backtop


Print 48 comment(s) - last by reiters.. on Feb 21 at 12:08 PM


Courtesy LiftPort Group
The LiftPort Group has a bold and interesting plan -- to build a massive space elevator before 2020

The LiftPort Group has completed a second round of testing on a prototype space elevator platform that stretches a mile into the sky, which allows a robots to climb and descend the ribbon that is between the two platforms.  The LiftPort Space Elevator would allow a revolutionary way to get cargo and supplies into space -- using a cable thousands of miles long tethered to  an object in geosyncronous orbit.  The company hopes to build the space elevator by the year 2018, but the task will obviously not be easy.  The observation and communication platform that robots climbed is properly dubbed HALE, High Altitude Long Endurance.  HALE was secured in place by several high altitude balloons for over six hours.

The ribbon that will hopefully stretch 62,000 miles from Earth into space will be made of carbon nanotubes weighing less than 1.5 pounds per mile.  Although initial testing was done in Arizona, the space elevator will likely be anchored to an offshore sea platform that will be located somewhere in the Pacific Ocean.


Comments     Threshold


This article is over a month old, voting and posting comments is disabled

Physics
By Bladud on 2/16/2006 8:14:58 AM , Rating: 2
I feel I should correct some of the physics from prior commenters.

Remember that the apparent "weightlessness" of orbit is not weightlessness at all; it is free fall. There is still a force on you, and you are still falling, but you don't notice it because it is a uniform acceleration (remember Einstein's famous lift?). However, the lower parts of the cable, being nearer the earth, are under greater acceleration, which is noticeable. The rope is therefore under (a lot of) tension. So the mass of the cable is very important, because if it were too great no material known to man could withstand the tension created.

The reason they go up to 63,000km is, I imagine, because the *center of mass* of the elevator has to be in geosynchronous orbit, at whatever height, so the counterweight has to be somewhat higher, and the cable proportionally longer.

Hurricanes and so forth are fairly negligable because the cable is very thin and very very heavy, making it correspondingly hard to move. That said, they could cause it to vibrate, like a guitar string, which could be rather unfortunate.

Lastly, using the cable itself to put more of itself into orbit would not work at all, because until it is finished and the counterweight attached, the cable has nothing holding it up (parachutes don't work where there is no atmosphere). I would imagine, however, that by 2018 the new NASA lifter will be ready, and if it isn't, well, transportation is a picayune compared to the problems they would have to solve to get that far.




RE: Physics
By oTAL on 2/16/2006 12:56:36 PM , Rating: 2
For ppl with any questions you should check out the VERY good Wikipedia article about the space elevator. It describes the problems and solutions in detail. Weather IS a problem. And you are all thinking in newtonian physics which is not the best one here. Think Lagrange and use the Earth as an acelerated referencial. At geosinchronous orbit the gravity becomes zero. Below this point it rises up till the ground where it is highest and over this point it is negative. What you need to get is an overall (slightly) negative gravity so that the cable is always under tension - as if something was pulling it from space. It's pretty simple, but you have to understand the concepts of orbit and geosichronous orbit pretty well to even try and understand this.


RE: Physics
By KristopherKubicki (blog) on 2/16/2006 3:45:31 PM , Rating: 2
quote:
The reason they go up to 63,000km is, I imagine, because the *center of mass* of the elevator has to be in geosynchronous orbit, at whatever height, so the counterweight has to be somewhat higher, and the cable proportionally longer.

Kind of. The reason it extends 62k MILES is because the cable will continue to stay in geosyncronous orbit -- even at that great of a distance. The tip of the cable moving that fast is actually what keeps the whole tether stable.... this way you don't need a coutnerweight.

I read someone earlier that the reason why we don't want to use counterweights anymore is because someone calculated that you would need several tons of counterweight at 32k miles.. or you would need just the weight of the cable moving at a much faster speed.... 32k miles further out. its a neat physics problem to work out.


"When an individual makes a copy of a song for himself, I suppose we can say he stole a song." -- Sony BMG attorney Jennifer Pariser











botimage
Copyright 2014 DailyTech LLC. - RSS Feed | Advertise | About Us | Ethics | FAQ | Terms, Conditions & Privacy Information | Kristopher Kubicki