Yesterday it was 11F (-12C) when I headed to the Music City Missile Club launch, and it wasn't a whole lot warmer when I got there. Temperatures maxed out around 38F.
We experienced a disturbing number of chuffs, including a Big Bertha on a Q-Jet D-motor that never got off the pad, just sat there and burned all the propellant, then ejected.
Burn rate and ignite-ability of composite propellant both decrease with temperature. Lesson learned: when it's cold, pack motors to be used in a cooler with a few heated bricks to keep the contents warmed. Or warm the motors in an inside pocket to bring them close to room temperature before installing in the rocket. Then get the rocket on the pad and launch while the motor's still warm. No need to be frantically hasty, once the motor is warm it will take a little while for the propellant inside to cool down.
Best -- Terry
We experienced a disturbing number of chuffs, including a Big Bertha on a Q-Jet D-motor that never got off the pad, just sat there and burned all the propellant, then ejected.
Burn rate and ignite-ability of composite propellant both decrease with temperature. Lesson learned: when it's cold, pack motors to be used in a cooler with a few heated bricks to keep the contents warmed. Or warm the motors in an inside pocket to bring them close to room temperature before installing in the rocket. Then get the rocket on the pad and launch while the motor's still warm. No need to be frantically hasty, once the motor is warm it will take a little while for the propellant inside to cool down.
Best -- Terry