Is it time for us to get serious about building a "Space Elevator?"
On August 13, approximately 280 people gathered at the Microsoft Campus in Redmond Washington for a "Space Elevator Overview" public lecture, with 60 attendees continuing on to be part of the four day long Fifth International Space Elevator Conference sponsored by Microsoft and JPL Foundation. Delegates flew in from Japan, Armenia and other far-off locations.
A proposal for a space elevator was first published by Yuri Artsunov in the USSR in 1960. At that time, the west knew little about Artsunov’s work, and the idea was re-invented independently by Jerome Pearson in the USA in 1975.
Essentially, the idea is to build a tether tens of thousands of kilometers long, and suspend it vertically upwards form the surface of the Earth to far beyond Geosynchronous orbit. If properly counterbalanced, the tether would be stable, and motorized "climbers" could pull themselves up the tether to geosynchronous orbit. Theoretically, a 1 kilogram payload could thus be injected into orbit for about $2 worth of electricity, quite a bargain when compared to the approximate $20,000 cost of a conventional rocket.The dramatic cost reduction would open the space frontier to an explosion of space industry, commerce and tourism. "There will be places in the space elevator for everybody," said conference chairman Dr. Bryan Laubscher.
The conference brought together a wide cross section of experts and members of the lay public to learn and exchange ideas and a strong NASA presence attested to the growing influence of the concept. Seeking innovative solutions to NASA’s technical challenges through prize competitions open to the citizen inventor, the space agency is holding two "Challenge competitions," and a competitor rose to the challenge in one of the categories at the conference itself. These were the Power Beaming and Tether Competitions.
The Power Beaming Challenge
The Power Beaming challenge is a practical demonstration of wireless power transmission. Teams build mechanical devices (climbers) that can propel themselves up a vertical cable. The power supply for the device is not self-contained but remains on the ground. The technical challenge is to transmit the power to the climber and transform it into mechanical motion, efficiently and reliably. In past competitions, some teams used power from the sun or ordinary spotlights, but all of the teams preparing to compete now intend to use lasers. Practical systems employing power beaming would have a wide range of applications from lunar rovers and space propulsion systems to airships above the Earth.
Power beaming is a likely tool for developing a space elevator and many of the competitors are elevator advocates. Ben Shelef, head of the Spaceward Foundation, described the NASA Power Beaming Challenge in depth. (NASA has contracted Spaceward Foundation to administer the two Challenge competitions.) In this challenge, contestants’ climbers must ascend a tether (whose length is increased each year) using solar power, lasers or microwaves. Beamed power competitions were held in 2005, 2006 and 2007. So far no team has met the ambitious criteria to win the prize, but some came close in 2007 and they are competing again in 2009. The purse this year is $2 million, which should make things interesting.
In the 2009 competition, the competitors will be expected to drive their laser-powered devices up a cable one kilometer high. The cables will be suspended from a helicopter. This promises to be the most visually impressive Centennial Challenge event to date. The 2009 competition is scheduled for August at the NASA Dryden Flight Research Center.
The Tether Challenge
The greatest technical roadblock to building a space elevator is the lack of current materials. Extremely high tensile strength is needed, and so far only carbon nanotubes (CNTs) promise adequate strength. Alas, today the longest CNTs are only a millimeter of so, a far cry from the tens of thousands of kilometers needed. Recognizing this problem, NASA created the "Strong Tether Challenge" — a contest to see who could first develop stronger materials and publicly demonstrate their strength. NASA chose to hold their contest at the conference.
This is a challenge in materials engineering in which the tether provided by each team is subjected to a pull test. In order to win the $2 million prize, the tether must exceed the strength of the best available commercial tether by 50 percent with no increase in mass. A tether that can win this challenge would be a major step forward in materials technology. Such improved materials would have wide range of applications in space and on Earth. In past years the Tether Challenge was held in conjunction with the Power Beaming Challenge at an event called the Space Elevator Games. In 2009 the events will be separate.
Some space enthusiasts see the potential of wireless power transmission and high-strength tethers being combined to realize the space elevator, a concept that would bring about a revolution in space activity. The space elevator and even space solar power may be many years away, but dramatic improvements in power beaming and tether materials that result from these challenges can lead to many near-term innovations in a wide range of fields.
The 2009 Tether Challenge was held live at the conference on August 14. This demanding challenge requires a significant advance in materials technology. Although there were expressions of interest from several potential competitors, only one team from Shizuoka University in central Japan, led by Yoku Inoue, came to the event. The team brought a 2.2-meter length loop of carbon nanotube material.
Inoue presented an impressive briefing of their system for manufacturing CNT ribbons and showed a fascinating video covering every step of the entire process. The video starts with a bed of many fibers, each about 1 mm long, grown on a substrate of Iron Chloride. Yarn is easily drawn using tweezers by pulling out the edge of the array. The yarn is spun into a ribbon over 40 meters length by a weaving machine. On the ribbon, the CNTs were bonded together by electrostatic force without using any chemical binder. Hence the strength of this ribbon was much lower than the theoretical strength of single crystal CNT fiber. Nevertheless, this was history because it was the first time that CNTs had been subject to a public pull test.
After the presentation we moved to a room where a "pull machine" stood about 6 feet high. The assembly had a calibrated load cell and applied a measured tension to the samples. After a demo test, using a sample of Zylon, the Shizuoka sample was installed on to the pull tester. The hushed crowd looked on tense with anticipation — but hopeful. A volunteer turned on the switch to start the pull. We watched the stress meter counting up rapidly, but within just a few seconds, there was a loud snap and the sample failed. The loop failed at a level well below its expected strength, but the fabrication of the carbon nanotube loop itself was a significant accomplishment and its presence at this competition is cause for optimism regarding the possibility of very strong and lightweight tethers in the not-too-distant future. The 2010 Tether Challenge will be conducted at approximately the same time next year.
