National Geographic News
An illustration of space elevator.

Nanotechnology could provide the very high-strength, low-weight fibers that would be needed to build the cable of a space elevator.

ILLUSTRATION BY PAT RAWLING, NASA

Joseph Bennington-Castro

for National Geographic

Published March 5, 2014

A trip to the moon on gossamer strings? A "partial" space elevator that could carry satellites to geosynchronous orbit might be just the ticket. (See also: "Escaping Earth: Could a Space Elevator Work?")

A space elevator untethered to Earth, with both of its ends hanging in space, might cut the costs of space travel to high orbit by 40 percent, researchers report in a new Acta Astronautica study.

Inspired by science fiction maven Arthur C. Clarke's 1979 novel, The Fountains of Paradise, scientists have long studied the concept of a full space elevator, which would stretch from an equatorial spot on Earth's surface into space about a quarter of the distance to the moon. A partial space elevator would be less than half as long and wouldn't need to be anchored to Earth.

"I think in parallel to full space elevators, partial space elevators are definitely worth exploring more," says space engineer Stephen Cohen, a physics professor at Vanier College in Montreal, Canada, and author of The Engineer's Pulse blog, who wasn't involved in the new study.

Underlying the idea of a space elevator is the high cost of space rockets. It now costs about $25,00 per kilogram (2.2 pounds) to put something into geosynchronous orbit, where communications and television satellites reside.

Today's materials aren't strong enough to support a huge, full space elevator to those heights, the McGill University study argues. Instead, a much smaller elevator looks less far-fetched.

"We could view it as the first building blocks of a [full] space elevator," says study co-author Pamela Woo of McGill University in Montreal, Canada. "We might start off with the partial elevator and then maybe extend it to Earth."

Saving Energy

The base would sit somewhere in low Earth orbit, which extends from roughly 99 miles (160 kilometers) to 1,243 miles (2,000 kilometers) above the planet's surface.

If built, a partial space elevator would have four parts: a base, a counterweight, a tether, and a climber.

The actual elevator, or “climber,”

would ascend the tether from the base to deliver its cargo to geosynchronous orbit.

 

A strong, ribbon-like cable called a tether would connect the base to a much higher counterweight above geosynchro-
nous orbit.

The goal of the elevator would be to carry satellites from this base to geosynchronous orbit, some 26,200 miles (42,164 kilometers) above Earth.

Counterweight

60,000 miles

from Earth

Base

Climber

Tether

Earth

Art: Stefan Morrell. Sources: Ben Shelef, Peter Swan, Ted Semon, International Space Elevator Consortium

Rocket vs. Elevator

In the study, Woo and her McGill co-author Arun Misra calculated the energy requirements for sending a spacecraft from low Earth orbit to geosynchronous orbit along two different paths: In the first, a rocket carries the spacecraft straight to geosynchronous orbit; in the second, a rocket carries the spacecraft to a partial space elevator's base, where a climber then transports it to geosynchronous orbit.

For most scenarios, the partial space elevator was far more efficient than the traditional, rocket-powered transportation. "In general, using longer tethers resulted in more energy savings," Woo explains.

The costs of low-Earth orbit launch are lower than those of geosynchronous launches, at around $5,000 to $10,000 per kilogram (2.2 pounds), accounting for some of the savings.

If the elevator is solar powered, it may be even more energy efficient, Cohen suggests. Still, a full elevator would be better, as it does away with rockets altogether, he says.

Peter Swan, president of the International Space Elevator Consortium, agrees: "If we keep working with rockets, we are destined to live in a shake, rattle, and roll world of high costs to orbit."

23 comments
Aravind Pillai
Aravind Pillai

space elevator .  the interesting part of such project is that , it can bring in much needed energy efficient technology to be used on earth .  

Zamin Mamiyev
Zamin Mamiyev

it is very interesting field, I would like to work with any group who work on the space elavator. I think it is the best modern and reality next level scientific act. lucky way to space :)

Scott Henrie
Scott Henrie

I am pretty sure that all this will do is pull the satellite out of the sky...

m s
m s

Yep as soon as they develop the Carbon nanofiber filament and induction coil transportation we'll be on our way.

