I don’t think magnesium suffers quite the same surface agglomeration issues as
Al for higher metal contents and Wickman claimed (back in the day) that the
activation temperature for Mg in solid propellants was over an order of
magnitude less than Al which also helped reduce 2 phase flow losses through the
nozzle (again, for higher metal contents). Mg has a lower electronegativity
than Al (more reactive reducer) but Al has a higher density.
Uncoated Mg does have a tendency to slowly react with AP it’s exposed
directly to to produce Magnesium perchlorate which yields a propellant grain
that needs to be well sealed from moisture exposure (ie humidity).
I’ve never played with Magnalium and can’t really comment much about it other
than consistently hearing that the properties are pretty much a cross between
the 2 metals.
I have done much characterization and measurement of an APCP with 75%AP
(200um) 5% Al (5um) 2% Mg (2um) remainder organics that consistently yielded
measured resulted that were smack bang on the theoretical 230(ish) sec Isp even
for small 29mm diameter motors.
Troy
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Vertical Limits
Sent: Wednesday, 4 April 2018 7:53 PM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Aluminium vs Magnalium
Hi list,
When making a fairly straight forward APCP with 70/8 AP/Al what would be the
benefit of exchanging the Al for Magnalium? I see some pretty big motors from
the CSXT and Qu8k using Magnalium. Or in general: what are the benefits of
adding magnesium to an all Al propellant?
For a short introduction:
After a intermezzo of about 15 years I rediscovered the arocket list and
subscribed again. Last year I changed from using sugar motors to APCP motors.
On <http://www.verticallimits.nl/> www.verticallimits.nl a recent static test
of a 10kNs APCP motor can be found. I will be flying this motor in 3 weeks’
time, all going well.
Regards,
VL