Tag Archives: carbon nanotubes

Elevator to SPACE

29 Aug

In August of this year, Washington will be hosting an event that will no doubt capture the imaginations of scientists and sci-fi nerds alike; The Annual Space Elevator Conference. Over the course of three days, researchers, designers, and space enthusiasts will meet up to discuss the challenges of constructing a US$8 billion ribbon that will connect Earth and sky.

The current design consists of a tether fastened to the Earth’s equator, extending to a counterweight about 96,000km away (a quarter of the distance to the moon!). Elevator-riders’ destination will be a space terminal sitting at 36,000km above Earth’s surface. To put this distance into perspective, NASA grants astronauts their space travel wings at an altitude of 80km, Virgin Galactic will take you to 110km for the small sum of US$200,000, and Earth’s atmosphere ends at an altitude of about 1000km. The cable, counterweight, and terminal will orbit Earth as the planet rotates, with the terminal itself existing in ‘geosynchronous orbit’; essentially orbiting at precisely the right distance and velocity to ‘keep up’ with Earth’s rotation.

Getting to 36,000km in a space elevator will involve more than just hitting the ‘up’ button and standing awkwardly in a box, desperately avoiding eye contact with fellow lift-users. Travelers will be zipping along the Earth-to-space tether at 200km/h for about a week, contained in a shuttle capable of deflecting potentially fatal radiation.

For the past five years, NASA has been offering a US$2 million prize to groups that successfully develop a tether capable of withstanding the physical demands of space elevator travel. No group has won this NASA Strong Tether Challenge yet, but 2012 might be the year that changes.

Developments in the technology have put carbon nanotubes at the front of the materials-race for space elevator application. Consisting of a ‘mesh’ of carbon atoms rolled into a cylinder of about 1 nanometer diameter, carbon nanotubes are the strongest known material in terms of tensile strength (withstanding stretching or pulling). Carbon nanotube fiber with a cross section of 1 millimeter squared would be capable of holding about 6400kg. That’s like dangling a Hummer from a ukulele string.

Using this super strong material, the ‘ribbon’ space elevator tether design becomes feasible. A 20cm wide, paper-thin ribbon of carbon nanotube fibers would be sufficient to link Earth to the space terminal, before widening to about 1m to join the terminal to the counterweight.

Before the development of the space elevator can commence, a method for seamlessly joining carbon nanotubes together to form a 94,000km ribbon must be perfected. Spinning fibers together like spinning yarn from wool might be an option, but there is no room for shortcuts where a project of this scale is involved.

The Obayashi Corporation in Japan has announced that they will be capable of building a space elevator within the next 40 years, so there’s every chance we will be lucky enough to witness one of the staples of science fiction becoming a reality.