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Boeing has patented a laser powered propulsion system for airplanes. A number of sites reported on the patent, with eye-rubbing headlines that told the story. BusinessInsider headline read, "Boeing just patented a jet engine powered by lasers and nuclear explosions." Benjamin Zhang said the US Patent and Trademark Office approved Boeing's application for a laser and nuclear-driven airplane engine.
Zhang noted that presently the Boeing Dreamliner is powered by multiple turbofan engines with their fans and turbines in place to compress air and ignite fuel to provide thrust. The engine presented in Boeing's patent application takes another route. Zhang said the laser engine may also be used to power rockets, missiles, and spacecraft.
The new engine would work "by firing high-power lasers at radioactive material, such as deuterium and tritium," said BusinessInsider. "The lasers vaporize the radioactive material and cause a fusion reaction—in effect a small thermonuclear explosion," said the article. "Hydrogen or helium are the exhaust byproducts, which exit the back of the engine under high pressure. Thrust is produced."
In this approach the inside wall of the engine's thruster chamber coated in uranium 238 reacts with the neutrons from the nuclear reaction and generates immense heat. "The engine harnesses the heat by running coolant along the other side of the uranium-coated combustion chamber," said Zhang. "This heat-energized coolant is sent through a turbine and generator that produces electricity to power the engine's lasers."
Three inventors named in the patent application are Robert Budica, James Herzberg and Frank Chandler of California. The applicant is listed as The Boeing Company in Chicago. The patent was filed in 2012.
Original Submission
(Score: 2) by That_Dude on Monday July 13 2015, @04:13AM
There's already enough "background" radiation that hardly anyone will notice! It's a safe bet that it will never reach 100% efficiency therefore releasing more than just hydrogen and helium.
(Score: 3, Interesting) by takyon on Monday July 13 2015, @04:26AM
It's the kind of propulsion I envision for spacecraft using ground-based lasers, not laser fission-fusion chambers in airplanes.
https://en.wikipedia.org/wiki/Laser_propulsion [wikipedia.org]
http://www.gizmag.com/laser-propelled-ablation-space-rockets/34505/ [gizmag.com]
http://motherboard.vice.com/read/engineers-stumble-on-a-whole-new-method-of-laser-based-spacecraft-propulsion [vice.com]
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 3, Insightful) by c0lo on Monday July 13 2015, @08:44AM
https://www.youtube.com/watch?v=aoFiw2jMy-0
(Score: 2) by turgid on Monday July 13 2015, @08:00PM
You just need a very long cable to make an electrical circuit.
I refuse to engage in a battle of wits with an unarmed opponent [wikipedia.org].
(Score: 2) by Immerman on Monday July 13 2015, @09:55PM
I would think it would tend to be a self-correcting problem: Space is full of ionized particles, especially around planets with magnetic fields to capture them. Your positively ionized graphene "sponge" would tend to "soak up" ambient electrons from those ion clouds until it reached equilibrium.
Of course that would likely mean that your thruster might only be really useful for minor course adjustments near planets, but the solar wind is blowing past at several hundred km/s, so there's probably always a decent influx of new electrons to capture, so long as you don't spend them too quickly.
(Score: 1) by sce7mjm on Monday July 13 2015, @09:10AM
Unfortunately the noise this thing makes won't allow it to be used at the proposed runway at heathrow.
https://www.youtube.com/watch?v=A8BFrd1ckSw&t=0m44s/ [youtube.com]
(Score: 1) by sce7mjm on Monday July 13 2015, @09:13AM
bad link
should have been
https://www.youtube.com/watch?v=A8BFrd1ckSw&t=0m44s [youtube.com]
whoops
less funny now
joke over nothing to see here...etc.
ahem...
(Score: 2) by turgid on Monday July 13 2015, @12:11PM
Would the U-238 not breed Pu-239 via neutron capture? I can foresee political problems, not to mention technical ones. How much fusion is being done, and how much heat needs to be extracted to keep the engine from melting and to produce the electricity to drive the lasers?
I refuse to engage in a battle of wits with an unarmed opponent [wikipedia.org].
(Score: 1) by AnonymousCowardNoMore on Monday July 13 2015, @04:20PM
Would the U-238 not breed Pu-239 via neutron capture?
