Canadians Vie for Space Elevator Victory

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."

Comments

Canadian Laser Powered Climber

[iendedi]

From TFA:

The machine is being entered in one of the two parts of the elevator competition, known as the Power Beam Challenge, in which competitors build a machine that can climb at a rate of at least one metre per second up a ribbon suspended nearly 61 metres (200 feet) from a crane. The climber must be powered by a light source.

"We developed a high-powered laser to power our climber," Ruszowski said.

Which is all good and well, I suppose, for a cable suspended from a crane. But what happens when the space-elevator ribbon has to cut through the entire atmosphere of the earth, weather and all? Tracking the lateral movement of the elevator precisely in unpredictable weather does not seem trivial to me.

Do any of you actually believe we are close to being able to produce one of these monsters? I am guessing we are still thirty years away from the appropriate tech.

Re:Canadian Laser Powered Climber

[mdfst13]

The difference between an elevator in a skyscraper and a space elevator is that the elevator in the skyscraper has a building around it while the space elevator is just a big cable. The space elevator is held up by the fact that part of the cable (possibly with a counterweight at the end) is actually far enough away that angular momentum is pulling it *away* from the earth. It's the tension between gravity pulling it down and angular momentum pulling it up that makes it work. Break that into segments and some segments will go away from the earth while others go down. If you tie the segments together, then you just have one long cable again (with joins that are either heavier or weaker than the rest of the cable; if we had a lighter and stronger material, we'd just make the whole cable out of it).

The World Trade Center system worked because the building was there and they attached the segments to the building. A space elevator is problematic because we simply don't have the ability to build a building that tall to hold up segments (if we did, we'd just make the building the cable and crawl up the side). Each segment would have to be self-supporting.

The minimum cable length (to be self supporting) is determined by the angular velocity of the earth, the radius from the center of the earth to the cable mount, and the mass of the earth. There is no way to make a shorter cable that is self supporting.

Your solution requires something to hold up the segments. We don't have that something. We are somewhat closer to being able to build a single cable of that length than we are to building a segmented solution (which requires something like anti-gravity). Further, if we did have the tech to build a segmented solution, we probably wouldn't need to do so. With anti-gravity, we'd just float up -- no elevator cable needed.

I think that what's confusing you is that in buildings, the cable pulls up the car (which is just a big box). In a space elevator, the "cable" has a role more like that of the elevator shaft or the rails of an incline. The elevator "car" is propelled by something else. Maybe they should change the name to something more static, like pillar, shaft, or stem.

Gravity Kite

[Programmer_Errant]

Forget space elevators, I'd use gyroscopes so as to use the earth's angular interia to leverage them and a payload into space. Leverage being the key word here. You'd need some tethers or boons to control the contraption and keep it from precessing in the wrong directions. Of course once it's up there, it might look a lot like a space elevator.

I was there!

[apsmith]

It was pretty cool seeing the teams trying to climb the tether. I only saw a couple make it to the top (200 ft), but several got part way. I don't believe anybody beat the 1-minute time limit to meet the goal.

One interesting thing is that, having to power the climbers from beamed power, they had to make them as light as possible, relative to the area of solar panels trying to capture energy. So these were pretty flimsy looking devices, and you could see wind causing trouble. Stripped bolts and computer glitches also caused their share of failures...

It was also nice to see all those young teams of excited people trying to do this - mostly undergraduate engineering students, but there were even some high school students participating.

And having John Carmack hanging out chatting with the crowd while his crew was trying to get his "hover" craft back in shape was fun. They had jumbotron displays for their challenge attempts, but you could also see it just hovering there a hundred feet up (not too close to the crowd, but quite visible). Of course the crashes had a bit of a car-wreck interest too... The most successful things seemed to be some straightforward high powered rocket launches. But there was a big enthusiastic crowd, and lots of sideshows. Definitely worth a trip to the El Paso area if they do this again!

Re:North Pole?

[donotdespisethesnake]

> The rotation of the earth is exactly what keeps the elevator up, much like swinging a weight on the end of a rope. Although it
> would be theoretically possible to anchor the cable at the pole, the additional problems would far outweigh the benefits.

I am amazed at the many incorrect comments here, this is a typical one which doesn't make any sense. I thought we were supposed to be nerds who know about this sort of stuff?

It is almost completely unlike swinging a weight on the end of a rope. It's the rotation of the elevator cable itself that keeps it in orbit, not the Earth. A space elevator would effectively be a long thin satellite in geo-stationary orbit. Therefore, it can only be built near the equator.

While theoretically quite possible, a space elevator has huge practical problems to overcome, and for those reasons I doubt it could ever be built. Not least is the problem of powering the car over a 35,000+ km journey. I will be very impressed if they can achieve even 1% of that distance. Then there are the political and insurance implications to be dealt with.