LaserMotive Finds Success In Space Elevator Competition

Bucc5062 writes "LaserMotive has achieved the first step towards the creation of a working space elevator by qualifying for the $900,000 prize in a contest sponsored by NASA. To achieve this first level, LaserMotive needed to propel a platform up a cable dangling from a helicopter at over 2 m/s. They hit a top speed of 4.13 m/s. The next level of qualification will be to achieve a climb speed greater then 5 m/s. LaserMotive beamed roughly 400 watts of laser power to a moving target at a distance of 1 kilometer, as part of the vertical laser alignment procedure. The target was a retro-reflective board a little larger than 1 meter on a side. The contest will continue for another two days with at least two other teams challenging for the prize. To win the Power Beaming competition, the LaserMotive system uses a high-power laser array to shine ultra-intense infrared light onto high-efficiency solar cells, converting the light into electric power which then drives a motor. 'Our system will track the vehicle as it climbs, compensating for motion due to wind and other changes. Building on our experience from last year’s competition, we are designing an improved system able to capture the full $2,000,000 prize.'"

Comments

Professor Myrabo at RPI

[Gothmolly]

Leik Myrabo at RPI has been working on this stuff for years. In his words, if we can hit an enemy ICBM travelling at many times the speed of sound with a laser, surely we can keep one focused on a friendly target with a known/desired trajectory. These projects will NOT become accidental Death Stars. Given the absurdly high percentage that fuel makes up of a vehicles launch weight, anything you can do to power the craft externally gives you huge savings.

Re:Professor Myrabo at RPI

[v1]

I was thinking about the test and the first thing that came to mind is: ok they're beaming up radiation of some sort, probably more-or-less straight up, (since basing the power at the same spot the platform is tethered makes sense) and they're suspending it from a helicopter.... which would place the platform approximately directly between the beam generator and the heli...

so isn't this going to be a little bad for the heli / its crew?

The only way I see to avoid this would be to beam up the energy from somewhere other than at the anchor point. And that would have to substantially increase the difficulty of targeting the platform, since the distance between platform and beam source will increased if you move the beam source away from the anchor.

I suppose for actual "space elevator" applications the same thing will apply, only you'll be irradiating the floating counterweight or whatnot, and the destination.

Re:Professor Myrabo at RPI

[Anonymous Coward]

There is a difference of course: If we can stop 50% of ICBMs, that may already make the investment worth it. For an elevator that sort of reliability might not be enough...

Re:Professor Myrabo at RPI

[Joce640k]

Can't they attach a parabolic mirror the the elevator and use the sun for power.

They could get more than 400W from a mirror, easy...

Re:Professor Myrabo at RPI

[natehoy]

Well, they're basing the tests on a helicopter, so the beam is relatively small. So for the test, they could easily beam the power from somewhere other than the anchor point. Having the beam come from a different direction wouldn't invalidate the important concept of "can beam power from ground to power the platform".

Not to mention, this test is based on a laser capable of delivering 400 watts of power to the target using infrared. Your average aluminum helicopter skin isn't going to vaporize under those conditions. Heck, I doubt you'd even scorch the paint.

In the "real world" use of this, the suspension unit is going to be much further away and specifically designed with protective shielding. In fact, the endpoint might have solar panels pointed back to Earth so any "stray" IR could be caught and used at the station - though it's far more likely they'd have a solar panel up there, too, and beam IR down to the elevator once it reaches a certain point and the beam from Earth starts dissipating too much.

Re:Professor Myrabo at RPI

[vivian]

I too would love to see this work - though they are going to have to be moving a hell of a lot faster than 5 M/s (18 kM/h) for it to be anything like a practical solution.

Since there is no tangential velocity, unless the thing gets up to geo, there's going to have to be a big rocket to supply the additional deltav to reach orbit.
To reach geosynchronous orbit (about 36000 kM above sea level, I think) is going to take about 2000 hours, or 83 days.
I imagine you wouldn't want to take more than a week or so to climb a cable.

To make it to geosynchronous orbit in a week you would have to be moving at about 214 kM/h, or approximately 60 meters/second.

The only other option is to have a climber that can carry enough fuel up with it for a rocket to give the additional delta v needed for orbit.
Since I'm not a rocket scientist, I'll leave the calculation of how much fuel you'd need for that to someone else. Just how much additional velocity is needed if you make it say, half way up? Could you use a scramjet or something like that instead of a rocket since you would be in thin upper atmosphere with plenty of drop available to get the thing firing?

at any rate, I think we will probably have a viable ribbon or cable material before we have a viable climber.

Re:Professor Myrabo at RPI

[ClosedSource]

"In his words, if we can hit an enemy ICBM travelling at many times the speed of sound with a laser, surely we can keep one focused on a friendly target with a known/desired trajectory"

But we haven't demonstrated that we can hit an enemy ICBM with a laser, so what's the point?

Re:Professor Myrabo at RPI

[natehoy]

400W is only the test unit, and probably had almost no payload. A mirror capable of generating 400W of focused light is probably going to be too heavy for the small test platform they were testing with.

The purpose of this was a scale test of a proposed much larger (and therefore useful) elevator box that could carry some payload, and that would need to be powered by a necessarily much larger ground-based laser.

If and when this ever reaches the point where they are talking about putting people or useful cargo onboard, the only thing I'm unclear on (because I don't have the time or the knowledge to do all the maths) is whether we'd be talking in megawatts or gigawatts. Probably megawatts.

It's probable that any mirror large enough to focus sunlight in useful quantities to raise a payload would be too large to be raised as part of that payload, regardless of scale. Even if it's possible, it cuts severely into theoretical payload. Leave the mirrors on the ground and you can use all that saved weight for payload.

Re:Professor Myrabo at RPI

[realityimpaired]

They sell small solar panels that you can attach to the roof of your house which will produce 400W of juice.

The reason that it's not feasible for this project is that you need it to be able to work in all weather, and presumably at all times (5m/s is relatively quick, but it's still a long way up to space, which is the ultimate goal of this project). Also, when you start scaling it up to the power requirements for moving a significantly bigger payload into space, you start needing much more juice, and the weight requirements for the solar panels would be prohibitive. Developping ways to beam the energy from ground-based stations will allow you to focus more energy on smaller panels, reducing the weight requirement.

A parabolic mirror *would* allow the focusing of much light on a central point, but it would be a lot of extra weight and of limited use for generating electricity. When they're employed as part of a solar power array, usually it's to heat water for steam, or salt to store heat... If you're using that heated water to generate electricity, you add an awful lot of unneeded weight for limited improvement in efficiency: a flat panel that has the same cross-section area facing the sun would trap the same amount of light, and would weigh significantly less. When the amount of power you need to drive the thing is directly reliant on the amount of weight you need to move, a parabolic mirror becomes a bad idea.

Re:Professor Myrabo at RPI

[IndustrialComplex]

But we haven't demonstrated that we can hit an enemy ICBM with a laser, so what's the point?

Is the focus on the word on enemy? Hitting an ICBM with a laser is possible.

The challenges:

A. Of course, we aren't testing with 'enemy' ICBMS. At that point I wouldn't call it 'testing'. I'd call it 'Oh shit I hope this works'

B. Keeping the laser on target with enough energy to damage the warhead (premature detonation, breaking it's heat shield, etc)

C. Getting the laser on the ICBM prior to separation of the warhead to damage the rocket portion.

Hitting a high velocity target with a laser is the challenge they were talking about, and that IS doable.

Re:Professor Myrabo at RPI

[John Hasler]

> They could get more than 400W from a mirror, easy...

Even if it wasn't too heavy to lift itself such a system would require that the cable be much, much larger and therefor much, much, much more expensive. It makes much more sense to minimize the weight of the car and put as much of the big, heavy stuff on the ground as possible.

Re:Professor Myrabo at RPI

[ClosedSource]

"Hitting a high velocity target with a laser is the challenge they were talking about, and that IS doable."

So you say, but has it been done?

Re:Professor Myrabo at RPI

[Anonymous Coward]

The angular momentum is stolen from Earth's rotation. You don't need extra rockets for it.

Re:Professor Myrabo at RPI

[bjomape]

400W focused in one small point - that's about the power you'd get from focusing direct sunlight using a magnifying glass with a diameter of 0.7m (2 ft). Not even scorch the paint? I'd like to see that.

Re:Professor Myrabo at RPI

[AGMW]

... I suppose for actual "space elevator" applications the same thing will apply, only you'll be irradiating the floating counterweight or whatnot, and the destination.

Why not cover that side of the counterweight in the solar panels as well, and scoop up as much power as you can for use on the station ... Perhaps even send some back down by having a power laser pointed down to fire energy at the top of the climber for when it gets nearer the top ...

Is there also an issue of having more than one climber on the cable at any one time - surely that means you'd want to be firing the power laser at a suitable angle anyway, to power a specific cable car.

Re:Professor Myrabo at RPI

[khallow]

It all depends on the area that the power is focused upon. For example, the 400 W is focused on a target a meter across. In comparison, sunlight is about 2.5 times as intense. Sure if the power were instead focused on a 1 centimeter target, it'd be melting steel. But it's not.

Re:Professor Myrabo at RPI

[IndustrialComplex]

So you say, but has it been done?

An object that is 0.6m across, moving at approximately 1 km/s, and is 384,000 km away.

Yes, about 40 years ago. http://science.nasa.gov/headlines/y2004/21jul_llr.htm

Re:Professor Myrabo at RPI

[timeOday]

What's wrong with taking 83 days? How often do launches occur now? And couldn't many payloads climb in parallel?

Re:Professor Myrabo at RPI

[PeterBrett]

Since there is no tangential velocity, unless the thing gets up to geo, there's going to have to be a big rocket to supply the additional deltav to reach orbit.

That's correct. The space elevator design calls for the elevator to stretch from the surface, to a large space station in GEO, to a point the same distance the other side of GEO. That way you can get a big bunch of the velocity needed for an interplanetary trajectory simply by going to the outer end of the space elevator and letting go!

And you're also quite right in saying that 5 m/s is too slow for human transit to GEO, but it's probably good enough for cargo payloads. One of the biggest problems, though, is that the elevator would travel through the van Allen belts, and you don't want to spend long there or the radiation will destroy your electronics.

Re:Professor Myrabo at RPI

[timeOday]

I'm sure there must be a good answer to this, but why does a space elevator require laser power at all, instead of just running electricity up the "rope"?

Re:Professor Myrabo at RPI

[Dan Ost]

As the elevator gets further from Earth, the pull of gravity decreases. Therefore, the energy required to move 5m/s close to Earth might allow the elevator to go much faster than 5m/s as the elevator's altitude increases.

But even if it doesn't, 83 days might not be unreasonable if we're talking about cargo rather than astronauts.

Re:Professor Myrabo at RPI

[stevelinton]

The rope is too long. You'd lose too much power to electrical resistance along the way.

 

Re:Professor Myrabo at RPI

[jcochran]

I suspect that it's speed is dependent upon the amount of work the climber needs to perform.
Interestingly enough, the required work decreases as the climber gains altitude. After all, the gravitational pull gets reduced with the greater distance from earth due to the inverse square law. And, yes, I'm aware that the efficiently of the power transmission also goes down with the inverse square law, but I'll assume they step up the power as required to keep the amount of power the climber gets as close to the maximum power the climber can handle.

So starting at sea level, the climber is running at 5 M/s. A rather modest rate.
By the time it's climbed to 2640 km, it's speed is up to 10 M/s.
At 6380 km, it climbing at 20 M/s.
The 60 M/s rate is reached at about 15700 km.
I estimate that a climber capable of 5 M/s at sea level due to its increasing speed as the amount of work it's doing per meter decreases, can reach geostational altitude in about 300 hours. There's quite a bit of slop in this estimate since I didn't account for orbital velocity which would tend to decrease the amount of work required (for example, my spreadsheet has the climbing fighting a downward acceleration of 0.22 M/s at geostationary altitide when in reality it would be fighting nothing. Also I haven't bothered to take into consideration deceleration which would obviously be required since you wouldn't want your payload to go zipping by in excess of 218 M/s as it passes geostationary and heads on out to deep space.

Re:Professor Myrabo at RPI

[spitzak]

Gravity actually goes down faster than the inverse square law. It is zero at geo-synchronous orbit level, which is smaller than the non-zero 1/n^2 of inverse square.

The reason is the centrifugal force of the cable spinning around with the earth.

Re:Professor Myrabo at RPI

[BattleApple]

I'd just put mirrors all over the bottom of my helicopter and let the people on the ground worry about it

Re:Professor Myrabo at RPI

[Hadlock]

It takes something like 9 days (on a good week) for a container ship to cross the pacific to California, plus another 2-3 days to reach it's final destination (if you're lucky with customs). Like the ocean, a cable could hold more than one "ship". I would imagine once this is commercially viable, you'd have three cable; one up, one down, and an emergency backup, with two to three climbers on each cable.
 
