Thanks for the quick responses.

MAYBE Class E? Where do you intend to launch this balloon so that it will
definitely pass through Class G and Class A airspace but perhaps not Class
E?

I may have it wrong, but my understanding is in the U.S. Class G is
uncontrolled airspace, and Class A is everything from 18000ft to
60000ft. Well, the balloon will definitely go through Class A in this
case. As far as Class E and G, maybe I am reading the charts all
wrong.

Looking at the Skyvector site, lets say I were to launch at 36N 87W
near Nashville. If the wind were to push the balloon east or north it
could drift into Class E space briefly. Otherwise, the balloon would
only be in Class G then A. No?

Does it half a payload release and recovery parachute on it so you can
bring it back down on command?

Yes.

-John