London, March 30 : A new study has suggested that building and maintaining a hypothetical space elevator would be an even bigger challenge than previously thought, as it would need to include built-in thrusters to stabilise itself against dangerous vibrations.
According to a report in New Scientist, the idea behind a space elevator involves deploying a cable stretching from the ground near Earth's equator far enough into space, and centrifugal forces due to Earth's spin will keep the cable taut.
Vehicles could then climb up the cable, also called a tether or ribbon, to get into space, powered by lasers on the ground or other Earth-based power sources.
The idea could dispense with expensive rocket launches, making access to space much cheaper.
But, the concept has been stuck on the ground floor for decades, and not just because constructing a tether strong enough for the job is beyond current technology. Nanotubes might be up to the task, but they would have to be made longer and with fewer defects than any that can be fabricated today.
Also, a new study makes the prospects appear even gloomier.
"Even if a space elevator could be built, it will need thrusters attached to it to prevent potentially dangerous amounts of wobbling," said Lubos Perek of the Czech Academy of Sciences' Astronomical Institute in Prague.
"The addition would increase the difficulty and cost of building and maintaining the elevator," he added.
Previous studies have noted that gravitational tugs from the Moon and Sun, as well as pressure from gusts of solar wind, would shake the tether. That could potentially make it veer into space traffic, including satellites and bits of space debris. In fact, a collision could cut the tether and wreck the space elevator.
If it turns out that thrusters are needed on the cables, they could pose a serious challenge to building a space elevator.
"I am sure that having thrusters hanging off the cable at regular intervals is going to be a serious annoyance in terms of maintenance, refueling, and simply the logistics of attaching them and having the elevator bypass them," said Perek.
People have previously considered the idea of smoothing out disturbances in the tether by making the Earth-based anchor for the tether movable, and jiggling it in carefully designed patterns to counteract the vibrations.
But according to Perek, that may not be enough. "Previous proposals for a passive tether controlled from the ground do not seem stable to me," he told New Scientist.