AHC: Fission Powered Civilian Aeronautic Industry and Transport.

[omnimercurial]

As it says on the tin.

Bring about the Atompunk dream in the 50's and 60's via Passenger and Freight Airliners of Huge Size.

Electric Jet Turbines powered by Fission.

How much quieter than conventional Jets would they be?

How much more efficient would they be?

What Country is more likely to develop them?

Which Nation would have the most? Or have the most advanced Aircraft?

Which would be more likely? Privatised or Nationalised Aircraft Manufacturers and Airlines?

Which would be more successful?

 

[Carl Schwamberger]

Do get that air car I was promised back in 1959???

 

[Delta Force]

It's impossible to get private insurance for land based nuclear power plants in the United States, so I wonder how the airlines would be able to insure their nuclear powered aircraft.

 

[Dathi THorfinnsson]

Also look at the power produced by eg a nuke sub plant, vs its weight. Then calculate the power used by a major aircraft. The plane couldnt even get off the ground, and thats not even allowing for all the extra shielding and crash protection youd need. The only way to get the necessary power to weight ratio would be either running your reactor on almost bomb grade fuel or running the reactor at such high temperatures that the reactor can heat outside air as hot as burning het fuel. Which, since the fuel cant touch the air, unlike with jetfuel, means the reactor has to be even hotter yet. So, youre looking at a molten salt reactor, probably.

No way either of those could go wrong in the event of a crash, eh?

So, no, no way. Not unless you have a dystopic society even less worried about the environment than otl's Soviets.

 

[asnys]

Also look at the power produced by eg a nuke sub plant, vs its weight. Then calculate the power used by a major aircraft. The plane couldnt even get off the ground, and thats not even allowing for all the extra shielding and crash protection youd need. The only way to get the necessary power to weight ratio would be either running your reactor on almost bomb grade fuel or running the reactor at such high temperatures that the reactor can heat outside air as hot as burning het fuel. Which, since the fuel cant touch the air, unlike with jetfuel, means the reactor has to be even hotter yet. So, youre looking at a molten salt reactor, probably.

An MSR would be a good approach - the tech was actually originally developed for the Aircraft Nuclear Propulsion project - but it's not the only one. The historical ANP put most of its resources into a direct-cycle engine with an air-cooled reactor and solid ceramic fuel elements. By 1960 they pretty much knew how to build a nuclear-powered plane, and had tested three nuclear-powered turbojets out in Idaho. The A-Plane would be huge, expensive, and slow, but it would fly.

Later on, in the late 60s/early 70s, NASA-Lewis did some work on civilian nuclear-powered aircraft. They calculated that it could only be economically feasible if it was extremely large, they were looking at flying wings in the 2-20 million pound range. The reason is that, unlike conventional engines, the mass of a nuclear turbojet scales sublinearly with power - the mass is dominated by the shielding, which is proportional to the system surface area, while the power is proportional to volume. So if your aircraft mass increases by a factor of eight, the mass of the engine - and its cost - increases only by a factor of four. But it's got to be very big to make it work financially - how big depends on a lot of factors, but certainly the minimum is 2 million pounds, which is in the neighborhood of the biggest planes ever built historically.

Their plan was to use indirect-cycle engines, reactors with solid fuel elements and cooled by liquid sodium or pressurized helium, which would power heat exchangers in the engines. They planned to make the shielding do double-duty as crash padding, and actually tested some mockups using rocket sleds. I've got some pictures somewhere around here.

Needless to say, all versions of this used weapons-grade nuclear fuel.

Anyway, while nuclear-powered aircraft are quite feasible on a technical level, it's very difficult to see being done. I'm not sure if it's possible or not. You'd definitely need a very different public attitude towards radiation, including widespread acceptance of a linear threshold model of radiation carcinogenesis. And you'd need somebody to be willing to put a lot of money into airports capable of handling 20-million-pound megajets - for reference's sake, that's big enough to airdrop a Saturn-V rocket.

 

[LeX]

Besides transport, what would the jet be used for? Sure it can fly around the world many times but is that useful? Also I've heard that extremely large planes have issues where the wings have lots of strain put on them? I wonder if this could be solved simply through reinforcement at the place where the wing meets the fuselage.

 

[b0ned0me]

How much more efficient would they be?

Is this a trick question?

 

[Mike Stearns]

Also look at the power produced by eg a nuke sub plant, vs its weight. Then calculate the power used by a major aircraft. The plane couldnt even get off the ground, and thats not even allowing for all the extra shielding and crash protection youd need. The only way to get the necessary power to weight ratio would be either running your reactor on almost bomb grade fuel or running the reactor at such high temperatures that the reactor can heat outside air as hot as burning het fuel. Which, since the fuel cant touch the air, unlike with jetfuel, means the reactor has to be even hotter yet. So, youre looking at a molten salt reactor, probably.

