smartplanet.com / Smart Technology / Thinking Tech

Space elevator looks both closer and farther away

By Dana Blankenhorn | Aug 18, 2009 |

Last week’s Space Elevator Conference, hosted by Microsoft, threw some cold water on fans of cheap space lift, but may have also made the dream seem more real as real solutions came under test.

At the heart of a space elevator is a line of super-strong material that can rise from Earth to a geosynchronous orbit, then back down to Earth. (Picture from NASA.)

Cars would go to a station in space, matched by cars following gravity down, so the costs of reaching space and escaping Earth’s gravity well would go down dramatically.

A highlight of this year’s conference, described in the Space Elevator Blog, was a test by a Japanese team of some tether based on  carbon nanotubes. The strength of a tether determines whether an elevator made with it is practical and, unfortunately, this one failed to beat the “house” tether, the local champ.

But the Japanese will be back. They even plan their own meeting later this month.

Even before a real elevator is constructed, advocates envision a shorter tether that would go part-way up. As described by Michel van Pelt in his new book, “Space Tethers and Space Elevators,” even this dream looks distant given the present limits of material science.

This does not mean the dream is dead. The repeated failures of Michael Laine’s LiftPort seem to have only fired his imagination and that of other enthusiasts.

So where are we in terms of the space elevator?

We are at the Robert Goddard stage of space elevator development, where hobbyist-engineers try, fail, and try again. Goddard’s name is now on the NASA space flight center in Maryland . Goddard made his first successful test of a liquid-fueled rocket in 1926, 35 years before the first manned space flight.

“It is difficult to say what is impossible, for the dream of yesterday is the hope of today and the reality of tomorrow.” That’s from Goddard’s own high school valedictory speech, given in 1904. This year’s conference was also geared heavily toward schools and kids, admitted organizer (and Microsoft exec) David Horn.

NASA is backing Elevator 2010, a series of contests aimed at finding stronger tethers for space elevators and a power beam that would allow a ribbon-climbing robot to go ahead. Maybe one of the school-age engineers who attended this year’s conference will win it.

So, kids, do you think we’ll have a space elevator in your lifetime?

 
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  •  
    1

    thewhitedogdad@...

    08/19/09 | Report as spam

    John Brubaker

    The problem I see with the Space Elevator, although it sounds at first like a great idea, how is this device going to deal with the massive electrical charge it will pickup as it travels through space. I have ask this question before, but none of the proponents seem to want to answer me.
    This charge may be thousands of watts, depending on the solar output.

  •  
    2

    mheartwood

    08/20/09 | Report as spam

    Not much of a charge

    There are several sources of charges on orbital devices.

    The first is caused by the object flying through the magnetic field of our planet. When a metal moves through a magentic field, electric currents are generated. This is the principle on which generators work. As satelites fly overhead, they pass through the magnetic field and thus currents are generated within their metal skins. The amount of current is based on how fast the satelite moves relative to the magnetic field. As the earth rotates, the magnetic field rotates more-or-less with it. Thus, a satelite in geosynchronous orbit does not have much current generated within it.

    On the other hand, satelites in a lower orbit, such as ISS, move through the magnetic field at a faster rate, thus generating these currents and slowly leading to a build up of negative ions at one end of the station and postivie ions at the other. Every so often, ISS needs to be "swept" to have this diaelectric imbalnce neutralized. I recall reading a report earlier this year where they said it was being done on that mission.

    The other primary source of charge occurs from impacts with charged particles, such as the solar wind. In most of these cases, the charges are equal as both ions of negative and positve charges are received.

    A third charge comes from sunlight itself. However, this charge is neutral, highly localized, and temporary. Unlike generators which need to have their generated currents dissapated, solar panels and their ilk require no such thing. Solar energy excites electrons in the semiconductors allowing them to move. Unlike a generator, they are not forced to move. With any object placed in sunlight, the same effect occurs. But allowing electrons to move, doesn't mean that they move, unless they are given a path in which to move along. This means that the electrons freed of their atoms by the sunlight return to them when the sunlight is removed. For a satelite in geosyncronous orbit, this will happen every 12 hours out of every 24.

    So the answer to you question is that the problem is not actually a large one. There will not be huge numbers of coulombs of carge building up, and since there is so little of a voltage differential, there will not be many Watts to worry about.

  •  
    3

    Namorado_TX

    08/22/09 | Report as spam

    RE: Space elevator looks both closer and farther away

    . . . The credibility of "mheartwood"'s factual response is somewhat tarnished by the obvious error of his statement that " ... when the sunlight is removed. For a satelite in geosyncronous orbit, this will happen every 12 hours out of every 24." Apart from dropping letters in spelling "satellite" and "geosynchronous", ihe "12 out of 24 hours" occurs only on Earth's surface, at equinox or the equator. At geosynchronous elevations, the satellite would be in front of or alongside the planet for most of its orbit, and behind (eclipsed by) the planet from sunlight only a small fraction of the time. Whether that would affect accumulation and discharge balancing is not mine to say. . . . But I add to the argument, what about maintaining the vertical alignment of the ribbon-tether, in the uneven pressure of solar wind? While such wind-pressure would be minuscule, any device to straighten a gradually misaligned tether-tower would add to its weight, even if restricted in location to the cargo vessel itself. If I remember correctly, as originally designed, the geosynchronous part of the tether would come at its mid-point; an appendage extending a distance far beyond that height is required to hold the part down to the surface.
    . . . This is all pretty primitive stuff, barely above combustible-fuel rocket propulsion. Will it be the 23rd Century, C.E., before we develop teletransport portals to the Lagrange points around Earth? wink

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