To answer your question though, these would be traveling to geosynchronous orbit (26,199 miles) and traveling at 5m/s (11.18 mph). So that's actually 97 days one way. Or 48.8 days if you double the speed to 10m/s (I believe gravity has a measurable lesser effect the further you go from earth).

Re:Professor Myrabo at RPI

[Zarniwoop_Editor]

Why would you not just use the cable itself to transfer the power rather than a complicated laser system?

Re:Professor Myrabo at RPI

[ClosedSource]

I didn't know ICBMs traveled in a known path like the moon does. But the main topic is a space elevator so that's where the ICBM analogy fails anyway.

Re:Professor Myrabo at RPI

[amorsen]

What do you use for return wire?

Re:Professor Myrabo at RPI

[StrategicIrony]

The only "rope" we know of that would have the strength is a high-tensile, ultra thin, uninsulated "ribbon" of solid woven carbon nanotubes.

What's the conductivity of a micro-think carbon nanotube ribbon and how would you go about carrying a current (in a circle) through it? :-)

Re:Professor Myrabo at RPI

[StrategicIrony]

Because it's a micro-think carbon nanotube ribbon that isn't even close to possible to manufacture at this point and has unknown properties (maybe it's a semiconductor?).

We're not talking about a steel cable. Steel isn't nearly strong enough (by a factor of like 15).

Re:Professor Myrabo at RPI

[Anonymous Coward]

Having it travel faster would be useful, yes... however 18km/h isn't really that bad. Remember, this is up, not horozontal.

Have it run for one day. One 24hr period, and it's 432km's away from the surface of the earth. That's higher than the international space station!

Re:Professor Myrabo at RPI

[falconwolf]

The space elevator design calls for the elevator to stretch from the surface, to a large space station in GEO, to a point the same distance the other side of GEO.

Do you mean the elevator would require the cable, or ribbon, to stretch past geostationary orbit? And if what I've read the cable would have to go more than the same distance past geostationary orbit. Whether it's right or not I don't know but the wiki article on space elevators says the counterweight would have to be 144,000 KM past geostationary orbit which is 35,786 km up. I may be wrong but I think the distance past geostationary orbit the counterweight would have to be would depend on the mass, the larger the mass the closer it could be. Another Slashdotter should know if either of these are correct.

Falcon

Re:Professor Myrabo at RPI

[MrKaos]

Is there also an issue of having more than one climber on the cable at any one time - surely that means you'd want to be firing the power laser at a suitable angle anyway, to power a specific cable car.

If there is more than one car you should be able to beam power *from* cars that have escaped earths gravity and have begun to "fall". The same motors that were being used to climb could be used as a generator much the same way trains use regenerative braking to put power back into the grid when they are going downhill.

Re:Professor Myrabo at RPI

[IndustrialComplex]

For Pete's sake....

BALLISTIC MISSILES. They follow a freaking ballistic path, it's one of the easiest damned things to predict. High school level physics teaches you how that motion will work near the surface of the Earth, and first year physics in college will give you enough information to predict it's motion when you factor in atmospheric and changes in gravitational attraction at higher altitudes.

The hard part isn't hitting it with a laser.

The hard part is hitting it with a laser in the right spot with enough power to somehow prevent the warhead from reaching it's destination and compensating for any countermeasures that might be employed.

Their analogy is fine, you are just breaking it down to some argument about the feasibility of an entire anti-ICBM defense system.

Re:Professor Myrabo at RPI

[ClosedSource]

The missiles are called "ballistic" because they have a coasting phase. They are certainly not "ballistic" in the bullet sense since they carry fuel and are initially self-propelled. There is no technical reason why these missiles can't be improved to use guided decent to produce a more unpredictable path.

In any case, my point was just that a space elevator platform doesn't move like either the moon or a conventional ICBM anyway.

Re:Professor Myrabo at RPI

[v1]

that's actually not a bad idea. If you had say, a pair of these units per cable, one going down and one going up, then you could have the one going down beaming power to the one going up. They wouldn't meet in the middle though... you'd get little energy from the descending unit at the start and that's when you'd need the most for the ascending unit. So there's probably no practical way to make the ascender's power curve match the descender's, but it could boost it. It would be best to continue beaming power to the ascender even well after they'd passed on the cable because that's when the power available from the descender would be approaching its max.

That would at least lower the power requirement. The problem then is to see how much weight that adds to both units... can you make the addition of a second receiver panel plus the addition of a regenerative breaking system plus the addition of a laser assembly pass break-even? Even adding a single pound to the unit has got to have a severe affect on the total energy required to lift it.

The good news is the total energy requirement won't increase with the square of the weight of the unit as it does with rocket fuel, since when you add fuel, you have to lift that too.

I recall reading something about one of the female astronauts cutting off her long hair to a short cut because that small reduction in weight was going to save several thousand dollars in fuel for the shuttle launch.

Re:Professor Myrabo at RPI

[MrKaos]

That would at least lower the power requirement. The problem then is to see how much weight that adds to both units... can you make the addition of a second receiver panel plus the addition of a regenerative breaking system plus the addition of a laser assembly pass break-even? Even adding a single pound to the unit has got to have a severe affect on the total energy required to lift it.

I think in time the whole thing would be powered from space anyway eliminating the vagaries of terrestrial weather, probably keeping some ocean based power as a backup for cars climbing in heavy storms. Ideally the cars would be powered by multiple power sources that the cars aligned with a sighting/ranging/data laser from the car - responded by a power laser.

One thing is definitely interesting - people have stopped laughing at the idea, it might even happen in our lifetime - one can only hope.

your sig has always cracked me up btw

Re:Professor Myrabo at RPI

[CarpetShark]

These projects will NOT become accidental Death Stars.

Perhaps small death-moons.

Re:Professor Myrabo at RPI

[AGMW]

Having the cars pass each other on a single cable will be interesting.

OK, so lets assume we have a "train" of cars ascending, followed by a similar "train" of cars descending. Any power generated on the descent could be beamed back to the ground and/or the counter weight for use on the next ascent.

Could the cars have "power" panels top and bottom and repeater lasers top and bottom to form a "power chain" throughout the "train"?

Maybe that wouldn't be necessary though: Power the bottom (and top?) car via the beamed power and when it touches the car above it could physically "connect" to it thereby transferring the power to the next car, etc - ie it becomes a "train" of cars which are linked in the way "trains" are traditionally envisaged.

This could also be the basis of a fail-safe for if a car fails - a "tug" (or perhaps "push") car could be sent up to connect and take control of the defective car to push or lower it to safety.
Actually, equipping the cars with a parachute could afford a cheap and quick rescue option of just letting go of the cable if they were low enough, though the thought of building in any mechanism to allow the car to "let go" does seem as foolish as the Bond Villains always building in an obvious self destruct button in their lairs!

Finally

[Shane112358]

Ad Astra! Ad Luna! Ad Lagrange Point 2!

Good to hear.

[jellomizer]

I hope to see a functional space elevator in my lifetime. This would help space travel immensely by taking making the issue of getting out of our atmosphere a relatively dull process it allows us to put more focus on ships that can be bigger and designed for long term space travel. Say to mars

Re:Good to hear.

[Interoperable]

Maybe if we develop a longevity vaccine within your natural lifetime you will.

Re:Good to hear.

[Ractive]

A longevity vaccine would prevent longevity, there's no need to develop that one, you could use a gun against your head for that purpose, you mean an Aging vaccine.

Re:Good to hear.

[wisdom_brewing]

Who modded this down?!

Re:Good to hear.

[FiloEleven]

making the issue of getting out of our atmosphere a relatively dull process

...until someone creates space elevator music. Then it will become a dull, agonizing process.

Re:Good to hear.

[blueZ3]

At 5m/s, that's a lot of Celine Dion < shudder >

Re:Good to hear.

[falconwolf]

At 5m/s, that's a lot of Celine Dion

Celine Dion I can listen to singing though not for days on end. On the other hand though Britany Spears, I don't think so. However maybe she can give lessons in semiconductor physics.

Falcon

Uh-oh

[Pete Venkman]

What if someone farts in the space elevator? You'll be stuck for way more than a few floors.

Re:Uh-oh

[thijsh]

Don't worry, like Ridley Scott said: "In space no one can hear you fart".

Re:Uh-oh

[natehoy]

Small methane processing plant = more energy for the motors. Remember to load up on beans before you go onboard, and fit your flatulence intercept unit on your butt before you close up your spacesuit.

Re:Uh-oh

[Trails]

Easy, just open a window!

Err... better hang on to something though.

Re:Uh-oh

[infinite9]

Just keep pushing the button. The elevator will arrive faster... (off to file a patent for a placebo button powered space elevator...)

Re:Uh-oh

[jbezorg]

What about the Muzak?

Re:Uh-oh

[Anonymous Coward]

If two people are in a space elevator and one of them farts, everyone knows who did it.

shouldn't they be able to design the cable also?

[wisebabo]

Congratulations to LaserMotive and I hope that they (or one of the other participants) quickly claim the remaining prizes.

Still, it occurred to me that the real system (capable of climbing to Geo-sync and beyond) won't be designed in a vacuum (ha ha). I mean, the cable on which these climbers ascend will be exquisitely engineered as well, probably down to the nano-level if it's going to work at all. So shouldn't the contest be that of a cable/climber combination? I mean like what if the cable or climber or both was using some nano patterned material like the underside of a gecko's foot (which lets them cling upside down to ceilings). Or maybe if there was some sort of nano (or not, I saw one made out of large metal bits) "velcro" like material in which case there would have to be hooks on one surface and clasps on another.

As long as the surface of the cable didn't add appreciably to the weight of the (supposed) carbon nanotube structure, it could add tremendously to the gripping power of the climber while still allowing for a practical cable.

Are we serious?

[Kupfernigk]

The key word that's part of ICBM is "ballistic", from the Greek ballein, I throw. It's travelling through extremely thin gas, and its trajectory is therefore practically simple Newtonian dynamics. Its position from moment to moment should be extremely predictable. Now consider an object attached to a rope in the atmosphere. It's subject to constantly changing wind forces in three dimensions. Even when it's out of the atmosphere, the beam is subject to deviation caused by atmospheric effects, which is why stars twinkle and big telescopes need clever adaptive control systems. Its path is many times less predictable. In a nutshell, it's the difference between catching a lofted cricket ball or baseball, and catching a fly. It is not an object with a "known/desired" trajectory.

The problem is, I'm sure, soluble, but the technical difficulty should not be underestimated.

Re:Are we serious?

[Anonymous Coward]

Well, the adaptive optics problem that you talk about with big telescopes was originally solved to allow lasers to shoot through the atmosphere. It was a "Star Wars" technology adapted to telescopes, not the other way around, so that is a non-issue (relatively speaking, of course).

Re:Are we serious?

[blueg3]

The problem is, I'm sure, soluble

Soluble, sure, but only in aqua fortis.

Or did you mean solvable?

Re:Are we serious?

[Anonymous Coward]

Wow, a couple letters misplaced, and you actually have so little shame as to admit that you are not smart enough to know what was meant. Sad really. Perhaps some english classes would help you?

You really have no place being on a technology site, where a certain level of smart is assumed.

Re:Are we serious?

[IndustrialComplex]

Soluble, sure, but only in aqua fortis.

Or did you mean solvable?

Well Archimedes did say, "Give me a powerful enough solvent, and a large enough bathtub, and I'll dissolve the Earth."

Re:Are we serious?

[John Hasler]

> In a nutshell, it's the difference between catching a lofted cricket ball or
> baseball, and catching a fly.

Some of these people have already built laser systems that can shoot a fly out of the air.

Re:Are we serious?

[Chris Burke]

The key word that's part of ICBM is "ballistic", from the Greek ballein, I throw. It's travelling through extremely thin gas, and its trajectory is therefore practically simple Newtonian dynamics. Its position from moment to moment should be extremely predictable.

In theory, yes. In practice, it's going to depend on how accurately you can measure its position and velocity at any given moment. The missile is moving very rapidly relative to the target size it presents, so small errors in measuring its position will result in larger errors in the extrapolated arc and could easily result in a miss. Also, since Star Wars none of the anti-ICBM techniques have focused on the peak of its trajectory where it is a purely Newtonian ballistic projectile. They either target the lift phase where it is most decidedly not ballistic, or the descent phase where air resistance cannot be ignored. The ones who designed and programmed the missile can't predict its trajectory to within one missile-width, so why assume it's easy for the defender to figure this out? It's not an easy problem at all, which is why the Missile Defense Shield has met with only limited (read: assisted) success.

Even worse would be to assume that technology is limited by the Latin roots of words used to describe it. "Ballistic" already applies to only a portion of the flight, and as Russia was quite keen to point out during the height of the MDS push their missiles have descent phase countermeasures like, um, dodging.

