I was watching one of the Discovery channels the other night, when they had a documentary on ballooning. Specifically, long distance (and round-the-world) balloon flights. They mentioned that it was basically impossible to circumnavigate the Earth in a pure hot air balloon because there’s no way to carry enough fuel for the entire trip.
That got me thinking: naturally, that would apply to conventional fuels, like gas or oil…but what about unconventional sources?
So I come to my question: Is there any way to use a nuclear energy source (such as a Radioisotope Thermoelectric Generator) to power a hot air balloon (Either by directly heating the air, or powering an electrical heating system)?
My only requirments would be that it be small enough to fit on a craft roughly the size of a normal balloon or thermal airship (say, [url=Breitling Orbiter - Wikipedia]“Breitling Orbiter” size, max.), and that the radiation not kill the crew. (And preferably not badly irradiate the rest of the world as it flew, but that’s technically not a deal breaker.)
So, I’m sitting here with my girlfriend, and was about to impress her with my badass knowledge of like, “Well, yeah, you know. . . NASA and the Air Force tried building a nuclear-powered missile . . .”
The big problem with this is the fallout from the reactor itself. Granted, the SLAM vented hot friggin’ magma of Uranium out, thus leaving a trail of fallout wherever it went. I would think this hot air balloon would do the same. Plus, what if it came down rather uncontrolled?
Tripler
I’m going to venture a vote of “Possible, but not practical.”
I’m thinkig that it’s unlikely. A nuclear reactor requires a metric ass load of water to cool it. That means it’s pretty tough to make a mobile one, unless you happen to be conviently moving across a large body of water.
To get a balloon up, you’re looking at a LOT more heat than one of those can provide. The burners on a baloon put out 10-15,000,000 BTUs apiece… The biggest RTG on Wikipedia there puts out 7000 BTUs at it’s absolute peak.
You’re definitely not going to find a nuclear option that could fit in to a payload the size of a normal basket, and put out the neccessary heat…
To get the maximum lift from your nuclear power source, you could use the ultimate lifting gas, very hot hydrogen. Then hang your power unit from the gondola from a very long extension cord to minimize the need for shielding.
Of course hot hydrogen, like a balloon dangling a reactor at the end of 100M of rope, presents a slew of engineering hurtles. Could it be done, I guess. Easily? Probably not.
It might be possible, but entirely impractical to create a very dangerously unshielded hot air balloon that maintained air temperature through convecting air directly through some sort of a radiator attached to a smaller reactor such as http://en.wikipedia.org/wiki/Aircraft_Reactor_Experiment
Of course you couldnt’ fly it since without the shielding you would fry.
But would a RTG be sufficient to power a dirigible on Titan? That is, supply enough heat to inflate the balloon and power whatever is in the gondola beneath?
I just ran that through an online converter, and that’s telling me that that’s equivilant to…4.3 megawatt/hours. Is that how much power I’d need to generate to create that much heat electrically, or did I completely botch the numbers?
What about a pebble bed reactor? using a fresh air intake, and the heated air directed into the ballon.
Hang your basket far enough below the reactor and radiation is not a problem.
You would need some type of ducting system to dump excess hot air when the ballon is full.
The Eviromental Impact Report will be left as an exercise for the student.
I think it can be done, but by taking liberties with the working fluid outside the ballon.
The easiest way is to use water instead of air, then a nuke powered sub might even qualify.
If we are to stay with a gas as the working fluid, then if we move from earth to a gas giant with a very dense atmosphere a nuke powered ballon might not only work, but might one day be used for exploring those places.
Myself, I’m going to instead look at the balloon membrane. If we make the membrane a sufficiently good insulator, we can use an arbitrarily low power to heat the air inside the balloon. I don’t know what the current materials limits are for insulating membranes, but I don’t think there’s any inherent upper bound.
IIRC those are too low powered. Perhaps a quantum nucleonic reactor, which the Air Force has been considering for use in drones. If nothing else, it has a cool name.
