What You Should Think About Space Elevators

November 23, 2007

“When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.”

–Arthur C. Clarke

In the novel Fountains of Paradise, Arthur C. Clarke creates a vivid tapestry of one plausible future. At one point in this work, penned in 1979, the leader of a major project does research online in preparation for a media appearance alongside a pundit skeptical of his work. While Google, Wikipedia, et al. provide a reality strikingly similar to Clarke’s vision of the future, another of his predictions has not yet come to pass. Yet there are encouraging signs of a sort.

The focus of the novel is a creation comparable to a vertical railroad for purposes of hauling mass into space. With thriving colonies on the Moon and Mars, rocket propulsion was becoming prohibitively expensive and taking a heavy toll on the upper atmosphere. Everything changes when an engineer finds out about a special sort of filament that is virtually indestructible. The incredible strength of this technology makes it possible to string wires from the a hub in geosynchronous orbit to a fixed point on the surface of the Earth. Building out a rail line from that radically changed the economics of human activity in space.

In reality there are no breakthroughs in the field of indestructible filaments. Yet work in carbon nanotube synthesis offers another striking parallel to Clarke’s foresight. Experts in the field today suggest the not-so-distant future may be home to a space elevator consisting primarily of a newspaper-sized ribbon of material synthesized to possess downright astounding tensile strength. Promising leads in the field of nanotechnology could make it possible to synthesize a ribbon that would remain unbroken while stretching the full distance from a ground station to an orbital anchor/spaceport.

In the halls of power, this remains an idea far ahead of the times. Though it may be less bold than America’s push to put men on the Moon, at present federal involvement seems limited to the occasional small grant along with NASA’s decision to assign one engineer to monitor and support ongoing research. Already this ongoing research offers much promise. In particular, carbon nanotube synthesis is subject to aggressive exploration by a mix of private and public institutions. Fantastically strong materials would have obvious commercial applications.

In that area I favor more publicly funded research. It seems that having such a fundamental technology in the public domain would produce more and better economic activity than allowing it to be controlled by a single vendor. Products produced by many corporate R&D departments working with the material offer much more promise than work with the fundamentals of making long carbon nanotube lattices shrouded in trade secrecy. Yet even if that winds up being a proprietary innovation, a space elevator project could provide the kind of enormous bulk order needed to get mass production underway promptly.

Assuming there is no crippling corruption in procurement, credible estimates suggest as little as $8 billion could finance implementation of this idea. That is no small price tag, but it does come in under the cost of two months additional funding for the occupation of Iraq or less than 1/10th the resources consumed by the missile defense budget. In fact, a consortium of private investors could pull together a project like this if the technology becomes available and this application is not pursued by any major government.

Be it private or public, the end result would be an ability to lift people and freight into space and return them safely to Earth at a small fraction of the cost involved in operating a rocket-propelled launch vehicle. Vast amounts of energy required to produce vast amounts of rocket fuel could give way to a solar farm in space and a single power plant on the ground to energize carriages traversing the elevator. The journey might be slower, but it would combine much reduced cost with much reduced physiological stress — opening up space travel to a much broader range of human beings.

Already teams of academics and engineers engage in competitions to produce the most effective or efficient vehicles for climbing or descending a prospective space elevator. Since the actual material has yet to be produced, variety in the format of these competitions builds up a flexible knowledge base. When the time comes that there is an actual need for space elevator carriages, many engineers will be capable of bringing years of experience to the project.

Using existing methods, it costs thousands of dollars to rocket a kilogram of cargo into space. The most wildly optimistic estimates about the future efficiency of ordinary spacecraft are in line with the most extreme pessimistic estimates about the cost-to-weight ratios made possible by a working space elevator. If we go beyond pessimism, the possibility exists of producing multiple Earth-based space elevators, not to mention lines for lunar and Martian shipping without the use of rocket fuel. Getting ample supplies to permanent settlements on those celestial bodies, and facilitating economically significant exports back to Earth, would be a huge advance on the journey to venture beyond humanity’s cosmic cradle.

In fact, a lack of interest among Earth’s rocket science establishment leads the protagonist in Clarke’s novel to look to Mars first. Lighter Martian gravity means that a much shorter tether is required to reach from the surface to a facility in stable synchronous orbit. As in reality, the book depicts the challenges posed by one of Mars’s small moons with a transequatorial orbit. The story resolves this problem by deliberately maneuvering the span to avoid the swift little moon as it races past.

Without significant economic activity on Mars, it is a poor place to look for space elevator funding. Yet were these feats of engineering to be accomplished on both worlds, substantial settlements and real interplanetary trade could be sustained with a much smaller energy budget than any rocket-based approach would require.

For now, the space elevator remains an intriguing idea more than it is a concrete proposal. Yet it is already much more than a pipe dream. No one would be enormously shocked to encounter headlines about the successful synthesis of carbon nanotubes in a format with properties suitable to the space elevator application. It is a result many scientists are already laboring to achieve as a logical extension of existing work in that field. So long as that result has not come to pass, perhaps it is wise that our government does no more than token work on space elevator planning and development.

Yet when it becomes possible to produce materials up to the task, swift and decisive action is warranted. Whichever government, intergovernmental agency, or private conglomerate manages to get an wonder like this to function will abruptly acquire a tremendous competitive advantage when it comes to launching and collecting spaceborne mass. Both the human adventures and the economic opportunities to follow from the initial achievement could make the following decades an age of marvelous progress.