Friday, December 04, 2009
An interesting interview with Space Elevator technology expert Brad Edwards on Next Big Future. I have highlighted:
"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: 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.
This is an extremely positive assessment. Even the 12-15 year timeframe seems to be based on doing it relatively cheaply. When Kennedy made his Moon speech about getting to the Moon "in this decade" possibly Werner von Braun thought it possible but no other expert was that certain. Kennedy simply decided it would be done "not because they are easy but because they are difficult" & inspired the nation to throw everything at it. One may argue that Kennedy had personal feet of clay & that the goal was not the best possible but his willingness to make America make the effort for greatness makes him an outstanding leader.
$20 billion (£12 billion) over 15 years is small beer. As projects go this is clearly much more important to space development than the Moon landings, though what they proved is that American missiles were bigger & tougher than Russian.
By comparison the Apollo programme & Moon landings cost ($25.4 bn in 1969 dollars. That is listed as $145 bn in 2005 dollars but that is the inflation cost. As a proportion of GNP. As a relative share of GDP the Moon landings cost $373 bn in 2009 money.
So a Space Elevator costs about an 18th, as a proportion of GDP, than Kennedy persuaded the US people to pony up, in what may or may not have been more adventurous, certainly more optimistic, days. By any objective standards the gains from a Space Elevator are far greater than the Moon landings could have been because once you have built it you have more than just photos, feel good & technical knowhow. You have an extremely valuable property that allows very cheap entry to space, indeed if the cable is extended outward you have a system, using the Earth's centripetal force, to reach anywhere in the solar system without using power. Also the builder of the first Elevator can very cheaply supply crew & materials to build lots of others. Sounds like lots of money for new rope.
In fact if the USA isn't willing to do that there are a lot of possible contenders for new kid on the block. $373 is 0.039 of 1 years US GDP, which is what was sacrificed for the Moon landings. $20 bn for an Elevator 5.4% of this so any country with an economy 5.4% of the current US economy could afford this as easily as the that. That is an economy worth $774 bn a year. That is the richest 17 countries down to Turkey. It easily includes Brazil (10th) through which the equator runs. Indonesia (19th), through which it also runs, would have a slight stretch. Singapore (44th), a tiny but extremely innovative country, through which it also runs would have to pay a 4 times higher proportion of GNP (but then they wouldn't have to fight the Vietnam war at the same time).
This makes 2 assumptions - that Edwards' costs are about right & that there wouldn't be lots of other investors eager to put in a little bit. The first, I suspect, may be optimistic & certainly is if money is a lesser object than getting it built in under 12 years. The second is unbelievably pessimistic. I suspect Ecuador (71st & 1/14th the optimum size) could afford this by [providing not much more than the site & a few guarantees). We may see China & Japan competing to finance one in Singapore. I suspect that any country putting up 1/3rd of this as an X-Prize will see it won.
Note that he specifically says that endpoint of this should be at sea so that it can move about. That puts it within the capacity of virtually any country. The equator is over 400 miles from Ascension Island so outside technical national waters but certainly close enough to provide a main base. the US has several Pacific islands suitable including Baker island which is 13 miles from the equator.
For the attention of British politicians note that this £12 bn is only double NERC's budget alone for 12 years producing reports of which the more valuable are about how bees enjoy their environment & the more useless pushing the global warming fraud. Or we could have it 2/3rds privately financed & only 1/3rd by a prize. If we can afford NERC we can easily afford to build a Space Elevator. Only one of these will bring on a massive economic boom.
So will somebody get on with it! Who wants to be the national leader who says "We choose to build this within a decade"?
Saying the technical bits are solved is typical for a scientist: if it's proven in a paper, or a one-off in the lab, welp that's as good as done.
Except it's not. He's ignoring a whole bunch of testing and development that needs to be done.