LaserMotive Finds Success In Space Elevator Competition 258
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.'"
Professor Myrabo at RPI (Score:5, Interesting)
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.
shouldn't they be able to design the cable also? (Score:4, Interesting)
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? (Score:5, Interesting)
The problem is, I'm sure, soluble, but the technical difficulty should not be underestimated.
Re:They could but there is a problem, (Score:3, Interesting)
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.
dumb questions (Score:2, Interesting)
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)
Next time, check the dictionary before posting. (Score:3, Interesting)
Re:Professor Myrabo at RPI (Score:3, Interesting)
... 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:What a waste of time (Score:2, Interesting)
I'm English, will that do? (Score:3, Interesting)
Re:What a waste of time (Score:3, Interesting)
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 (Score:3, Interesting)
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.