NASA Power Beaming Challenge is On For November 2nd

carstene writes "The NASA Centennial Challenge Powered Beaming competition, to develop technology for uses such as a space elevator, or to power a rover in a shadowed crater on the moon, was delayed indefinitely due to trouble setting up the kilometer-high race track. It has now had the kinks worked out and is rescheduled for the week of November 2nd. The competition involves using a high-power laser to beam power to a robot that climbs a kilometer-high cable attached to a helicopter. The competition was previously covered on Slashdot."

Why not just use wires?

[slifox]

Why must we beam the power to a space elevator?

Wouldn't it be reasonable to use wire conductors? If we will be able to build the support lines that can span from the earth to orbit, why couldn't we also make a couple of smaller ones inside the main one for carrying power? Or why not just use the support lines themselves to provide power (assuming there are multiple support lines for redundancy)?

Can anyone provide some more insight into this? I haven't been able to find a decent explanation

Allow me to elaborate...

[Xaedalus]

WHOOSH

your understanding of Kilgore Trout needs some serious work. I'm thinking orders of magnitude

Re:Why not just use wires?

[beefnog]

The tensile strength of an eventual space elevator material is not related to its electrical conductivity or resistance. 10,000 miles of a conductor will (currently) weigh more than its own tensile strength could support.

Re:

[lobiusmoop]

um, what? I'm assuming the OP meant bonding a separate conductor pair to a high-tensile elevator cable. If the cable is strong enough to support its own weight, it should really be strong enough to support a few extra tonnes of wire.

Re:Why not just use wires?

[Rei]

"a few extra tonnes"? First off, space elevators aren't exactly high payload devices; the margins in most designs are generally tiny compared to the elevator's mass. But the big problem with what you wrote is that geosynchronous orbit is 26,199 miles up; a space elevator must be *at least* that long. You're looking at something like one ton per 10,000 miles, or one pound per five miles, or 17 milligrams of conductor per foot. Do you really think that's going to power anything? Even if you only provide power for part of the way up, it's still just not going to happen.

Re:

[Rei]

The Edwards design calls for launching a reel that weighs several hundred tonnes up to GEO and lowering it down. The initial tether would be tiny, feather-light. You'd then have a series of increasingly large climbers that "glue" additional strips onto the side of the ribbon, carrying the ribbon up with them instead of payload, and very slowly expanding it. After a couple years, it's ready for cargo.

Obviously whether that's even possible depends strongly on what the mystical elevator material is like.

Re:

[Tiger4]

No, space is 50 or 62 miles up [wikipedia.org], depending on who you ask.

Re:Why not just use wires?

[Rei]

Yeah, even if you use ridiculous voltages, it's just not going to happen.

Plus, these competitions always seem like putting the cart before the horse. The elephant in the room is that we have no material close in terms of properties to what is needed to make a remotely feasible space elevator on Earth (at least 100GPa at the density of graphite), and it may not even be physically possible. Some people have theorized that SWNTs could be that strong, but the strongest SWNTs measured so far are about 60GPa -- and that's for *individual nanotubes*, let alone nanotube bundles, let alone composites made out of nanotube bundles many thousands of miles long. MWNTs have been measured somewhat stronger, but they're a lot denser, so that doesn't help. I mean, even if you ignore the other issues that have been shown to be huge stumbling blocks with space elevators, such as oscillations, that's really a killer.

These competitions come across as though someone started promoting their new "Levitation Shoes" with the following exciting announcement:

"Good news, Levitation Shoe engineers! We will be hosing a Levitation Shoe shoelace-development contest. As you all know, we need to solve the issue of shoelaces being able to withstand the wearer getting buffeted around by high altitude winds without breaking or becoming untied, so we've reserved a site with a huge fan that you can test your shoelace prototypes on! This will bring us one step closer to the dream of Levitation Shoes."

Honestly, much more realistic than a space elevator appears to be a Launch Loop [wikipedia.org]. No nonexistent (and possibly even impossible) materials required.

Re:

[Gerzel]

Agreed but beamed power does have other very real and current day uses so the competition isn't entirely moot.

Re:Why not just use wires?

[gurps_npc]

It is totally correct that we can't make a space elevator right now.

But we could make a space elevator.

1. Take a particle accelerator, preferably one built at a high altitude. You should be able to start at least 4000 meters above sea level (China's Qinghai-Tibet Plateau averages 4,500 meters.

