perfidy

A while back, Murdoc had a post about the Liftport Group and its efforts to build a beanstalk. Liftport is researching the technologies that will be essential to the creation of a working geosynchronous elevator once materials science finally develops the requisitely strong materials for the beanstalk’s cable. With the invention of carbon nanotubes, it seems that the unobtanium is becoming, possibly, closer to being obtanium.

There was a spirited discussion in the comments to that post, enlivened by the appearance of one of the people working at Liftport, Brian Dunbar. I thought I had (as I seem to have a positive gift for) left the last comment, but surprisingly, a month later, Brian reappeared
and responded to my post. And it’s interesting stuff.

For your ease in reading, I have reproduced below the relevant earlier parts of the thread, so as to make it intelligible. It’s long, but interesting to see someone who is working for a company that is actually trying to build a beanstalk defending his idea on a blog. Sweet. Brian here was responding to some of the more critical commenters:

Fine - we need and encourage critics.

Note however that there are reasons why the old ideas remain ideas and not working systems. Too expensive, too impractical, not the right time, etc.

We think this could be a reasonable alternative. It is an idea worth exploring. If it doesn't work, then we'll know and can move on. If it does then we've got inexpensive access to space.

Which is the real prize, and why I work there. I don't care if CATS comes from laser launch, mass-produced Virgin Galactic SpaceShip2s or fricking magical swans. I do feel that the species needs a way to get to space that doesn't cost an arm and both legs - this is my contribution to that effort.

But the goal is, in the end, access to space.

posted by Brian - August 6, 2006 08:24 AM

The conversation moved to discussion of two-stage to orbit vehicles, and Dfens made the point that, “If it's a good idea that needs a technological jump before it's feasible, then I wait for that technology to improve and revisit my idea. That's the difference between science fiction and actual engineering.” Brian responded to that:

Point taken. Brief nutshell, here is what we're doing;

We think the only thing that requires a technological jump is the ribbon material. People are working on that, but not for space elevator applications. Practical CNT that an Edwards SE would require will be useful in hundreds of applications - enough so that there is a huge incentive to develop it. We might hope it would be sooner than later. Anything can happen to delay this option, so we accept that potential roadblock and move on.

We can't enter that arena and build an R+D effort to catch up with the established labs - no problem. We're not interested in the material so much as using it.

What we're doing is working on the other bits that will be required for a working space elevator. The lifters, for one, and an early result is the subject of this blog post. Politics and legal issues for another - and those two are essential to master for any project.

You're not wrong - but if things do work out then when the CNT does become available a small group of people will be - with some care and luck - in the right position to take advantage of the situation.

It may _not_ happen - the odds are long. But it just might.

posted by Brian - August 7, 2006 01:48 AM

This, I think, is one of the more interesting features of the Liftport project. The way technology moves now, you can actually more or less plan that someone will, in fact, invent what you need – so long as what you need is broadly useful. Finally, we get to the important part, where I comment. I said:

Me, I vote for fricking magical swans.

One thing that hasn't been mentioned - at least here - is that this isn't an either-or proposition. Whether it is a two stage to orbit (Dfens' quarter century old idea, or Rutan's next project, take your pick) a big dumb rocket, Orion nuclear pulse or indeed fricking magical swans, cheap access to space is a *prerequisite* for Brian's magical beanstalk. No matter how stupendously advanced the eventual material, no one has yet (that I'm aware of) come with an idea for a self-deploying beanstalk. We will have to get into space to build it. And that means getting beyond our primitive space technology.

Likely, there will be a great need for testing of the beanstalk concept elsewhere before anyone allows one to be built here on earth. Tethers, rotovators, maybe a lunar beanstalk would likely be necessary (for legal/ safety/ bureaucratic/ product liability reasons. People would want to see that a beanstalk works, and continues to work for a significant period of time before allowing a 100000km carbon nanotube whip to be placed over their heads.

