For release December 2, 2005
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 Dr. 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.
Steve Stasko explains how orbiting tethers might carry supplies into space.
–UTSI Photo
Writer: Weldon Payne (931) 393-7222
wpayne@utsi.edu
