Understanding the Operation of Space Elevators

On April 12, 1981, the Space Shuttle Columbia launched from Kennedy Space Center in Florida, marking the beginning of the first space shuttle mission and fulfilling the vision of a reusable spacecraft. Since then, NASA has carried out over 100 missions, yet the cost of space launches has remained largely unchanged. Whether using the space shuttle or the non-reusable Russian spacecraft, each launch costs about $10,000 per pound ($22,000 per kg).

A groundbreaking space transportation system currently in development could make daily trips to Geostationary Earth Orbit (GEO) possible and revolutionize the world economy.

A space elevator constructed with a carbon nanotubes composite ribbon anchored to an offshore sea platform would extend to a small counterweight about 62,000 miles (100,000 km) into space. Mechanical lifters affixed to the ribbon would ascend it, transporting cargo and people into space, at a cost of just $100 to $400 per pound ($220 to $880 per kg).

In this article, we will explore how the concept of a space elevator is transitioning from science fiction to a tangible reality.

Space Elevator Ribbon

To grasp the idea of a space elevator, imagine a game of tetherball where one end of the rope is attached to a pole and the other to a ball. In this scenario, the rope represents the carbon nanotubes composite ribbon, the pole symbolizes the Earth, and the ball represents the counterweight. Picture the ball spinning endlessly around the pole, creating enough force to keep the rope tight. This is the basic concept behind the space elevator, where the counterweight rotates around Earth, keeping the cable firm and allowing robotic lifters to ascend and descend along the ribbon.

According to LiftPort’s design proposal, the space elevator would stand about 62,000 miles (100,000 km) high. LiftPort is among the companies creating plans for the space elevator or its components. Teams from around the world will compete for the $400,000 grand prize in the Space Elevator Games at the X Prize Cup in October 2006 in Las Cruces, New Mexico.

The core element of the elevator will be a ribbon made from carbon nanotube composites, measuring only a few centimeters in width and almost as thin as a sheet of paper. These carbon nanotubes, which were first discovered in 1991, are what give scientists confidence that a space elevator could actually become a reality. Dr. Bradley Edwards from the Spaceward Foundation states, 'Before, the material challenges seemed insurmountable. But now, with the progress being made in producing carbon nanotubes and developing machinery capable of generating the long lengths of material needed, we are getting closer to creating a ribbon that can extend all the way into space' [ref].

Carbon nanotubes possess the remarkable strength to be up to 100 times stronger than steel while being as flexible as plastic. This incredible strength stems from their unique structure, which resembles a soccer ball pattern. Once fibers can be created from these nanotubes, it's possible to weave them into threads that would form the elevator's ribbon. Previous materials were either too fragile or lacked flexibility, making them unsuitable for the task.

'They have an incredibly high elastic modulus and exceptional tensile strength, all of which point to a material that, theoretically, would make constructing a space elevator much easier,' says Tom Nugent, Research Director at LiftPort Group.

There are two possible methods for constructing the ribbon:

Once a long ribbon of carbon nanotubes is formed, it would be wound onto a spool and launched into space. Upon reaching a certain altitude, possibly Low Earth Orbit, the spacecraft would begin to unroll the ribbon, lowering it back toward Earth. Simultaneously, the spool would continue its journey to an even higher altitude. Once the ribbon reaches Earth's atmosphere, it would be captured, then gradually lowered and secured to a floating platform in the ocean.

The ribbon would act as a kind of railroad into space. Mechanical lift systems would then ascend the ribbon, making their way up into orbit.

Riding a Space Elevator to the Top

Though the ribbon remains a conceptual idea, the other essential components of the space elevator, such as the robotic lifter, anchor station, and power-beaming system, can be built with current technology. By the time the ribbon is ready, the rest of the infrastructure will be nearly complete, making it possible for a launch by around 2018.

Lifter

The robotic lifter will utilize the ribbon as a guide to ascend into space. Its traction-tread rollers will securely grip the ribbon and pull it, allowing the lifter to climb the elevator.

Anchor Station

The space elevator will begin from a mobile platform in the equatorial Pacific, where it will fasten the ribbon to Earth.

Counterweight

At the top of the ribbon, a substantial counterweight will be positioned. The earliest designs for the space elevator involved capturing an asteroid and using it as a counterweight. However, more recent designs from LiftPort and the Institute for Scientific Research (ISR) propose utilizing a man-made counterweight. In fact, the counterweight might be created using materials and equipment employed in the construction of the ribbon, including the spacecraft used to launch it.

