I was involved briefly with a project trying to set a high altitude glide record back in about 2004.
They were trying to beat NASA to establish a glide at over 100k ft.
The plan was to use one of my larger delta wing designs dropped from a balloon at 120k ft. and try to pull out to establish the glide
about 100k. ft.
it's incredible how fast things accelerate in the absence of air.....
I believe they told me it would be doing about 700mph. within the first 4 second of the drop, so the initial 20k. zone really didn't offer much time to establish flight. Not really my area of expertise, or even in the same galaxy...
NASA was using a full scale glider, maybe a Discus, don't remember, but I was told they kept pulling administrative strings to make sure the other group would NOT get clearance to fly...
They were talking about going to Canada, or Iceland to do the flight....