🚀 go-pugleaf

>Popular Science magazine had a photograph of a "mysterious" contrail that
>looks like -+-+-+-+-+-+, and very thin compared to other trans-sonics.
>This was ?September 1992 (this year anyway)

I've seen this contrail.  It was on a north/south track out over the ocean
west and south of San Fransico, approx. August 1992.  The trail was well above
and further out to sea than the normal air traffic pattern that runs along the
west coast of the US.  The regularity of the pattern is what really stuck in
my mind.

At the time I thought it was the contrail from a Nasa modified U2 that
flies out of Moffet Field near San Jose.  The altitude seemed reasonable
for a U2.  The contrail was relatively close to a U2 base. The pulse pattern
is the only thing I can't explain.

Are there any known jet engines (military or commercial) that produce
a regularly pulsed contrail at high altitudes?  Could the pulsing just be
the result of a fuel saving modification to an old U2 engine?
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