Steve Stasko, a doctoral student at The University of Tennessee Space Institute, believes an electrically-powered “space elevator” may some day ferry supplies to the moon at far less cost than rocket-propelled vehicles. Such an elevator – using only electrical energy — would provide a “bridge to orbit” and make cheap access to space a reality in contrast to the estimated $10,000 to $20,000 cost per pound required to lift the space shuttle into orbit, Stasko says. “Lowering the cost to space is about mass (weight) and how to manage it without expending lots of fuel,” he noted. “Typically 85 to 95 percent of the weight of a launch vehicle is fuel that gets burned up getting into orbit.”
One idea involves putting a satellite into geostationary orbit about 22,000 miles above Earth. At that altitude its orbital speed would match the earth’s rotation, and viewed from a point at the equator, it would appear fixed in the sky.
“If you could extend a rope or line down from that satellite to the earth’s surface, you essentially would have a ladder extending 22,000 miles to Earth,” according to Stasko. “You would also extend a line on the other end to balance the mass around that point in its orbit. The satellite would be turning at the same speed of Earth’s rotation. This would allow us to climb into space via an elevator car without burning any rocket fuel, using only electrical power.”
It is not a new idea, the Philadelphia native notes, but has existed for more than a century as a theoretical alternative to getting into space without expending fuel for rockets. The same scientists writing about rockets in the early 20th century
also wrote about the space elevator, but he thinks they viewed it as a “thought experiment, not something you could actually build.” One problem was the lack of adequate material for the tether.
Stasko, in his work toward a doctorate in Aerospace Engineering, is exploring a second approach, optimistic that this version of the elevator will become an actual alternative in the near future.
“I’m not necessarily working on a full ground elevator,” he says, “but on a simpler plan, and from what I’ve found so far, one that could be built with available materials.”
This version would feature a large satellite, with lines extending up and down, orbiting the earth at an altitude of about 2000 kilometers. The bottom end of the tether would be about 150 kilometers above Earth’s surface. At the center of gravity would be a propulsion system used to maintain the satellite’s orbit.
“Gravity would hold such an orbiting space elevator normal to the surface of the earth at all times,” Stasko says. “The lower end would always be hanging down towards the ground, while the upper end pointed up away from the earth.”
A launch vehicle would ferry payloads to the lower end of the tether, which is only traveling at approximately 70 percent of orbital speed at that altitude. This vehicle would be smaller than the shuttle and require as little as half the fuel needed to reach orbit. The payload would be loaded onto electrically powered “elevator cars” in a couple of minutes and begin their trip up the tether.
Depending upon the length of the tether, payloads released at the upper tip would go on one of three possible routes: (1) A tether 2,700 kilometers long would transfer payloads to geosynchronous orbit, where most communication satellites reside; (2) A tether 4,000 kilometers long would place objects on a “free trip to the moon;” and (3) A 4,600 kilometer long tether would be used for interplanetary trips.
“The big savings is that with the tether, you can get going to the moon or other planets by only expending the fuel required to reach 150 kilometers,” Stasko says.
It is the lunar voyage that most interests Stasko, whose major professor Gary Flandro has suggested man might “mine” the moon’s abundant supply of Helium 3 – “a perfect source of clean fusion energy.”
“The second option (4,000 kilometers) would be a great method for placing mining equipment on a trip to the moon,” Stasko says. “It is a great system to go into high Earth orbit, lunar exploration, or farther beyond, but it is not really good for reaching lower orbits,” such as trips to the International Space Station.
“You get nothing for free,” Stasko emphasized. “When the orbiting tether releases its payload, the tether’s original orbit is going to drop; it would lose some speed at each launch. So we must find some method to keep it from dropping too low and burning up in Earth’s atmosphere.” He mentioned solar power as a possible solution or even trolling the electric magnetic field with a long wire, so called “electrodynamic propulsion.”
A major benefit of the second plan, he thinks, is that the tether could be built out of commercially available materials such as Kevlar or Spectra, which are commonly used in body armor, bow strings, and climbing equipment.
“The only material to make the full ground-to-orbit elevator is carbon nanotubes. This is still very experimental, and there are questions about its strength.”
Stasko thinks the system can be “used over and over again, like roads and bridges.” He looks “at this as a piece of infrastructure. Like a highway, you make an investment to use for the long term.”
Son of Ed and Marie Stasko of Philadelphia, Stasko graduated from the Archbishop Ryan High School and earned a bachelor’s degree from Drexel University. He got his master’s degree in Aerospace Engineering at UTSI in December, 2001, with Flandro as his major professor. Steve and his wife Molly reside in Tullahoma.