Boeing Patents an Engine Run By Laser-Generated Fusion Explosions

MarkWhittington writes: Boeing has had a patent approved for an aircraft engine that uses laser-generated nuclear fusion as a power source, according to a story in Business Insider. The idea is already generating a great deal of controversy, according to the website Counter Punch. The patent has generated fears of what might happen if an aircraft containing radioactive material as fuel were to crash, spreading such fuel across the crash site.

Comments

WHAT radioactive materials?

[Anonymous Coward]

Fusion doesn't use any.

Re:WHAT radioactive materials?

[beelsebob]

Go and read the article - the fusion is only a source of neutrons that then impact U-238 and cause fission to generate heat.

Re:WHAT radioactive materials?

[erice]

Elemental tritium would certainly not be spread over any crash site, not unless it was carefully packaged. Otherwise it would head directly for space.

Half right. Tritium is chemically hydrogen. As a gas, it would not spread over the crash site except for a small bit that might bond to solid materials if there is a fire. Most would go into the atmosphere where it would eventually bond with oxygen forming radioactive water. Fun.

Secondary radiation, however, is a different matter. And someone said that the fusion was only a source of neutorns to enhance fission. (That seems like a pretty wierd idea, since we don't currently have fusion working.)

Secondary radiation from the tritium is a non-issue. It is a beta emitter (free electrons) so it can't cause other materials to become radioactive. The neutrons from fusion and the induced fission, on the other hand are quite up to task.

Using fusion as a source of neutrons for fission isn't all that weird. We *do* have fusion working. What we don't have is fusion that produces more energy than it consumes. That is not a problem for a neutron source. It has the advantage over direct fission that bomb making material is never available. If you have a strong enough neutron source, you can fission Uranium 238 directly. No need to breed plutonium, like you would in a breeder reactor.

Re:WHAT radioactive materials?

[Type44Q]

we don't currently have fusion working

We don't currently have economically viable, contained fusion reactors working.

Re:WHAT radioactive materials?

[Rei]

It's worse - as is noted below, it's not actually a fusion engine proposal, but rather a hybrid fission/fusion proposal. It's not a new concept, but the key is, a lot of (read: "most of") the power is to come from fission.

I really can't think that Boeing would be so daft as to think that anyone would ever use this on Earth. Surely the point of the patent is to use it for exploration of other planets. Right? I hope so...

Note that it's not 100% necessary for neutron bombardment to create radioactive material. One of the nice things about incident induced radioactivity is that it's avoidable and/or manageable... albeit with tradeoffs that usually mean that accepting some radioactivity is the best option. You could for example have enough of a neutron absorbing material to fully consume the neutrons - for example, boron, which breaks down via the huge cross section B10(n,alpha)7Li reaction. 7Li neutron capture produces 8Li, which quickly decades into 8Be (releasing a ton of energy), which virtually instantly breaks down into two alphas. B10 neutron capture (much rarer than (n, alpha) yields B11, which is stable. B11 neutron capture produces B12, which very rapidly breaks down into C12 (stable). C12 neutron capture is rare and turns into stable C13. The only way you get to anything that's radioactive that doesn't instantly break down is to get a rare neutron capture of C13 after going through all of those previous steps, some of which are rare. And that "radioactive isotope" is only C14, which is a naturally occurring radioisotope we're evolved to live with, with a not very powerful decay. And if you isolate it (which isn't anywhere on the difficulty scale of, say, removing actinides from nuclear waste), it's highly valuable.

Another good example would be to make your structure out of beryllium. Beryllium is a superb metal in almost every respect and would be widely used in the world if not only for two niggling details: its dust is highly toxic and it's very expensive. But things do get built out of it (and it's not hazardous when there's no dust). 9Be capture produces 10Be, which is radioactive, but with a half life of 1.5 million years, the radiation level is extremely small, you'd need a lot of it to present a hazard. Which would never happen; 10Be has a reasonably high neutron capture cross section, becoming 11Be, which breaks down into 11B, which we've already covered above.