For those reasons, cheap space access is even more necessary for a beanstalk. A beanstalk will be a like a railroad - people will have had to already gone ahead and prepared the way before it can be built. But once built, it will make going to space infinitely cheaper. First though, we've got to make it at least reasonably cheap.

All that aside, I am all for Brian and his comrades spending as much money as they can get their grubby hands on to do the research needed so that when the time comes we will have that beanstalk.

posted by buckethead - August 8, 2006 10:50 AM

I told you all of that, so I could tell you this. Brian responded to my comment:

And that means getting beyond our primitive space technology.

Maybe not.

In terms of material needed we can - we think - get the job done with six to eight Delta IV launches, plus on-orbit assembly.

The last is tricky - it's not like anyone has done this before ... unless you count ISS and MIR. We'll need a place for the assemblers to work and live. Again, it's a new application of somewhat established concepts. But it's been done before.

This is not to poo-poo the difficulty involved, merely to note that it's possible with technology we have now.

People would want to see that a beanstalk works, and continues to work for a significant period of time before allowing a 100000km carbon nanotube whip to be placed over their heads.

Wrong imagery. Any forces that would impart enough energy to play crack-the-whip will shred the material. The stuff is going to be strong, but that level of strong it ain't.

A break? Stuff that is below the break will come down. Stuff above goes up and might be controllable in it's altitude by moving the cars up and down.

The stuff coming down? It's light - kg's per kilometer. It's messy and there are (maybe) some long-term implications if we don't police up the stuff. And if the break is way up there and we have thousands of kilometers coming down? The bits that survive the shock of the breakup will burn on re-entry.

Which is not to make light of any of this - we've got studying to do before we can say with assurance 'yes we can do this' but some basic physics and engineering dictate that a whip hovering over our heads it's not going to be.

More seriously and of longer-term impact - we've got to live here too. We're working hard not to build something that could wrack the planet. Many eye-balls help - and I hope you and other bloggers like you will keep an eye on us and keep us honest.

Enron I don't want to be.

I think that six to eight launches seems optimistic – but that is besides the point. We’ll need a lot of experience in real space construction before this becomes feasible. More to the point, we’ll need a lot more experience with tethers and other long, stringy objects and how they behave in freefall conditions. As I recall, the one time that NASA attempted a tether experiment, the cable got rather tangled. Unspooling a cable the length of a beanstalk will pose significant engineering challenges all by itself. Don’t get me wrong – as any longtime reader of this blog will know, I am a huge space nut. I wrote a twenty page essay on space strategy, as a ferinstance.

Brian knocks me on my space whip imagery. And while I know, and he knows, that a break in a beanstalk would not result in a crack the whip scenario, you can be damn sure that luddites and other undesirables will use exactly that image. The fall of a beanstalk would nevertheless be a significant event, and could be a good deal more damaging than just having a plane or rocket fall on your head.

The real point is, I don’t think we’ll get a beanstalk before we’ve solved, at least to a great degree, the problem of cheap access to space. It gets to the whole bootstrap paradox with space exploration – once you’re there, things become easy. But to get there, things need to get easy.

The potential of the technologies that Brian’s company is researching right now are enormous, and extend far beyond use in a Earth beanstalk. Beanstalks on other worlds will make all that stuff currently trapped at the bottom of deep gravity wells accessible. Rotovators have the further possibility of reducing the cost of travel even between worlds – a network of spinning tethers in free space could play catch with payloads throughout the solar system – some like to pitch and some like to catch. No need for messy and mass-costly rockets, just load on the midlle of a flinger, and lower yourself to the tip, and let centrifugal force fling you toward your destination. A couple of course corrections, and then get caught by another flinger, crank down to the middle, and you’re there. If a beanstalk can be made compact enough to be carried aloft in six or eight Delta IV launches, we could without too much difficulty ship ready-made beanstalks to all the interesting parts of the solar system ahead of any large scale manned exploration missions.

That is the wonderful thing about thinking about space exploration – the possibilities are so entirely open.