“…Science Fact or Science Fiction”

In a recent post on the Space Travel Exploration and Tourism website, the author(s) talk about the Space Elevator and bring up several potential problems.

The first one is the lack of a material strong enough and of course this is true.  As we all know, however, this problem is being worked on by an ever-growing body of scientists and engineers.

The article also says that “laser-power-transfer systems have never been built“.  The authors are clearly unaware of the NASA-Spaceward Space Elevator Games – Climber / Power Beaming competitions where several teams have built precisely this type of system.  Yes, they are small and essentially prototypes, but they show the concept works and a little birdie has told me that the next Power Beaming competition will be even more ambitious.  Also, there is at least one company (LaserMotive) that is now in business to provide precisely this type of product.

They also bring up the problem of Space Debris – perhaps I should send them a copy of the recently released ISEC Report on the topic (which concludes that this is a solvable engineering problem).

Finally they bring up the issue of what happens ‘when the cable breaks’ – they say you certainly wouldn’t want to be under it when that happens.  Let’s remember that the tether will be shaped as a ribbon for the great majority of its length (the length outside of the atmosphere).  This will not ‘fall’ to earth, but rather ‘float’ to earth.  It will almost certainly be winched in while it is fluttering down.  Messy, yes.  A disaster for those underneath it, no.

Finally they say that “Heights of up to 65,000 km have been suggested.”  Actually, the working model is 100,000km in height, not 65,000 km.

Publicity is almost always good of course, but at some point I hope that people will do a bit of research about the current ‘state-of-the-art’ of the Space Elevator before writing about it.

8 thoughts on ““…Science Fact or Science Fiction”

  1. Joseph Cowles

    I’m interested in learning about the turbulent conditions a space elevator is likely to encounter during a ribbon climb between Earth and weightless space. Have you recommendations for papers or articles I can consult regarding this subject?

  2. Ted Semon Post author

    I’m not sure what you mean by “turbulent conditions”. There may be some, depending on wind conditions, in the atmosphere, but that is just a tiny fraction of the entire trip. The tether will also oscillate, of course, due to many factors, but these oscillations should be slow and not an issue.

  3. Stephen Cohen

    I can accept a local newspaper article getting certain facts wrong about the space elevator. The journalists involved usually have little scientific background, and the space elevator is, after all, a little bit out there.

    But, I find it a bit hard to accept that a website entitled “Space Travel” should be so clueless on the subject. It indicates that the public outreach for this subject is sadly still in its infancy.

  4. dmal

    Somebody needs to refer us to a research paper regarding wind “turbulence”. It seems wind is the earliest extreme condition of the trip, and I don’t remember reading anything about why the lower parts won’t accelerate and oscillate and go out of control in the atmosphere. Anybody?

    Regarding turbulence caused by radiation? So, if you mean radiation, start with Dr. Brad Edward’s paper, “Leaving the Planet…”. He talks about the fact that humans will not likely ride the elevator, initially.

    I think Edwards says that proper shielding of a passenger compartment needed for a relatively slow cruise through the Van Allen Belts could be solved with a few inches of water barrier. An encasing of the “climber” vehicle passenger compartment would be heavy, and probably won’t be in sight for the first or second generation of climber.

    The first generation (I think) would be almost entirely to “weave” additional strands of carbon fibers to the ribbon; the second for some telecom payloads (Return on Investment/Cash!), and maybe later, a passenger payload for research and exploration.

    To be sure, radiation shielding is part of the design requirements.

  5. Ted Semon Post author

    dmal, why would a climber “accelerate and oscillate and go out of control in the atmosphere?” What would cause that?

    Current design calls for a base station to be located in a place where the weather is extremely boring – next to no storms, lightning, etc. Also, in the atmosphere, the tether will probably be shaped like a cable (rather than a ribbon), cutting down wind resistance even more. And, finally, the length of tether IN the atmosphere is only a tiny fraction of the total length. I just don’t see this being a big issue…

  6. Stephen Cohen

    I addressed the fundamentals of atmospheric effects in my thesis, Space Elevator Dynamics.

    High winds for extended periods of time have two effects:
    1) Locally, the portion of tether within the atmosphere will sway from its equilibrium position significantly, and its change in shape will be seen most near the surface.
    2) Globally, the libration angle of the ribbon will be affected by milliradians (similar to the effect of a single climber ascending).

    Neither effect is devastating, but both must be understood and accounted for.

    I don’t think the ribbon could be tubular in the atmosphere, as the climbing mechanism (in my mind) uses friction between wheels on either side of the flat thin ribbon to scale it.

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