Nuclear powered aircraft?

[nachtjaeger]

Here's one for the aviation geeks and science geeks on the forum.

Got into a discussion on nuclear rockets in a Facebook group. We've also had previous (sometimes heated) discussions on the viability of nuclear powered aircraft. It's not science fiction- they actually flew an operating reactor on a B-36 Peacemaker, although it wasn't hooked to anything except a cooling system. And GE got the external-combustion turbojets working around the same time. Those ran on (I think) an "indirect cycle" where the "hot" (radioactively as well as thermally) primary reactor coolant transferred heat to a secondary coolant which flowed to the engines.

So, here's what one guy came up with- please let me know what you think about the technical aspects (not touching the regulatory or political concerns.)

Start with one of the three surviving B-1A airframes. Those were rated for Mach 2.2, and have an "crew escape capsule" instead of ejection seats.
Subtract the empty weight from the MTOW and you have about 285,000 pounds to play around with for the reactor, shielding, and payload. Water injection could be used in the nuclear turbines as an "afterburner", but without affecting combustion (because none occurs in the engines.) The plan is, take the NB-1A to the highest altitude and fastest speed it can manage for a short sprint (before the skin melts) and then release the payload.

The "Payload" will be an aerospace plane, also with a compact reactor on board. This one can use WAY less shielding, and the more efficient direct cycle, since the engines won't operate until above 60,000 feet or so. Start out the trip to orbit with direct-cycle nuclear scramjets. No worries about maintaining enough oxygen for combustion, just about having enough airflow to make the ramjet work. When you run out of air, switch to a "steam rocket"- just run water or alcohol or whatever through a superheated reactor core, and let the reaction propel the ship. Once you're in orbit, the reactor will provide plenty of power for VASMIR type plasma thrusters for orbital control.

Thoughts? Other than the fact that "Radiophobia" and politics would never let a nuclear powered anything in the air, I think it's totally doable with existing technology.

[henrybauer]

Lockheed Martain is saying they will have a fusion reactor in the next 5 years which could make for an interesting possibility.

[Mynock]

I think it would work but at 100x the cost of a regular liquid fueled rocket, and you'd have the same maintenance nightmare that the Shuttles turned into trying to make a reusable orbital/sub-orbital vehicle. Learned that lesson for 20 years.
On the other hand for a dedicated space vehicle, that's built in space, gets maintained in space, and never comes back down, a nuke pile is a great idea. Been saying for years that they ought to ditch the stupid solar panels all over the ISS and just send up one last module with a reactor in it. Gotta refine the VASIMR rockets so they have a better thrust to weight ratio, then the power plant and the actual rocket are connected only by a nice safe electrical cord.

[Duncan Edwards]

I'm not a rocket scientist but I did want to be one when I was little kid. That mostly involved making things go BOOM! and worrying my mother.

Obviously there's a staggering amount of basic math and engineering missing from every one of your assertions. In nutshell you're describing finished technologies that do not exist and would cost vastly more to develop than they would ever yield in benefit. If the thrust to weight ratio of a single stage nuclear aircraft is bad then it will not improve at all with an additional stage. In fact it will only become far worse. You offer that the second stage can get by with far less shielding but if it's going to ever fly in earth's atmosphere at all it would have to have the same factors as your proposed NB-1A. Basic aerodynamics says you would be better off putting dynamite under an anvil. Beyond the other factors like environmentally disastrous, expensive, unsafe, unneeded, etc. this is what finally played a part in grounding the NB-36 after a few test runs. There just wasn't enough benefit to be derived.

Then you have to begin answering the practical questions like "why?" If all you want to do is put something in orbit, which is all your proposed contraption might do even on a good day, there are much simpler, less expensive, and less dangerous ways to do it.

[Fred588]

Just because something CAN be done is not a good reason to Do it. On the other hand, if something can NOT be done, that IS a good reason to NOT do it.

[nachtjaeger]

You make some good points.

Finished technologies? No. Proven technologies? Yes. GE had working prototypes of nuclear turbojets in 1956, and a working nuclear ramjet was successfully tested in 1957. I stand corrected on one point- the GE turbines were direct-cycle, so not the best option for a reuseable aircraft being operated from runways. Pratt & Whitney was working on the indirect cycle engines (not a large technological leap) when the program was cancelled.

The whole point of two-stage-to-orbit is to minimize the amount of expendable fuel (or in this case, expendable reaction mass) the orbiter has to carry. In this scenario, the thrust-to-weight ratio can be fairly low, since neither the carrier aircraft nor the orbiter has to lift itself vertically off the launch pad.