Inoue reported that in his lab the sample had been good to ~ 750 Mega Pascals. Though he failed to win the prize, with a beaming smile, Inoue said "we will be back next year!". The main speaker on behalf of NASA’s IPP office, Andrew Petro, explained that NASA has a very broad mandate of missions, ranging from short term operational to long term futuristic. "There is a constant competition between the two," said Petro. "We are always interested in farther range technologies." The NASA IPP is being expanded to include a new "Innovation Fund," but the details have not been finalized.
A major controversy this year was whether to use a single stationary tether (with climbers), or a moving pair of cables like conventional elevators. Most speakers assumed the single tethers "Edwards" design would be the best, but Keith Henson (founder of the L5 Society) and Gaylen Hinton advocated in favor of moving tethers. Moving tethers would greatly increase the rate of cargo throughput, and reduce the amount of input energy consumed by the climber. Critics argued that if the two tethers touched when stationary, they would stick together and could not be separated. If they touched while in motion, catastrophic system failure would result. Furthermore, stresses in the system would be higher, similar to how a pulley system doubles force.
Space Debris remains a major hazard for a space elevator, and the problem worsens every year. Peter Swan described how thousands, perhaps millions, of pieces of space junk range in size from tiny paint flecks to huge rocket casings, and many of these could sever the SE tether. The SE base station (a ship) can be moved to avoid the large pieces, but much of the debris is too small for NORAD to detect. A single Chinese missile test in 2007 increased the debris by 40%.
In February 2009, for the first time, an operational spacecraft (an Iridium communications satellite) was hit by Cosmos 2251, a dead Russian satellite, creating yet another huge cloud of debris particles. Although NORAD was tracking both objects, they predicted a miss and the collision was a complete surprise. This is causing a major review of internal procedures and the SE will get hit, according to Swan. It’s just a question of how often and how badly. There is no easy solution.
Regarding proposals for removing space debris, Swan commented, "I have heard a thousand ideas." When Henson suggested using large lasers, Swan replied, "Now I have heard 1001 ideas!"
The most technical presentations addressed the bewildering problems of oscillations or wobbles in the tether. There are two types of oscillations; first longitudinal waves where the tether does not move, but ripples of stretches and compressions occur (like shunting a train). Then there are "transverse" waves, like cracking a whip. With varying frequency and phase, both kinds of waves will exist together, and transverse waves can radiate in any and all directions at once. It is vital to properly understand and predict all these motions. Otherwise, if a resonance builds up, the tether might shake itself or its cargo into pieces.
Two papers were presented on this problem — the first by Stephen Cohen of the University of McGill in Canada and then from Dr. Karen Ghazaryan of the National Academy of Sciences in Yerevan, Armenia. The discussions covered internal damping of the tether material, but it was generally agreed that external damping will be required to keep the oscillations under control. This could be accomplished by moving the base ship around, but that could interfere with its efforts to avoid space debris. It could also be possible to put rocket thrusters on to the climber, or to vary the acceleration of the climber to mitigate longitudinal compression waves.
Liftport Group, led by Michael Laine, was the most noticeable presence from the world of commerce. Their multiple papers addressed business basics, challenges, "Noumenia processes," Lessons Learned and media coverage.
Liftport has developed this “Noumenia Process,” which is a project management tool-set on steroids that was specifically designed for use in the Space Elevator community, but it can also be used in any ‘large project’ environment. Laine explained that it is a “To-Do” list, a calendar, and a project management tool rolled into one — picking up where Gantt charts and dependencies leave off. Essentially, the Noumenia Process is a tool to help the manager put a sub-project into context of the greater, much larger, program. "To be blunt" Laine said "I don’t know how we are going to build an Elevator to Space without this tool. The project is simply too big to succeed without an organizational structure behind it.
"This project is on the scale of the Large Hadron Collider, " Laine continued, "but we do not even know the right questions to ask yet." Noumeni, incidentally, means the festival of the new moon, which the ancient Greeks considered to be the appearance of the first sliver.
After Liftport intern Chelsea Barackman addressed PR via social media, Liftport rep Tom Marotta, a proposed an Academic Research Center for SE research. then Dr. Arun Misra of McGill proposed a Space Elevator Institute, starting virtually and then expanding. This seems like a necessary point of focus, as present SE efforts are fragmented and somewhat uncoordinated. The SEI — as proposed by Misra — would be open to everyone for a nominal fee and act as a repository and clearing house for research and data.
One innovative feature of the conference was a "shotgun science" track for ideas not ready for prime time. I tried my hand at this, proposing an idea to speed up bi-directional flow. Climbers can move in opposite directions until they meet, and then exchange cargo canisters. That solves the problem of waiting for all the climbers to travel from one end of the tether to the other before they can begin a trip in the opposite direction. Apparently this was a new idea. Nobody had heard of it before.
However much the SE concept may be picking up steam at NASA and other places, with just 60 people attending the full conference — one could not help notice the empty seats. However, Ed Gray, the PR Manager for the International Space Elevator Consortium (ISEC) commented "Given the crushing effect of the economy on trade shows and conferences that I’ve attended over the course of the year, I think these numbers are remarkable." The group is optimistic that next year will be bigger and better.