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Space Elevator Prototype Climbs MIT Building
Jackie O writes "According to an employee blog on the Liftport Group website, their prototype robot for the Space Elevator has just successfully climbed a 260-foot building (in a driving snowstorm, no less) at MIT. Now all they have to get it to do is climb over 60 thousand miles into space, carrying things. Good luck there." Update: 11/17 05:17 GMT by T : Liftport has posted some photos from the ascent, too. Thanks!
Are we going to start measuring stuff in MIT building heights now?
I heard the real purpose of the test was to place a police car on the roof.
Exactly, for example, scaling fish is dangerous work and rather nasty as well.
Unknown host pong.
http://liftport.com/progress/index.php?blog=9&cat= 28
As cool as this idea is, there are some problems (especially for the lower altitudes). Some of the problems are more serious than others:
Wind shear: winds at various altitudes can differ widely. Both the cable and anything climbing it will be affected.
Resonance: a cable will tend to vibrate; it will be necessary to dampen the vibration. Usually this is done with strategically placed weights. With an object climbing the cable, however, the resonance will be constantly changing.
No Adspace: There will be no place to put banner ads, so the thing will never be profitable.
Environmentally Harmful: birds could run into it and die. Doesn't anyone consider birds?
sigs, as if you care.
I can't help but think about all the political hurdles that'll delay the space elevator more than any technical setbacks. And then I get to thinking about how slow and unromantic a space elevator ascent would be compared to the exciting phallic-rocket launch. Still, the space elevator is about the only way to eventually get launch costs below a dollar per pound; chemical rockets are too energy-wasteful to ever reach that point.
--
Power to the Peaceful
60000 miles = 316,800,000 feet.
316,800,000 feet / 29 feet per minute = 20.77 years
Or does it mean that it was fairly windy, snowing abit and it totalling a couple of centimeters on the ground and people who had watched to many catastroph-movies lately bandied about in Libraries burning books and being faintly surprised about how little warmth it produced?
"" How about taking the safety labels off everything, and let the stupidity-problem solve itself? """
They're making this sound like it's a step towards achieving their goal, but really what they did today wasn't a stretch of the imagination like the final goal is.
If I claimed that I can jump to the Moon, you'd look at me like I was crazy, because the laws of physics would be completely in opposition to my claim (for example bones would shatter long before you could exert the force to jump even 50 feet). Now if I showed you that I could jump 3 feet, would that really convince you that I'm making progress towards my claim of jumping to the Moon?
To get back to this space elevator idea, climbing 260 feet is no big deal at all using cables that we have today. It's simple work. However, making a cable that is 30,000+ miles and able to support its own weight plus the weight of the payload is impossible with these cables. They'd need a material that doesn't yet exist.
The real hurdle in this project is not making the robot climb the short conventional cables that are readily available, the real hurdle is getting a hold of cables of unbelievable strength made of a substance that doesn't yet exist.
Yeah...this is slashdot so ignorance is acceptable. Let me quickly explain how a space elevator is supposed to work.
y /space_elevator_020327-1.html
An EXTREMELY strong tether is fixed to a large mass far out in orbit, this mass along with the earth's rotation hold the tether very taut and allows for smaller masses to scale up it. Much like if you tied a small weight to a string and whirled it around your head, imagine a small robot climbing the string...thats the idea of a space elevator.
The issue with the idea of a space elevator currently is the technology that would go into the tether. It is believed that many strands of carbon nano tubes, those tiny super strong tubes grown/created long and attached together, would be able to withstand the stress.
Next the tether would not be round like a rope, but flat like a belt. Being flat, it would be much harder to get twisted if sufficient force is applied to each end, pulling the ends apart.
So that is the general idea the theory behind space elevators...I am sure I left some details out and all, but here is a decent link if you want to learn more. http://www.space.com/businesstechnology/technolog
Copyright © 1996 by Joshua W. Burton( burton AT het DOT brown DOT edu). All Rights Reserved.