So think of it more like hitting an unconscious fly that is traveling as fast as a fastball, could at any moment wake up and start flapping, and you aren't trying to catch it in a glove, you're trying to spear it with a toothpick before it gets too close.

Solvable? Oh sure probably for any given iteration of the enemy's missile. Obviously easier than hitting a relatively slow-moving target that wants to be hit and thus can be broadcasting its position (like the test missiles did in the descent-phase anti-missile tests)? Yeah I'm not so sure about that.

The problem is, I'm sure, soluble, but the technical difficulty should not be underestimated.

No, its certainly not an easy task. I just think hitting a missile that doesn't want to be hit is comparable if not harder to achieve (because while the missile will be modified to make it harder to hit, the elevator will be modified to make it easier).

Re:Are we serious?

[khallow]

The key word that's part of ICBM is "ballistic", from the Greek ballein, I throw. It's travelling through extremely thin gas, and its trajectory is therefore practically simple Newtonian dynamics. Its position from moment to moment should be extremely predictable. Now consider an object attached to a rope in the atmosphere. It's subject to constantly changing wind forces in three dimensions. Even when it's out of the atmosphere, the beam is subject to deviation caused by atmospheric effects, which is why stars twinkle and big telescopes need clever adaptive control systems. Its path is many times less predictable. In a nutshell, it's the difference between catching a lofted cricket ball or baseball, and catching a fly. It is not an object with a "known/desired" trajectory.

You have it exactly backwards. The professor was right. The object attached to the rope is predictable because you'll know exactly where it is all the time (say via GPS stuck right on the vehicle, some tracking signal, or other means) plus it's not moving very fast. The ICBM will be fired by someone who doesn't want you to hit it and they'll have plenty of tricks to keep you from doing so. They won't tell you where they are. The missile will be traveling at hypersonic speeds. They'll bring decoys. They'll fire retro rockets so that the trajectory is constantly shifting in a non-ballistic fashion. And they'll harden the missile so that more energy (and more time on target) is required to kill the missile. And they might fire hundreds of missiles with several warheads each in order that some get through.

Re:Are we serious?

[Anonymous Coward]

"ballistic", from the Greek ballein, I throw

ballein is the infinitive. ballw = I throw

Re:Are we serious?

[PeterBrett]

The key word that's part of ICBM is "ballistic", from the Greek ballein, I throw. It's travelling through extremely thin gas, and its trajectory is therefore practically simple Newtonian dynamics. Its position from moment to moment should be extremely predictable.

That's why penetration aids were invented. Sure, it's easy to hit something, but picking out which of the 20-30 ballistic targets is the actual warhead that's trying to blow you away is hard.

Re:Are we serious?

[FiloEleven]

A certain level of smart-assery is also assumed. You have the assery down, but you need to work on the smart.

Re:Are we serious?

[mhajicek]

ICBM's don't strictly adhere to a ballistic trajectory anymore. I believe both Russia and China have missiles designed to thrust laterally in a difficult to predict manner to avoid kinetic kill devices.

Re:Are we serious?

[amplt1337]

Not to mention that if you're beaming power, you can always make the target a good bit wider than the beam.

Just sayin.

Re:Are we serious?

[Anonymous Coward]

While in a nutshell?

Re:Are we serious?

[CompMD]

Adaptive optics and deformable mirrors with microactuators already exist to account for atmospheric effects and scintillation. We use them in laser weapon platforms like MTHEL, SSHCL, and ABL.

Re:Are we serious?

[Hadlock]

Demanding a youtube link. Thanks in advance.

Re:Are we serious?

[SleazyRidr]

I think he was talking in English and meant soluble. Maybe Slashdot should think about adding an English-American translator to the site.

Re:Are we serious?

[Anonymous Coward]

Soluble

1. (Of a substance) Capable of being dissolved in some solvent (usually water).
2. Susceptible of solution or of being solved or explained.

Re:Are we serious?

[StrategicIrony]

This one's sarcasm circuit is malfunctioning. Take it away for recycling.

Re:Are we serious?

[StrategicIrony]

So think of it more like hitting an unconscious fly that is traveling as fast as a fastball, could at any moment wake up and start flapping, and you aren't trying to catch it in a glove, you're trying to spear it with a toothpick before it gets too close.

The mental image of Albert Pujols flinging toothpicks at a high speed unconscious fly made me ROFL

Re:Are we serious?

[Anonymous Coward]

Well, you really should know that by now, "ballistic missiles" aren't really following a ballistic trajectory-- that makes them far too predictable. They now bob and weave and rotate and generally try to avoid being anti-missile bait...
Captcha: dashed...

Re:Are we serious?

[MrKaos]

Well Archimedes did say, "Give me a powerful enough solvent, and a large enough bathtub, and I'll dissolve the Earth."

Archimedes, the oceans are the earth's bathtub you insensitive clod.

Re:shouldn't they be able to design the cable also

[Anonymous Coward]

Two different fields:
  climber: electrical/mechanical/controls engineering
  cabel: material scientist

Not many people are both.

They could but there is a problem,

[Kupfernigk]

The sun is effectively at infinity, so the reflection from the parabolic mirror will come to a focus at some distance from the mirror and thereafter diverge. This won't work. You would need, in fact, a large array of flat mirrors which were steerable so they all converged on the target, and continued to do so as it rose. This could be technically very difficult indeed. It makes a lot more sense to use electricity to power one laser which then only requires steering. You can generate the electricity with solar panels if you like.

(A C Clarke had a story in which large numbers of flat mirrors were used to vaporise a football referee. Obviously, everybody holding a mirror had to steer it. In reality, the target would have been so bright they would probably not have been able to aim effectively.)

Re:They could but there is a problem,

[natehoy]

Possibly. MythBusters did a test where they took relatively large but not ungainly array of flat mirrors and rigged them into a parabolic array, and set some dry wood on fire with it. I think it involved a few dozen small mirrors, but they were all pre-calibrated to aim at the same point.

Assuming bright sunlight approximately straight up in the sky (so everyone in the audience has access to some sunlight they can aim), Clarke's story might be considered "plausible" on the MythBusters scale. If you have 50,000 fans in the stadium all with 4-square-foot mirrors (2' x 2'), you'd only need a few hundred of them, maybe a thousand, to aim accurately in order to cause the ref some serious harm. Even if only 5% of your audience could guess at their aim with any level of accuracy, I think your ref would have a pretty tough time of it. Issue welding goggles with the mirrors, and it's probably barbecue time.

Hmm, I ought to send that one in. Seeing them try to scale this one up could be fun.

Re:They could but there is a problem,

[swillden]

Hmm, I ought to send that one in. Seeing them try to scale this one up could be fun.

Poor Buster...

Re:They could but there is a problem,

[gaggle]

Oh cool, that's not a story I'm familiar with. I went and googled for the answer I was about to ask:
"In his short story "A Slight Case of Sunstroke", Arthur C. Clarke writes of a stadium full of disgruntled soccer fans barbecueing the dishonest referee by reflecting sunlight on him with mirrors found under their seats."

Re:They could but there is a problem,

[flibbajobber]

Not necessarily, as a parabolic reflector could be followed by a lens (at approximately the focal point) which refocuses the apparent source to infinity again; thereafter the beam would be trivial to 'steer' using a single flat mirror.

Re:They could but there is a problem,

[MrKaos]

Hmm, I ought to send that one in. Seeing them try to scale this one up could be fun.

indeed, could also be an interesting slashdot effect experiment.

Re:shouldn't they be able to design the cable also

[CopaceticOpus]

Nobody is able to design the cable. We simply don't have the technology, which is why they're focusing on the climber instead.

This is a bit like having a contest to design a cool hat to be worn while using an anti-gravity belt. If someone wins the contest, then we are one step closer to being able to float while wearing a cool hat - all that's left is the bit with the belt.

"In a nutshell,

[circletimessquare]

it's the difference between catching a lofted cricket ball or baseball, and catching a fly."

to complete your allegory in terms of childhood classic movies, the solution to the problem is less bad news bears and more karate kid

Re:shouldn't they be able to design the cable also

[MrTester]

If the contest is to develop combination cable/climber technology, the only entrants will be those who have the means (financial AND intellectual) to do both. They are two very different scientific skill sets. You would weed out a lot of teams who can bring great value to only one, or the other.

Keep them as seperate contests, running in parallel.

Helicopters in Space

[digitalPhant0m]

Now we've just got to get the helicopter to drop the rope from space, and we're set.

Re:shouldn't they be able to design the cable also

[mengel]

I thought these guys had it pegged?

Carbon nanotubes, with a tensile strength of up to 100 GPa, are the strongest material ever discovered [10]. To exploit this superior property for practical applications, individual carbon nanotubes have been assembled into macroscopic fibers [11,12]. However, these macrofibers show a very low tensile strength of less than 3.3 GPa [12 15]. This is mainly due to the clustering of nanotube ends, internanotube slippage and intrananotube defects. In contrast, the CCTs have demonstrated much improved mechanical properties compared to carbon nanotube fibers of similar sizes. Figure 4(a) shows the maximum tensile strength of 6:9 GPa of a CCT.
....
The CCTs synthesized here have a unique architecture with rectangular macropores across the tube walls and layered crystal structures in the solid walls. This unique architecture renders them a combination of superior prop- erties, including ultralight weight, extremely high strength, excellent ductility, and high conductivity. These unique architectural and physical properties give them great po- tentials for a variety of advanced applications. For ex- ample, the diameter and the length of CCTs are com- parable to those cotton fibers and the tenacity of the CCTs is 224 times that of cotton fibers. This suggests that conventional textile technologies can be used to make CCT fabrics that are much stronger than any current fabrics for applications such as body armors and light- weight, high strength composite structures. Other potential applications include making in situ self-healing composite structures, medical devices to deliver/release multiple drugs simultaneously, and microelectromechanic al sys- tems, to name only a few.

Of course, producing enough of the stuff and making the belt out of it is still non-trivial...

Re:shouldn't they be able to design the cable also

[Anonymous Coward]

This is a bit like having a contest to design a cool hat to be worn while using an anti-gravity belt. If someone wins the contest, then we are one step closer to being able to float while wearing a cool hat - all that's left is the bit with the belt.

Thank you. I just don't get the space elevator love on Slashdot.

I'm not impressed by a climb up a 1km strand of anything.

Build me a 1km suspension bridge with a mass limit of 100kg, and call me when someone's cute little robot can walk across it. Then I'll be impressed.

Space elevators are materials science problems, not robotics problems. The mass of the climber is negligible in comparison to the mass of the elevator. Stop dicking around with the robots and start building suspension bridges over college campus footpaths, using cables the width of a human hair.

Mod parent up.

[thatseattleguy]

Mod parent up- right on. The cable needs to be made of "baloneyium" (as someone famously opined about the composition of Niven's Ringworld). Its composition and engineering are way beyond our current capabilities - not so far that it's not worth pursuing, mind you, but this contest does seem to put the proverbial laser-powered cart before the carbon-nanotube horse.

Re:Mod parent up.

[IndustrialComplex]

Let's say that at our current progress it would take us 30 years to develop a way to manufacture the cable. Then let's assume that it will take 15 years to develop a machine capable of climbing that cable.

Since the two technologies are completely distinct from each other (i.e. the solution will come from different industries) Doesn't it make sense to develop them in parallel rather than wait for the cable to be developed and then have to wait an additional 15 years for the climber technology to mature?

I've certainly polished my shoes while waiting for the limo to arrive. If the limo didn't arrive, it would have made the shoe polishing pointless, but I wouldn't want to pay for a limo to wait while I got ready.

Re:Mod parent up.

[RockClimbingFool]

I am going to go out a limb here and state that creating the cable is several orders of magnitudes harder than creating a machine to climb it. Maybe even an order of magnitude more orders of magnitude.

All these little contests do is try to generate support and interest in the space elevator concept. I don't think anything revolutionary will come out of them.

Its all about the cable.

Re:Mod parent up.

[FlyingBishop]

Meh. Laser propulsion likely has other uses if we develop it to the point where it's useful for space elevators.

Re:Mod parent up.

[khallow]

All these little contests do is try to generate support and interest in the space elevator concept. I don't think anything revolutionary will come out of them.

Wake me when you come across a problem. All I'm hearing are advantages so far.

Re:Mod parent up.

[natehoy]

Actually, this company isn't developing propulsion. Propulsion is an electric motor. This company is demonstrating energy transmission. LaserMotive is even skeptical about the concept of a space elevator, but participated because they wanted prize money to fund further development of energy transmission for more, shall we say, earthly profitable pursuits.

Long before this could be used for an elevator (due to the lack of "baloneyum" as someone else put it), this technology will probably be perfected and in use for getting power to areas where cables aren't practical, and even under very controlled circumstances maybe even beaming power down from orbit or other interesting applications that have been talked about since the 60s or earlier.

