Space Elevator Rebuttal From LiftPort Founder

TropicalCoder is the reader who submitted the story about the possible demise of LiftPort a couple of weeks back. The resulting discussion was mostly negative about the feasibility of building a space elevator. TropicalCoder writes: "At one point during the discussion, LiftPort founder Michael J. Laine personally entered the discussion, but for the most part remained invisible since he hadn't logged in. I responded to his comment that if he would like a chance to rebut the criticisms, he should contact me and I would undertake to interview him and post the resulting story on Slashdot." Read below for the story of how Mr. Laine's detailed reply and rebuttal to that Slashdot discussion came about. TropicalCoder asks, "After reading LiftPort's rebuttal to Slashdot critics, do any of you now feel your pessimism somewhat dispelled?"

Michael Laine called me long distance via cell phone that very day from his back yard near Seattle, and spoke with me for over an hour. Michael came across as a rather sober, likable fellow, not at all like the crackpot image one would conjure up from reading many of the Slashdot comments. He was clearly wounded by the stinging criticisms in the Slashdot discussion, and I couldn't help empathizing with him. Here was man who had put his money where his mouth was, risking everything on his dream, perhaps suffering his darkest hour, and enduring ridicule on top of that.

At no point during the conversation did I get any impression of a huckster who would sell you the Brooklyn Bridge, something that I was on the lookout for. It was clear to me that he sincerely believes in what he is doing. Whether he succeeds in the end or not, I would prefer to call him a "visionary." After all, for every great visionary you can recall from history, there must have been a thousand others who tried and failed, but are no less visionary because of that. The jury is still out on LiftPort, and rumors of their death would be premature. They continue their research, and as I write are preparing for the "Tethered Towers" demo on Thursday June 28.

At the end of the conversation it was agreed that I would summarize the Slashdot discussion for him and offer him an opportunity for point-by-point rebuttal. I completed this summary (in which many Slashdot readers will recognize their own words), and sent it off to him the next day. He acknowledged receipt and promised an answer shortly. A few weeks passed, and I imagined that he must have decided in the end that the criticisms were so severe, perhaps it would be best just to try to forget it. It was a total surprise to me when a thoroughly detailed response arrived in my mailbox today, demonstrating that the people at LiftPort at least are still convinced that building a space elevator is possible.

Space elevator themes have been celebrated in science fiction and many Slashdot readers have shared the dream, only to become disillusioned with the apparent pending demise of LiftPort. After reading LiftPort's rebuttal to Slashdot critics, do any of you now feel your pessimism somewhat dispelled?"

Re:Objection: Asked and Answered

[bodan]

I don't AGREE with this claim.. I've seen no study which shows this to be the case, and all the other problems other than the material to use are not solved.. but he has already addressed the objection that you NEED carbon nanotubes.

That's because you didn't read enough. Most contemporary studies only deal with economically-feasible designs, which is why they only mention very-high-strength materials. This is because using lower-strength materials requires hugely more material, which is simply very hard to send up to orbit.

I have seen calculations for a steel elevator. Yes, it's physically possible with a very tappered design [wikipedia.org], but it would have a diameter of several hundred kilometers at the thickest part. (Given that its several hundred thousand kilometers long, that's rather thin if you think about it.) However it would need the entire Earth's steel production for a few thousand years, probably, and even longer for rocket fuel to get things started.

However, steel isn't a very good choice because of weight (and it's not that strong, either). The optimal diameter at the thickest point is an exponential of density/tensile strength (with a pretty big constant). This means that even small (relatively) advances in that component will greatly decrease the cost, and we have materials much, much better than steel in that respect.

It's perfectly doable technically, without any major breakthroughs, it's just because of economics that you've never heard of that. With the best technology we have now it is still probably doable within a reasonable multiple of the world's GDP.

We need breakthroughs not to build it, but to build it with less than a country's GDP.

Space Guns anyone?

[Ignatius]

I know it's slightly offtopic, but I always wonder why a highly speculative and fragile concept like the space elevator which is barely theoretically possible is getting so much press, while space guns, which are cheaper, more robust and don't require any new technology, are practically ignored.

In case you're not familiar with the concept: It's basically about accelerating a small vessel (by a light gas gun, a RAM accelerator, electromagnetically or a combination thereof) in a relatively short (about the order of one km) barrel / tunnel to about orbital speed. The vessel itself will only require enough fuel for circularizing its orbit, so unlike conventional boosters, a much bigger part of its mass can be actual payload as the exponential regime of the rocket equation can be mostly avoided.

While the capital costs will be high, a space gun is still dirt cheap compared to a space elevator, and isn't prone to be completely destroyed when hit by lightning, space debris or, for the matter, a shotgun.

http://en.wikipedia.org/wiki/Space_gun [wikipedia.org]
http://www.fas.org/news/iraq/1998/05/980500-bull.h tm [fas.org]
http://www.astronautix.com/lvs/julncher.htm [astronautix.com]

Re:Increased Pessimism

[Atragon]

Q: You'll never see a fully functional space elevator on earth. The requirements are too close to the edge of what is even theoretically possible.
If it weren't for the costs, we could build one this year.

To put it bluntly - this is an outright lie. Period. if it were true - why is LiftPort spending money on R&D rather than production?

Probably because the costs exceed their budget by several orders of magnitude and they are doing RND to reduce these costs and/or improve the end result.

Re:Ok, here's my comment

[vrmlguy]

Most claims made about space elevators can be seen at the Wikipedia article [wikipedia.org], which includes detailed info about building one from steel and why it is impractical (but not impossible). I'll conceed that it's barely possible that the entire article is a plant by LiftPort, however there are a lot of links to other companies that are doing independent research. Of particular interest is Gizmonic Inc. [gizmonicsinc.com], who seem to have adopted space elevators as a corporate hobby, doing lots of spare time R&D and provided lots of calculators so you can check the math yourself. Hans Morovec wrote a research paper [cmu.edu] in 1978 investigating the feasibility of using Kelvar. Not related to your question but also interesting, Tethers Unlimited, Inc. [tethers.com], aren't working on space elevators but are working on lots of related technology.

Re: Right...

[Firethorn]

From what I've seen, one of the first priorities once you get the first ribbon set up is to set up a second. That way if something does happen, you still have another ribbon.

That and you'd still be able to max cargo transfer for two ribbons at prices that net you more money than the prices you can get for the cargo capacity of one ribbon. (IE 1X$800/kg < 2X$600/kg)