NASA Still Wants Space Elevator

Jerry Smith writes "The Guardian reports 'Each of the groups that will gather in New Mexico is competing to win a NASA prize set up to encourage entrepreneurs to start development work on the technology needed to create a space elevator.' It still might take a while though, progress is slow, so slow."

Comments

12m

[Ricken]

FTA: As New Scientist magazine reported last week, the best performing robot last year managed an ascent of only 12 metres up a cable before it stalled, while no material came close to meeting the standards needed for building a space elevator.

Hopefully won't be too hard beating that, my mindstorm robot can do better!

Re:WHY?

[LiquidCoooled]

They won't waste time and resources to create a folly, this principle is a worthwhile venture (if it can be pulled off).

Once you get one tether you can send runners down it with additional strands.
It would be strengthened and grow like a pearl from an initial seed.

The problem is getting that seed line up there.

Re:What happens

[Jeremi]

when a plane runs into the elevator? It only takes one crazy pilot

Most likely, the cable would break, the 99.999% of the cable above the impact point would start to drift upwards, and the 0.001% of the cable below the impact point would fall harmlessly to earth. It would then be a bit of a chore to repair the cable, but not impossible. Fortunately this wouldn't happen, because the cable's base station would be located somewhere in the middle of the Pacific ocean, in the middle of a no-fly zone several thousand miles in diameter. For a crazy pilot to get to the site of the cable, they'd have do evade detection by radar for several hours, and avoid getting shot down by the SAMs or military aircraft whose sole job is to guard the cable against this sort of attack.

Now a question for you: What happens when a plane runs into the Space Shuttle during launch? It only takes on crazy pilot.

Re:WHY?

[Aaarrrggghhh]

The variables that need to be addressed are vast. Aside from the material needs I wonder if they are addressing the IT needs. The quickly changing variables such as adjustments from the moon gravity to atmospheric disturbances to maintenance and repair will require great models and this thing will need an amazing nervous system to detect problems before they bocome disasters. BTW: Where will the lower parts of this thing fall when there is a disaster?....

Re:What happens - FAQ

[Lord Prox]

I have been following this for some time... Here are a few links for ya.
http://www.isr.us/Downloads/niac_pdf/contents.html Study
LiftPort Group. Company wants to beat NASA.
Reference Site



Place a curse on the RIAA/MPAA

An artist's concept

[pcx]

and a rather good image (I use it as my wallpaper)

http://www.mondolithic.com/06Gallery08.htm

Re:Fundamental flaw?

[chriso11]

Won't be cheap getting something like 23000 mi up.

Actually, all you need is a space elevator that can bring up a few pounds - then you keep running it, loading the mass at the counterweight. Then build a bigger cable, wash/rinse/repeat. Soon you are sending tons up at a time. Yes, it is expensive, but compared to blasting the stuff up into orbit, greatly cheaper.

Re:Fundamental flaw? THE SE IS NOT IN ORBIT!!

[Bob Munck]

The Space Elevator is not/will not be in orbit!! None of it! No part of it! There will be a small section, 35,800 km from the ground, that happens to be traveling at the same velocity and in the same direction as would a satellite in orbit at that point. We can climb up to that level, let go, and just drift around; that point corresponds to what's called Geosynchronous Orbit. Everywhere else if we let go we fall away from the SE. The parts of the SE below that point are traveling slower than orbital velocity where they are, and those above it are traveling faster than orbital velocity. If you go high enough and let go, you'll fall all the way to Mars.

The SE is a rock on the end of a very, very long string, being whirled around by the Earth's rotation. That's what keeps it up -- what's sometimes called centrifugal force. Pulling inward/downward on the string doesn't cause the rock to fall; if the rock is whirling fast enough, it won't even be pulled down, and when you stop pulling, the rock is still there. There's no real notion of "center of mass" of the SE as a whole. The majority of the mass is well above GEO.

The "rock" will actually be all the construction machinery that was used to build the SE, a few hundred machines that climb it and add a tiny bit of material all along its length while they're going up. They will have a total mass of about 650 tons and be at an altitude of 100,000 km. The CNT ribbon will have a mass of about 950 tons. We'll be able to send up a 20-ton climber with a 13-ton payload every four days, or a 10-ton climber with a 6.5-ton payload every day. (Gravity falls off so quickly that a given climber is down to 50% of its weight when it's 2600 km up. That's what makes it possible to send up smaller climbers more often than you'd expect.)

That's not physics

[mangu]

essentially an 11km tall tower (think pylons rather than skyscrapers, based at sea), with evacuated airless launch tubes, using nuclear reactors to power a maglev or pulley system to accelerate vessels to escape velocity

If you accelerate something to escape velocity, it does exactly that: escapes the gravitational attraction of the Earth and never comes back, unless it's decelerated by some unspecified means. And escape velocity at 11km height means it will be burned to ashes very quickly, remember the Columbia. With our current technology level, building a ship that can fly at escape velocity at 11km height is much more difficult than building a space elevator.

OTOH, if you want to put something in orbit around the Earth, then you should give it orbital velocity, which means it should have a very high tangential velocity around the Earth. You cannot do that with a vertical tower, unless that tower reaches the synchronous orbit altitude of 36000km, which is the whole idea of a space elevator. Remember, velocity is a vector. It has both magnitude and direction. If you want to reach orbit, it's useless to throw something straight up with a high speed, because it will fall straight down.

Well, you may say, let's make the top of the tower curved, so the ship will be accelerated tangentially. Do the math. Find out how big the curvature radius must be so that the ship isn't subjected to deadly accelerations in order to convert that vertical velocity to orbital, i.e. tangential, velocity. That math has been done even before artificial satellites reached orbit. I have an old book, "Flight in Cosmic Space", written in 1952 by Russian scientist Ari Sternfeld, where he analyzes, among other concepts, the idea you have proposed. A practical accelerator to send a ship into space would have to reach a 100km height and have a curvature radius so great that it would be several thousands kilometers in length.

There are some alternative approaches

[Goonie]

There are some alternative methods to get things out of the Earth's gravity well besides the space elevator that don't rely on the creation of unobtanium.

There's the idea of laser launch - instead of providing the energy to vapourize propellant with chemical reactions, you aim a laser at the spacecraft to do the job.

Secondly, there's a variety of space tether schemes that don't go all the way down to the surface; instead, they dip down to an altitude and relative velocity where they could be met by hypersonic rockets. These have the rather large advantage of not requiring super-nanotubes. here is a NASA-funded study on the idea.

And, of course, there's always Project Orion - explode nuclear bombs beneath a gargantuan steel plate to push the thing along...but somehow I don't see that one getting approved any time soon :)