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Feb 23, 2009 06:45 PM | 11
Nearly a decade ago, Leik Myrabo shared with Scientific American readers his vision for the future of space travel: a "LightCraft" pushed out to the stars by a pulsed infrared laser beam from the ground or pulled into space by a laser beamed down from a solar-powered station orbiting Earth. (Read the article here.) Myrabo, an associate professor of engineering physics at Rensselaer Polytechnic Institute in Troy, N.Y., described in his April 1999 article a grand plan for constructing these orbital stations and a beamed-energy craft that could transport passengers out to space.
Ten years—and reportedly 140 test flights using small prototypes—later, he foresees laser flight carrying people around the globe and into space by 2020, Wired.com reported from "Expanding the Vision of Sustainable Mobility," a conference hosted last week by the Art Center College of Design in Pasadena, Calif. For this scenario, ground-based lasers called LightPorts would provide the energy needed to propel the crafts, although Myrabo acknowledges that this won't become viable until more powerful lasers are developed and jet fuel becomes expensive enough to force the aviation industry to search for an alternative.
Skeptics say that LightCraft are severely limited by the power of lasers, the small size of the craft and the tiny amounts of propellant they carry. "The propellant runs out before the LightCraft gets very far," Phil Coyle, a senior adviser to the Center for Defense Information, a Washington, D.C.–based think tank, told Wired.com. "It's sort of like trying to blow a paper airplane across the room with your own breath. You can give it a push with your first puff, but then the paper airplane is too far away and you can't blow enough air to keep it going."
Still, Myrabo appears optimistic: If his laser propulsion system is capable of at least in the short term launching satellites into low Earth orbit, he says, the technology could reduce the cost of orbital flight by a factor of 1,000.
Image © Lightcraft Technologies, Inc.
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11 Comments
Add CommentI think laser power scaling is going to hamper this effort for far more than 10 years. Right now they're pushing less than a kilogram around with 800 J pulses (10 kW CO2 laser). Scaling to a MW class laser is expensive and non-trivial and probably requires going to a solid-state or fiber laser in the long term. Furthermore, the aperture sizes required to keep the beam reasonably well collimated up to LEO are going to be very large and expensive. They'll also necessitate a larger target size, thereby adding mass that doesn't go into the payload. At the powers required, I suspect that thermal blooming and/or atmospheric turbulence are going to make it difficult to keep fluence on the target for any length of time. You're going to have to have adaptive optics and a pretty robust and sophisticated closed-loop tracking system. What's the longest propagation distances that people have done in these test flights? I've only seen 400 ft. or so in the literature horizontal.
Reply | Report Abuse | Link to thisI guess my end point is that while none of these factors are deal breakers, per se, they're going to likely drive the price point up significantly, both for the initial R&D and the ultimate final products. That's hard to justify for only launching nano- or picosats.
I'm afraid I agree with "ultrafastx". Laser beam propulsion is not capable of providing truspace transport even to near earth orbit. Not enough energy to overcome mass/inertia of real size craft, to reach orbit velocity. You would think a person smart enough to do this kind of work would work out flight dynamics first and then work the numbers for the propulsion system. Maybe the information developed will be useful for something else, as most such experiments do.
Reply | Report Abuse | Link to thisMaybe I'm missing something, but 'pulling' a craft towards you using a laser would seem to violate conservation of linear momentum. If the craft gains momentum towards you as a result of being struck by the laser, something else must gain momentum in the opposite direction. The laser can hardly speed up even further, as it is, by definition, already going the speed of light.
Reply | Report Abuse | Link to thisIt's not really important, as you could just push upward with a ground-based laser, but this seemed odd to me.
It's all just fluff. Designed to get people thinking - it worked. Now that you've debunked the theory, come up with something REALLY new....
Reply | Report Abuse | Link to thisTo have a light craft, you need a very lite craft. That is low mass/inertia, low gravitation effects. My 50 years of study of this problem leads me to believe that this can be done with proper EMF ( electro-motive force ) fields. An electric / electronic propulsion system. Gravity and mass/inertia are both results of the 3 dimensional effects of the electro-static-magnetic fields of the atomic structure acting over distance on the Aether (dark matter/dark energy).
Reply | Report Abuse | Link to thisLow mass/inertia, low gravitation effects = lite craft, even if it's not. Although I prefer Maser rather then Laser propulsion as it's simpler in an EMF propulsion system. The question is does anyone want to build such a system?
The technical and quantitative pros and cons of this propulsion system, BTW, are in a chapter of a recent AIAA book "Advanced Propulsion Systems and Technologies. Today to 2020", ed. by A.Accettura and C. Bruno, AIAA, Reston, VA, 2008. Yes, laser power is a problem, but there is classified work done at Northrop-Grumman that gives some hint to what could be a realistic system.