Plus, frikkin' satellites, with frikkin' death ray laser beams!

Re:Mod parent up.

[gv250]

RTFA:

LaserMotive's two principals, Jordin Kare and Thomas Nugent, said they were relieved after two years of work. They said their real goal is to develop a business based on the idea of beaming power, not the futuristic idea of accessing space via an elevator climbing a cable.

Re:Mod parent up.

[eabrek]

You could build a space elevator out of bubble gum (although you'd probably need so much that it would screw with gravity). You want a light tether to reduce launch costs... (and there is a separate tether competition/reward).

The climber really is the hard part. You need power delivery, reception, and drive. Not to mention heat dissipation.

Re:Mod parent up.

[jnmontario]

I seem to remember that a charge is produced in an object (conductor) that is strung vertically in the atmosphere. People smarter than I surely have considered harnessing this as part of the elevator?

Re:Mod parent up.

[Iron Condor]

Let's say that at our current progress it would take us 30 years to develop a way to manufacture the cable.

No. Let's say that it will take us three days to develop the cable.

I mean - as long as we're saying random stuff that has no connection with reality, we might as well say nice, positive, cool, fun things.

Once you've made it clear that you have no interest whatsoever in reality and are merely writing scifi, you might as well make it scifi that is worth listening to.

Re:Mod parent up.

[BJ_Covert_Action]

Since the two technologies are completely distinct from each other (i.e. the solution will come from different industries)

And therein lies the limiting assumption of your argument. Something as complicated and grandiose as a space elevator is going to be an extremely complex system of interdependency. Developing the system as a set of discrete parts that can be duct taped together in the end, while it probably will produce a solution, will more than likely produce an expensive, hacky, less robust and less elegant design than if the entire system is approached cohesively as one unit from the start. This is the fundamental approach taken to solving most missions in the space industry right now. Rather than saying, "We want to monitor this type of activity on this celestial body, so let's have someone build a camera, and have someone build some solar cells, and have someone build the bus, and then do our best to slap it altogether afterward," the space industry has matured and now says, "We have problem X, let's brainstorm some solutions with all of our subcontracting friends that build cameras, solar cells, and frames, and monitor/oversee the activites of each one to make sure that all components of the entire system utilize the strengths of other subsystems and account for the weaknesses of other subsystems." Thus, we are capable of delivering extremely complicated solutions (ISS) to extremely complicated problems (living in space) without having to constantly hack and rehack the whole damn system together (Mir).

Taking the fundamental assumption that there will be A) a climber and B) a cable, and that the two should be developed in parallel will allow a fork in the design path that leads to later interfacing issues. If the mission is approached on a unified front from the get go , "How can we use the climber, cable, and orbital anchor together to reduce overall system complexity and duplication," a more robust and elegant solution will fall out.

That being said, a space elevator is, indeed, decades if not centuries away. The fact that we are focusing research and development efforts on ANY part of it right now is extremely exciting and inspiring in my opinion. It just goes to show that there are still some mad-scientist badasses working for NASA pushing the envelope on crazy and acceptable. I am extremely elated to see NASA funding something other than an outdated jobs program. High five to whoever proposed and fought for this contest/challenge.

On a similar note, we should also be funding R&D contests for Launch Loop and Space Fountain designs....wikipedia them if you haven't heard of them, it's worth your time.

Re:Mod parent up.

[Hurricane78]

Yes. But you start with the cable. And you then start with the machine, when the first 15 years of developing the cable are passed.

You don't start with the machine. And forget about the cable!

That was the precise argument of GP!

Re:Mod parent up.

[StrategicIrony]

Won't somebody PLEASE Think of the TAXPAYERS!!!?!!!!!!111one!!!

There.

Re:Mod parent up.

[StrategicIrony]

Except that the machine would take 3 years of dedicated design time and the cable is likely 50-80 years in the future, to be honest.

Re:Mod parent up.

[StrategicIrony]

No you couldn't.

The problem is that not many (any) materials have the strength to weight ratio to support their own weight.

Steel, for example, is too heavy. A 1" cable stretching to getosync orbit would outweigh it's own tensile strength and hence it's ability to hold itself aloft by a factor of 10 or 15.

The cable REALLY is the hard part.

Re:Mod parent up.

[eabrek]

You don't build a straight cable, rather a tapered one (which is where I get the bubble gum comment). The current guys are shooting for ~8x increase in strength over today's strongest materials. That is due (largely, IIRC) to limitations in current lift systems (i.e. chemical) and maintenance requirements.

If we deployed gas core nuclear lift, everything changes.

Re:Mod parent up.

[StrategicIrony]

Didn't I read somewhere that a steel cable would be like 50 miles in diameter at the base in order to support it's own weight, when tapered.

Bubble gum? Your elevator would have more gravity than the earth, making it hard to establish escape velocity... in fact.. i can't even picture a Jupiter sized wad of bubble gum stuck to the side of the earth. :-)

Re:Mod parent up.

[MrKaos]

Its all about the cable.

No it isn't. It's about the impetus to do it. Once there was an impetus to go to the moon we got there in less than 10 years, not because it was easy - but because it was hard.

Re:Mod parent up.

[eabrek]

Possibly. Steel is commonly used because it is cheap and effective (for terrestrial use). For a space elevator, lighter is almost always better (think kevlar, teflon, strong plastics).

See the tether competition (another $2mil available from NASA) for where things are going (using materials containing nanotubes). The Spaceward guys are very positive about the effects this challenge are having on research.

I'm not saying the elevator is going to be built tomorrow, but it is doable. We will be a little late on providing sufficient lift capacity to launch all lawyers into the sun.

Re:Mod parent up.

[PMBjornerud]

Except that the machine would take 3 years of dedicated design time and the cable is likely 50-80 years in the future, to be honest.

And if they had postponed the machine, some people would argue the energy transfer to the machine might be impossible and thus there is no point building a cable.

You do both.

When one project completes, that's one less thing to worry about. Cable research will only benefit from knowing that everything else is proven technology, all that remains is the cable. All the easier to get funding for the "hard" project.

Carbon Nanotubes anyone.

[Anonymous Coward]

Thats the stuff that these cables will be made off

Realigning

[Ksevio]

I wonder how fast this is at realigning the laser to aim at the elevator. You wouldn't want a gust of wind to push it a few feet to the side and have the laser give the helicopter cancer.

Re:Realigning

[ubercam]

That would be terrible! Imagine having to get tumors removed from the rotors or putting the chemotherapy additives into the poor thing's fuel tank... Sure it would probably be able to fly for a bit, but it would probably crash and start puking up oil everywhere. Awful stuff.

Re:Realigning

[nschubach]

Poor Helicopter. If only the cost of treatment wasn't so high. I wonder if it has insurance.

Could the ribbon conduct electricity?

[Anonymous Coward]

I am not an engineer,so I have a stupid question. Why not use the ribbon as an electricity conduit? The electrical field might send the rover into the future?

Re:Could the ribbon conduct electricity?

[Dan Ost]

I think the real issue is that if the ribbon is made of a conductor, then the currents created in the ribbon as it sways though Earth's magnetic field will damage the system (the ribbon, climber, and/or anchors).

Re:shouldn't they be able to design the cable also

[Anonymous Coward]

You mean of course designing a cool hat to be worn while using anti-gravity belt that could be invented when we understand and are able to control gravity.

I would really really REALLY like to know how they are going to deploy the fracking tether, won't we need a spaceship like the B.S. Galactica for that?

Please could anyone shed some light on this, ideas? So far no-one has even mentioned this.

Now if only..

[nightfire-unique]

..we had some great engineers to rush this projects. :)

Re:Now if only..

[FauxPasIII]

Eh, just convert all the hammer-producing cities to Wealth and then switch civics to Universal Suffrage. We'll be there in no time!

Quick Progress

[PingPongBoy]

At the rate of this progress, the space elevator will be in place well before OBL is located. Well done.

Re:Quick Progress

[Benzido]

OBL is most likely dead. So you are most likely right.

Re:Quick Progress

[ubercam]

Well at least it'll be finished before Duke Nukem Forever!

Is there a plan for equipment failure?

[PSaltyDS]

Is there an obvious plan for the crawler failing half way up the cable? In this test you just set it down with the chopper, but what do you do half way to geosync orbit?

I guess a second crawler has to go up underneath the failed one, trigger some kind of mechanical release and carry its dead weight down.

Re:Is there a plan for equipment failure?

[John Hasler]

> Is there an obvious plan for the crawler failing half way up the cable?

Yes. The passengers rappel down.

Re:Is there a plan for equipment failure?

[Dudibob]

half way between the Earth and the Moon!? ha I'm wondering what would happen if the cable somehow snapped when the elavator was in space?

Re:Is there a plan for equipment failure?

[natehoy]

You'd employ exactly the same technology you'd use to lower the empty elevator car normally. Probably turn the electric motor into a regenerative brake and beam the power back to Earth for storage to use on the next mission, or something.

Re:Is there a plan for equipment failure?

[John Hasler]

> half way between the Earth and the Moon!?

No. Only about a tenth of the way.

> I'm wondering what would happen if the cable somehow snapped when the
> elavator was in space?

It would either go up or down.

Re:Is there a plan for equipment failure?

[nschubach]

Escape pods with parachutes. Damn, where's my patent money on that.

Re:Is there a plan for equipment failure?

[falconwolf]

half way between the Earth and the Moon!? ha I'm wondering what would happen if the cable somehow snapped when the elavator was in space?

The same thing that happens when you're kicked in the balls while on the asteroid.

Falcon

Solar power eh?

[Anonymous Coward]

Outside of the fact that we can't effectively design the cable, how high would the cable be placed out in to space?

If it is out far enough, it could probably use the sun directly for power.

If not, how much power would be required to carry up your average weight to geosync and how reliable are long-term batteries?
How well do flywheels work in space?

Re:Solar power eh?

[khallow]

Outside of the fact that we can't effectively design the cable, how high would the cable be placed out in to space?

The counterweight has to be beyond geostationary orbit. So at least 25k miles. Plus the whole assembly will be dragged along by the part connected to Earth so it's not going straight out to geostationary. I've heard something like 60k miles.

Re:Solar power eh?

[tsotha]

Plus the whole assembly will be dragged along by the part connected to Earth so it's not going straight out to geostationary. I've heard something like 60k miles.

lol no. The whole point of putting the top anchor into geostationary orbit is so it hangs directly overhead without putting stress on the cable. It might be a tiny bit higher to balance out the mass of the cable, but we're just talking a few kilometers here.

Re:Solar power eh?

[Hadlock]

Yeah but geostationary orbit is closer to 26,199 miles. If you drop stuff off there, it's already floating in geosync orbit. If you climb up to 60k anything you unload there is going to drift away from earth at a pretty steady rate. Now there might be an argument for deploying another cable on the far side of the tethering rock to help "climb" to a higher altitude to launch an interplanetary mission, but there's no reason you cant drop your cargo off at any point along the cable, including geosync orbit.

Re:Solar power eh?

[khallow]

lol no. The whole point of putting the top anchor into geostationary orbit is so it hangs directly overhead without putting stress on the cable.

The counterweight has to be beyond GSO or it won't be stable.

Re:Solar power eh?

[falconwolf]

The whole point of putting the top anchor into geostationary orbit is so it hangs directly overhead without putting stress on the cable.

The upper or space end has to go beyond geostationary orbit. The dock or platform would be in geostationary orbit but a counterweight has to go considerable farther than that.

Falcon

ALmost solved the

[geekoid]

least difficult problem. Now when all the magic technology rolls out we will be good to go!

Space elevator is this centuries flying car.

Re:ALmost solved the

[4D6963]

Dude's got a point. Yeah, wow, they developed something that's basically a bunch of wheels around a rope powered by solar panels. The cool and novel thing here is the power transmission by laser thing, but the machine itself is something NASA could develop in no fucking time if it wanted to. And there's no scaling problem for that thing, if it can climb at ground level it can climb 80 km above. It's just a goddamn elevator, only powered by a light beam. The entire problem is the cable.

dumb questions

[zogger]

These are probably really dumb, but what the heck..

This theoretical tether eventually...they can't run the power up from the ground inside the tether, or maybe down from the geosynch anchor point that has some huge solar power array? Why does the power have to be beamed to the traveling module? Ya, I realize it is a huge distance, but seeing as how they are considering some carbon nanotube structure for the tether, and carbon nanotubes (some) can transmit electricity very efficiently as well (1,000 times better than copper according to some wiki thing I just read)...

And with that said, to counteract that, how the heck are they going to avoid lightning and static electricity and so on on *any* tether? Won't this aspect imperil any construction and use of this for a space elevator, has this been theoretically solved yet, or is it even a problem? (yes, this is all googleable, I would rather get a clear short synopsis from folks who know about this better)

Re:dumb questions

[Anonymous Coward]

I would rather get a clear short synopsis from folks who know about this better)

There are no dumb questions on inquisitive idiots.

