Route of ejection gas?

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Well-Known Member
Feb 10, 2017
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I was cleaning my rockets today after launching them Saturday with H motors. What seemed odd was that the red caps on top of the Aerotech motors were still there, and the wadding was still in place in 2 of the rockets. This got me wondering about the route of the ejection gas. How can the gas blow through the hole on top of the motor without ejecting the red cap or the wadding but with enough force to eject the nose cone and parachute?
by displacing the air above it, and that air pops the top?

Also, likely a lot of blow- by going on. the red cap pops off and goes to one side, and the bulk force of the charge goes past it.

I shook all 4 of these out of my optima one day last year. didn't know they were piling up in there.

Last edited:
Ejection is done by pressure. The charge pressurizes the tube. It doesn't need to have the charge itself move things. The burning powder creates an expanding gas that causes all the gas (air) in the tube to equalize pressure throughout the tube until something releases it. That is the nose cone popping off the end of the tube. That is why piston ejection works so well. The air above the piston equalizes the pressure until the nose cone pops off, but the expanding gas of the ejection charge doesn't stop expanding until the piston leaves the tube.

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