Reply | Report Abuse | Link to thisLeik "The Flake" is STILL peddling his lightcraft? Man, we thought he was insane back in college, and looks like he hasn't lost any of his loony edge. :)
Reply | Report Abuse | Link to thisSure, cool concepts, but still pie in the sky.
Leik Myrabo is a great inventor and scientist, but his light craft concept is a “stone age” technology with no practical use now and in the foreseeable future.
Reply | Report Abuse | Link to thisPresently a new technology is tested and will be patent it this very soon which is at least 175 times more effective than the light craft and uses only 600 w laser on board and can be incorporate on all mode of transportation: spacecraft, satellites, airplane, cars, ships…
In my view Mr. Philip Coyle is correct about the concept (a senior adviser to the Center for Defense Information, a Washington, D.C.–based think tank).
Mr. Myrabo is still thinking “inside the box” and the great inventions are always developed “outside the box” of thinking. In my view he is wasting his talent for invention which may be possible sometimes in a distance future in 200 years or beyond, but not now.
I am also surprise to see so many publications are publishing the article “Are laser-powered spacecraft…”
Gejamesceo at gmail
For those interested in the new invention can requested more info at above address.
In my view laser propulsion has many practical uses, but not using the ideas and principle presented by Leik Myrabo. Can anyone prove me wrong?
I am not an expert in laser propulsion and I do not have a degree in US, but I am going to apply for 5 patents in laser propulsion in US, Asia, EI and possibly in Russia where my ideas for laser propulsion originated in the lab of supersonic jet engines.
well Prof Myrabo has been able to fly something in open air with a vastly inadequate laser (wrong frequency, pulsation, power, etc.) while all the groups in the world (china, Germany, US, Brazil, Japan, etc.) have flown only in a lab, and his first flight was higher than goddard's (which the naysayers at his times said he was going nowhere with about the same arguments i've just read). In this last ten years he has been working on solving the physics problems and transforming them in engineering ones, there are still things to be solved for sure but i feel we are on the verge of a major breakthrough in the way we move things.
Reply | Report Abuse | Link to thisFYI: Myrabo Lightcraft launched vertically thus far has reached its record at 71 m (233 ft) altitude on 10/02/2000. The mass of the vehicle was 50.6 gram and it required approx. 360 laser pulses of 450 Joules each, corresponding to efficiency (work done / energy used) of 0.02%. All this does not mean that laser propulsion is not feasible, this is just the data for a given particular design which, by the way, cannot be "linearly" scaled up to drive a manned module.
Reply | Report Abuse | Link to thisThere is a rule of thumb in laser propulsion: 1 kg of a payload per 1 MW of laser power. For example, the spacecraft Vostok 1 which carried Yuri Gagarin in space has mass of 4,725 kg. In order to lift something of that mass into an orbit one will need ~ 5 GW of laser power. Such laser does not exist today and it will hardly will be built in 11 years from now.
If we will weed out hype from the science, we still can find that there are many other types of application for beamed-energy propulsion, some of which are feasible today, some are worth a development so they will be used within a decade (microthrusters, in-space propulsion, beam-powered aircraft, more). Laser-driven launches from earth to LEO of nanosats might be possible in a near future, but this would require much more investment right now, than we actually have (about next to none).
If interested, please, visit http://aibep.org , the site of American Institute of Beamed Energy Propulsion, where you will find some answers to the questions raised here.
wilbur, i agree with you but i have to do some distinguo, what myrabo is doing is a technology demonstrator, we don't need big masses, that's where most of the people make a mistake, comparing BEP with current thrust systems.
Reply | Report Abuse | Link to thisWhat we need is to demonstrate that we can send to orbit or Leo even 50 grams using a laser, i can bet with you that if this is accomplished the funds for further developments will arrive right away.
BTW you don't need to use big masses to "open up" space, even a kg payload will be great, you will spur a whole industry of "lego blocks" to be used in space for construction, if it's cheap and replicable many times a minute why not? Not to mention the market for point to point transportation for the military or sensitive docs by fedex and similia and what about ISS resupply, where we still pay a huge amount of money per mass, indipendently of being it totthpaste or a nuclear reactor, finally there was a study in the 70's done by Grumman on a machine able to build trusses out then complex structures starting from aluminium rolls of foil, what if we can send up the rolls one after the other in a cheap way? i think the reference is "Space Fabrication Demonstration System" final Report, NASA-CP-161286, Grumman Aerospace Corporation, march 15, 1979"
so to me if Myrabo pulls it out demonstrating that you can go to orbit using a laser beam it will change everything. And i'm confident he will.