You can also get additional reactions to the above cases with fast neutrons, but they generally only improve the situation.

Pretty much anything out of light elements poses little to no hazard from induced radioactivity. You start to get a bit once you get to aluminum, but not much - aluminum has to go through an awful lot of captures to turn into a silicon or phosphorus isotope with a relevant half life, the amount transmuted is pretty irrelevant in most situations. It's only if you need higher strength or heat tolerance than aluminum (or better, lithium-aluminum) can give you that you start getting into problems - titanium, iron, iron alloying agents, other common structural metals, they all have significant issues with induced radioactivity. But even with them, it's still nothing on the scale of, say, waste fuel rods.

Re:WHAT radioactive materials?

[Rei]

Some people freak out about tritium because it's radioactive. But really, while tritiated water is poisonous, we deal with lots of stuff in our everyday lives that are far more dangerous, with far lower LD50s. And outside the body it does nothing, the beta is just too weak to penetrate. And given that tritium costs about $50k per gram, you're never going to encounter a large quantity of it at once.

Re:WHAT radioactive materials?

[WheezyJoe]

Not if the neutrons are energetic enough. The reason H-bombs run away to such high yields is that the U-238 tamper jacketing the device becomes a massive source of fissile bomb-fuel once the fusion "spark" ignites and blasts high-energy neutrons in all directions. Just sayin'. Have a nice day.

Re: WHAT radioactive materials?

[Rei]

Well, usually one uses electron volts to measure the energies in the above reactions, but if you want watts just divide eV/s by 6.24e18.

Re:WHAT radioactive materials?

[quenda]

but the key is, a lot of (read: "most of") the power is to come from fission.

I really can't think that Boeing would be so daft as to think that anyone would ever use this on Earth.

I think you may have missed that only the fusion products come out the back. The fission products are contained, and its relatively easy to contain the fission chamber in the event of a crash, unlike nuclear-powered spacecraft, which re-enter with 1000 x the energy of a subsonic aircraft.

Surely the point of the patent is to use it for exploration of other planets. Right? I hope so...

It has the advantage of operating without fuel or oxygen, but why would a planetary explorer need a jet engine? Whats the hurry?
They can just float around with a small solar or RTG-powered propeller.

Even if the technical challenges can be overcome, its hard to imagine this being economically viable over a conventional jet engine, even if you have to synthesise the fuel on the ground with nuclear power.
I miss the days when to get a patent you needed a working model, instead of just a vague idea that might never work.

Re:WHAT radioactive materials?

[redwraith94]

Tritium (1 Proton, 2 Neutrons) decays be emitting an electron (and an anti-neutrino, and a gamma ray), converting itself to Helium 3 (2 Protons, 1 Neutron); it doesn't produce neutron radiation at all.

Re:WHAT radioactive materials?

[Anonymous Coward]

Go and read the article.

You made me cry. "The concept is just in the patent stage and is a long way from even being a design, not to speak of a prototype". Once upon a time patents were meant to protect inventors who had come up with actual inventions.

Re:WHAT radioactive materials?

[dissy]

WHAT radioactive materials?
Fusion doesn't use any.

I'm almost certain any such device will contain at least one atom with an atomic weight above lead, which by definition is a radioactive particle :P

Re:WHAT radioactive materials?

[peragrin]

what's the hurry? Space is big, it is so big your ego will get lost.

Right now our longest closed deployment is submarines. they go 4-6 months between restocking. Even at that point all the fresh food was gone months before hand.Just to get to mars with typical engines is a 4-6 month process, plus time to evaluate and study and the return flight.

The moon is only 3-4 days away that need to be reduced to a 12 hour flight. Then we can begin sending supplies for a colony to push farther afield.

We need really fast engines in space just to make travel time practical.

Re:WHAT radioactive materials?