No way either of those could go wrong in the event of a crash, eh?

So, no, no way. Not unless you have a dystopic society even less worried about the environment than otl's Soviets.

What about using Thorium as fuel? It has almost 100 times the energy density of uranium and emits far less radiation. That means a smaller reactor, less shielding and more power.

 

[Alternate History Geek]

It's impossible to get private insurance for land based nuclear power plants in the United States, so I wonder how the airlines would be able to insure their nuclear powered aircraft.

Why is that?

 

[asnys]

What about using Thorium as fuel? It has almost 100 times the energy density of uranium and emits far less radiation. That means a smaller reactor, less shielding and more power.

Thorium doesn't work that way.

Thorium advocates say it has 100 times the energy density because modern reactors don't tap the full energy potential in their uranium fuel. Basically, because uranium's cheap, and the sort of reactors that can get all of the energy out of it are expensive. But it's not an issue here because they'd be using weapons-grade uranium, and even existing reactors can get the full potential out of that. And I don't know what you mean about "far less radiation".

Why is that?

They are actually insured, up to $375 million each. But the potential damage from a meltdown is a lot greater, more than any private company can credibly insure. So the government insures them.

That said, the reason the potential damage is so high is because of the LNT hypothesis for radiation carcinogenesis. If you're flying A-planes around you're using the linear threshold hypothesis, and that means the potential damage from a nuclear accident is a lot lower.

 

[e of pi]

It's worth thinking about servicing costs. There's a lot more than the combustion chamber to a jet engine, and nuclear thermal turbine engines still have bypass fans, compressors, turbines, and nozzles. These do require inspection and overhaul, which would likely have to be radiation-hot work, since most nuclear jet engine designs I've seen have the rotating machinery very close to the reactor. That'd make the job a lot harder. Also, even if you're presuming a linear radiation model, I don't think you can get away without shielding, so the engine has to be buried inside the fuselage, and you need omni-directional shielding to be able to have ground crew and baggage handlers move around the plane, so the engines will still be very heavy compared to a standard jet, which means lower payload for the same weight of aircraft. I'm just not sure that the benefit of nominally infinite range and no jet fuel costs can compensate for a less capable and much harder to service aircraft.

 

[asnys]

It's worth thinking about servicing costs. There's a lot more than the combustion chamber to a jet engine, and nuclear thermal turbine engines still have bypass fans, compressors, turbines, and nozzles. These do require inspection and overhaul, which would likely have to be radiation-hot work, since most nuclear jet engine designs I've seen have the rotating machinery very close to the reactor. That'd make the job a lot harder. Also, even if you're presuming a linear radiation model, I don't think you can get away without shielding, so the engine has to be buried inside the fuselage, and you need omni-directional shielding to be able to have ground crew and baggage handlers move around the plane, so the engines will still be very heavy compared to a standard jet, which means lower payload for the same weight of aircraft. I'm just not sure that the benefit of nominally infinite range and no jet fuel costs can compensate for a less capable and much harder to service aircraft.

It's only lower-performance at low masses. Because of the way the shielding mass scales (about the 2/3rd power of mass), at high airplane masses it will actually have a higher payload fraction than a conventional jet, because you don't have to carry much jet fuel. They have to be big, though - the breakeven in terms of economic performance depends on who you believe, but it's certainly north of a million pounds, possibly getting close to ten million.

 

[TFSmith121]

What's the business case for this?

It's only lower-performance at low masses. Because of the way the shielding mass scales (about the 2/3rd power of mass), at high airplane masses it will actually have a higher payload fraction than a conventional jet, because you don't have to carry much jet fuel. They have to be big, though - the breakeven in terms of economic performance depends on who you believe, but it's certainly north of a million pounds, possibly getting close to ten million.

I mean, there's a reason nobody was investing in hydrogen-filled dirigibles in the 1940s...

Best,

 

[Coalition]

Here are a couple pdfs that are about nuclear aircraft. Be careful, they are a bit dry.
Aircraft Nuclear power plant designs
Reactor designs

I'm trying to find one PDF that had estimates of the minimum distance needed to travel before nuclear aircraft would carry more cargo than a conventional aircraft. It was interesting.

 

[Delta Force]

They are actually insured, up to $375 million each. But the potential damage from a meltdown is a lot greater, more than any private company can credibly insure. So the government insures them.

Is that $375 million in private or public insurance? I thought the nuclear power plants all paid into a government insurance pool that would be used to pay any claims, and that it's around a billion dollars or so. I might be confusing that funding pool with the nuclear waste disposal pool, however (I think there is one to fund a permanent disposal site as well).

 

[MattII]

Besides transport, what would the jet be used for? Sure it can fly around the world many times but is that useful?

Not really, since it would have to use propellers, and be thus lower-flying and slower than jets, and you could do a non-stop flight anyway with aerial refuelling.