2. Put a bend in the output - straight up.

3. Detach the final u turn that bends the particle stream down again.

4. Add some magnets to recover power from the particle stream. Use it to power the magnets in the final U bend, that is now detached.

5. Focus the energy so that the it is self-centers the now detached final U.

6. Up the power. The detached U bend now floats.

7. Keep raising the power. U bend keeps going up.

8. At low altitudes, the atmosphere will drain massive energy. So build an air-tight 2000 meter tower around the particle stream. At the very least this should take you 6000 meters above sea level. Air pressure is now 50% sea level. This will reduce power consumption

Problems: 1. Power requirements will be HIGH. We will need to build a Nuclear power plant (probably a 2nd on as a backup). 2. We will building the tallest man made structure on Earth, at one of the highest points on Earth. 3. A lot of untested engineering, although the physics is known.

Re:

[Rei]

That's not a Space Elevator. That's a Space Fountain [wikipedia.org]. And the power requirements of actively-suspended structures don't need to be high -- you only need to "pay" for any initial increase in gravitational potential and kinetic energy, and from there on, any leakage.

Re:

[gurps_npc]

Namewise you are correct, I meant to say space fountain, not elevator. Power costs will only be low if we can keep air outside of the fountain core. I am not as sure as some people are that this will be cheap. In general, power costs tend to be higher than people estimate. Note, the power costs are only really high when we are raising the U bend. Once it gets up there, costs become minimal. The most important part is that we have the technology to build one TODAY.

Re:

[jfengel]

Or, as I read here on Slashdot once:

First, build a bridge that goes 40,000 millimeters across a ditch on a college campus out of this material. Then we can start to discuss how we're going to build 40,000 kilometers of it straight up.

Re:

[mcrbids]

Carbon nanotubes in the "armchair configuration" AKA 5,5 configuration, are excellent conductors of electricity along with having fantastic tensile strength properties.

To see this at work:

1) Get a metal, NON-magnetic tube (eg aluminum)

2) Get a magnet.

3) drop the magnet down the tube. The magnet will go VERY SLOWLY down the tube because of the magnetic field it generates. It never touches the tube. That's because of the electricty inducted by the magnet creates its own magnetic field. Since there's nowhere

Re:Why not just use wires?

[Rei]

Let's say you're looking at a 100GPa cable (I can show you why you need a cable this strong later if you need me to). That's 14.5 million pounds per square inch. Let's give it a two-fold safety margin, so we have 7.25 million psi to work with. Let's say we want to carry a payload of 10 tons. That means we need a cross-section of 0.00275790291 square inches. Don't think that makes our cable super-light, mind you -- it must thicken as you go up, and will weigh hundreds or thousands of tons in net weight.

I don't know the resistivity of 5,5 armchair CNTs, but let's just go with copper for now. As we all know:

Resistivity = (Resistance * Cross-Sectional Area ) / Length

If we only care about the craft climbing up to GEO (42,164km), that means we have:

0.0000000168 = Resistance * 0.0000017792886414156 / 42164000
Resistance = ~400,000 ohms

Good luck with that. :P

Re:

[Rei]

Oh, and a couple more things:

1) I was generous and assumed a cylinder for the cable rather than a ribbon, as most designs call for, for easier climbing. If you go with a ribbon, you'll get a lot more resistance.
2) If your solution is "superconductors", that'll help, but they break down at high currents, so it's still not a solution.
3) If your solution is "extremely high voltages", you get coronal discharge (which occurs even in the partial vacuum of near-space).

Re:

[decipher_saint]

I believe that the cable used for a space elevator must be as lightweight and strong as possible. Running power through that infrastructure will add weight and weaken the structure (maintenance access, etc). Not to mention drive up costs and add complexity.

I dunno, just shooting from the hip here.

Re:

[jimbolauski]

Carbon nanotubes are conductive so the same lines that could be used to hold the elevator up can be used to transfer electricity, the problem is that the elevator would need the lines exposed to use them for power which would make it highly vulnerable to lighting.

Weight

[NoYob]

I'm guessing it's a weight issue. Putting a conductor necessary to carry that much current in with the carbon-nanotube ribbon (that is still the preferred tech isn't it?) would just add so much weight as to make the elevator impracticable. Just look at the size of the copper to power a 120v outlet. Could they make the carbon strip itself conductive?