Dwayne LaGrou
Dwayne LaGrou

I think it would be possible to do away with the "Rocket" part all together. Just use balloons to bring it to the lower end just like Felix Baumgartner did for his sky dive from space. Also I am wondering if it would be possible for it to be self powered by the electrical differential between the top and bottom sections. I seem to remember an experiment on one of the shuttle missions where they suspended a sphere or something like that from the shuttle with a wire that was a few miles long to see if it could generate enough power to be useful, And it DID!!

Same principle that makes lightning.

Tell me, Does this sound possible?

Thank You, Dwayne

Alan Lieberman
Alan Lieberman

How much will this little project cost and who will flip the bill?

Gustavo Martinez
Gustavo Martinez

this is great  i really hoping the one day everybody will be able to go to the moon and spend Honey  moon over there,,,,

Stephen Webb
Stephen Webb

The orbital PERIODS would be identical, with the orbital VELOCITY being (or course) much higher at the outer terminus of the tether. 

Tim BAiley
Tim BAiley

Imagine the mess when such a contraption falls back to earth, as all satellites eventually do.

kevin woolf
kevin woolf

It would be interesting to see an explanation (missing above I believe) of how a partial space elevator would compensate for the differing orbital periods of its two ends.  Or am I mistaken that the lower orbiting end could not be geosynchronous?

Stephen Cohen
Stephen Cohen

@Scott Henrie  A climber that scales a partial space elevator tether does have some effects on its dynamics, but not as drastic as your comment suggests.  Research (in this case, a dynamic analysis) takes us from a shot in the dark (or "pretty sure" as you describe it) to "sure".  Just a suggestion: when you post a thought on a science topic you have not studied before, consider starting it with, "I wonder if..." instead of "I'm pretty sure that".

Stephen Cohen
Stephen Cohen

@Dwayne LaGrou  Baumgartner's balloon cannot work where there is no atmosphere.  Balloon's can never allow us to reach even low altitudes of space, where there is a vacuum, because 'you can't be lighter than nothing'.

Earl Lionts
Earl Lionts

@Alan Lieberman The people who would make fortunes off of it could 'flip the bill', but they would probably scheme to get the governments (a.ka. you and me) to pay for it.

But your comment sounds like the other people I know who are made stupid by their selfishness.

Diane Lavoie
Diane Lavoie

@Alan Lieberman  Less than the rockets that do the work today, or it will not be built.  At 5000 $ per kg, a 2 ton upper stage is worth 10 million dollars, and serves only once.  If this cable weighs less than a few dozen tons, then it may make sense.  If it could transport 10 satellites per year, for example, giving it a revenue in the order of 50 million dollars per year to pay for it's financing and if it lasted 20 years without major repairs, then it might finance itself with about 1 billion dollars of total revenue.  A lot of money, but  probably not enough to pay for all the design required, and the cost of it's own launch 

Ryan Remus
Ryan Remus

@Tim BAiley Actually I doubt that would be a problem, first of all having the counter weight positioned at one end keeps it from reentering, and secondly if the counterweight was susceptible to orbit degradation you could make systems to control that.

Tom Mengel
Tom Mengel

@Tim BAiley  It will burn up in the atmosphere like 99.9% of the satellites now do, no big issue.

John Lakeman
John Lakeman

@kevin woolf I agree. Something occurred to me after thinking about it. My guess is that a partial space elevator from LEO to HEO would not be geosynchronous in the way space elevators are typically imagined. Relative to the Earth itself the cable would be static & move with the planet. However, relative to any given equatorial location its location would change as the Earth rotates. (ex: At 6 am GMT the base is over Indonesia. At 6 pm GMT the base is over Brazil.) Thoughts?

Atanu Nath
Atanu Nath

@kevin woolf  Orbital periods won't be different, the two ends will have different velocities but same angular velocities. 

Scot Alexander
Scot Alexander

@kevin woolf The inner part would be traveling at suborbital velocity, and would want to fall back to Earth; the outer end, which would need to be well beyond geosynchronous orbit, would be traveling in excess of orbital velocity, and would want to fly away from Earth.  These two would balance around a center of mass located in geosynchronous orbit, maintaining balance.  The whole assembly would then spin around it's axis once per day, locked in place by tidal forces.  Satellites often have an "anchor" weight that they point down at Earth in a similar fashion, to utilize the tidal forces to maintain attitude.

Dwayne LaGrou
Dwayne LaGrou

No, I understand it could not reach the FULL way to the base, But a balloon could reach at least a quarter of the way to the base which would reduce the amount of fuel needed to reach the lower end by a considerable amount!

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