The space elevator concept relies on tethering an object to the ground and letting the rotation of the earth keep it up. Way up. Over 20 miles up.
The “elevators,” or climbing pods, would ride up and down the tether, taking cargo and people from the earth’s surface through the atmosphere and into the realm of near-zero gravity. From there, the payloads and people could launch into deep space to colonize other planets, mine for minerals—or snap some awesome selfies.
Talk about a lofty goal.
The space elevator concept has been around for over a hundred years and was more recently popularized by the venerable Arthur C. Clarke in Fountains of Paradise. However, it continues to be a dream.
But for every sci-fi reader who has twirled a weight around his or her head to mimic the seemingly simple concept of a space elevator and wondered why not, there may be an engineer shaking his or her head because that isn’t how it works.
Why an Elevator?
Leading the most recent initiative to bring the space elevator to life is Shuichi Ohno, chairman of the Japan Space Elevator Association (JSEA). Ohno, who presented at SOLIDWORKS World 2016, leads with what he considers the compelling economic reason for the space elevator. Rockets are such a waste, he said.
“If we are going to travel to space on a regular basis, we need a reliable and economic form of transportation,” said Ohno. “Anywhere from 75-90 percent of the weight of a rocket is consumed by fuel. Physics places a limit on how efficient a rocket can be, so we cannot rely on them as transportation.”
“But if we have a space elevator, we can travel to geosynchronous orbit or high-earth orbit relatively economically,” Ohno added. “If we were to build a space station there, flights to more distant destinations like Mars can be launched without having to overcome the gravitational pull of the earth.”
Manned Space Elevator Climber (concept) designed by Shuichi Ohno, JSEA. Designed and rendered in SOLIDWORKS. (Image courtesy of JSEA.)
Lack of Materials Makes for an Uncertain Future
“Does anybody take you seriously?” asked David Pogue, former tech writer for Scientific American, during an interview with Ohno onstage. Pogue spoke for the many engineers in the audience, who no doubt were desperately searching for some frame of reference.
Is there anything at all even remotely like a space elevator in the real world, something that has worked and can prove the concept? The space elevator relies too heavily on “centrifugal force,” which leaves many an engineer skeptical about its success.
Perhaps the biggest engineering challenge is the strength limit of current materials. The tether would need to be stronger than anything we have ever built. The space elevator was practically grounded without a material breakthrough.
This material breakthrough came in the form of carbon nanotubes, which are 100 times stronger than steel.
According to Devin Jacobsen of the JSEA, “The tether needs to be made of carbon nanotubes. There is potential for this material to be light and strong enough for the cable. We don’t yet know how strong we can make materials. To achieve this strength, we will need to be able to generate materials at the molecular level, but there isn’t a clear path to a chemical process to make such a carbon nanotube cable.”
A space elevator would also require that these nanotubes become much longer than current versions. The longest carbon nanotube so far? According to IEEE, reporting from last year’s International Space Elevator Consortium, it would “barely reach a child’s knee.”
The Great Escape
The current method for moving objects into space relies on escaping most of earth’s gravity by achieving escape velocity, a mind-boggling 25,000 mph (11 km/s). The space elevator preempts the need for expensive rocket fuel and throwaway fuel tanks and engines by lifting its cargo to a point where gravity isn’t nearly so strong.
Testing to 1 Kilometer and Beyond
The JSEA claims it is putting the concept to the test with its annual competition. It has been able to test space elevator components, primarily the climbers that will carry payloads into space. In this case the role of the space station is played by weather balloons, which allows for small-scale testing of climbers.
Climber carrying payload up to a weather balloon.
The balloon system has a tether that is approximately ¾ of a mile (1.2 km) long. When you allow for sagging, the height that the climbers reach is approximately 1,094 yards (1,000 m). The following video shows several teams competing to achieve maximum height, maximum speed and maximum payloads.
Since 2009, more than 100 space elevator climbers have been built. These experimental devices climb a belt-shaped tether made of Teijin’s Technora para-aramid fiber. According to Shuichi, “the fastest climbers can climb at up to 150 km/hr,” and “can carry their own weight of around 15 kg, plus perhaps 10-20 percent more. One team carried a payload of 100 kg, but it did not make it to the top.”
The current climbers tend to use off-the-shelf components such as lithium-ion battery packs and electric motors to stay within their self-imposed budget constraints. Shuichi said that the typical total cost for a climber is in the range of $3,000 – $5,000.
Climber for Space Elevator Competition designed in SOLIDWORKS.
Jacobsen said battery power won’t work for a real space elevator, which will have to go 20 times the distance of any tests. He spoke of an “IR laser or microwaves to send energy through the atmosphere. Unfortunately, this system would lose up to 95 percent of the energy on the way to the climber.”
Political and Financial Challenges
The next major milestone for the space elevator project will be a tethered balloon system that floats 3-5 km above the earth. Unfortunately, such a system is not legal in Japan, which brings Shuichi and his team to Nevada, where regulations are relaxed along many fronts.
That 3- to 5-km balloon test will allow for incremental experimentation with more height and more payload.
Shuichi Ohno said that the lack of a legal system is a big barrier to funding. “There is an international space treaty and the current treaty may not allow a space elevator. We would have to create some sort of exception for a space elevator and a new legal entity.” He explained that a project of this magnitude will require a lot of funding.
The JSEA team testing its space elevator design.
When Can We Get a Ride?
Don’t expect to be elevated up to space any time soon—or even in your lifetime. There is no expected date for a real space elevator. When pushed on the subject, Jacobsen replied, “It’s not possible to predict a feasibility date or whether it is, in fact, feasible. Before the end of this century we should know whether the space elevator is possible.”
About the Author
John Hayes is the president of ENGINEERING.com.