Re:

[vertinox]

Wouldn't it be reasonable to use wire conductors?

Because a space elevator will have cables over 90 km which will either need repeaters every so often or some hellacious voltage to push power that far over high voltage power wires.

And if you have seen close up on those high lines... Are rather thick bundles.

And 90km of that stuff is not going to be able to support its own weight.

Re:

[pixelpusher220]

It will not have to support it's own weight. No more than the wire running to the rooftop antenna of a skyscraper supports it's own weight. The power cables would be attached to the elevator ribbon along the way.

Now, whether that adds too much weight to make the space elevator unworkable is an entirely different concept. But the power cables wouldn't have to support themselves. As other posters have said, other issues exist with it, such as electrical interaction with lightning (1.21 gigiwatts anyone

Re:Why not just use wires?

[fred fleenblat]

aside from the weight issue, shouldn't the cable specifically be designed to be an insulator anyway? Shorting out the fair weather return current and/or tapping into particle storms in the upper atmosphere seems like it could lead to some nasty little electrical issues.

Re:

[Anonymous Coward]

There are limitations to the length of power lines for other than mechanical reasons. It is 36000km (22000miles) to Geosynchronous orbit, which is where we ultimately want to go with this thing. Using cables for anything near that is highly problematic. (longest power line on earth is about 1700 km)

http://en.wikipedia.org/wiki/Electric_power_transmission [wikipedia.org]

Re:

[Gerzel]

Really I'd rather see the beam being used w/o the cable. You should be able to move the beam and get correction for trajectory information sent back on a wider down stream beam. I think that would be a lot safer, and technically more reasonable than a full fledged elevator and signifigantly cut the fuel load.

Re:

[khallow]

Why must we beam the power to a space elevator?

Unless you're using superconducting wire in your tether, beamed power loses far less energy. Common loss rates for regular copper wire is something like several percent per 100 km. That's about as good as it gets. And the mass is way too heavy.

Typo?

[n3v]

"or to power a rover in a shadowed creator on the moon"

s/creator/crater/

?

htmm

In other news....

[snspdaarf]

High-powered laser shoots down helicopter. Film at eleven.

I see a problem.

[WoRLoKKeD]

This is all well and good, but how are they going to keep the sharks focused on the kilometer-high robot?

Why a helicopter?

[AJWM]

Wouldn't it make a lot more sense and be a lot easier to hold the cable up with a balloon? (Or rather, hold the balloon down with the cable.)

Re:

[NoYob]

Wouldn't it make a lot more sense and be a lot easier to hold the cable up with a balloon? (Or rather, hold the balloon down with the cable.)

Because a balloon can't be held stationary? It will be blowing around with any wind up there.

Re:

[jimbolauski]

1 m^3 of helium has about 1kg of buoyancy, to lift 1km cable along with the elevator would require a very large balloon, the winds at 1KM are much stronger then on the surface so the giant balloon would be blown all over the place with a laser pointed at it I'm sure you can figure out the rest.

Re:

[UnglueD]

They could have some kid, preferably named falcon, sit in the balloon to make sure it stays put.

Re:

[quercus.aeternam]

And what happens if you miss and hit the balloon?

Balloons are a lot more susceptible to lasers than helicopters (or so I hear...)

Re:

[PitaBred]

Warning: Do not look into laser with remaining eye

Re:

[jnaujok]

I dunno, reflective mylar? If only we could build a balloon that could reach the stunning altitude of 1 kilometer (that's about 3000 feet) and be large enough to hold up that cable (guessing around 1000 to 2000 pounds) and keep itself still...

Why, what a miraculous craft [wikipedia.org] that would be!

Re:

[quercus.aeternam]

That's just crazy talk. Everybody knows that you can't /really/ fly. They just do it in movies and stuff to speed up plot...

Oh, and the Hindenburg was just some aliens crash landing. Because they can't fly, you know.

On a more serious note, it's probably easier to get a hold of a helicopter than a suitable airship, but who knows? I've never tried.

Regardless, it would seem that NASA thought so - though that is very much debatable considering the status of manned spaceflight...

Re:

[palegray.net]

And what happens if you miss and hit the balloon?

I'm still trying to work out how you can miss and hit it at the same time. Is this like some story I once heard about a cat?

Re:

[Zerth]

They want to be able to screw with the contestants, which sort of requires a self-moving endpoint.

