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Aircraft Nuclear Propulsion (wikipedia.org)
44 points by llambda on May 25, 2013 | hide | past | favorite | 24 comments

Context: At this point in history, the USA and USSR had aircraft fleets on constant patrol with tanker resupply. The concept was to simultaneously shorten the response time of strategic nuclear forces by having them "idle" nearer the target zones than their home bases and more importantly to reduce the potential losses of such strategic strike forces to a "bolt from the blue" preemptive & disarming attack. In a world where the President and SAC command would have to wait hours for B-36 & predicessor aircraft to make their way to their targets in Russia.

There were three real issues with this project: shielding weight, landing weight and politics. 1. Shot down or crashing, one of these aircraft would be a "dirty bomb" and could generate a nuclear contamination disaster. This alone made the project risky. Remeber, during the heyday of strategic nuclear bombing shootdowns were expected & ariplane to target assignments were made on the basis of the expected (and dismal) survival rate of inbound bombers. Also a single crash on US soil would have been... politically unpopular. 2. The lead, graphite and cement used to shield static nuclear facilities doesn't exactly work when trying to build an airplane, which made crew shielding dubious and reduced the loiter time of such a vehicle to the radiation tolerance of the crew. 3. A mich more minor issue was that of building landing gear that could hold the weight of the reactor on landing let alone a crash.

All that asside, a flying nuke plant is a great idea and I for one would not be surprised to see this idea resurrected for extreme loiter duration robotic aircraft :/

Could they use a drone instead of manned aircrafts to address point 2? So there's no need to shield and thus saving the weight.

IIRC some work was done to evaluate shielding only the relatively small area around the crew and avionics, saving considerable weight. However, it was soon discovered that radiation exposure can dramatically reduce the fatigue life of metallic materials. So, some (large) amount of shielding is still necessary.

Our computers are even more sensitive to radioactivity than our bodies.

Maybe yes with a drone based on TTL or some other "old" standard. Probably no with CMOS... Well, with a nuclear plant on board, I guess one can generate enough energy for a TTL computer.

But computers don't take up nearly as much space. You would only need to shield that one specific spot where the computer was rather than the whole cockpit.

Wouldn't you need to shield the wiring too? That stuff goes everywhere. Im not certain on the need for this though.

Yes, every particle crossing the copper can create an anomalous signal that can switch a 0 to 1 or visa versa. If you have enough of those, the program(s) will eventually crash. On the processors themselves the L1/L2 caches are vulnerable, but beyond that, the ROM could also get corrupted making hard resets impossible even after a crash.

Fiber optic cables aren't immune to this either : http://misspiggy.gsfc.nasa.gov/tva/meldoc/cabass/rad.htm

I think you are talking about SEUs.


Arguably, but the D-21 drone [1] was... a mess & a failure. Line Of Sight radio control was the only real option.

[1] http://en.wikipedia.org/wiki/Lockheed_D-21

I'm confused. The D-21 wasn't nuclear, and we've clearly fixed the problems with drones they had during that program. What's your point?

Unmanned aircraft were impractical during the Cold War, which is the only point in history when nuclear-powered aircraft were seriously considered. Drones are workable now, but political considerations alone make nuclear aircraft a non-starter today.

The guy on the other end says, "Is this Professor Feynman, of Cornell University?"

"That's right."

"This is Mr. So-and-so from the Such-and-such Aircraft Company." It was one of the big airplane companies in California, but unfortunately I can't remember which one. The guy continues: "We're planning to start a laboratory on nuclear-propelled rocket airplanes. It will have an annual budget of so-and-so many million dollars . . ." Big numbers.

I said, "Just a moment, sir; I don't know why you're telling me all this."

"Just let me speak to you," he says; "just let me explain everything. Please let me do it my way." So he goes on a little more, and says how many people are going to be in the laboratory, so-and-so-many people at this level, and so -and-somany Ph.D's at that level . . .

"Excuse me, sir," I say, "but I think you have the wrong fella."

"Am I talking to Richard Feynman, Richard P. Feynman?"


"Yes, but you're.."

"Would you please let me present what I have to say, sir, and then we'll discuss it."

"All right!" I sit down and sort of close my eyes to listen to all this stuff, all these details about this big project, and I still haven't the slightest idea why he's giving me all this information,

Finally, when he's all finished, he says, "I'm telling you about our plans because we want to know if you would like to be the director of the laboratory."

