December 01, 2009
Interview of Brad Edwards - Space Elevator Expert by Sander Olson
Here is the Brad Edwards interview. Dr. Edwards received his PhD in physics in 1990, and worked at Los Alamos National Lab for 11 years. After leaving Los Alamos, Dr. Edwards has dedicated his career to researching and developing the space elevator concept. All of his research indicates that the space elevator concept is valid and feasible. He currently heads a company called Black Line Ascension, which is actively promoting the space elevator concept. He has published several books on the space elevator, including The Space Elevator: A Revolutionary Earth-to-Space Transport System, and Leaving the Planet by Space Elevator.
Question: Tell us about the Black Line Ascension
Answer: Black Line ascension is a corporation that was created a couple of years ago in order to develop components for the space elevator. It is doing research on carbon nanotube materials, elevator design, and other technologies necessary for a space elevator.
Question: Some have argued that an orbital tether system would be a simpler, easier approach than a space elevator.
Answer: I've done research on it and spoken with various people about it. Although it is much simpler than the elevator concept, the application is much different. A space tether system would require refueling. The elevator is definitely harder from a materials standpoint but is less hampered by orbital debris and objects in low earth orbit. In short, the orbital tether is a less expensive system that would be easier to get up and running but would provide only a fraction of the capabilities of the space elevator.
Question: Current nanotubes are not sufficiently strong to be used in a space elevator. How much progress do you anticipate in nanotube technology during the next decade?
Answer: Small quantities of some nanotubes have been made that are sufficiently strong to be used in a space elevator. We would obviously need to produce hundreds of tons of such nanotubes to build a space elevator. With sufficient funding, we could create a nanotube-based material appropriate for a space elevator within a couple of years.
Question: How much of an improvement is needed from nanotubes?
Answer: Nanotubes of lengths up to an inch can already be created. These materials can be bundled together to form arbitrarily long lengths of cable that would be appropriate for a space elevator. So the primary problems at this point are not technical but rather economic and political.
Question: Are any other materials, such as graphene, seriously being considered as ribbon material?
Answer: Graphene has some wonderful properties and will undoubtedly be used in a number of capacities, but nanotubes are the only material known that could be used in a space elevator. Graphene has edges that make it unsuitable as a building material. But nanotubes have a strength of 63 Gigapascals, which is greater than that of any other material, and nanotubes do not have any edges.
Question: To what extent are the space exploration prizes facilitating space elevator development?
Answer: These prizes are stoking interest in the concept, and have the potential to address some of the initial hurdles of the project. But what is really needed is a larger scale effort
Question: Some critics have claimed that microscopic cracks will propagate through any ribbon at the speed of sound.
Answer: The ribbon isn't solid, but rather is composed of 10-40 thousand strands of nanotube fibers. Individual fibers will get broken and recoil, so the ribbon needs to be designed to recoil only short distances. So short lengths of fibers will get broken, but the breaks won't propagate in such way as to destroy the ribbon. The ribbon will unquestionably be hit by micro meteors, and these will damage small areas. But the ribbon will be designed to absorb these areas and still remain fully functional.
Question: How difficult will it be for a space elevator to avoid satellites and space debris?
Answer: Any debris that is a centimeter or smaller will hit and damage the ribbon. Objects larger than a centimeter will be tracked continuously monitored. The elevator, which will be located in the ocean, will need to be moved approximately once every 14 hours in order to avoid hitting larger debris. So these issues are by no means intractable.
Question: Current plans call for climbing vehicles to be propelled by lasers. How large, efficient, and powerful will these lasers need to be?
Answer: For a 20 ton climber, a 20 megawatt laser would be needed. Boeing has already demonstrated thin-disk solid state lasers that are 50% efficient, and Boeing is capable of bundling these lasers together to create a megawatt laser today. So by employing 20 of those megawatt lasers in concert we would have the requisite laser power.
Question: How long would these lasers need to operate?
Answer: They would need to operate fairly continuously for years. The aluminum-free lasers have operational lifetimes of years, so operating these lasers for years presents tractable problems.
Question: What about radiation issues?
Answer: The space elevator would employ both active and passive radiation shields. I did research on using a large toroid and that would eliminate most of the charged particles. A small amount of additional shield would absorb the remaining radiation. The weight penalty issues would be rather modest - only a few tons. Four tons of extra weight on a twenty ton satellite is not prohibitive.
Question: How many launches would be required to get a space elevator up and running?
Answer: The initial stage would require 4 launches of a heavy lift, Saturn V class rocket. After that it would take several years of sending up climbers. The initial rocket launches would put up two 10 centimeter ribbons. The climbers would attach additional ribbons, like a spider spinning its web. There are scenarios for 8 launches, but the general concept is similar.
Question: How long would it take and how much would it cost to develop and assemble the space station?
Answer: The entire process of building and deploying could be done within a decade. Initial estimates are that it would cost $10 billion to build. Even assuming cost overruns and delays, the project could be built in a dozen years for not more than $20 billion.
Question: Has NASA been supportive of the space elevator concept?
Answer: To some extent, yes. But NASA is driven by forces other than simply what is good for space exploration.
Question: Are any corporations or institutions funding space elevator technology?
Answer: Unfortunately, no organization is seriously funding this effort. Corporations are looking for shorter term returns and most other organizations are not willing to fund such a radical concept.
Question: Given proper funding, when is the earliest that you could see the space elevator becoming operational?
Answer: Given sufficient funding, I am confident that the space elevator could be up and running within 15 years. There are no insurmountable technical issues to the concept. The show stoppers at this point are funding and support. This is unfortunate given that the space elevator has the potential to reduce the cost of getting to orbit to perhaps $20 per pound, including human passengers. The space elevator, more than any other project or concept, has the capacity to quickly open up the field of space and create a massive space-based industry.