Before the knee-jerk "E-gads! Flying Nukes to Kill us All!" gets out of hand, I'd like to point out that pebble reactors have been talked about as useful for transportation because of their crashability. Blow one up and you get hundreds of thousands of "pebbles" that are slightly radioactive in themselves but not enough to prevent relatively easy cleanup.
Along those same lines (low level fuel pieces assembled in a destruction-proof container), aren't various companies working on micro-reactors or "nuclear batteries"?
"The fuel is uranium of a type that isn’t worth much to a terrorist. The reactor operates with principles that shut themselves down so meltdowns and other horrors for the neighbors simply don’t exist."
I'm not saying all the bugs are worked out. But it looks like enough has changed since TMI that we could/should take an honest, open look at what we can do with nuclear now that we couldn't back then. At least to me it has.
"Professor Poll said an alternative to carrying nuclear reactors on aircraft would be to develop aircraft fuelled by hydrogen extracted from sea water by nuclear power stations." Somehow, I'd feel a bit better flying across the US knowing there wasn't a nuke reactor underneath me.
Well... there are hundreds of cities where people live fairly close to a reactor, with the same lethal outcome in case of failure. They live there 24/7 and you're opposed to an idea of spending at most tens of hours a year right next to one?
The biggest issue is radioactive contamination in case of an ordinary plane crash, and parachuting a reactor doesn't sound like especially convincing solution: when planes crash, it is usually because a lot of things go wrong onboard, with parachuting system possibly being one of them.
I think we'll be much better off investing into development of new generation of speed trains: they can easily be made electric (thus taking advantage of cheap nuclear energy), riding on electro-magnetic fields friction-free at crazy speeds.
Not so, it's a lot easier to put extra safety equipment on the ground then on an airplane.
I quite agree that parachuting the reactor is not going to work - if you were flying the thing, and you had a 50% chance of saving the plane if you had a power plant, but a 100% chance of crashing if you let it drop - would you do it?
The military is trained for such choices, civilians are not.
This is totally nuts. Talk about a flying dirty-bomb! Plus, jettisoning the reactors and bringing them down with parachutes only works if you know you're going to crash at a high enough altitude, which does not include takeoffs and landings.
Technically the reactors could be encased in materials proven to be unbreakable at these lower altitudes.... then the only danger would be high-altitude crashes in which case the reactor parachuting would be an answer... except you can't guaranteed the parachutes would be in working condition after a _________ miles up in the air. A normal engine failure could be rescued from, but, say, a mid-air collision at high-altitudes between two planes (regardless of how unlikely it may be) may leave the reactor rescue and parachuting systems in no condition to guarantee a safe ejection.
I'm not gonna pretend to be an expert on reactor safety, but I do note that the article mentions that a pebble bed reactor is kept inside a big concrete building designed to withstand aircraft crashes.
I assume this means that an aircraft crash involving a pebble-bed reactor _not_ inside a big concrete building could be bad. The second layer of containment (two-meter thick walls) also sounds pretty difficult to make fly.
Wow. If you'd told in October 2001 that in seven years people would be seriously proposing putting nuclear reactors in aeroplanes I'd think you were crazy. And yet, here we are. Have we forgotten? How quickly we swing from one kind of hysteria to another.
in the worst-case scenario, if the armour plating around the reactor was pierced there would be a risk of radioactive contamination over a few square miles
And that's supposed to make us feel better? Fun fact: the area of Manhattan is 23 square miles, and 1.8 million people live there.
Seriously, I'm a supporter of nuclear power if it's used sensibly, but strapping wings to nuclear reactors and sending a couple of hundred to fly over every city on Earth every day doesn't sound like "sensible" to me.
there is no reason not to explore this line of thinking, however, there would be an even greater likelihood that someone would want to steal a planes reactor to make some sort of bomb.
i think it would be safer to have the nuclear reactors and fuel on the ground and to somehow transmit that energy to the plane.
another option would be lightweight, high density batteries that can be charged in minutes. planes could then at first fly several hundred miles, touchdown, refuel and then take off without much time loss. CNT (carbon nanotubes) might produce batteries/capacitors that are upto the 'charge'.
"He said that, in the worst-case scenario, if the armour plating around the reactor was pierced there would be a risk of radioactive contamination over a few square miles. "
So, even if these planes were to exist, we would need to build a new network of remote nuclear airports (nukeports) miles away from any urban development ---plus a transportation infrastructure to shuttle between the nukeport and urban centers.
The cost wouldn't be the flight itself, but the adhoc transportation network of several dozen miles from the nukeport to urban centers. It could take several hours to get from the nukeport to the city in poor traffic. That's why this is impractical for civilian use, though maybe it could work for mass military transport or freight.
Most airports are already out in the boonies, (having something to do with runways taking up space.) especially international ones, which would be for what these planes are used. I don't think is would be that big of a deal. Now if a plane crashed in an area with some kind of population, now that might be a concern.
Just out of curiousity, where do you live? I can't name an international airport [1], in the USA at least, that isn't in a part of town that has traffic issues during rush hour. Industry pulls itself to airports possibly faster than any other physical attribute.
[1] This assertion definitely excludes small potatoes airports that earn their international name by serving the one country closest to them (i.e. small town WY or MT airports serving Canada).
I live in N. Virginia and my airport is Dullas. It's true that there are people living near it and a lot of traffic by it, but that happened after the airport was built not before. It's certainly not in the middle of a major city. It's already hours from DC and where I live in good traffic. Poor traffic is a nightmare.