"Have you really got the right fella?" I say. "I'm a professor of theoretical physics. I'm not a rocket engineer, or an airplane engineer, or anything like that."

"We're sure we have the right fellow."

"Where did you get my name then? Why did you decide to call me?"

"Sir, your name is on the patent for nuclear-powered, rocket-propelled airplanes."

"Oh," I said, and I realized why my name was on the patent, and I'll have to tell you the story. I told the man, "I'm sorry, but I would like to continue as a professor at Cornell University."

What had happened was, during the war, at Los Alamos, there was a very nice fella in charge of the patent office for the government, named Captain Smith. Smith sent around a notice to everybody that said something like, "We in the patent office would like to patent every idea you have for the United States government, for which you are working now. Any idea you have on nuclear energy or its application that you may think everybody knows about, everybody doesn't know about: Just come to my office and tell me the idea."

I see Smith at lunch, and as we're walking back to the technical area, I say to him, "That note you sent around: That's kind of crazy to have us come in and tell you every idea."

We discussed it back and forth--by this time we're in his office-and I say, "There are so many ideas about nuclear energy that are so perfectly obvious, that I'd be here all day telling you stuff."


"Nothin' to it!" I say. "Example: nuclear reactor . . . under water. . water goes in . . . steam goes out the other side ... Pshshshsht--it's a submarine. Or: nuclear reactor ... air comes rushing in the front... heated up by nuclear reaction ... out the back it goes ... Boom! Through the air- -it's an airplane. Or: nuclear reactor ... you have hydrogen go through the thing ... Zoom!--it's a rocket. Or: nuclear reactor ... only instead of using ordinary uranium, you use enriched uranium with beryllium oxide at high temperature to make it more efficient ... It's an electrical power plant. There's a million ideas!" I said, as I went out the door. Nothing happened.

About three months later, Smith calls me in the office and says, "Feynman, the submarine has already been taken. But the other three are yours."

So when the guys at the airplane company in California are planning their laboratory, and try to find out who's an expert in rocket-propelled whatnots, there's nothing to it: They look at who's got the patent on it!


But what about the dollar?! (a reference to the rest of this short story)

This entire book is an amazing read that I recommend to anyone. You can usually find it for less than $5 at a used bookstore.

Maybe we could sleep better in such an airplane. How do they protect the crew from radiation in a nuclear submarine? Can't they do the same in a very big and silent plane?

Submarines need to be heavy. A major reason they're so cramped on the inside is because they'd float too well if they had more internal space. The weight of reactor shielding is basically free in that context.

Airplanes need to be light. Tons and tons of lead shielding is a harder proposition there, especially where every pound of shielding is one fewer pound of bombs you can carry.

As a thought - time distance and shielding were the 3 features of my education on radiation safety. What if the plane was very large - such that the crew were a long way forward of the reactor? Would some kind of hydraulic movement to shift the cockpit forward once altitude was gained work? This sort of thing happens to wings, why not cockpit?

Distance will help, but I imagine the plane would have to be absurdly large. The reduction in radiation exposure from each additional foot of distance will go down the farther out you go, and at some point, the additional fuselage will weigh more than the equivalent shielding. It wouldn't surprise me if that point was not all that far out.

Submarines are supported by buoyancy as a result of water displacement, so they can be a lot heavier than aircraft which are supported by lift generated by air moving over the wings.

The noise on a modern airplane is due mostly to the 500MPH airflow outside, not the engines. (Edit: a turbofan engine powered by nuclear-heated air would also likely be about as noisy as one powered by burning fuel)

> The noise on a modern airplane is due mostly to the 500MPH airflow outside

Where are you pulling this from? Every interview I've seen with people who have been on planes where the engines had quit talked about how quiet it got.

Nuclear ships are not a trivial matter. Here is an interesting part of the wikipedia page for the Russian nuclear icebreaker Lenin:

"The second accident was a cooling system leak which occurred in 1967, shortly after refueling. Finding the leak required breaking through the concrete and metal biological shield with sledgehammers. Once the leak was found, it became apparent that the sledgehammer damage could not be repaired; subsequently, all three reactors were removed, and replaced by two OK-900 reactors."

Poor bastards had to break into a nuclear reactor with sledgehammers.

I'be actually seen these engines in person. We did a tour for a class at INL. They are huge, much bigger than you could fit in a 747.

Imagine just how much "radioactive pollution" these engines were putting out if even the military wouldn't use them.

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