That's exactly it. U-238 has an insane half-life of more than 4e9 years, making it useless for power generation. The reactor must breed Pu and run off that.
How much fusion is being done, and how much heat needs to be extracted to keep the engine from melting and to produce the electricity to drive the lasers?
Keeping the engine from melting shouldn't present much of a problem over other thermal rockets but your other observation is notable: Even the best fusion reactors in the world release barely more fusion energy (I mean total, not usable) than it takes to run the reactor. This rocket looks like it will be twenty years in the future for the next forty years.
I can foresee political problems
Agreed. I don't see how it could fly without major changes in the political climate.
(Score: 3, Interesting) by turgid on Monday July 13 2015, @07:49PM
So, the Pu-239 is fissile. However, it also decays, producing heat. If the energy spectrum of the neutrons produced during the D-T fusion is suitable, then there would be induced fission in the 239Pu, so there would be another source of heating. If not there would only be heating from the 238U to 239Pu conversion (decay) and maybe the odd neutron hitting the casing.
If it's just decay heating, then you've effectively got an RTG to produce your electricity and a fairly low pressure but high speed exhaust from the fusion reactions.
Otherwise, you've got a hybrid fusion/fission fragment rocket, since the (very hot) fission products from the 239Pu fission will be ejected out the back of the engine with the fusion products, significantly adding to the thrust.
I would imagine that with fission going on as well, you would probably want some kind of neutron reflector to get better neutron efficiency and to keep the neutrons away from the rest of the craft. Gas-cooled reactors (Magnox, AGR) used graphite bricks, cooled with carbon dioxide or carbon dioxide mixed with methane to limit erosion.
Would you want to contain the fusion plasma in some kind of electromagentic rocket nozzle to keep it from physically touching the walls of the engine.
These are idle thoughts, but since Boeing marketeers are shouting about it, I don't feel too stupid putting in my tuppence-worth.
I'd really, really like to live to see a nuclear-powered space craft used for scientific exploration, especially one with a human crew. I won't be the one building it, because my brain isn't big enough, but I can dream...
There was a significant amount of research and development done decades ago for nuclear engines to put on the upper stages of the Saturn V. What might have been!
I refuse to engage in a battle of wits with an unarmed opponent [wikipedia.org].
(Score: 2) by turgid on Monday July 13 2015, @07:58PM
What a goat. I originally read this story on my phone and the text was so small I didn't notice the link to the phys.org story, just the Business Insider one. Yes, they're expecting fission from the 238U. I suppose fission fragments are the way to go. Not sure about the fusion part. If it's insignificant in terms of thrust, maybe there could be a cheaper and simpler source of neutrons? Tritium isn't cheap, it's difficult to handle and has a short half-life.
I refuse to engage in a battle of wits with an unarmed opponent [wikipedia.org].
(Score: 2) by gnuman on Tuesday July 14 2015, @04:12AM
Yes, they're expecting fission from the 238U.
Which means it is dead concept for terrestrial engines. It is also a dead concept when it comes to rocketry considering other, more exotic means,
https://en.wikipedia.org/wiki/Spacecraft_propulsion#Table_of_methods [wikipedia.org]
(Score: 1) by KBentley57 on Monday July 13 2015, @12:16PM
I understand sensationalism in media, but sheesh. It's no more powered by lasers than by atomic bombs, steam engines, or Pelteir elements.
On another note, with the huge public fear in nuclear power facilities, I can't imagine our congress critters would be ok with these engines flying overhead. The space application seems more useful, in terms of a fuel/weight concept. However, It would be helpful to see a comparison between this, conventional fuel, regular xenon ion engines, solar sails, ect...
(Score: 2) by Immerman on Monday July 13 2015, @08:36PM
Okay, so at first glance this patent sounds like a prior art "safe harbor" investment - by the time we master fusion well enough to pull it off efficiently, the patent will likely have long since expired. Unless Boeing has been keeping quiet about some really interesting research.
