Canadians Vie for Space Elevator Victory 99
unc0nn3ct3d writes to mention a CBC article about some plucky Canadian teams planning to go for NASA's space elevator challenge. From the article: "Teams based in Saskatoon, Vancouver, Edmonton and Toronto are among thousands of space enthusiasts expected to converge on a desert site in Las Cruces, N.M., on Friday and Saturday for the X-Prize Cup, a festival mounted by the X-Prize Foundation ... The competitors are gearing up for the Spaceward Foundation's Space Elevator Challenge, which requires them to surmount technical obstacles in the development of a new type of vehicle that would take people and cargo from Earth into space."
Re:Canadian Laser Powered Climber (Score:4, Informative)
Re:Canadian Laser Powered Climber (Score:2, Informative)
Which is why one length of cable simply will not do. Instead the cable must get thicker as you move upwards, so that each strand only carries a small enough amount of weight. Honestly, a 1000km cable of this kind is more than within ourability to construct, but getting all 1000km of its ever increasing frame into space will be the trickiest part. Keeping it up there will be the next.
Space elevators are a "look good on paper" plan, as long as its a green paper. Hypersonic is the way to go into space.
Re:Space elevator (Score:4, Informative)
As for the ionosphere, they've actually done a lot of research entirely unrelated to the space elevator including physical tests. From what I've read on it, they're not ignoring the problem, it's just not significant. The proposed carbon nanotube cable isn't really conductive and would only be affected by the very local area anyway. That doesn't ammount to much. They've even bothered to calculate whether having a conductive cable could generate any useful power. The answer was no, there's just not enough energy there to do anything useful with. Even if the cable could act as a lighting rod, lighting is the result of built up potential. Having a lightning rod to the clouds would prevent any potential from building!
A concern you didn't raise, that's nonetheless of interest (to me anyway) is the scale of the project. IIRC, the individual wires that make up the cables of the golden gate bridge if placed end to end would actually be as long as the space elevator. Probably heavier as well. Since the cable has so much surface area, and most likely would be cut very very close to the ground (ie still in atmosphere), the cable would flutter harmlessly to earth. So disaster situations are unlikely.
Re:Canadian Laser Powered Climber (Score:3, Informative)
It's an engineering problem like the World Trade Center. It was impractical to have elevator shafts running up the entire building (in the WTC, I believe there was only one shaft that did so).
In the case of a space elevator... why not temporarily "lock" the car at a certain height, then have a mechanism unhoist the cable and change it to another hoist motor? (repeat as necessary)
The net effect that the elevator would have to "rest" at certain periods on the way up and back down. A zero-G elevator would need to use friction... so the last part of the trip would just be using toothed-gears along a similar linear tooth track.
Re:Space elevator (Score:4, Informative)
In addition, the current idea is that the cable will be made of short filaments of carbon nanotubes glued together in some as-yet-to-be-developed fashion. The glue alone would probably make the cable non-conductive.
As a material, nanotubes have very flexible properties. By the time we're able to produce the quality and quantity necessary to make a feasible cable, we'll probably have the technology to pick and chose its attributes.
Re:Canadian Laser Powered Climber (Score:5, Informative)
Right now the largest disadvantage for lasers is the inefficiency in creating electricity from photovoltiacs. The team i'm on - Punkworks [punkworks.ca] is hoping to use a microwave rectenna [wikipedia.org] array to convert 2.4 GHz RF energy into a few hundred watts of electricity. Right now we're lending our transmitter to another team, and have reached a deal to split the prize 50/50 if they win with our transmitter. The reason we're using microwaves is due to the conversion efficiency, there's lots of journal papers on microwave rectenna design indicating a maximum efficiency of 85%. This is a huge improvement over the ~30% you'd get from a solar panel.
My team has yet to compete, and I'm eagerly waiting to hear how our climber performs. Right now they made us move to another location at the test site despite our approved application from the FCC. Apparently the airport doesn't like the idea of us beaming 13 kW of microwaves into the sky
unfortunately I'm not in New Mexico for the competition, but a number of my teammates did the 44 hour drive.
Re:Canadian Laser Powered Climber (Score:3, Informative)
Which just means the cable has to taper more. No matter what, any sane civil engineer would have designed it with at least a safety factor of 3.