Using electrodes to create pockets of plasma in an aircraft's
exhaust plume could reduce noise during take off, say aerospace
engineers at Ohio State University in Columbus, who recently
applied to patent the idea. Mohammad Samimy and colleagues have
shown that inserting eight electrodes into a laboratory-scale
exhaust pipe creates pressure differences in the exhaust plume.
"The net outcome of this should be a reduction in jet noise,"
says Samimy, though this remains to be demonstrated. Engineers
recently began adding fixed, chevron-shaped ridges to jet engine
exhausts. These do reduce noise but also increase fuel
consumption. The advantage of the electrodes would be that they
could used during take-off, when the noise is greatest, and then
switched off. The electrodes' charge and strength could also be
optimised to suit weather conditions, or perhaps used by stealth
planes to reduce the heat of their exhaust. Dennis McLaughlin,
an aerospace engineer at Pennsylvania State University, says the
work is promisin