On the other hand this seems like it just might hold the seeds of the "holy grail" of a high-power adjustable radiothermic generator. Instead of a rocket bell, cover the inner walls of a vacuum chamber with U238. Then install an energetic neutron source, even a simple Farnsworth Fusor, in the center. Those have been getting tantalyzingly close to break even for over half a century, but even that's not the point - the point is that most of the energy is released as energetic neutrons which would then trigger fission reactions in the walls of the reaction vessel, generating far more energy which then gets captured as heat in the coolant. Want more heat, pump more power/fuel into your fusor and bombard the walls with more neutrons.
Runaway reactions would be virtually impossible, since the fissile material is at sub-critical densities - the instant you cut power to the fusor, the fission essentially stops as well. You'd still have issues with lingering radioactivity, but so long as the fusor is insufficiently powerful to trigger a runaway reaction a meltdown would be impossible. In fact, forget traditional fusion reactor triply-redundant safety system, I'd bet it could be relatively easily to design a fusion-catalyzed fission reactor such that a runaway reaction was physically impossible.
Hmm, actually, that's sounding not completely unlike the fusion reactor under development by Lockheed Martin [eweek.com] and partners. The difference being that instead of trying to generate power from fusion, and then breeding new fuel incidentally from the low-energy fission of the lithium shielding, you're using a far more fissile shielding to generate the bulk of the power, and a far simpler fusion "catalyst" that need not even be break-even itself.
(Score: 2) by turgid on Tuesday July 14 2015, @01:22PM
The fusion doesn't have to be energy-positive or even break-even as long as the total energy from the fusion, fission and decay is greater than the energy required for the fusion. I doubt the heat to electricity conversion could be much more than 40% efficient in practice. Still, why they'd use such an expensive fusion method isn't clear other than to bagsy the patent. Big companies often have PHB, legal and Marketing-driven patent quotas. At one place I worked, towards the end of the quarter the email would go out to the engineers saying "you're 40% short of your Invention Proposal target again."
I refuse to engage in a battle of wits with an unarmed opponent [wikipedia.org].
(Score: 2) by Immerman on Tuesday July 14 2015, @04:40PM
>The fusion doesn't have to be energy-positive or even break-even as long as the total energy from the fusion, fission and decay is greater than the energy required for the fusion.
Exactly.
As for their engine, it has a rather different design goal - instead of generating energy efficiently, it's designed to produce thrust, which means you need high-velocity exhaust, which is what the fusion is providing. Fission doesn't do "fast" very well - the energy-to-mass ratio of the fragments just isn't high enough. Plus they tend to be locked into solid fuel pellets so that the energy is thermalized almost instantly. The fission is just there to power the lasers to sustain the fusion.
As for an "expensive" fusion method - for extended operation in a rocket chamber I can't really think of any better alternatives offhand. Farnsworth-style fusors are unlikely to provide an attractive energy density without vaporizing themselves, tokamaks are far too massive to incorporate into a rocket, and most other techniques are still unproven laboratory curiosities.
(Score: 2) by darkfeline on Monday July 13 2015, @11:13PM
>The lasers vaporize the radioactive material and cause a fusion reaction
Wouldn't that make this cold fusion, or at least getting more output energy than input energy?
Join the SDF Public Access UNIX System today!
(Score: 1) by anubi on Tuesday July 14 2015, @01:36AM
Now that you've brought it up... has anyone found anything interesting on Rossi's E-Cat?
Most of the stuff I find is on PESN, and I hardly consider anything I read from them to be the truth.
So far, I believe most of what I have seen has been either magician-style illusion:
- A video I saw had them holding up hose venting steam while hot water is collecting in the rest of the hose. Siginificant heat production is misrepresented if all of the water is not being turned into steam. The video I saw did not have steam ejecting at the end anywhere near the velocity I had expected given the apparent diameter of the exit orifice. I did not consider it consistent at all with the claims of how many joules/sec it was supposedly producing
- Or energy released by corrosion of the innards of the device.
The inability to inspect the device leads me to speculate a lot of prestidigitation is going on. I have worked with enough test equipment to know I can get meters to read nearly anything I want it to read if I hide a resonance in just the right place.
Needless to say, I am extremely skeptical, however I have yet to prove to my satisfaction that cold fusion won't work. As long as the matter/energy is all accounted for.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]