing in general. But it doesn't mean that rockets are going away at all, much less anytime soon. In fact, if a space elevator is built, it's the smaller firms, flying cheap designs like the Falcon series, that are likely to stay in business, while LockMart et al look for the fastest way to get out of the market or lock in guaranteed government funding.

Posted by Big D at August 22, 2005 03:57 PM

>> Soon, there are calls for NASA to put a large amount of money into the new technology.

> I haven't heard or read any such calls except from a few Slashdot fanboys...

Then you haven't been reading this thread: "If this coming article in Science magazine turns out to be as revolutionary as it looks on the outside, NASA's going to rapidly find much of its budget augmented or set aside for the express purpose of developing a space elevator."

> The total NASA commitment to date has been for two reports and two prizes
> (for tether strength and power beaming, both of which have many uses
> besides an SE).

Key words being "to date." To build a space elevator, rather than just studying them, will require vastly more money.

At the San Jose ISDC, a spokesman for the space elevator group said they were "budgeting" $400 million for legal fees alone. With a straight faced, he went on to say he consiered that a very reasonable amount, given the size of the project.

> They've put far more than that into one demo contract
> for CEV wiring using CNTs, and probably more still into CNTs for strong
> materials.

I wasn't comparing it to CEV, but to practical means for lowering the cost of space transportation in the near term. NASA's still spending less on that they are on wiring their CEV.

> I'm told the total capitalization of alt.space is maybe 1/30th of NASA's
> annaal budget;

"Total capitalization" means cumulative investment. Comparing that to NASA's annual (not cumulative) budget shows how small the total really is.

Using your figure, the total capitalization for all alt.space firms is roughly equal to what the space elevator group proposes to spend on legal expenses alone.

> well, total spending on SEs since 2000 by *everyone* is maybe 1.5% of alt.space.

We're talking about NASA spending, not alt.space spending. There's also scramjets, linear aerospikes, and a host of other bleeding-edge technologies that NASA's spent billions on, without reducing the cost of launch at all. Looking at the results, I can't see any justification for NASA continuing down the same road instead of buying launch services from the private sector.

> It's just an idea, and will remain so until real CNT materials get a lot
> stronger. Relax. Get some perspective. It's not going to take your rockets away.

But they can take away a potential market if NASA decides to spend billions trying to build a space elevator instead of purchasing commercial launch services.

Posted by Edward Wright at August 22, 2005 05:37 PM

Before this thread gets too far from the original post, a couple observations; my understanding (purely as an interested layman) is that an elevator would consist of more than one "leg" each anchored at it's GEO terminus and counter-weighted from there so it really doesn't matter engineering-wise where it's located on earth as long as that place is within 10 degrees or so of the equator. Also, in all the cost/price discussion no one's taken into account the fact that the nanofiber material is electrically comductive and so permits for the elevator to generate at least some of it's own operating power and potentially to sell excess power to the commercial grid (charging batteries, fueling fuel cells for sale?). Additionally, if a "waystation" at ~ 100k ft was established from which to launch cargo/passengers to distributed delivery points or into orbit, how would that effect launch costs?

Posted by Will Brown at August 22, 2005 07:29 PM

What bothers me is that when saying "space elevator" people automatically think of beanstalk-type elevator, from ground to GEO.
Obviously there are a lot of other options and some space-tether type applications would be doable even with todays materials.
Like the Single-Stage-to-Tether described here:
http://spacetethers.com/

IOW, a _combination_ of rockets and tethers could prove much more practical in the long run than just either one on its own.

Posted by kert at August 23, 2005 12:56 AM

But they can take away a potential market if NASA decides to spend billions trying to build a space elevator instead of purchasing commercial launch services.

Come on Ed, you have to admit this stuff is cool. For the last 5 years discussion about the space elevator's been stuck at the assumption that nanotube ribbons were Unobtanium. Millions of research dollars and the best anyone had done was equalling Spectra--and that with LOTS of work, and all the suddent there's this rediculously easy method that looks almost as easy as pulling Nylon and you're not enthusiastic? Come on! That's

Sure, nobody knows if this method will lead to the 30 Gpa limit or whatever they say they need for the space elevator, and even then if atomic oxygen will destroy it on the way down or whatever--who cares! This is very exciting stuff! Don't worry, Nasa won't commit significant funds until the science and methods are clear-->after all, this is space access we're talking about, not climate science.

Posted by cuddihy at August 23, 2005 01:32 AM

I hope your bridges between continents are designed to change size, because continents drift. 1-10cm per year. Maybe sideways, maybe front and back. Doesn't sound like a lot, but in 100 years your bridge may have been shifted sideways by 30 feet, or lengthened or shortened by 30 feet. Pilings that are on one plate will move with respect to pilings not one the plate. if one plate slides under the other, the relative heights will also change. Also, earthquakes are going to affect parts of the bridge and not other parts.

I don't think we'll be building nanotube bridges across oceans any time soon. However, extremely high tensile strength materials may allow us to build lighter planes, better engines, and improved cost efficiencies along every step of our current supply chains.

Posted by Dan at August 23, 2005 12:37 PM

> Come on Ed, you have to admit this stuff is cool.

Yes, just as scramjets are cool, zero-point energy is cool, and quantum teleportation is cool. However, I don't believe that coolness (technological immaturity) is the proper figure of merit for the next generation of space transportation systems.

> Sure, nobody knows if this method will lead to the 30 Gpa limit or whatever they
> say they need for the space elevator, and even then if atomic oxygen will destroy
> it on the way down or whatever--who cares! This is very exciting stuff! Don't
> worry, Nasa won't commit significant funds until the science and methods are
> clear-->after all, this is space access we're talking about, not climate science.

Did lack of science and methods stop NASA from committing funds to NASP, X-33, et. al.?

NASA has spent a great many fortunes on cool, sexy, bleeding-edge approaches to space access. It's spent next to nothing on realistic approaches. Despite all the talk, NASA still hasn't committed one penny to a commercial contract for ISS ressuply. Many of us fought for NASA to offer prizes to support projects NASA wouldn't ordinarily be interested in -- and what happens? The space elevator people, who are already funded by NASA, get their hooks into that money, too.

It's nice that NASA's developing technology for Captain Kirk, but Kirk isn't a US taxpayer. I would like to see some of NASA's money spent on things that might pay off in our lifetime, not Kirk's.

Posted by Edward Wright at August 24, 2005 12:27 PM

LOX/RP-1 propellant cost is ultimately somewhere around $5-$10/kg to LEO, so energy costs are not immediately significant.

In the drymass comparison the space elevator will out weigh the rocket by a couple of orders of magnitude, so assuming CNTs are not dirt cheap, the rocket wins on drymass and cost.

Assuming traveling times of a week for the space elevator, and a few hours for the rocket, well the rocket can win on flight rate.

Going beyond LEO the comparison gets a bit more complicated, even so, I do not see space elevators working without a very high speed maglev system. It is the only way I can see of getting the payload mass flow rate up to competitive levels.

Posted by Pete Lynn at August 25, 2005 03:09 AM

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