Aerospace engineer Brad Edwards’s plan for a space elevator
centers on a carbon-nanotube-composite ribbon 62,000 miles
long (roughly eight times longer than Earth’s diameter),
three feet wide, and thinner than a newspaper page. The competing
forces of gravity at the terrestrial end of the elevator and
centripetal acceleration at the deep-space end would keep the ribbon taut
and stationary over a single position at Earth’s equator.
Climbing vehicles powered by Earth-based lasers striking solar cells
would haul cargo and people to various orbits. If a climber
released a cargo or passenger vessel at the far end of the ribbon, the craft
would have enough velocity to travel to the moon, Mars, Venus,
or the asteroids. At a cost ranging from $6 billion to $24 billion,
Edwards says that the elevator is within the means of
several of the world’s governments as well as some large
private companies.
—B. L.
ANCHOR STATION
A refurbished oil-drilling platform displacing 46,000 tons of water would serve as both the anchor station for the space elevator and a platform for a laser to propel the climbers. A key advantage of an offshore anchorage is mobility; the entire station could be moved every few days to allow the ribbon to avoid large chunks of space junk. Edwards’s plan calls for placing the station off the coast of Ecuador, which has the advantage of being a relatively lightning-free zone and also fairly accessible to the United States.
RIBBON OF NANOTUBES
Carbon nanotubes, discovered in 1991 and now synthesized in many laboratories worldwide, have a tensile strength 100 times stronger than steel at one-fifth the weight. The space elevator’s ribbon will consist of thousands of 20-micron-diameter fibers made of carbon nanotubes in a composite matrix. The fibers will be cross-linked with polyester tape at roughly three-foot intervals.
CLIMBER
Ascent vehicles will vary in size, configuration, and power, depending on function. All will climb via tractorlike treads that pinch the ribbon like the wringers of an old-fashioned washing machine. Power for the motors will come from photovoltaic cells on the climbers’ undersides that are energized by a laser beamed up from the anchor station. At least two additional lasers will be located elsewhere in case clouds block the anchor station’s beam.
COUNTERWEIGHT
A deployment booster, carried aloft in pieces by a vehicle such as the space shuttle and assembled in low Earth orbit, will unfurl two thin strips of ribbon stretching from Earth to deep space. Once the strips are anchored to a site on Earth, 230 unmanned climbers will “zip” together and widen the strips. Those climbers will then remain permanently at the far end of the ribbon, just below the deployment booster, to serve as a counterweight. >
