Ben Brockert wrote:
I did a number of FEA tests on sugar propellants using material
properties experimentally found by Nakka and showed that you can't
make really large case bonded sugar rockets with aluminum cases
because the case stretches more than the propellant and it cracks.
I remember some folks at FAR working on an "inside out" sugar motor
design which was intended to avoid the stretching/cracking problem
(which was blamed for an observed tendency for explosions): they
were planning to cast the propellant around a central support (a
threaded rod with some nuts along it to keep the grain from sliding
off) and burn it inward from the outer surface. (I don't know how
well that worked - this was several years ago - but it seemed like
a possibly clever idea.)
