Message posted by robb on November 18, 2002 at 8:08:57 PST:
I recall reading an interesting paper a couple of years back regarding the "donuts on a rope" contrail business. What it boiled down to was the author took into account an assumed rough size, weight, and lift for a potential aircraft, and the distance between "donuts" that has been observed behind these unknown aircraft, and what that meant in terms the rate of a pulsing propulsion system. Basically, in order to maintain lift at the possible rate observed, he had to have pretty big "explosions" behind the aircraft, and subsequently a pretty substantial shielding system to protect it from the explosions. The weight of that shield made these explosions impractical, in terms of keeping an airframe in flight. This isn't to say a pulsing system wouldn't work, just that it would more likely be implemented on the order of dozens of smaller "explosions" each second, ruling out any observable difference in contrails. Just a little physics to ruin our fun. ;)
In Reply to: Puffing contrail; 928, 965, 953: pictures posted. posted by Scott on November 16, 2002 at 21:16:33 PST:
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