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Old 11-04-2011, 08:15 PM
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CPMcGraw CPMcGraw is offline
Join Date: Mar 2005
Location: Mobile, Alabama
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Default Dual-Deploy Engines??

THIS THREAD prompted my asking the question here, Is a dual-deploy time delay even possible for a single model engine?

Can you have a single initiator for two delay chains, maybe side-by-side, with two blow-through "tunnels" that would allow the "long-delay" charge to "by-pass" the short-delay charge and pressurize a separate compartment for the main recovery system?

Seems like we bounced this about a while back, maybe when the SVDT was first fired up.
Craig McGraw

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Old 07-15-2021, 10:20 PM
olDave olDave is offline
Join Date: Sep 2015
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Default One way to do this with existing BP motor manufacturing

(and yes, I know it's kinda late coming back to this thread with a reply)

You could use conventional motors, as already designed, to boost-coast-eject-at-apogee. The ejection charge would still be used to separate the lower portion of the rocket from the upper, while simultaneously igniting another "pyro" unit in the upper portion, the same way as an upper stage BP motor would be ignited.

Here is the trick: the upper pyro unit could be manufactured from existing materials and designs. The upper unit would use a standard motor case, have standard delay element materials in standard units of burn time, and a standard ejection charge (and retainer). The upper unit would not contain any propellant. It would need enough nozzle to restrict/block the rearward flow of ejection charge gasses, but could use one of the standard nozzle designs. (This all assumes that delay charge material can be successfully ignited from ejection charge material.)

The upper unit would be ignited at apogee when the rocket breaks into two tethered pieces. This "staging" bay could be long/large enough to contain tracking powder but should probably not try to take the form of gap staging.

The falling rocket would descend while the second delay charge burns, and then finally eject the recovery system at a lower altitude than apogee.

Does that do what you want to accomplish with your dual-delay system?
NAR 20602
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