 

[Gunnarnz]

Not really, since it would have to use propellers, and be thus lower-flying and slower than jets, and you could do a non-stop flight anyway with aerial refuelling.

That turns out not to be the case. Check out the wikipedia article, but the work done on nuclear powered aircraft was using turbojets, not propellors. There are reasons to doubt the practicality of nuclear aircraft below about the 5000 tonne mark, but "they have to use propellors" isn't one of them.

 

[asnys]

Is that $375 million in private or public insurance? I thought the nuclear power plants all paid into a government insurance pool that would be used to pay any claims, and that it's around a billion dollars or so. I might be confusing that funding pool with the nuclear waste disposal pool, however (I think there is one to fund a permanent disposal site as well).

Under the Price-Anderson Act, they're required to buy as much private insurance as the free market will provide, which is currently about $375 million. Then, since that's obviously inadequate to cover potential damages under the current radiation regulations, there's a government-sponsored pool: in the event of an accident, each reactor in the country pays up to $121 million into a pool to cover the damages, which amounts to about $12 billion at the moment. If damages exceed that amount, Congress is supposed to decide what to do about it - though I should note that, under the Price-Anderson Act, the per reactor levy can be increased above the nominal maximum.

I mean, there's a reason nobody was investing in hydrogen-filled dirigibles in the 1940s...

Well, yes. I'm not sure it's possible to actually make this happen. But I love the idea so much I keep trying.

The only logical way to do it is to have the military lead the way. If we can get the military flying nuclear-powered megajets, it's a lot easier to get those jets into civilian service. I've done a lot of thinking about what the Air Force could do with a 5,000,000-pound plane, and there are some potential roles, although I'm not sure they couldn't be substituted for by more conventional approaches:

• Transport (obviously).
• Command & Control airplane, for use in a nuclear war.
• Air-launched ICBM carrier.
• Cruise missile carrier - think of it as an "arsenal plane".
• Flying aircraft carrier (seriously, it's big enough).

 

[TFSmith121]

Given the lunacy of the historical ANP program, anything is possible with the USAF

Well, yes. I'm not sure it's possible to actually make this happen. But I love the idea so much I keep trying.

The only logical way to do it is to have the military lead the way. If we can get the military flying nuclear-powered megajets, it's a lot easier to get those jets into civilian service. I've done a lot of thinking about what the Air Force could do with a 5,000,000-pound plane, and there are some potential roles, although I'm not sure they couldn't be substituted for by more conventional approaches:

• Transport (obviously).
• Command & Control airplane, for use in a nuclear war.
• Air-launched ICBM carrier.
• Cruise missile carrier - think of it as an "arsenal plane".
• Flying aircraft carrier (seriously, it's big enough).

I admire your dedication, but still - under both DDE and JFK, they had other things to worry about, notably creating the strategic bomber/tanker force and then adding the liquid and solid-fulled ICBMs to the force structure. Which were, of course, trumped by the SLBM force's development.

I mean, reality ended the AF's manned space program(s); ANP seems equally marginal.

There were limits, even for DDE.

Bizarrely enough, I could see ANP going forward in the USSR; they did all sorts of weird and uneconomic things.

Best,

 

[asnys]

I admire your dedication, but still - under both DDE and JFK, they had other things to worry about, notably creating the strategic bomber/tanker force and then adding the liquid and solid-fulled ICBMs to the force structure. Which were, of course, trumped by the SLBM force's development.

I mean, reality ended the AF's manned space program(s); ANP seems equally marginal.

There were limits, even for DDE.

We can definitely get smaller nuclear-powered jets flying. If we have more consistent DoD support for the ANP program under Eisenhower, a prototype could be flying by 1960, something in the 500,000 lb. range. Then, my plan has been to replace JFK with Brien McMahon. McMahon died young, of cancer, in 1952 IOTL, but that could easily be butterflied away. He was the sponsor of the original McMahon Act and by all accounts I've found an extremely able statesman - JFK supposedly said he expected McMahon to be the first Catholic president.

McMahon could keep us out of Vietnam, so we have the money for more bizarre defense programs. And he made his name on nuclear technology, so he's likely to be favorably disposed towards projects like this. That gets us more airplanes flying, perhaps a small force of nuclear-powered bombers and C3I craft in the 500,000-lb. range.

Getting from there to the megajets of my dreams is harder. My thinking so far has been on changes to nuclear strategy, putting greater emphasis earlier on on sustaining combat operations past the initial exchange in a nuclear war.

Bizarrely enough, I could see ANP going forward in the USSR; they did all sorts of weird and uneconomic things.

The USSR did have their own version of the ANP program, but I so far haven't been able to nail down precisely how far they got. English-language sources disagree; they definitely had their own version of the NB-36, but some sources claim they actually flew a nuclear-powered jet. I think that's unlikely, but I can't quite rule it out.