[Antique Geekmeister]

All current fusion reactor designs rely on deuterium and tritium. Tritium is _quite_ radioactive, with a half-life of 12 years. There is also very little of it. The world supply is on the order of 20 kilograms, and it's all accumulated from fission reactors. quoting Wikipedia, "Commercial demand for tritium is 400 grams per year and the cost is approximately US $30,000 per gram." Tritium cannot be reasonably refined: all tritium on earth in quantities large enough to refine is from fission reactors. Growing commercial production could improve the price tremendously, but it's source remains dangerous and expensive and inefficient to produce tritium.

Deuterium is stable, and available, but also quite expensive at $1000/kg. for deuterium oxide. With an atomic weight of 2, with two oxygen atoms of atomic weight of 16, the deuterium is only 2 / 34 of the mass. So the cost for pure deuterium itself is roughly $17000/kg, or about $17/gram. It's refinable from water, but the dollar cost reflects the energy costs of refining it.

The only large scale source of either isotope that would not be prohibitively expensive or rely on quite large scale fission generators is the solar wind. But much like large scale fission generators to create tritium it's senseless in terms of energy production. If you're bothering to build the plant for tritum, why not simply harvest the energy of the plant itself? A solar sail in orbit gathers roughly 2 kilowatts/square meter, and a roughly square kilometer mirror is quite feasible. That would be roughly 2 Terawatts of power. One could theoretically harvest deuterium and tritium from it, but with such a large power source, there seems to be no need to harvest it for fuel production for a much less efficient and quite radioactive system.

Great

[thinkwaitfast]

Now we won't have laser ignited fusion powered aircraft for another 20 years.

absolute BS

[frovingslosh]

Once again we have a patent issued for something that wasn't built, can't be built and likely will never be built. Boeing has no idea how to build a fusion engine, and if they could then they could and should build a ground based fusion power plant based on their magic technology. About the only thing that can ever happen with this patent is to be used by a troll in case anyone does really manage to build a fusion power plant that uses some of the same terms used in this science fiction document, such as lasers.

Re:absolute BS

[msobkow]

This.

The time has come for the patent offices of the world to mandate that you must have at least a prototype implementation of a system in order to be able to patent it.

Re:absolute BS

[gstoddart]

Yeah, it essentially sounds like they've patented magic here.

I didn't realize you could patent tech you can't create and which has huge gaping holes of "and a series of scientific breakthroughs happen here in the middle but we don't know how".

This patent seems to rely on step 2 of the underpants gnomes business plan -- which means it's not so much a patent as a concept with some wishful thinking and creative writing.

Can I patent my anti-gravity device if I don't know how to do anti-gravity?

Re:absolute BS

[sumdumass]

Perhaps this patent is part of a psychological operations in which someone wants to make someone else believe we have capabilities we don't.

This is where the rabbit wearing glasses thing comes from. We hid our radar capabilities in the early days of the cold war by saying carrots improved your vision and our pilots ate tons of them. This had the added benefit of spys recording locations of orange people and we got good ideas on locations of Soviet air bases as well as identities of suspected pilots that could be worked for info.

Re:absolute BS

[khallow]

I'll beseech Eris on your behalf for an anti-blessing to counter the blessing. No charge.

Re:Even U238 isn't radioactive.

[beelsebob]

But the plutonium produced by firing neutrons into it is.

Quote of the day

[P1h3r1e3d13]

Sustainable fusion reactions aren't quite reality yet.

Re:Even U238 isn't radioactive.

[beelsebob]

U238 will happily absorb neutrons (which are produced by the fusion) and become U239. U239 will happily absorb beta radiation (also production by the fusion) and become Np239. Np239 will also happily absorb beta radiation and become Pu239. Pu239 is nasty stuff that you don't want to get anywhere near you.

This is in fact exactly the reaction used in the production of Pu239 for nuclear weapons.

Re:Even U238 isn't radioactive.