So you are on slashdot so all you'll get is someone "summarizing" a wikipedia article(which was probably written by someone who googled and found a slashdot question)

Re:dumb questions

[bill_mcgonigle]

People have proposed building merely tall (a few miles) towers to generate electricity. Given an elevator-sized structure, you'd think the static charge ought to be great enough to power the vehicle.

Re:dumb questions

[natehoy]

Well, I'm not a scientist but several obvious ones come to mind.

For starters, you are going to have resistance greater than air through all but superconductive materials. Second, you're going to have trouble grounding it unless you have two cables, then you're going to need to keep the cables separated or shield them which means two discrete materials. Third, you'll have the issue of voltage surges through (as you've stated in your post) lightning strikes, static electricity, etc - very bad for electric motors.

Plus, they haven't sorted the cable part yet. The power problem is trivial compared to the cable, so the ideal here would be to free the cable designers of as many requirements as possible. "Strong enough to hold a crapload of miles of its own weight PLUS a payload and manage the various issues like wind, long-term exposure to UV/sunlight, rain, errant airliners, and vacuum long-term" is already a tall order beyond our technological limits by a pretty ridiculous margin at the moment. It's probably best not to limit the possible solutions to "also has to be a superconductor with separately superconducting ground line" if we can solve the power problem another way and just let the cable geniuses focus on the "supports its own weight, etc" problem.

Maybe someone will come up with a shielded carbon nanotube superconductor that also happens to be incredibly strong.

At that point, all this time spent on power transmission still has other applications anyway, so it's not really wasted.

Re:dumb questions

[John Hasler]

Even if there was enough "static" to supply power less than .04% of the elevator will be in the atmosphere.

Re:dumb questions

[John Hasler]

Weather is hardly an issue when less that .04% of it will be in the atmosphere.

Re:dumb questions

[sexconker]

Not dumb questions.
It's retarded that they want to beam power to it when they can literally run a wire up the structure itself.

Re:dumb questions

[natehoy]

That 0.04% still represents a good chunk of distance to be covered. A fall is still fatal even if only the lower 0.0001% of the cable fails due to weather.

Now, maybe they'll have a different material near the bottom, one that is more weather-proof where the stuff further up is more radiation-proof. But you've still got to solve for the WHOLE cable. 99.96% of a complete cable is precisely as useful as 0%

Re:dumb questions

[EvanED]

That 0.04% still represents a good chunk of distance to be covered. A fall is still fatal even if only the lower 0.0001% of the cable fails due to weather.

The nice thing is that any capsules that are going up the hypothetical elevator are likely to be able to deploy parachutes without much problem. Sure, the 'chutes will hit the same weather as what hit the cable, but presumably they wouldn't deploy a mission if there was weather that looked like it'd cause a problem around.

Re:dumb questions

[natehoy]

OK, then how do we attach a new end to the cable?

My mention of "weather" as one of the obstacles to overcome had more to do with the parameters you need to solve to design a cable. If getting a cable wet a few hundred times a year is going to cause a problem with the chosen material, then you'd best not plan the first 100,000 feet or so of it with that material. My point was that removing the requirement of superconductivity made the rest of the problems easier to work with, though still FAR beyond material science as we know it today.

And, yes, there are also issues with "weather" in terms of wind/rain/etc causing stresses on the climbing module (elevator car) as well. Those risks can be mitigated, as you say, by simply not using the elevator on bad days. But the cable's gonna be hanging out there 24/7 for hopefully a VERY long time.

Re:dumb questions

[bill_mcgonigle]

Even if there was enough "static" to supply power less than .04% of the elevator will be in the atmosphere.

True, I don't know what the energy requirements are either. There were folks talking about putting up 3 mile tall conducting towers (in Australia maybe?) and it was claimed that they could generate enough power for thousands of homes each. But, that might as well be dog-heat per furlongs for all I know about lifting up a space elevator.

Re:dumb questions

[John Hasler]

> OK, then how do we attach a new end to the cable?

You lower more cable down from above.

Re:dumb questions

[Iron Condor]

And with that said, to counteract that, how the heck are they going to avoid lightning and static electricity and so on on *any* tether?

Forget about static or lightining: any such tether is going to short the ionosphere against ground. Good luck with that.

Oh, and then it's going to electromagnetically connect Earth's magnetic field (i.e. the geodynamo) with the magetotail (i.e. the solar wind, which is a pretty long lever arm pointing always away from the sun). Watch Earth's rotational energy being dissipated in form of electric current through your tether. Fun.

Oh, and of course there's never going to be an accident of any sort or even a terrorist attack that might blow up your tether anywhere, raining kilotons of tether material onto the earth (it doesn't really matter what you propose making it from; if a ton of it lands on your head, you're dead).

Oh, and feel free to integrate two vee cross omega along a 180000km climb straight up.

Oh, and bring something to read for the three months ride.

And remind me: you're getting this into orbit how, again?

Re:dumb questions

[falconwolf]

Not dumb questions.
It's retarded that they want to beam power to it when they can literally run a wire up the structure itself.

And how heavy will this wire be? Can a wire 50 miles long, forget the 23,000 miles to geostationary orbit, be able to hang without breaking? A few solar panels under the crawler will weigh a lot less than a cable. Of course that changes if carbon nanotubes are used. But you still have problem with stuff like static electricity.

LaserMotive, the company that made the laser isn't even into space travel. They are working on a method to transmit energy wirelessly for those areas where it is impractical to lay cables. If they can transmit energy for a space elevator their technology should be able to be used elsewhere.

Falcon

Re:dumb questions

[sexconker]

Make the conduit part of the structure.
Not the whole structure.

What problem with static electricity?

Re:dumb questions

[falconwolf]

Make the conduit part of the structure.

It still has to support it's own weight, unless you're going to make the whole thing larger increasing the weight even more.

What problem with static electricity?

Have you even seen what lightening, yes static electricity, can do? I was sitting in the bed of a pickup truck once when lightening hit a tree on the side of the road just as we were passing by. We just got a gleams of it then but we went back later and the tree was split. I wouldn't have wanted to be under it.

Falcon

Re:dumb questions

[sexconker]

Airplanes fly and get hit by lightning all the time.
It's not an issue.

You make the conduit part of the structure.
They can make conductive and non conductive carbon nanotubes you know.

Re:dumb questions

[falconwolf]

Airplanes fly and get hit by lightning all the time.

Airplanes are not grounded except when they are on the ground too. A space elevator would have to be grounded. Also lightning is suspected in the crash of an Air France flight from Brazil to France. 228 people are dead from that.

They can make conductive and non conductive carbon nanotubes you know.

Do you have a reference for this? Next, how big would it have to be to conduct enough electricity? And what would it's weight/strength ratio be?

A conductor long enough to stretch from the ground to geostationary orbit is also long enough to conduct ionized energy from the ionosphere and magnetosphere to the ground as well.

Falcon

Re:dumb questions

[sexconker]

Lightning won't be a fucking issue.

No I don't have a reference, go look one up yourself.
To answer you: Not very big, and similar weight/strength properties as compared the rest of the structure.

Spewing babble from Wikipedia like that just proves how little you know.

Re:dumb questions

[falconwolf]

Lightning won't be a fucking issue.

What is your qualification to make that statement?

No I don't have a reference, go look one up yourself.

You're the one making statements as fact, if you want to convince people you have to provide3 evidence to back up your position. Just saying "go look it up yourself" shows either you have no intension of convincing others or you're talking shit, trolling.

Spewing babble from Wikipedia like that just proves how little you know.

Trolling

Falcon

Re:dumb questions

[sexconker]

I'm making statements as fact, yes.
But it is not up to me to prove them.

It's up to you to KNOW these same facts in order to maintain any semblance of discourse on the subject.
If you don't know them, learn.
If you don't believe them, then challenge them with evidence.

Asking for references is the internet equivalent of a 5-year old saying "Oh yeah? Prove it!".

Re:dumb questions

[falconwolf]

If you don't believe them, then challenge them with evidence.

I did challenge it but you ignored the challenge. Perhaps because you can't prove it's safe and want to keep spewing garbage.

Falcon

Next time, check the dictionary before posting.

[Kupfernigk]

If you care to investigate you will find that (according to Merriam-Webster among others) soluble has both meanings. If you knew any Latin - and you obviously don't, despite referring to nitric acid as aqua fortis - you would know that u and v in Latin are interchangeable, and that soluble and solvable are from exactly the same root. While I'm exposing your linguistic inadequacies, I should perhaps explain further that the Latin root means to "loosen", and so is applicable both to loosening the bonds of a solid in a liquid, and loosening a "knotty" problem.

Re:Next time, check the dictionary before posting.

[Anonymous Coward]

how about "loosening" your tight ass

Re:Next time, check the dictionary before posting.

[edumacator]

Did someone pee in your Corn Flakes this morning?

I really think it was meant as a tongue-in-cheek remark. Maybe it will help to know, even if there wasn't an alternate, if somewhat archaic, definition, no one with half a brain would really question your intelligence, unless in jest.

Re:Next time, check the dictionary before posting.

[Gilmoure]

A lot of times, Americans require a "sarcasm" tag so that they know their panties should not be in a wad.

Re:Next time, check the dictionary before posting.

[MrKaos]

If you knew any Latin

A Latin grammar Nazi - I guess there's one in every language.

Re: a laser capable of delivering 400 watts

[MRe_nl]

Surgeon General's Warning:
Don't look down with remaining eye.

Re: a laser capable of delivering 400 watts

[natehoy]

True, if I were the helicopter pilot I'd want to be wearing some good sunglasses just in case. ;)

Re:shouldn't they be able to design the cable also

[khallow]

Nobody is able to design the cable. We simply don't have the technology, which is why they're focusing on the climber instead.

This is a bit like having a contest to design a cool hat to be worn while using an anti-gravity belt. If someone wins the contest, then we are one step closer to being able to float while wearing a cool hat - all that's left is the bit with the belt.

This is an inappropriate metaphor for two reasons. First, the crawler is an integral part of the system. It's not a "cool hat", but part of the belt. Second, it is something we can attain. We don't have the technology yet for an Earth to orbit system (though current technology is good enough for a lunar system), but we know enough that we can design the system even if we can't yet make the materials that we'd build the elevator out of.

Re:shouldn't they be able to design the cable also

[bobbuck]

Even if they could make the cable how are they going to dampen swings and bounces? In space there's no air to dampen the motion and there's no nowhere for the accumulating energy to go except to make the anchor bounce and sway more and more. The bad part is that the more it swings the higher the gravity will be. Does anyone remember riding the rotating sail-swing ride at the amusement park? It'd be like that but instead of your 150 lb best friend pulling on the cables it'll be ton of potential satellite trying to get up to orbital velocity. The good news is that the period of a 17000 mile pendulum might give you enough time to evacuate.

Human qualified?

[petes_PoV]

So when this thing gets scaled up for carrying passengers, just how powerful a laser will it need.

Personally I'd be very wary of traveling in what's basically a lift (american: elevator) with a honkin' great laser firing at the capsule.

Re:Human qualified?

[natehoy]

Compared to riding into space on a rocket? I'll take "giant laser" for 10,000,000,000, Alex.

Re:Human qualified?

[malakai]

The idea isn't to use laser power solely. The laser climber is for the early work when there's a very thin cable connecting the two points. Slowly, after year(s) of trips, the cable would be reinforced with more cables. Each new cable increases the tether capacity and allows a larger climber. Eventually lasers are ditched and the bigger climbers rely on other on board energy sources.

Re:Human qualified?

[petes_PoV]

Fair point, so basically the choice comes down to possibly being blown up by the rocket, or fried by the laser. Luckily the third option (i.e. none of the above) is the default.

Re:Human qualified?

[natehoy]

If you're lucky, you'll live 100 years. Almost 100% of the population will die without experiencing weightlessness, or seeing Earth from orbit.

Once I get my daughter through school and all my earthly obligations are pretty much met, if the opportunity arises to do that in person, I'm all over it.

Of course, by then I wouldn't be able to tolerate a rocket ride, but as long as they've got a bathroom in the elevator, dude, I'm there.

I'd put a speaker on my front door so I can look through a telescope down at my house and REMOTELY yell at the kids to get off my lawn. That's be a first.

Re:Human qualified?

[4D6963]

Right now we can't even make the damn tether, let alone carry anything of any weight using it.

Re:shouldn't they be able to design the cable also

[Anonymous Coward]

Lets build a 100 km pyramid instead, there's plenty of room in sahara, and it seems someone already began over 4000 years ago so we've got a head start.

What a waste of time

[ShooterNeo]

A (practical) space elevator is NEVER, EVER going to be built. With any advances in technology.