Power Beam

The lifter will receive its energy from a free-electron laser system located near or on the anchor station. This laser will transmit 2.4 megawatts of power to photovoltaic cells, possibly composed of Gallium Arsenide (GaAs) attached to the lifter, which will convert the energy into electricity to power conventional niobium-magnet DC electric motors, as outlined by the ISR.

Once the space elevator is fully operational, lifters will be making daily trips up and down. These lifters will vary in weight, initially starting at five tons and later reaching up to 20 tons. The 20-ton lifter will be able to carry up to 13 tons of payload and offer a total space of 900 cubic meters. Lifters will transport a variety of cargo, including satellites, solar-powered panels, and eventually even humans, traveling up the elevator at speeds of around 118 miles per hour (190 km/hour).

Space Elevator Maintenance

The space elevator will stretch a staggering 62,000 miles (100,000 km), which exposes it to numerous threats, such as severe weather, space debris, and potential terrorist attacks. As the design of the elevator progresses, developers are carefully considering these hazards and finding solutions to address them. In fact, to ensure consistent operation, they plan to construct several space elevators, each one more affordable than the last. The first elevator will serve as the foundation to build subsequent ones. This strategy ensures that even if one elevator faces challenges, the others will remain functional to continue transporting payloads into space.

Avoiding Space Debris

Similar to the space station and space shuttle, the space elevator must be equipped to avoid collisions with orbital objects, such as space debris and satellites. The anchor platform will utilize active avoidance techniques to shield the space elevator from such hazards. Presently, the North American Aerospace Defense Command (NORAD) tracks objects larger than 10 cm (3.9 inches). To safeguard the space elevator, an orbital debris tracking system capable of detecting objects as small as 1 cm (0.39 inches) would be needed. This technology is already being developed for other space ventures.

"Our plan is to secure the ribbon to a mobile platform located in the ocean," explained Tom Nugent from LiftPort. "This will allow us to move the anchor and adjust the ribbon’s position to avoid interference from satellites."

Repelling Attacks

The space elevator’s remote location plays a critical role in reducing the likelihood of terrorist attacks. For example, the initial anchor will be situated in the equatorial Pacific, 404 miles (650 km) away from any air traffic or shipping routes, as per LiftPort's plan. Only a small portion of the elevator, up to 9.3 miles (15 km) above the surface, will be vulnerable to attack. Moreover, given its immense value as a global asset, the space elevator is expected to receive protection from the U.S. military and other international forces.

Space Elevator Impact

The potential global influence of the space elevator is often compared to another major transportation milestone—the U.S. transcontinental railroad. Finished in 1869 at Promontory, Utah, the railroad first connected the East and West Coasts of the United States and accelerated the settlement of the American West. It cut cross-country travel from months to just a few days, opened up new markets, and sparked the creation of entire industries. By 1893, there were five transcontinental railroads in the U.S.

The concept of a space elevator shares many similarities with the transcontinental railroad. A space elevator would establish a permanent Earth-to-space link that would operate continuously. While it may not speed up travel to space, it would make such trips more frequent and open space to an entirely new wave of development. One of the primary drivers behind the space elevator is the potential to drastically cut the cost of sending cargo to space. Unlike the space shuttle, which costs $10,000 to $20,000 per pound to launch, the lifters could reduce that price to around $400 per pound.

Current projections estimate that constructing a space elevator would cost around $6 billion, with an additional $4 billion for legal and regulatory expenses, according to Bradley Edwards, author of 'The Space Elevator, NIAC Phase II Final Report.' (Edwards is also Dr. Bradley Carl Edwards, President and Founder of Carbon Designs.) In comparison, the space shuttle program, which was estimated to cost $5.2 billion in 1971, ultimately ended up costing $19.5 billion. Each space shuttle flight now costs around $500 million, which is more than 50 times the original estimate.

The space elevator has the potential to replace the space shuttle as the primary vehicle for space travel, enabling satellite deployment, defense operations, tourism, and further exploration. For exploration, a spacecraft would ascend the elevator's ribbon and then launch toward its destination once in space. This method of launch would require significantly less fuel than traditional launches, which must overcome Earth’s atmosphere. Some designers even envision the possibility of building space elevators on other planets, such as Mars.

NASA supported Dr. Edwards' research for three years. However, in 2005, it only allocated $28 million to companies investigating the space elevator concept. While NASA remains highly interested in the project, it has chosen to take a more passive approach for the time being, preferring to wait for more substantial advancements before committing further.