The plan will be to keep the first launch as normal as possible to
lower the number of unknowns, so I will probably just use Helium.
The balloon is a sounding balloon that I got years ago I think it is
5m.
The first launch will be about testing the communications and getting
good video for YouTube and pictures for the site and testing recovery
systems.
The subsequent balloons will be zero pressure balloons made for welded
sheets of 1mil or thinner PE scaled to the weight of the payloads.
None of the early ones will be that large but I was wondering if I
could make one out of black plastic to create a hot H2 balloon to get
really high up.
The later launches will also go up with a simulated guidance system
for the rocket.
MisterQED