> >>>Can the smoke trail of a rocket engine cause a lightening strike to
> >>occur? I saw this on the cable channel. They were launching in a sever
> >storm, using pneumatic tubing instead of wire to initiate the launch.
>>>>They also used a device to gather information about the electrical
>of the cloud. Apparently, you have to launch just seconds before a bolt
>comes from the cloud. It took them many, many tries, and even with some
>very sophisticated equipment, had a huge failure rate.
They were measuring the potential gradient of the atmosphere. The
voltage of the atmosphere has a pretty strong gradient (~100 v/ft) under
normal conditions and even higher when a thunderstorm is in progress. A
lightning strike drains the charge and reduces the gradient for a while
until it charges up again.
This effect has been used by a model airplane guy named Maynard Hill
to run an autopilot for an R/C airplane. I do not know exactly how the
sensor works but it involves ion sources and some sort of ion sensor to
make a ultra-high impedence voltmeter. The plans have been published, but
I am not sure where ( early Model Aviation?). It is not excessively
Unfortunately for autopilot purposes, sometimes the DIRECTION of the
gradient changes during thunderstorms, resulting in some interesting and
>Only a complete idiot would try this as an amateur. Even with a wire
>leading from the cloud to the launch-pad, there is nothing that says the
>lightening bolt can't hit anything on the field, or within a large
>You can get thas a remotely plausible or reliable scientific method of
determining the exact path that lightning will take. You would never get
me to blow into that tube!