Why is that? It's simple.

A space elevator, even if the cable could be made, has a ridiculous design flaw. Literally, a single failure anywhere in the cable, and there goes billions and billions worth of hardware. It is always teetering on the verge of catastrophic failure. (imagine what will happen to the station at the top of the cable)

Further, you can only launch one climber at a time, which has to slowly crawl to the top, taking hours to days.

There's a much better launch method, that has been around for years. Instead of building just enough laser to power a climber, why not build 1000 times as many lasers and beam up enough energy to get into orbit in about 10 minutes?

The spacecraft would just be an inert block of propellant and some stabilizing fins and gyros. The intense light would vaporize the propellant block in sections, and the pulses would be timed to give planar shockwaves. Presto, a high ISP engine with no nozzles or complex flight hardware needed. Laser modules stay on the ground, run on electricity. Could make another launch every 10 minutes or so. Look at the old laser launch usenet posts archived on google, where some NASA PhDs discuss the idea.

Re:What a waste of time

[Wolvenhaven]

You are thinking of a vehicle which completely wraps itself around the cable, why not a space elevator which has several dozen cars moving on it at all times by having multiple "rails" and sending vehicles behind each other like our current train system. When a vehicle gets to the top or the bottom it is disconnected and moved out of the way for loading/unloading. Even two "rails" would allow for a circuit transfer while having 6+ would mean a constant flow of travel.

Re:What a waste of time

[tsotha]

A space elevator, even if the cable could be made, has a ridiculous design flaw. Literally, a single failure anywhere in the cable, and there goes billions and billions worth of hardware. It is always teetering on the verge of catastrophic failure. (imagine what will happen to the station at the top of the cable)

Once you have one cable up adding more is comparatively easy. The loss of a single cable wouldn't be catastrophic.

Re:What a waste of time

[KonoWatakushi]

You seem to be rather ignorant of the idea, and all of your concerns are addressed directly in Edwards' book, The Space Elevator.

A single climber on a single cable is the first step, as it is most cost effective to launch. Once it is up, the first priority is widening the ribbon, and producing more ribbons. Once they are in place, loss of any single ribbon would be not be very significant, as the ribbon itself is cheap, and deploying it is now cheap.

Next, the goal was always to run multiple climbers up the ribbon, in a single direction, as that makes best use of the ribbons capacity. For climbers spaced along the ribbon, the force of gravity is greatly reduced the further up you go, so you can fit considerably more on the ribbon as compared to a single heavy climber. Still, you have the option of clearing the ribbon and sending up very heavy items, it would just cost more.

Anything else you can think of has also likely been addressed in that book, from technology to economics.

Re:What a waste of time

[ShooterNeo]

Nope, won't work. The limitation on a space elevator cable is that if the mass of the car(s) is too much, the cable will snap. No matter what you build it out of, it's always going to be teetering on the edge of tearing itself apart from it's own weight alone.

Economically, it's a bad investment. All that cable has to exist just to get one or two lightweight cars up. If you want to carry more cars, you gotta back the cable lots thicker. Your costs right proportionally.

Re:What a waste of time

[ShooterNeo]

Go check your physics book. The force of gravity isn't reduced much.

Anyways, go read an article on laser launch. We can build the laser modules now, using ultra cheap LED pumped doped fiber optic lasers. A few billion bucks, and we'd have a launch system that could launch a small satellite dozens of times a day. 100 billion or so, and we could launch 10 space shuttle loads a day or more.

I don't really care about the details of the space elevator : it has too many problems, and is a non starter. It's friggin obvious that :

1. If enough of the ribbons snap at any one point, the whole project is lost
2. You have to manufacture every part of the cable to extreme tolerances, and if you mess up at any point, you lose it all
3. Capacity : no matter what, an enormous amount of expensive ribbon is going to be tied up and needed for every climber you have climbing.

With laser launch modules, you can build 10% more laser modules than you need, and if they fail during a launch, you lose nothing.

Re:What a waste of time

[KonoWatakushi]

I have a degree in physics, maybe you should go check your book. The force of gravity varies as 1/r^2, so the vast majority of the ribbon is not at all deep in the potential well.

If that is difficult to understand, here is an example, straight from the book on page 167: you can have 24 50 ton climbers spaced along a 200 ton capacity ribbon. They even developed a formula for it: "Within an upper limit of 1/3 of the ribbons capacity, the maximum number of climbers is 6C/M, where C is the ribbon capacity, and M is the mass of the proposed climber."

As for your three points:

1. The ribbons are not expected to fail often. It will happen eventually, but it just won't be a big deal.
2. That is not an insurmountable engineering problem, and depending on where they break, you may not even lose the whole thing.
3. It is not enormous, nor expensive; the first 200 ton ribbon discussed masses 8,900 tons, and is expected to cost $5B. (For perspective, the Sears Tower weighs in at 222,500 tons, and the Golden Gate Bridge at 419,800 tons.)

It is "friggin obvious" that it will happen at some point, it is only a matter of when. The necessary materials may be difficult or impossible to produce with current methods, but once molecular nanotechnology arrives, they will be both manufacturable, and extremely cheap, without question.

For comparison, the first ribbon (20 ton capacity) is estimated at ~$6B. While I won't discourage you from advocating laser propulsion in the near term, the capacity and economics will never allow for large scale manned space operations. It is not and will never be a replacement for the space elevator,

Re:What a waste of time

[falconwolf]

A space elevator, even if the cable could be made, has a ridiculous design flaw. Literally, a single failure anywhere in the cable, and there goes billions and billions worth of hardware. It is always teetering on the verge of catastrophic failure. (imagine what will happen to the station at the top of the cable)

Like catastrophes have never happened with a Space Shuttle. Oops, it has twice, with the Space Shuttle Challenger and the Space Shuttle Columbia.

Falcon

Re:What a waste of time

[ShooterNeo]

Yes, but this is more like losing all of Cape Canaveral and Houston whenever a bolt breaks in a Space Shuttle during liftoff.

Re:What a waste of time

[ShooterNeo]

Well, my degree is engineering, and I am going to simplify my argument for you to understand it.

See, the reason the Space Shuttle and aerospace operations in general is so darn expensive is because rockets are very large, complex assemblies of hardware whereby if a small number of failures occur, you lose the entire mission. You have to design and build a rocket to handle the enormous amounts of vibration and G-forces of launch, yet every ounce you add reduces payload because chemical rockets have such low ISP. This permeates to every aspect of design. Then, during manufacturing, you have to have ridiculous levels of quality control, with every assembly step taking place in a clean room. You have to use the most expensive available materials, such as titaniums and carbon fiber and stainless steel, because the cheaper materials are too weak and weigh too much. The whole endeavor becomes ridiculously complex, with enough paperwork to make Communist Russia proud.

A space elevator still fundamentally has the same constraint. Every bit of elevator cable has to be made in a similar clean room, paperwork happy environment. Every mission has to be done as carefully as a space shuttle mission, with many missions dedicated just to conducting yet another inspection of the cable. Every bit of weight you add to the cable as you are building it (whether that weight be for safety systems or whatnot) reduces the cargo capacity, yet making the cable lighter makes it more expensive and unsafe.

You've basically solved nothing by going with a space elevator, and cost estimates in that book you read are probably off by at least an order of magnitude.

Remember, it only costs a bit over a million dollars (I'll find the exact number if you like) to fuel the space shuttle. All the rest goes to costs like I mentioned above.

With laser launch, all the important hardware (the lasers and mirrors) stays on the ground. It can weigh any arbitrary amount, and be built to whatever shoddy standard you want. It only has to work well enough such that enough lasing modules are online during an entire launch. You can mass produce the modules in China, and you don't need to have paperwork tracking the fate of every last bolt going into a laser module : because if the module fails, it's not going to compromise the mission. (unless a LOT of modules all were to all fail at once)

Rather than a thousands of miles long cable, you have a big campus of buildings spread across many square miles. Nothing short of a megaton range nuke is going to take out your ability to launch spacecraft.

The spacecraft itself will not fail if you don't make it in a clean room. It's just a bolt of inert metal strapped to a radio beacon. You don't actually even need the beacon to work. The payload can be anything you want, and once laser launches are in full swing, spacecraft and satellites will be made to much lower, mass production standards since if the spacecraft fails while in orbit, you don't lose as much money as you would today. Even manned missions will rely on redundancy much more than high quality hardware, since it's cheaper to launch everything and the kitchen sink than it is to make your manned space habitat to the exacting standards of today.

A comparable anology is to compare the cost of computing when google does it versus the mainframes of the 1960s.

I look forward to your rational as to why laser launch "It is not and will never be a replacement for the space elevator"

Seems like you could get a lot more cargo up into space if you are launching 200 tons every 10 minutes (a full scale laser launcher with as much light output as the space shuttle main engines) than 200 tons every few days.

Re:What a waste of time

[falconwolf]

Yes, but this is more like losing all of Cape Canaveral and Houston whenever a bolt breaks in a Space Shuttle during liftoff.

If Challenger has blown up a minute earlier than it did you may of seen Kennedy seriously damaged. That's right a minute. Instead of blowing up on the pad or withing seconds of launch where it could cause damage, it blew up 73 seconds after liftoff.

I recall that day, I went to class late to watch the launch, being in Orlando as long as the eastern view wasn't blocked we had good views of launches from the Cape. A minute after it went up those of us watching had an unusual sight, a split into a "Y". A bunch of us ran back inside to see what they were saying on TV, about how it exploded. After watching the news for a few minutes a couple of use went to our class, in physics, to announce what happened. What made some in the class angry was when the professor said it would be on TV all day so we should get back to the class subject. If what happened didn't have to do with physics then what did it have to do with? Another physics professor I had would have worked it into the class, perhaps by asking for theories of what went wrong, if there was a physics problem.

Falcon

Re:What a waste of time

[KonoWatakushi]

Comparing the complexity of the space shuttle to a space elevator is seriously disingenuous. The shuttle is perhaps the single most complex device created by mankind, and entails enormous maintenance efforts, as would your proposed scheme.

The elevator, well, is a cable, with a relatively modest support infrastructure. It is extremely simple, and economies of scale provide immense advantages. Manufacturing tolerances are just another specification, and it isn't like the cable needs to be defect free. (It is made from numerous strands, each from numerous nanotubes, neither of which need to be particularly long.)

Even if laser propulsion is super efficient, it is still basically a rocket, which must be powered from the ground. An enormous infrastructure is required to provide that power. The numbers I have seen for the Isp are on the order of 1000s, so it isn't as if it is a free ride.

The key point, is that a rocket still has to supply the entire delta-V to reach orbit and beyond. That kinetic energy, with the v^2 term, is huge just to get to orbit--to say nothing of other destinations. For an elevator, you only need to supply the change in potential energy--the momentum comes from the earth itself. (Plus a small correction for orbit insertion, but that is insignificant.) For a trip to Mars or Jupiter, you just get off the ribbon at a greater altitude. It's nearly free.

You are dismissing the space elevator out of hand, without even reading about it, and proposing another scheme. At the very least, I think you should provide more information. 200 tons every 10 minutes sounds great; at what cost? For reference, the SSMEs output about 28GW. Even assuming 100% efficiency, you are talking about utilizing the full capacity of dozens of nuclear power plants.

Re:What a waste of time

[ShooterNeo]

A few comments :

Again, if you add up the cost of the electricity, it isn't much. A few tens of dollars per kilogram. I'll do an exact calc if you really care. Efficiency is about 10%, so you can calculate it yourself. Energy isn't the driving cost, and the improved ISP means that you don't need as much of it. You wouldn't need 28 GW. (space shuttle ISP is a mere 363, so actually an ISP of "only" a few thousand is a MASSIVE improvement)

I disagree with you 100% on the idea of the cable being "simple". Remember, this puppy is made of carbon nanotubes that don't even exist on the macroscale yet. ANY section of the 29,000 mile long cable that is "bad" due to a messup in manufacturing, and you lose ALL of it. THAT's why the space shuttle is so damn expensive : it has thousands of onboard systems, and in theory a failure in just one or two of them and you lose the orbiter. You're basically spreading your engineering problem out over 29,000 miles of a cable made of a material that does not exist yet and has to be made to incredible tolerances or it comes apart. I would venture that is no less of a problem than trying to maintain the space shuttle, which ultimately IS just a really really complex aircraft/rocket hybrid.

While with the lasers, you would have several thousand modular laser systems. If a few HUNDRED of them fail, at worst the rocket slowly begins to descend and you activate your escape module if it's a manned mission. AT the end of the disaster, you still have your laser array. If the cable snaps, you lose everything.

Anyways, as an engineer, I prefer real solutions that you can design today. Do you know how the laser launch people do research today on the costs? They call up the parts suppliers for the lasers and the mirrors and ask for a quote. You can buy everything you need TODAY. No super materials needed.

