Hybrid Thermal Airship

Wednesday, October 26th, 2011

Everyone is familiar with hot-air balloons, and most people are familiar with helium-filled blimps, like the Goodyear Blimp, if not with hydrogen-filled zeppelins, like the Hindenburg.

I found it a bit jarring when I first read about hot-airships, but the concept makes sense.

Once you have motors mounted on a balloon that needs hot air, it’s only natural to harness the waste heat from the motors to heat the air, rather than relying on burners. (Or you could laser-power it, I suppose.)  Turbines are light and give off a bit more heat than other engines of the same power; so they might make a good choice.

One of the key advantages of hot-air over helium is that you can afford to vent hot air, if you have too much lift, and you can make more, through heating, when you need more lift.  Helium is extremely expensive in airship-sized volumes, and you can’t get it back once you let it go.  (Hydrogen’s not so different from hot-air, in that it’s cheap enough to vent off, and you can generate more, from the right raw materials, when you need it, but the public is terrified of it.)

If you puzzle over this a while, you may decide that the best course involves a static volume of helium, providing just enough lift for the vessel itself, combined with hot-air to make up the difference needed to carry any cargo — a thermal hybrid airship, like this concept from Boeing, which they did not end up pursuing:

(Hat tip à mon père.)

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