The reactor in the orbiter isn't going to operate below at least 60,000 feet. So, no worries about irradiating the ground crew or making the runway glow in the dark. That means you only need enough shielding to protect the crew and payload. Trying to make air radioactive? Not that effective. It's radioactive material IN the air that causes problems in a reactor accident or nuclear weapon hit. Figure out how radioactive air coming out of the direct-cycle scramjets is, then divide that level by all the cubic miles of air between there and the ground. Detectable (with the most sensitive equipment)? Possibly. Hazardous? No.

Environmentally disastrous? Compared to burning thousands of gallons of petroleum fuel every aircraft trip?

(Will finjish this later)

The Nuclear Bomber was cancelled for the same reason as the XB-70 Valkyrie and the B-1A. The concept had been overtaken by events- specifically the invention of high-altitude antiaircraft missiles.

I'm not a rocket scientist but I did want to be one when I was little kid. That mostly involved making things go BOOM! and worrying my mother.

Obviously there's a staggering amount of basic math and engineering missing from every one of your assertions. In nutshell you're describing finished technologies that do not exist and would cost vastly more to develop than they would ever yield in benefit. If the thrust to weight ratio of a single stage nuclear aircraft is bad then it will not improve at all with an additional stage. In fact it will only become far worse. You offer that the second stage can get by with far less shielding but if it's going to ever fly in earth's atmosphere at all it would have to have the same factors as your proposed NB-1A. Basic aerodynamics says you would be better off putting dynamite under an anvil. Beyond the other factors like environmentally disastrous, expensive, unsafe, unneeded, etc. this is what finally played a part in grounding the NB-36 after a few test runs. There just wasn't enough benefit to be derived.

Then you have to begin answering the practical questions like "why?" If all you want to do is put something in orbit, which is all your proposed contraption might do even on a good day, there are much simpler, less expensive, and less dangerous ways to do it.

[Duncan Edwards]

Environmentally disastrous? Compared to burning thousands of gallons of petroleum fuel every aircraft trip?

Compared to no jetliner ever had to have a plane load of paratroopers follow it around in case it crashed and they had to cordon off a poisonous site. This was a feature of the NB-36.

[Mynock]

Agreed, politics and nuke-phobia aside, there is a serious safety issue there. Your containment vessel better be able to survive a plunge from 30,000 feet, otherwise fuck letting that thing fly over my house.
My bet is anything that operates in an atmosphere is going to be burning dead dinosaurs for a long time yet, if for nothing else than cost effectiveness. Nothing beats the horsepower out vs. dollars in ratio of a jet turbine. They also burn very clean and run on what is essientially kerosene so the environmental impact is minimal.

[Duncan Edwards]

Agreed, politics and nuke-phobia aside, there is a serious safety issue there. Your containment vessel better be able to survive a plunge from 30,000 feet, otherwise fuck letting that thing fly over my house.
My bet is anything that operates in an atmosphere is going to be burning dead dinosaurs for a long time yet, if for nothing else than cost effectiveness. Nothing beats the horsepower out vs. dollars in ratio of a jet turbine. They also burn very clean and run on what is essientially kerosene so the environmental impact is minimal.

On top of all that there's just no requirement for unlimited endurance. The whole idea behind the NB-36 was you could keep a fleet in the air,safe from preemptive attack, and still go anywhere in the world. A 787 or 777-300 can fly 12,000km nonstop already. Military aircraft can stay aloft for days with mid-air refueling if need be. If you want a satellite launcher then conventional methods will get you there and the price per pound is going to take a big drop in the next few years.

But yeah, it would be cool if you could make it work.

[jadokast98]

We touched on one point briefly; keeping a bird in the air somewhat indefinitely. In the hysteria of the early to mid Cold War the West was very unsure that we had any supremacy and any advantage was going to be looked into. (Once the Wall came down and the Soviet Union dissolved, we saw what position communist forces actually were in.) Having a bird, or several in the air(on paper) looked great, much like a nuke sub. Roaming friendly and International airspace at will.
Once we observed the long-term affects nuclear fallout was causing, (Atomic Demolition Mines we drawn up with friendly purposes like... creating harbors. ) and other aeronautical improvements, the Atomic Bomber grew out of favor. I read an article several years ago about this concept. I was shocked as well. We were so sure the "The Reds" were very well along in planning invasions on the continental US, as well as nuking us.
I'm reasonably positive that the air to air mishaps during those times swayed their judgement enough to think better of it. I want to also think that our leaders then, who were more of a risk takers than the group we have now, were also doing a better job than the communists.