Do Sea Buoys Hold the Key to Space Elevators? 3

Thursday, June 12th, 2014
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The secret to building elevators which extend far into the heavens could lie in an object as humble and unassuming as the common sea buoy.

While the idea of the space elevator has been around since the end of the 19th century, when it was first proposed by Russian rocket Konstantin Tsiolkovsky, the staggering practical challenges such an undertaking would entail have thus far proven too great for even the most intrepid of engineers.

According to Peter Debney, a structural engineering expert from Arup, a space elevator could soon become a reality, simply by combining the latest material technology with the time-honoured methods used to keep conspicuously tall buoys afloat.

The method generally proposed for building a space elevator involves first positioning an anchoring satellite in geostationary orbit – which refers to the precise altitude at which the Earth’s gravity and centrifugal force cancel each other out, thus enabling orbiting bodies to precisely track the same fixed point on the surface of the planet.

The next step is to simply to lower an extremely lengthy cable from the geostationary satellite from its position above the earth to the fixed point beneath it, creating a connection that can be used for elevator transport.

It is at this point that difficulties, arise, however, as unfurling such an immense cable from the satellite would disrupt its centre of gravity and cause its altitude to decline, thus putting it out of geostationary orbit and causing it to shift to a different path relative to the earth’s surface.

In order to ensure that the satellite remains in the same geostationary orbit, Debney advocates using the same principle which keeps buoys afloat – the extension of a counterweight on the other side of the floating, or in this case orbiting, structure.

Buoys often come equipped with tall spires in order to heighten their visibility to boat pilots. This compromises their stability however, so in order to ensure they remain afloat, a counterweight of corresponding size and weight must be attached on the bottom of the buoy.

Debney envisages doing a similar thing with the satellite, extending a cable away from the earth in order to serve as counterbalance for the cable extending downwards towards the surface of the planet.

This system could be rendered more effective by attaching a  hefty counterweight to the cable, such as a conveniently situated asteroid of appropriate size, which would dramatically reduce the length required for the cable.

According to Debney, the remarkable strength of the latest modern materials makes the construction and deployment of such cables a highly feasible proposition. Candidates include carbon nanotubes or graphene, which has a breaking length of as much as 3,568 kilometres assuming a constant force of gravity.

Debney’s advocacy of the technique is already relevant to more than just idle theorising, with Tokyo company Obayashi Corporation unveiling plans in 2012 to construct an operating space elevator by mid-century.

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  1. Brent

    But geosynchronous orbit is 35,786 kilometers, 10 times the breaking length of graphene.

  2. Vladymir Rogov

    "This system could be rendered more effective by attaching a hefty counterweight to the cable, such as a conveniently situated asteroid of appropriate size."

    Among others, this must be quite a challenge.

  3. William Bliss

    The Lunar Elevator is clearly a smarter first step.

    Though longer, it has virtually none of the problems endemic to the Earth-based space elevator, and it can cheaply deliver lunar materials to Earth orbit. This could help Man clear out LEO space debris, removing the biggest obstacle to Earth elevator.