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Going up! The elevator that could take you into space

A major Japanese construction company, Obayashi Corporation, has announced plans to build a space elevator within 40 years, allowing people to be transported to space stations above the earth. The proposed…

A week is a long time to be stuck in a lift. MGM

A major Japanese construction company, Obayashi Corporation, has announced plans to build a space elevator within 40 years, allowing people to be transported to space stations above the earth.

The proposed design (see below) features a 96,000-kilometre-long cable connecting an earth-based spaceport to a counterweight in orbit, roughly a quarter of the way to the moon. An elevator car would then transport people along the cable between the spaceport and a research station 36,000km above the earth – a journey that would take roughly 7.5 days.

Obayashi Corp

But how realistic a vision is this? And what would a space elevator cable even be made of?

The space elevator concept first entered public consciousness through Arthur C. Clarke’s 1978 science fiction novel Fountains of Paradise. In the novel, an elevator made of a strong filament or cable was connected to a geosynchronous satellite to transport materials to and from Earth.

Literary fantasies aside, the reality is that the type of cable proposed by Obayashi Corp. can and will be made. Whether it works or not is another story.

Obayashi Corp’s proposed space elevator will utilise a material discovered in 1991 by Japanese physicist Sumio Iijima – carbon nanotubes (CNTs). CNTs are essentially single tubes (single-walled carbon nanotubes) or multiple concentric tubes (multi-walled carbon nanotubes) comprising sheets of graphene. CNTs are one of the strongest materials ever created, stronger than diamond, Kevlar, or even spider’s silk.

As such, CNTs would be the ideal material for creating a space elevator cable. Of course there are several issues that need to be addressed before this lofty goal can be realised.

The first, and most fundamental challenge, is that nanotubes can only be grown to around 20 centimetres in length, at present. So the first challenge is tethering these tubes together to form ropes, very much like the method used to make wool yarn.

An artist’s conception of a space elevator climbing through clouds. Liftport

CSIRO scientists have started to work on making fabrics out of sub-microscopic carbon nanotubes yarns, but the length of the CNTs being used – one to 300 microns, where 1 micron is one-millionth of a metre – make this a real challenge.

Nonetheless the technique of twisting nanotubes into a self-locking yarn has been highly successful.

So while we are close to making reasonably long nanotube yarns there is one intrinsic flaw: the self-locking mechanism in CNT yarns is held together by only van der Waals interactions – weak intermolecular forces between the nanotubes.

While the accumulation of these interactions along the body of a nanotube makes for quite strong bonding within the yarn, these forces are much weaker than if the tubes were “welded” to one another.

The ideal situation would be to fabricate an individual carbon nanotube 96,000 kilometres long. But this is unlikely: a CNT of this length, when stretched out, could wrap around the earth’s equator more than twice – hardly manageable in a lab.

SpaceElevatorGuy

Alternatively, scientists could chemically weld (via intramolecular covalent bonding) individual nanotubes, preferably end-on-end with a bonding structure similar, if not identical to, the structure of the carbon nanotubes themselves.

Current techniques can easily attach one nanotube to another or attach nanotubes to a variety of other materials, including nanoparticles, DNA, polymers and proteins. These nanocomposites have a broad range of applications from sensors to solar cells.

But in the context of a space elevator cable, the nanotechnologists' ambition of end-on-end carbon nanotube attachment is still elusive. Achieving this ambition may prove crucial before anyone will feel confident about being lifted into space by elevator.

Clearly without a strong enough material the entire idea of a space elevator is just an intellectual exercise. Happily there is a whole world of scientists out there working hard to turn our dreams into reality.

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7 Comments sorted by

  1. Dave Hudson

    Environmental Scientist

    Probably the most mind blowing article I've read for a while. I had to check the calendar to make sure it wasn't April 1st, given the incredible amount of work needed to make this a reality, if indeed it is even capable of becoming reality. I've never heard of Clarke's novel ... the first thing that came to my mind was the drill on the most recent Star Trek film, combined with the elevator from 'Charlie and the Great Glass Elevator'.

    Not saying it wont happen, but ... I'll believe this when I see it!

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    1. William Ferguson

      Software Developer

      In reply to Dave Hudson

      For a really insightful view on the economic imperative behind a space elevator I thoroughly recommend Kim Stanley Robinson's Mars trilogy (Red Mars, Green Mars, Blue Mars http://en.wikipedia.org/wiki/Mars_trilogy). It's also a damn good read.

      In reality for this to happen requires no new science, it is a matter of perfecting the engineering and sourcing finance. Although the engineering may take two or three decades to perfect.

      Much kudos to the Obayashi Corporation for making such long term plans. If only our governments could be persuaded to be similarly long sighted.

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  2. Dale Bloom

    Analyst

    With every rocket being launched into space, it inevitably leaves behind space junk, and the actual operation of every satellite also leaves behind space junk. At some point in time, there will be too much space junk to launch rockets to position or service satellites.

    There has to be some other way to get into space without leaving behind debris.

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    1. Dave Hudson

      Environmental Scientist

      In reply to Dale Bloom

      Remediation is what is needed, not just mitigation. I think that eventually market forces will cause more and more organisations to invest in researching ways of cleaning up the debris, given that it is imperative for many industries and services to have access to space equipment such as satellites.

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    2. Dale Bloom

      Analyst

      In reply to Dave Hudson

      Hi Dave,
      Apparently it is becoming more difficult to launch rockets because of debris in space, and debris seems to be accumulating at an exponential rate.

      If there is to be some type of space elevator, 40 years to build it may be too late. In less than 40 years, the debris may be too great to launch any more rockets. Cleaning up the debris may have to come first.

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  3. Andrew Chuter

    Mr

    The distance in the diagram to the station is 36,000km but the text says 36km. I'm assuming 36,000km is correct? That's an average speed of 200km/h to get there in a 7.5 days.

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    1. Matt de Neef

      Editor at The Conversation

      In reply to Andrew Chuter

      Hi Andrew. You're quite right - thanks for picking that up. We've amended the article accordingly.

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