Frozen AT motors

[ghp3]

The recent thread on frozen BP motors (stored in cold winter garages) and whether they would CATO or cause other problems prompts me to ask the same question regarding Aerotech and other composite propellant motors and reloads. I have several Aerotech E-F-G MPR motors in my garage that I'm now wondering about.

Thanks!

George
ghp3

 

[daveyfire]

Composite propellant is generally more resilient to physical abuse than black powder propellants -- they are somewhat flexible, allowing them to conform to the external conditions fairly easily. The only thing I wouldn't do would be to fire them while the propellant is frozen hard -- it may cause cracks in the grain, or chunks of the graing getting plugged in the nozzle, causing a CATO. Just warm em up to about 65-70 degrees before flying and you're good to go!

 

[Ryan S.]

if you fire them cold this could also cause O-ring problems

I dont know if this is true, but if they freeze and thaw, couldnt the actual propellant pull away from the casting tube? If so this could pose a problem

 

[Juerg]

Letting them freeze surely isn't the way how one should store any pyrotechnics, not only for mechanical reasons (cracks, although not an issue on AP motors) but also because the thawing may generate humidity on the surface.

The main problem when launching in cold weather is the O-rings, that's true not only for the Shuttle, but also for our motors. So keep them warm!

Juerg