I know what you're saying. It will still produce the same amount of energy, and the vibration of the airframe that would have produced sound will clearly not result in a vibration travelling through the surrounding medium (since there is none). This is not particularly significant to the aircraft, because all this would do in air is damp the vibration in the airframe *slightly*, while the rest of the energy would be converted to heat in the process of fatiguing the airframe. I would conclude then that in space, the rest of the energy that would have produced sound would be converted to heat and dissipated by E-M radiation.
Pie
[This message has been edited by Pielander (edited 27 June 2001).]