Perhaps my perspective is a bit skewed by living in Virginia though, development around here is really like anywhere else in the country.
No, most airports are within a few miles of major metropolitan areas because that's where people are located, and airports themselves are often significant bastions of human infrastructure.
Further, unlike an ordinary plane crash, a nuclear incident even confined within the bounds airport would close that airport for years, if not permanently. No major airport would risk shutting itself down forever.
Very well, small, remote airports may be qualified to service nuclear planes, but that defeats the purpose of massive transit of people between major urban centers.
I'm not trolling and I'd appreciate it if you wouldn't throw baseless accusations around. I may be wrong, but that's an entirely different matter.
Airports need to be in places where there is enough space for the airplanes to take off and land. This means that the airports themselves need to be built in places where there is enough space for runways and there are no tall structures to interfere with low-flying aircraft. At the time of building, this means significantly outside urban centers and it means that for a ways around, buildings can only be a few dozen stories tall.
As time passes, commerce and industry builds up around airports, but, in general, large airports are not located within major urban centers. They are at least as remote as many nuclear power facilities. While some airports would then be out of limits, many could be quite feasible.
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Now given that the primary purpose of nuclear planes would not be transportation between major cities but rather intercontinental flight, which, in case you've never been on one, already requires switching airports a number of times before you get to where you want to go, This could conceivably be quite practical. You would have one or two in the Us, one in Canada, One or two in Europe, one in Russia, one in China, one in Australia, etc. and you would transfer flights to get to where you were going. This is how intercontinental flight already works, so I don't see how it is infeasible or self defeating.
Don't waste your time. This isn't going to work - it's far too heavy to fly. And how would you power a jet from nuclear? It makes heat, that's it. No reaction mass. Maybe steam to power a prop? Sounds unlikely.
Much better to use nuclear power for homes and electric cars, and save the liquid fuels for airplanes.
I have not, but reading it now (thanks for the link) I maintain what I wrote (even though I got a lot of downmods): this is far too complicated to ever actually work.
Did you read the section on tolerances, and the temperatures? Do you really think such a thing would be reliable for day to day running on an airplane?
It's not impossible of course, but it's not practical, and it's a waste of money. Use the nuclear power on earth, and save the liquid fuels for the air.
No I don't think it would be a good idea for a whole bunch of reasons but it is possible with people having taken it to the prototype stage. Like you I'd spend the money on other things
A scramjet (supersonic combustion ramjet) is a variation of a ramjet with the distinction being that some or all of the combustion process takes place supersonically.
Did you bother reading the article? The US Army flew B-36 bombers with live, running, and fully-functional nuclear reactors on board that produced enegry and proved beyond the shadow of the doubt that it's both doable and feasible - albeit the fact that they the B-36 bombers themselves were powered by kerosene despite the availablility of nuclear power since it wasn't intended to be anything more than a proof-of-concept flight.
albeit the fact that they the B-36 bombers themselves ______were powered by kerosene_______ despite the availablility of nuclear power since it wasn't intended to be anything more than a proof-of-concept flight
I did read your comment, but it made no sense, so I assumed it was a typo.
You wrote: "proved beyond the shadow of the doubt that it's both doable and feasible" - and at the same time that they didn't do it.
So how did they prove "beyond the shadow of the doubt" something they didn't even do?
That made so little sense I assumed you didn't realize they didn't power the engines from the reactor.
Edit: maybe you don't realize that carrying the nuclear plant is the easy part (heavy lift vehicles exist after all), powering the engines is the very hard part.
To put it simply, the heated air is your reaction mass. Push cold air in, heat it so the pressure goes up, blast it out the back through a nozzle.
As mentioned elsewhere already, this is commonly referred to as a "ram-jet". The heat in such an engine usually comes from combustion, but any old heat source will do.
Heating air as reaction mass is far far more complicated then you are making out.
And that's NOT a ram-jet. Part of the thrust in a ram jet comes from the liquid fuel suddenly growing much larger as it's vaporized.
Using air directly would mean heating it to thousands of degrees. Then you need a material that can handle such temperatures (which don't exist), and still contain the nuclear fuel. And at those temperatures your fuel is molten.
When you burn liquid fuel - it burns at a thousand degrees or so, but then expands rapidly (and cools), so you don't actually have to contain anything at that temperature.
But if you heat air you do - and that's not easy.
Oh, and the entire point of ram and scram jets, is to provide oxygen without blowing out the flame (which is why it's so hard to do). That doesn't apply here.
During the Cold War the United States designed and ground-tested a nuclear-powered ramjet called Project Pluto. This system used no combustion - a nuclear reactor heated the air instead. The project was ultimately canceled because ICBMs seemed to serve the purpose better, and because a low-flying missile would have been highly radioactive.
If one were to build a nuclear powered airplane, a jet would be quite a bad choice. Propellers would be a much better propulsion system.
Honestly, though, a hydrogen powered plane is a more likely and more physically reasonable system. Hydrogen has a very high specific energy, and energy density isn't nearly as important as weight in a plane.
Along those same lines (low level fuel pieces assembled in a destruction-proof container), aren't various companies working on micro-reactors or "nuclear batteries"?
http://newenergyandfuel.com/http:/newenergyandfuel/com/2008/...
"The fuel is uranium of a type that isn’t worth much to a terrorist. The reactor operates with principles that shut themselves down so meltdowns and other horrors for the neighbors simply don’t exist."
I'm not saying all the bugs are worked out. But it looks like enough has changed since TMI that we could/should take an honest, open look at what we can do with nuclear now that we couldn't back then. At least to me it has.