[fuzzyfuzzyfungus]

So, if we can get this to the right scale; we can have a 'sustainable bomber' capable of all steps from enrichment to warhead delivery! It's like a seat on the security council in one convenient package.

The Fictional Radioactive Materials

[Crashmarik]

From a fictional engine that doesn't exist and won't exist until we actually have practical fusion.

Really this is what is wrong with the patent system. Now anyone developing engines using any kind of fusion is going to have a visit from Boeings lawyers over something they have done nothing to make work.

Re:Even U238 isn't radioactive.

[Type44Q]

Fuzz, I'm surprised you never heard of this...

Re:Even U238 isn't radioactive.

[Rei]

Well, if you want to absorb neutrons, you want a neutron poison like boron. If you want to moderate them, you want something rich in some combination of hydrogen (most effective, but too capture prone for some needs), deuterium (pretty good at moderating, extremely low capture, very expensive), helium (zero capture, fairly expensive, not a very efficient moderator, esp from a volume perspective), carbon (pretty low capture, fair at moderation, cheap, but need to avoid buildup of wigner energy), or oxygen (quite low capture, cheap, but subpar at moderation).

Re:Even U238 isn't radioactive.

[Hartree]

"Not radioactive"

Not true.

It's an alpha emitter with a half life of 4.5 billion years.

Re:Even U238 isn't radioactive.

[redwraith94]

Iron is the most stable nuclide (with Nickel being a close second), so creating elements above them requires energy. Not all heavier elements are radioactive though. The higher the ratio of neutrons to protons, the more likely the element is to be radioactive. There are so called 'islands of stability', just like with electron shells. Then there are also the double magic nuclei. I think that effect is the most interesting thing I have seen in all of Physics:

https://en.wikipedia.org/wiki/...

One of those higher magic numbered nuclei (elements we have not detected yet) are probably the fuel that the Annunaki used in their spaceships to enslave humanity 241,000 years ago...Just sayin.

I don't get it

[DrXym]

How are they going to suspend the sharks on the wings?

Re:Even U238 isn't radioactive.

[Rei]

Not exactly. 62Ni has a higher binding energy per nucleon than 56Fe. The misconception exists because not much 62Ni is produced in supernovae while large amounts of 56Fe is; for the most part, 56Fe represents the highest binding energy reached in a supernova..

Fusion is not currently possible

[CustomSolvers2]

There are quite a few worthy fusion/fission-related comments to this article, but it seems that certain idea is not completely clear to everyone: we haven’t ever built a working fusion reactor. Currently there is a (theoretically) serious attempt which is supported by various countries (and by lots of money) call ITER; although it is still a mere theoretical prototype. In fact this project has been systematically delayed during the last years.

A quick overview of how this reactor is expected to work:
1. Reaching an extremely temperature (i.e., the one in the sun), which will instantaneously melt any known material.
2. Containing the aforementioned hot plasma (i.e., self-sustained fusion chain reactions) with magnetic fields and with a very efficient refrigeration system.
3. Getting just a tiny fraction (i.e., what is required to boil water) of all this heat to generate electricity.

Thus, the main problem is that the required heat (the energy used to provoke the first fusion reaction) is so high that provokes quite a few other problems, like confining the hot plasma and extracting only what is required or even having a device able to generate so high temperatures

All these problems are logically much less relevant at much smaller scales (at the microscopic level), where the only successful fusion reactions have precisely occurred; and even at that tiny level, it is very difficult to create a self-sustained reactions generating more power than what is being put in (to not mention all the aforementioned issues associated with so high temperatures).

I have proposed an example in one my comments above which I will repeat here: looking forward to getting any reliable reference to a single successful experiment creating a macroscopic-relevant fusion reaction, like heating a cup of coffee during 5 minutes. I think that such a thing hasn’t ever occurred, but I would love to be proven wrong. Please, provide relevant references to support all your claims on the can-be-done front.