I did a lot of calculations about this a few years back; here are some results that might interest you. Here's the apparent strength of gravity as you go up the elevator, allowing for both the earth's rotation and the 1/r field:
Apparent gravity table 0km 9.8m/s
350km 9.0m/s
700km 8.0m/s
1200km 7.0m/s
1750km 6.0m/s
2500km 5.0m/s
3400km 4.0m/s
7500km 2.0m/s
10500km 1.0m/s
18500km 0.5m/s
Weightlessness comes at the Clarke point, of course, 35950 km up. Above that, there is a centrifugal effect, and the earth appears to be 'above' you---but you would have to be nearly 200,000 km up before the apparent gravity reaches -1.0 m/s. In practice, no one would build it out that far; you just want to go far enough to keep the center of gravity at the Clarke point, plus a bit more to put the lower end of the elevator in tension. A big mass just slightly above synchronous orbit is probably the way to go.
Midway Station, the lowest point where you go into an elliptical orbit instead of hitting the ground if you jump off, is 23450 km up, and has a tiny apparent gravity of 0.29 m/s. The total energy cost from ground to the Clarke point is just over 13 kW-hr per kg lifted, which means $100 a ticket at today's energy prices, minus savings for energy generated by the 'down' cars, plus (rather large) financing charges on the capital investment.
Next come strength-of-materials considerations. We need a material with the highest possible (breaking strength)/(density), which is a tough sell, because Kevlar, good piano wire, and nearly everything else has essentially the same optimum value for this parameter. They all have breaking strengths of a 'few' billion Pa, and a density of a 'few' thousand kg/m, where 'few' is the same number in both cases. The strongest high-tensile materials are the heaviest, by and large. Exotic materials like spun sapphire or diamond do better on the micron scale, and buckytubes get close to the theoretical limit (the strength of the chemical bonds themselves). In principle, such materials should be anywhere from 40 to 120 times stronger than the optimal value above, which I shall call '1x piano wire'. But Griffith theory teaches us that the length of the 'critical' crack (one that releases enough energy to drive its own spontaneous propagation) goes down as 1/(stress). So even if exotic materials can be machined in gigaton lots, we may find that they are unusable at the huge stresses we need. The first woodpecker that comes along may bring the whole thing down if the critical crack is a few microns long.
But let's assume we can cope with this issue, if necessary with nanobot inspectors checking for micro-cracks, or simply a sheath of unstressed material around the structural members. The tension is essentially zero at the bottom: if we wanted we could leave the cable hanging loose a foot from the ground. (We want some tension there, of course, when we build an actual elevator, or the dynamic oscillations will kill us.) At the Clarke point, where the stress is largest, the stress depends on the weight of the tower below, which depends on the strength of the material. It's like rocketry, ironically enough: the 'fuel' for the upper stages is 'payload' cost for the lower ones. In this case, of course, it's upside-down: we have to keep the lower part of the tower as light as we dare, so that the upper part doesn't have to be exponentially heavy. And a high-tensile steel tower, like a rocket powered by Wisconsin butter (happy now, Senator Proxmire?), just doesn't have enough juice.
Assuming each wire has to take a thousand tonnes of tension at the bottom (add wires as needed, depending on what you want to send up the tower...), we get a minimum thickness profile like this:
Minimum thickness table Strength/Density 5000km 10000km Midway Clarke Orbit
6 x piano wire r = 16cm
300 Gpa is the upper end of the theoretical spectrum. The best steels (and I mean ~the best~) are as much as 85+% of the max theoretical strength of steel. When carbon nanotubes reach 33% of their theoretical strength, we WILL build a Space Elevator. Let's collectively cheer on the researchers. If even 1/50th of the max strength is achieved, the world will change. Why aim to make bridges and elevators a little longer, or your tennis racket a little lighter? Let's aim for the big prize, the breakthrough, and grab the enhancements and improvements along the way.
mspeten@liftport.com