IT'S ALIVE! (Up from the ashes...)

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


Well-Known Member
Jan 20, 2009
Reaction score
After a harsh thunderstorm in the desert, the electrical voltage was properly applied, and the FrankenPhoenix awoke and took to the skies!

Only one month after suffering a 1-inch zipper, chute failure and a total fin-can collapse, the brute was back at it again, this time sporting a externally-braced fin can, TTW fins, a LOT of noseweight, and 4 E9-6's (yes, you CAN fit that many 24mm MMT's into a BT-80).

All 4 motors ignited (something which had failed on the previous flight), and the delay was perfect (ultimately the cause of the previous damage was early ejection prompted by an over-eager builder). The only damage this time was a singed hole in the 24-inch nylon chute.

Next step in the evolution of a monster: 29mm mount!

Pics to follow when I get them developed!

Originally posted by Ryan S.
sounds cool, 4 E9s, sounds like a cool G motor

Well the E9 is a pretty wimpy E (28.5Ns), so it would be a pretty wimpy G36 (114Ns), but with a relatively long 3.3 sec burn, still very cool in a BT80-sized rocket!
Were all 4 ejections used for recovery or did you vent some of them outside the airframe? I've always wondered if clustered ejections cause havoc on the recovery system.

It isn't necessary to vent the redundant ejection gasses in a cluster rocket. If the ejection charges don't fire exactly simultaneously, and the first one to fire deploys the recovery system, the remaining (or redundant) ejection charges are effectively vented through the front of the airframe now that the recovery system and nose cone are no longer in the way.

In fact, a little redundancy can't be all bad to ensure that your laundry *does* deploy. As long as you don't skimp on the wadding (no need to go overboard, either) everything works just fine.

I've had great luck with my 4 x 24mm Estes "E" powered Polaris upscale (BT80 based.)
All 4 ejections went nearly simultaneously (how's THAT for a coincidence!) and did cause some problems with the recovery. It blew past a nomex blanket and burned a shreddy-looking hole (about 2 inches across) in the chute, and left the back of the nose cone well-blackened. I've got pics of both, but they're still in the camera. I'm hoping to finish the roll sometime soon!

Well if the NC wasnt in the way when the other ejections fired , wouldnt that damage the Shock-Cord , unless you have a kevlar sleave for it ? If you was using reloads you COULD not install the ejection or is it attached to the delay charge? (Only ever flew BlackPowder you see lol)

These were only BP's also. I used a 3-foot Kevlar shock cord (120-lb), attached to a 24-inch Kevlar Elastic cord, so the shock cords were completely safe.

Ahh yes! Sorry i didnt read it properley! Ahh well even with all those ejection charges the kevlar would be left a bit black but untouched!
You could fly with two motors plugged, or two mounts plugged, and still have ejection redundancy

Or you could vent two overboard like Stones indicated.

Or you could select two motors with the nominal time delay, and use the other two motors with longer delays. That way, well after ejection (two seconds?), the extra ejection charges would pop.