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Old 07-08-2017, 05:49 PM
luke strawwalker's Avatar
luke strawwalker luke strawwalker is offline
Join Date: Dec 2007
Location: Needville and Shiner, TX
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Originally Posted by tbzep
It will eject to some extent, but it won't forcefully enough to have successful recovery on all models. Bob Kaplow used zero delay in SuperRoc before it was quickly outlawed. I wouldn't try it on a model that I spent a lot of time making look good.

Remember that the propellant breaks through before all of it is burned. Hot gases and small bits of BP blow forward to ignite the upper stage. This can sometimes create enough pressure to blow a nosecone, but sometimes it isn't enough to get the recovery system to follow. Centuri's Pass-port staging system was designed to vent the pressure so it wouldn't pop stages apart before ignition.


Not sure if the exact chamber pressure on a D12-0 but probly in the neighborhood of 80-100 psi... As the motor burns the propellant slug holds this pressure in the casing between the burning propellant slug back face and the nozzle inner end and nozzle hole, which is constantly expelling gas to create thrust. When the slug of propellant burns thinner and thinner till it's a disk, at some point it shatters from the chamber pressure behind it, instantly creating another much larger outlet for the pressurized flaming gas, that being the front of the motor case. This blows burning chunks of BP from the shattered disk forward, igniting the second stage. The chunks of burning propellant move slower than the expanding hot gas, which arrives first and can blow the stages apart before the burning particles ignite the upper stage, hence "pass-port" or other gas vent designs, or taping the motors together so they hold together until the upper stage motor repressurizes the booster motor case between the two nozzles, at which point the tape becomes the weak link and ruptures, allowing the pressure to blow the stages apart...

The problem is the volume of gas and speed it's delivered is smaller than that from a fast-burning BP ejection charge... Might not be enough to elect the laundry, especially from a large tube with large volume...

That and ZERO delay between thrust and "ejection"...

Later! OL J R
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