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Old 05-21-2009, 05:37 AM   #27 (permalink)
Bicycle Bob
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Rad thrust

Quote:
Originally Posted by winkosmosis View Post
I don't understand how the heat could result in thrust from the exit port. The heating and expansion of air wouldn't push air out the back any more than it would push it out the front. The way I see it, it should have no net effect on flow.
The theory is that the assembly is like a mild ramjet. Instead of adding fuel and burning it, it just adds heat from a heat exchanger. However, the pressure inside is higher than the air around it, and the back is bigger than the front. Hence, a tiny thrust. As to Net thrust, there are skeptics. . .

The folks who flew Voyager around the world on one tank of gas had to re-do all the standard tables on heat exchange at low speed, and wound up with 20% cooling drag overall, even with careful adjustment of flow by the co-pilot.
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