Do you know of any material strong enough that a large hollow cylinder of it would remain intact after a 600 mph collision head on into a concrete sky scraper or straight into the ground?

Flight data recorders seem to do a pretty good job of surviving most crashes and fires.

As pointed out earlier, I'm not saying it's going to be easy and may not be practical or possible, but until you try it you'll never know.

If a Nuclear Reactor is used to create steam, maybe they should design and build Nuclear Powered Steam Trains to test the theory......Now that would look cool....

If a Nuclear Reactor is used to create steam

Like this?

http://en.wikipedia.org/wiki/Image:BoilingWaterReactor.gif

http://en.wikipedia.org/wiki/Image:PressurizedWaterReactor.gif

Flight data recorders seem to do a pretty good job of surviving most crashes and fires.

That's partly due to their size and location in the airplane. Also, the recorders don't have to contain and shield radiation. If one gets a hole punched in it (which happens often), it isn't a big deal.

A big problem with this endeavor will be all the additional weight of the shielding material required to prevent the passengers from being irradiated during the flight. Unless that becomes a "bonus" service offered by the airlines.

Weight is going to be the problem for the nuclear fuel and generating system as well.

Of course if we get the "Mr. Fusion" from Back to the Future it will all be good.

No that is just a silly analogy. The amount of energy required to keep a jet at altitude is nowhere close to the amount of energy in a 4000MW power plant. That is like saying the explosion at the Sunrise propane plant is what could happen if have an accident with propane in your BBQ.

Edit: Note I said "at altitude". I suspect jet fuel will still be used for take-off and landings. That way the actual reactor can be of minimal size, have less shielding and be secured/shut-down during landings and take-offs.This would make it incredibly complex and infeasable. You would need 4 jet engines AND MULTIPLE NUCLEAR REACTORS. Here's the logic...

Let's assume the plane carries enough jet fuel to fly its entire flight route. You would end up with today's planes, handicapped by several tons of nuclear reactor plus water. And, let's face it, while super-heated water converting to steam will generate a significant amount of thrust, it'll come nowhere near the energy released by jet-fuel being oxidized at high temperatures. So you would need a signifcant reactor, plus a lot of water for use as propellant. I'm not familiar enough with the equations to run through the numbers, but my gut feeling is that it doesn't work very well. You effectively end up with a modern-day steam engine, and they don't seem to have succeeded in the skies.

OK, let's assume that the plane carries only enough fuel to take off and land. Let's say they have "nuclear engine problems", and the one "nuclear engine" dies on them hundreds of miles from their destination... oops. Ever seen a single-engined large-capacity passenger jet? Me neither. As a rock bottom minimum, you need 2 independant engines (i.e. 2 independant nuclear reactors) to achieve the necessary redundancy, ala the Boeing 737 and 757 models. Note also that 2-engined planes face lesser restrictions as well. They are required to stay within "gliding" distance of an alternate landing site. A 737 or 757 flying New York to London will take a "great circle route" that stays within gliding distance of Halifax, St John's, Norsaq and Angmagssalik (Greenland), Reykjavik (Iceland), and Belfast (Northern Ireland). For unrestricted passenger-carrying travel, a plane needs at least 3 engines (e.g. the old DC9).

And finally, you do NOT want to shut down and re-start engines inflight as a regular practice. Inflight engine restarts are an emergency procedure that pilots must know, but that's it.

There are more practical ways to save fuel...

http://www.cnn.com/2008/TRAVEL/05/02/flying.slower.ap/ NEW YORK (AP) -- Drivers have long known that slowing down on the highway means getting more miles to the gallon. Now airlines are trying it, too -- adding a few minutes to flights to save millions on fuel.
airplane

Southwest Airlines started flying slower about two months ago, and projects it will save $42 million in fuel this year by extending each flight by one to three minutes.
Same principle as not being a leadfoot on the highway; slow down, arrive at your destination a few minutes later, and save fuel.
fer-cryin-out-loud someone puh-lease do something about requiring jet planes to burn expensive fuel while idling in line waiting to take off
consider turbo-props where feasable
if you really, really want to get nuclear into the act, consider using electricity from a reactor to split water into oxygen and hydrogen, and use compressed hydrogen as fuel.

Let's assume the plane carries enough jet fuel to fly its entire flight route

Well right off the bat you made an error. Planes rarely fly with a full tank. They carry enough fuel plus some safety for a single flight. In an ideal hybrid system only enough for take-off and landing plus safety would be loaded. I'll counter your other points later.

Note also that 2-engined planes face lesser restrictions as well. They are required to stay within "gliding" distance of an alternate landing site.

Not that I think nuclear-powered flight will ever be practical on Earth, but that statement isn't accurate either. Google "ETOPS" and you'll see that these days, twin-engine airlines can travel pretty much anywhere in the world without restriction.

Not that I think nuclear-powered flight will ever be practical on Earth, but that statement isn't accurate either. Google "ETOPS" and you'll see that these days, twin-engine airlines can travel pretty much anywhere in the world without restriction.
I sit corrected. It's more a matter of how far the plane can limp along on 1 engine in a given time. It used to be one hour. The correlation with water is indirect, in that there aren't very many airports in the middle of the ocean. Recent extensions to ETOPS (90, 120, 180 minutes) have rendered even that obsolete.

There is still the matter of rquiring either...
two inependant nuclear powerplants, or
that the plane's jets have enough fuel left over AFTER TAKEOFF to satisfy ETOPS


Either case doesn't look feasable.

Plus, I would not want to shut down the jet engines in flight, with hundreds of passengers aboard.

In addition, I question whether expansion of superheated steam can come close to supplying the power created by expansion resulting from burning of jet fuel.

A more reasonable approach might be smaller, more economical, engines teamed up with small tanks of compressed hydrogen, The hydrogen would be injected into the combustion chamber, juicing up the power output at takeoff, when you need it most. After that, the rest of the flight would be on standard jet power (using smaller engines).