Re:

[pwmonroe]

The original plan was to use a tethered blip type balloon, but leasing a helicopter was deemed less expensive. It to comes with its own issues, not the least is the copter hovering at ~1km maintaining a constant tension on the cable as the climber ascends. I too expressed concerns about a manned aircraft having a 5KW laser beamed at it, but that seems to have been addressed. I was very briefly involved with one of the teams until my main job intruded, think that there is a lot to be learned from the effort.

Shadowed Creator?

[pavon]

The NASA Centennial Challenge Powered Beaming competition, to develop technology for uses such as a space elevator, or to power a rover in a shadowed creator on the moon, was delayed indefinitely due to trouble setting up the kilometer high race track.

Yes, well they should have known that you can't build Barad-dûr in a day.

It's watching

[get quad]

Our shadowed creator is always present with its noodly appendages at the ready.

simpler test

[slashkitty]

why don't they just try a 1km ground based test first? I can't imagine this is safe for the chopper. Much needless complication for testing the technology.

Re:

[mpoulton]

why don't they just try a 1km ground based test first? I can't imagine this is safe for the chopper. Much needless complication for testing the technology.

Because gravity goes down, not sideways? Seriously, that's simply not even remotely comparable. The entire challenge here is to climb a straight, vertical cable against a 1G vertical acceleration. Crawling along a horizontal catenary-shaped cable with a 1G sideways acceleration is a completely different problem to solve.

Re:

[pixelpusher220]

I think his point was that you could make a pretty straight 1 km bar along the ground. I thought the main thing being tested here is the ability to hit the target as it goes along the cable/bar to a distance of a km. Mimicing the resistance of gravity while moving in the horizontal plane is quite simple.

At some point though you do want a full system integration test, so perhaps that's what they are actually doing here.

I would wonder how 'stationary' the helicopter can actually be. I'd figure it wo

Re:

[account_deleted]

Comment removed based on user account deletion

Re:

[John Hasler]

No, they'd just have to do substantial construction work in a sacred national park.

I have no doubt that the helicopter is less expensive both financially and politically (not to mention that they would probably like to carry out the tests some time this century).

Why use a beam?

[Rough3dg3]

Surely for the purpose of a space elevator orbiting the Earth it would be more suitable to power it using solar panels that are also in orbit and just hook it up via that.

Re:

[criptic08]

IANAE but, transmitting power from cables has several drawbacks 1) Anything that adds weight to the cable is a very bad thing. 2) the power loss due to extreme length. 3) Redudancy directly affects 1 and 2. 4) 1 and 2 are mutually exclusive.

And as far as wireless power transmission goes, if its focused i think the powerloss is quite acceptable over those distance relatively to other means. The redudancy is exceptionnal too, you can have multiple beaming stations on the ground and/or in the air, ready to s

More useful applications

[Monkeedude1212]

These guys are thinking way too small. Think if we really got this project going, we could sell handheld energy beaming devices to everyone! Imagine the applications!

Forgot to charge your cell phone? Not a problem!
Car Battery Dead? Easy Peasy!
Girlfriend not turned on? Eh... Well....

Re:

[drjuggler]

That's when you call Big Jim Slade.

Nuclear

[lobiusmoop]

Just equip the lift with a nuclear engine. If it's good enough for submarines it's good enough here. High power output and 40 year lifespan.

Delay

[SnarfQuest]

Was the delay caused by problems with the shark tank?

I for one...

[Sawopox]

...will be staying inside, under my tinfoil hat on November 2nd.

Thank you.

(Also, need food, water, and ammo.)

Re:

[camperdave]

Tinfoil hat... Just what you need, a parabolic dish focused on your brain.

Day of the Dead

[LordByronStyrofoam]

Coincidence? I hope so...

Finally!

[seanthenerd]

My older brother is the design head for the University of Saskatchewan team, the front-runners of the past competitions. Suffice to say they're really excited about it, since this competition has been delayed month by month since about a year ago! It'll be neat to see everything actually all come together.

You can watch a sweet (if cheesy) video about the team on their website [usask.ca].

The Space elevators is going to be

[geekoid]

the flying hover car of the 21st century.

Count me out as an observer

[smoker2]

I wouldn't stand within a kilometre of this test. What if the helicopter has to ditch the cable in an emergency ? 1km of cable with attached crawler falling on your head would not be pretty.