Motor Physics

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Well-Known Member
Dec 24, 2003
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I have a question that may be weird to ask now - considering I want to do my L1 next week.

To date I have only used SU motors.

I opened up a G64 reload to practice assembling it, (The certification will be on an H165R) and looked at how it all goes together.

In a BP motor the fuel burns from the bottom up, and when it gets to the top, the delay starts burning, then the ejection charge pops. Simple....

In a composite, the fuel burns along the lenght of the grain, and the delay must begin burning at ignition. Does this mean what happens is the delay burs while under boost and essentially is just timed to last the delay period plus the burn period?
That's correct. The delay material is just a very slow burning type of propellant. The delay is calculated based on the burn rate of the delay material and the chamber pressure and burn time of the motor propellant.