Anyways, you wouldn't build your launcher for 200 tons every 10 minutes. I'm just pointing out a point you could reasonably scale to once space industry and travel became common. For a long time, you'd do your launches with something like 2 tons every 10 minutes. That's plenty for most satellites. Bigger satellites would be launches in several modular pieces that would dock with each other once in orbit. Hab modules for a space station could be inflatable. Astronauts would have to go up 1 at at time.

Even 2 tons every 10 minutes is more than enough capacity for dreamed about projects like an array of mirrors to reduce incident light to the earth and thereby control global temperatures. (and, with enough ability to maneuver the mirrors, you could potentially control a hurricane by casting a big shadow over a portion of the storm as it developed)

Huge Scales

[argStyopa]

To give you some idea of the scales involved, even traveling at the targetted 5m/sec speed continuously, it would take the climber nearly 3 MONTHS to get to geosynchronous height of approx 35,000 km.

Re:Huge Scales

[falconwolf]

To give you some idea of the scales involved, even traveling at the targetted 5m/sec speed continuously, it would take the climber nearly 3 MONTHS to get to geosynchronous height of approx 35,000 km.

That speed, 5m/sec, is only the start. Once that goal is met then they plan to work on 10m/sec. Also as the cabin, payload carrier, climbs it loses weight and so can go faster.

Falcon

More info @ SpaceElevatorGames

[blamanj]

Check out the web site for the space elevator competition. It includes videos of climb attempts, and lots of data about what they're trying to accomplish and why.

Retarded

[sexconker]

If we're going to be building a super crazy nano carbon magic tube elevator structure that can actually lift shit into space, then we sure as fuck can strap some copper wiring onto it to you know, deliver power.

Re:Retarded

[MyLongNickName]

Perhaps tens of miles of wiring would be kinda heavy?

Re:Retarded

[sexconker]

Not if they make it out of them fancy nano tubes (they already do) and incorporate it into the structure itself (they already can).

Re:Retarded

[black3d]

The electrical resistance would make this impossible after the first few dozen miles, and this would be tens of thousands of miles long. Providing excess power generation to counteract the resistance would mean huge cables (into the millions of tonnes of copper cable) which could never possibly be lifted into space (without a space elevator, that is ;)).

It is possible to provide some electricity through the carbon nanotubes themselves, but the conversion rate is not great. Solar power would be nice, but would require huge fins which dramatically increase the weight of the climber. Beamed power solves most issues.

IMO tho, nuclear batteries will make this whole debate obsolete. ;)

Re:Retarded

[falconwolf]

It is possible to provide some electricity through the carbon nanotubes themselves, but the conversion rate is not great. Solar power would be nice, but would require huge fins which dramatically increase the weight of the climber. Beamed power solves most issues.

Beam solar power. Some Slashdotters like to talk about satellites beaming solar power to the ground, well why not combine this with the space elevator? Beam power down to a receiving station near the space elevator pad and use it to drive the laser.

IMO tho, nuclear batteries will make this whole debate obsolete. ;)

And where will these batteries be? In the payload carrier, where they take up space and weight? I can see it now, the uproar over nuclear materials, people opposed the launch of Cassini with its nuclear generator.

Falcon

Re:Retarded

[falconwolf]

Not if they make it out of them fancy nano tubes (they already do) and incorporate it into the structure itself (they already can).

And make the whole cable or ribbon conductive? Someone up above mentioned how doing this will electrically connect the atmosphere and space with the ground, like them I wonder what effect this would have. What would lightening do for instance? More than Benjamin Franklin's kite I bet.

Falcon

Re:Retarded

[sexconker]

No, not the whole thing balloon boy, just the conduit.

Re:Retarded

[sexconker]

Uh, nano-scale conductors are much better than you think they are.

Solar panels wouldn't affect the weight of the ascender - you would strap them onto the structure itself at intervals.

5000th floor. Please wait while we recharge the ascender.

Of course nuclear power would solve it.
But nuclear power is viewed as the devil. Can't use that. So let's beam radiation through the atmosphere instead!

And besides - I'm still of the firm belief that space elevators are a fucking joke and we'll never actually do it.

Why Beamed Power?

[Kagato]

Maybe I'm just dense today, but why does the space elevator need to be beam powered? You've got a nono-tube ribbon the elevator is climbing, why can't there be power wires/rails on the sides? It just seems if the ribbon can't take the weight of power transmission lines that cargo is going to be extremely limited amount of cargo this thing can move.

Re:Why Beamed Power?

[mhajicek]

Because the weight of the cargo and vehicle is finite. Adding conductive pathways to the ribbon would increase the weight by a certain amount per unit length, and there's an awfully large number of length units. Grams per meter would add up to a huge weight, plus they would have to be nearly superconductive to be anywhere near efficient.

Re:Why Beamed Power?

[Kagato]

I'll buy the weight issue. Efficiency I'm not so sure about as beamed power isn't exactly efficient...

Re:Why Beamed Power?

[Zarniwoop_Editor]

Surely if the cable was already conductive the issue of mass would be non-existent. I guess it depends on the properties of the magical cable that will make all this work.

Re:Why Beamed Power?

[StrategicIrony]

The weight of a "transmission line" that is a ten thousand miles long is more than the entire annual payload of rocket launches in the world.

I think the payload could still be sufficient.

I'll point out that there are no metals who could even hold their own weight at that length. The cable's own weight would tear itself apart. That's why we're using nanotubes in the first place.

Re:Why Beamed Power?

[Kagato]

Ten Thousand? Isn't the internationally recognized boundary for space 100km (about 62 Miles)? A modern airplane has over 60 miles of wire on it.

Re:Why Beamed Power?

[falconwolf]

Ten Thousand? Isn't the internationally recognized boundary for space 100km (about 62 Miles)? A modern airplane has over 60 miles of wire on it.

International law has nothing to do with how far a space elevator would have to travel. As it is the dock or platform has to be in Geostationary orbit which is 35,786 km (22,236 mi) above the equator. Then a counter balance has to go a lot further.

Falcon

Re:Why Beamed Power?

[StrategicIrony]

The most popular design has the ribbon extending an equal amount above the GEO orbit, meaning 71,000 km of ribbon....

Heavy, heavy, heavy.

Re:Why Beamed Power?

[StrategicIrony]

Noting the reply below addresses the "100 mile" issue... how many Titan V rockets would it take to lift an Airbus into orbit? I'd think it would be at least a few dozen. ;-)

Re:shouldn't they be able to design the cable also

[joe_frisch]

There is an old Russian joke about a lab that is working to turn feces into peanut-butter. When the party official comes by to see how the work is going, the lab director replies "Wonderful - see how well it spreads". The problem with space elevator is the cable - everything else is trivial If a material (like carbon nanotubes) could be made that had the required strength, and was inexpensive enough to produce >10,000 Km of cable, that material could be used to drastically reduce the cost and weight of conventional launch vehicles. The fuel cost for a conventional launch is tiny - $50/Kg, while the total launch cost is ~$10,000/Kg. (this is for real existing launch vehicles) Fuel costs aren't the issue.

Am I the only one

[Wolvenhaven]

who thinks it would be easier to design the system like we design all of our mass transit which uses electricity? By sending the power through a rail and and having the vehicle pick it up that way. Having an array of lasers beaming energy to a vehicle, having it convert it using solar cells, and then turning it into motive power seems overly complex. Energize part of the elevator and use that to power the vehicle, it's a tested and proven method for transportation on the ground and involves a lot less variables and expense.

Re:Am I the only one

[cowdung]

mod parent up..
an interesting question.. maybe the cable can't handle it but adding copper cable segments with electricity? seems simpler than laser power for 60 0000 Km

Re:Am I the only one

[John Hasler]

> who thinks it would be easier to design the system like we design all of our
> mass transit which uses electricity?

No one who has looked at all closely at the problem.

Re:Am I the only one

[PrimaryConsult]

-You are assuming that some sort of frame is being built around this space elevator.
-Third rail electrical systems require substations spaced approximately every 1 mile (for 600 VDC). A more efficient form used in public transportation, 25kv AC on overhead wires, sill requires requires a spacing of every 20 miles. Also, putting the equipment required to convert electrical energy from an easy to transmit form to an easy to use form on the actual elevator would make it quite heavy.
In short, a 'space train' would be even more impractical than an elevator...

Re:Am I the only one

[hypergreatthing]

I guess using a hollow nanotube to send energy through it as well as for structure is too much to ask?

Re:Am I the only one

[stevelinton]

50 thousand miles of conducting rail is (a) heavy and (b) not conducting enough to prevent it losing a lot of energy to resistance. Over long distances sending photons through nice empty space is simpler and more efficient.

Re:Am I the only one

[falconwolf]

Energize part of the elevator and use that to power the vehicle, it's a tested and proven method for transportation on the ground and involves a lot less variables and expense.

Yea, that works perfectly fine on the ground where the cables do not have to bare the weight of 23,000 miles of cable. I bet you couldn't lift one end of a 50 mile long cable up in the air and let the bottom dangle off the ground, it'd snap before it ever got that high. But if you did you'd have a hell of a ground for static electricity like lightening.

Falcon

wired power ?

[Anonymous Coward]

Hey i got a dumb question, why should the elevator work with such laser beam power instead of incorporating in the tether a pair of cables ?

Re:shouldn't they be able to design the cable also

[Anonymous Coward]

George Boole invented a subset of mathematics that, for over 70 years, was apparently useless. Now he has data types named after him.

This is only a problem if...

[Anonymous Coward]

This is only a real problem if the contest were really about space elevators and less about energy beaming technology.

Just think of all the fun weapons a high power energy beam with auto-correcting aiming could create?

I'm English, will that do?

[Kupfernigk]

No conrflakes required. I'm afraid that's an example of the English sense of humour, which doesn't travel well and is why we need to spend so much on our Armed Forces.

Re:I'm English, will that do?

[edumacator]

lol... Touché...God I hope the French reference doesn't set you off...

Re:shouldn't they be able to design the cable also

[Beezlebub33]

Mod parent up: One of the arguments of the Augustine group against a return-to-Moon-first strategy is that we would have to first climb out of the Earth's gravity well, only to go into the Moon gravity well, and then have to climb out of that. If the space elevator would work on the moon (without unobtainium cabling), then it solves a large part of the moon gravity well problem.

In addition, a moon space elevator will not have a number of the serious problems that an earth space elevator would have, in particular flying space junk (though there is some around the moon at this point), hurricane force winds, and terrorists. Don't think for a minute that a space elevator is not a juicy target for some pissed off group that knows how to fly planes.

re: power from space

[eleuthero]

Assuming we want to avoid any kind of problems with changing weather patterns (since we dont really know the implications of beaming massive amounts of power down), as long as we have an 18000 mile long cable, couldnt we just run the power back down the inside of the insulated elevator cable?

CalTrans can't fix an old iron bridge, but..

[Paracelcus]

We want to build an unsupported vertical cable 20,000 miles long capable of not only supporting it's own trillion pound weight but also last forever without maintenance (it could not be repaired) be absolutely foolproof (the consequences of failure would be catastrophic beyond imagining) and have two way traffic (it would not be practical without more than one simultaneous carriage path) with payloads weighing thousands of tons each.

Absolutely, mind-bogglingly stupid!

Re:CalTrans can't fix an old iron bridge, but..

[falconwolf]

We want to build an unsupported vertical cable 20,000 miles long capable of not only supporting it's own trillion pound weight

No, more than twice as long, however the full weight of the mass does not have to be supported.

but also last forever without maintenance (it could not be repaired)

Crawlers could repair it.

be absolutely foolproof (the consequences of failure would be catastrophic beyond imagining)

Falcon

Re:shouldn't they be able to design the cable also

[Hadlock]

Attach it to multiple cables? Eventually the cables' period would sync up, but I think with the length of the cable, the climber would reach the top long before that happened. If you have multiple climbers on the cables, well then the effective length of each cable would be a lot smaller. Either way the period is going to be awful long, and probably easy to calculate when it will affect the climber. It would probably be easiest to just detach the climber from the cable briefly and let it freefall while any major cable turbulence occurs near the climber.

Re:shouldn't they be able to design the cable also

[2obvious4u]

... and high conductivity.

Why are we beaming power via laser when we are riding the lift up a conductive cable? Can't the cable itself transmit the electricity needed to power the elevator?

Not only that but a cable that long would generate enough electricity just by being there to propel the elevator without any external power. What am I missing?

Video, or it didn't happen!

[Hurricane78]

How can they do something that cool, and not make a video of it??

Where's the video??

Re:Video, or it didn't happen!

[blamanj]

http://nextbigfuture.com/2009/11/lasermotive-has-qualified-for-900000.html

Re:Video, or it didn't happen!

[falconwolf]

How can they do something that cool, and not make a video of it??

