Ejections

[Engineer Kelly]

When should i use seperate electronically controlled ejection charges (Timers, alts)? What width length ratio should i not even try to use the initial motor to eject the chute (Even with stuffer) ?

Im working in rock sim with a bt-80 dia. about 72 in. long. Im going to be launching it on probably E-G single motors. Most likely not G though. Is that too long, even with a stuffer tube to consider the ejection charge of one of those motors to pop the nose cone and chute out?

[Rocket Doctor]

When should i use seperate electronically controlled ejection charges (Timers, alts)? What width length ratio should i not even try to use the initial motor to eject the chute (Even with stuffer) ?

Im working in rock sim with a bt-80 dia. about 72 in. long. Im going to be launching it on probably E-G single motors. Most likely not G though. Is that too long, even with a stuffer tube to consider the ejection charge of one of those motors to pop the nose cone and chute out?

The Estes Mean Machines is 78 inches long. I can't see why you coudn;t use a stuffer tube. Build it in sections and you should be able to install a BT-50 stuffer tube, the diameter of Estes "E" motors.

[Engineer Kelly]

Yeah, i was originally going to build a mean machine. I think its only a bt 60. With 24 mm motors. Then i looked at the Colossus and decided to build one a little longer than that. bt-80.

[Doug Sams]

When should i use seperate electronically controlled ejection charges (Timers, alts)? What width length ratio should i not even try to use the initial motor to eject the chute (Even with stuffer) ?

Im working in rock sim with a bt-80 dia. about 72 in. long. Im going to be launching it on probably E-G single motors. Most likely not G though. Is that too long, even with a stuffer tube to consider the ejection charge of one of those motors to pop the nose cone and chute out?Electronic deployment is needed when:

o Motor delay is not available (eg, motors 54mm and up, hybrids, etc)
o Available delay is too far off from simulated optimum value
o Rocket topology precludes using motor ejection - eg, payload section is barrier between motor and parachute compartment

Volume is really not a factor. Yes, with electronic deployment, you can adjust the amount of ejection BP as required for the given volume. But with motor delay, you can also supplement the charge amount as well. In reloadables, it's fairly easy. In SU, it's a little more involved. For APCP, just peel off the paper cap, and pour in more BP. For BP motors, you'll need to scrape off the clay cap, then pour in more BP, then effect a replacement cap using some wadding and/or tape.

To determine the amount of ejection BP, use one of the online calculators such as this one: http://www.info-central.org/recovery_powder.shtml Remember to subtract out the amount of powder already in the motor. You may need to dig a little for that data; it will depend on the motor.

If all you need is more gas generation because of a larger volume, electronics isn't really necessary. OTOH, if you're looking to get your feet wet with electronics, then go for it :)

Doug


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[Engineer Kelly]

Ah, ok. Thanks a bunch!