Where's the video??

Here are some vidoes. Warning that first one may make you dizzy.

Falcon

Re:shouldn't they be able to design the cable also

[Anonymous Coward]

Boron nitride nanotubes and nanomesh. That is all.

Of course not

[Kupfernigk]

I am also a strong supporter of the EU. But I can't help my North London and Oxbridge upbringing, and the accompanying "sense of humour" which consists of taking the piss with as straight a face as possible. So merci pour votre comprehension, mon brave.

Re: power from space

[StrategicIrony]

I believe these cables will be micro-fine carbon nanotube weaves.

I'm not sure they're conductive, but the "strength to weight" ratio requirement for a space elevator tether pretty much rules out "insulation" and such.

In fact, the tether's tensile strength would have to be near the theoretical maximum of covalent bonds... which makes it pretty damn hard to build and maintain.

cable for space elevator

[falconwolf]

as long as we have an 18000 mile long cable

A 18,000 miles long cable isn't nearly long enough for a space elevator as far as I know. The platform or dock would be in geostationatry orbit which is 35,786 km or 22,236 mi above the equator. Then the counterweight would have to be further out.

What I wonder about is how much material would be needed to make a cable, or ribbon, that long. Just think of the volume of material needed for even a cable a foot in diameter. How many Mount Everests would it take?

Falcon

Re:cable for space elevator

[Captain Segfault]

What I wonder about is how much material would be needed to make a cable, or ribbon, that long. Just think of the volume of material needed for even a cable a foot in diameter. How many Mount Everests would it take?

A cable a foot in diameter and 22K mi long would require on the order of a thousandth of a cubic mile, much less than the volume of Mount Everest.

With that said, the trick is that the cable doesn't need to be anywhere near a foot in diameter, at least to start. A seed cable would be small enough that we could plausibly manufacture it on the ground and ship it into orbit.

If you have a material with enough tensile strength it doesn't need to be very thick.

Re:cable for space elevator

[falconwolf]

With that said, the trick is that the cable doesn't need to be anywhere near a foot in diameter, at least to start.

Could a cable of less than a foot in diameter carry the weight of 23,000 miles of cable? I know it wouldn't need to be it's full thickness right away, only enough to bare twice it's own weight as well as a crawler. Then as a crawler goes up it can bring more cable thus thickening it. Successive crawlers can add more and more cabling. That or crawlers can be lifted into orbit along with the cable which then crawls down the cable adding more. Perhaps have crawlers going up and down.

Falcon

Rotovator more feasible than earth to GEO elevator

[Big_Breaker]

It is much more likely that the first tether used to raise payload to orbit will be rotating in a LEO orbit. A hypersonic airplane (or gas cannon for high G tolerant payloads) would lift the payload to high altitudes where it rendezvouses with one end of the tether. This "two stage" to orbit version of the space elevator drastically cuts the engineering requirements of the tether. For a surface to GEO tether we can only speculate about near perfect weaves of carbon nanotubes. With a high altitude rotovator you can use Spectra or Spectra-like polymer cables.

In this case the power beaming would probably come from the counterweight on the opposite end of the tether. The relative position of the payload climber and the beaming station wouldn't change that much but the whole tether system would be rotating relative to the earth. I doubt the beam would be much trouble on the surface of the earth but it might make sense for the beaming system to defocus by the time it reaches earth - IE don't make it a coherent, low divergence laser.

This also means that the energy for the beam has to get to the counterweight somehow. A ballistic launch system like a gas gun would be very helpful in that respect. Most fuels don't might a few hundred Gs, especially not fissionables. A space elevator would be much more convenient but unfortunately we are on a 1g (9.8 m/s^2) planet. If our rock was smaller/less massive it would be much easier!

Re:shouldn't they be able to design the cable also

[Anonymous Coward]

There's a pretty big difference between 100 gigapascals and 6.9 gigapascals. I don't know how much tensile strength is needed for the space elevator cable, but even if I were only reading what you wrote, I could see that even if carbon nanotubes are strong enough in mono-molecular form to get us there, we're still quite far from that theoretical limit when you put a bunch of them together.

Re:shouldn't they be able to design the cable also

[stevelinton]

This one is actually easy. You have powerful computers, you know all the forces acting and you have (in computer terms) plenty of time to react. If you have a few ways of controlling some of the forces, you can work out how to apply them to damp out any oscillations

1. You can do quite a lot by scheduling cargo cleverly -- effectvely moving point masses up and down the cable

2. You can tug on the cable from the ground, the station at GEO or the anchor mass if there is one.

3. You can use high impulse low thrust rockets (ion engines say) powered by the same lasers you use for the climbers to thrust on the cable. They will need refueling occasionally, which uses up a little of your cargo capacity, but not very often

By the way, the same website that describes the competition describes the state of play on cable materials. It's not as bad as some people make out -- carbon nanotubes are strong enough with a significant factor to spare. We have to work out how to stick them together and make fibres and how to stick them together to make a cable, without compromising the strength. All of these are hard problems, but we don't actually need a fundamentally new material at the molecular level.

Curious..

[Taibhsear]

I don't know if this is part of the design or not, I haven't heard anything yet at least... But couldn't they have a laser firing from the ground to hit the platform from the bottom, and another one from space hitting the top of the platform? Thus adding redundancy and you'll only need have the juice to power it. Not to mention since you have one side already in space, I'd imagine the satellite or whatever could harness solar power in higher efficiency. Or just rig the cable to a motor/mechanism that pulls the cable up rather than a laser to tethered platform. I'm not an engineer, so this may be stupid, but figured I'd throw it out there.

cable for space elevator

[falconwolf]

Heavy, heavy, heavy.

There's that, weight, but there's also the amount, volume, needed. I asked in another post how many Mount Everests will it take. One of the things a space elevator may be good for is asteroid mining, but it may take mining asteroids to get the material.

Falcon

OK, then how do we attach a new end to the cable?

[falconwolf]

You lower more cable down from above.

Lowering more cable would be impractical if the cable is tapered, smaller in diameter closer to the ground. If the diameter is the same the whole length how will it hang down without snapping because of the weight it has to hold? Remember the end of the cable at the dock or platform has to bare the weight of 23,000 miles of cable.

Falcon

Re:shouldn't they be able to design the cable also

[dark grep]

Spider silk is strong enough isn't it? I understood something about 3-4 times the tensile strength of steel was needed, and some spider silk can be up the 10 times. Of course, that would lead to its own rather obvious problems. I for one welcome the rule of our new spider overlords. All praise the great one!

Re:shouldn't they be able to design the cable also

[bobbuck]

I hope you're right. I don't want a space elevator anchor landing on my house because someone forgot about tidal forces.

Re:shouldn't they be able to design the cable also

[MrKaos]

Of course, producing enough of the stuff and making the belt out of it is still non-trivial...

What about a NASA competition to produce the stands long enough?

For that matter what about forcing the coal industry to do it, surely the carbon is required to be in a vapor state when manufacturing the CNTs. I guess the only question is would there be enough thermal energy remaining to make the CNTs after the turbines - I mean they *talk* about sequestering carbon. Why not sequester it into something useful?

That is from my virtually non-existent knowledge of making CNTs, btw, but just maybe the coal industry might be able to do something with the massive profits they make from burning coal.

And who knows, if they help build a S.E maybe they could continue to mine coal and use the S.E to throw it at Mars and thicken it's atmosphere, thus they could maintain their relevance. Just sayin...

Re:shouldn't they be able to design the cable also

[MrKaos]

In addition, a moon space elevator will not have a number of the serious problems that an earth space elevator would have,

And a moonstalk can be built with conventional materials allowing us to practice solving the inevitable engineering problems, mass and shielding for space craft etc etc all outside of earths gravity well. So there are many reasons to build a moonstalk first.

Regenerative breaking

[BlueParrot]

Stick rechargeable batteries in climbers and have the ones
going down use regenerative breaking to charge their batteries.

When they meet an ascending climber have them swap batteries.

If you achieve a large efficiency the amount of energy you need
to supply to overcome friction losses should be small and could
probably be compensated for with solar cells or something.

Tell me one thing...

[SharpFang]

They are drawing a goddamned CABLE.
Would it be so much hassle to transfer some electricity through it?

No, not the whole thing balloon boy,

[falconwolf]

just the conduit.

The conduit still has to run the full length rubber whale.

Falcon

Re:No, not the whole thing balloon boy,

[sexconker]

And if it's part of the structure, then there is no difference.

What's your point balloon boy?

||||||
||||||
||||||
etc.

That's a 2D slice of your structure.
The center is conductive.
The outside is not.
It's all similar material, it's all load-bearing.

why a tether? part #1 (due to 503!)

[cdn-programmer]

Building the tether is the issue. I don't know if I believe it can be done. However some things about what they did do make sense.

One can use a dual system as was done in the Space Ship One project: http://www.scaled.com/projects/tierone/

The issue is this. There is a lot of atmosphere near sea level. However one can use a jet in order to get above 2/3 of the atmosphere. One can use a balloon to get much higher than this:

  http://en.wikipedia.org/wiki/Project_Manhigh

In Manhigh they were almost 20 miles up.

The thing is that if we can get high enough then I see little reason why we can't use space based lasers in order to beam power to a ship. The issue is that one has to get enough kinetic energy into the ship in order for it to go into orbit. In space it still has to be a rocket. But along the way it can be a hybrid.

The high cost of attaining orbit is not the high elevation. Its the kinetic energy and the fact that if we want to use rocket fuel then we need to start out with so damn much of it near ground in order to have a small amount left over when we get to orbit.

Most of that fuel is an oxidizer! The atmosphere is full of an oxidizer.

So as I see it - once we gain enough altitude using oxygen from the atmosphere - or a balloon - or a tether from a balloon - or some other system... then if we can get a space based laser system going to supply energy then we should be able to use what little atmosphere is up there as a reaction mass and one should be able to use that to gain orbit.

It would be a pretty expensive system mind you. However it might be worth it. If we can get a cheap enough lift system then maybe we could carry raw materials into space to be processed into say fuel! That has HUGE potential to create an industry worthy of the investments. Mind you we've been able to use nuclear for over 50 years! There are a number of options here.

1) we can use nuclear to split water and then use the hydrogen to combine with carbon to make synthetic fuels.

2) we can just use methane as a source of hydrogen.

3) if we can develop a good enough battery system then we won't need liquid fuels. But if we want use electricity to power our cars then we need to generate it from something. I rather think this comes back to nuclear. But I know many people are optimistic that solar and wind and other emerging technologies can do it.

If we don't want to use nuclear and the other technologies don't pan out then I suppose a workable lift system might do the job.

This still leaves us with the problem that even if we can get into orbit where there are vast amounts of cheap energy... how would be transport it back to earth?

Re:why a tether? part #2 (due to 503!)

[cdn-programmer]

One thing I do worry about is energy availability. When I saw Oil above $145 per barrel I thought Oh No! But for the short term I think we need to head at break neck speeds into synthetics. I'd love to see a lift system like alluded to in the article but I do figure its a long long ways off and at this point little more than a daydream.

So in the mean time I figure we've got to figure out what our real problems are and come up with practical solutions. One problem I see as being a major problem is liquid fuels. But nuclear is a key to solving this problem and we do have reactor designs sitting on the shelf such as the IFR (http://en.wikipedia.org/wiki/Integral_Fast_Reactor) and molten Salt Reactor (http://en.wikipedia.org/wiki/Molten_salt_reactor) and using this we do already have enough uranium mined to provide all the power we need for 6,000 years: http://en.wikipedia.org/wiki/Talk:Integral_Fast_Reactor see fuel efficiency! Quote: "Quite literally only about 0.2% of the starting uranium ends up being burned and of course most of this is the U235 fraction". The point is that newer reactor designs can get 300x to 1000x the mileage from the uranium we mine. And they will burn all the actinides.

The short and curlies is there is no reason for us to be in an energy crisis and ruin our economies. Maybe 100 years from now we'll have a cheap earth to orbit lift system and then we won't need nuclear. In the mean time I don't think a tether will work but it could maybe get us close enough to use another system which we also have not figured out.

Re:shouldn't they be able to design the cable also

[Anonymous Coward]

You don't need unobtanium for Lunar and Martian elevators. Due to the lower gravity well, Easilyobtanium would do you just fine.

Re:shouldn't they be able to design the cable also

[physburn]

They very different problems, the Cable and the Climbing module. I'm not sure that using laser power is the best way to power the lift capsule on a space elevator but it saves carrying a battery or other power sources. The LaserMotive system could just as easierly power an plasma rocket (needs upgrading to the Mega/Gigawatts though), so they not tied to a space elevator system. The cable problem isn't easy apparently carbon nanotech are strong enough but no one can yet make them long enough. The asteriod counterweight needed for a space elevator isn't exactly easy either.

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