NEFAR Launch
August 13, 2005

Sugar Rush A:

Video (12 megs .wmv file, 2 minutes playing time)
Nice launch, despite the old, sodden grains.  Apogee at 2227 feet, dual deployment worked, although I notice that the rocket falls quite a ways before the drogue pops out.  It's done that on the last few launches.

Sugar Rush B:


Video (12 megs .wmv file, 2 minutes playing time)

This is a more "interesting" flight.  It zig-zags severely upon leaving the launch rod, then swishes like crazy to 665 feet where the ejection charge fires right after burnout.  Good thing my drogue chute is in tatters, or I would have had a major zipper there.  Another "pop" is heard a second or so later, thought to be the second ejection charge firing.  But both of the parachutes are out already!  What gives?  

Upon disassembly, I saw that the altimeter was displaced toward the aft, jarred loose from its CPR-3000 retaining tube.  In fact, the fore-end sealing unit was broken off from the altimeter circuit board, which is now dangling by the ignitor wire.  So at first guess, it seems that the aft charge fired prematurely, popping off the aft section and deploying the drogue.  Inertia could have "ejected" the main chute, despite the single nylon retaining pin.  

A second or two later, the airframe passed the 600 foot mark, and the altimeter dutifully fired the second ejection charge, which was intended to deploy the main.

Problem with this idea is that the altimeter broke in the opposite direction, suggesting that it would have fired first, popped out the main chute, and the drogue was deployed by inertia.  Looking at the video, this seems quite possible.  But that is backwards!  No only should the drogue have fired first, but what was second "pop" at exactly the right time?  

One possibility is that the violent oscillations somehow shook the altimeter into a "test" mode, where one ignitor is fired precisely (?) one second after the other.  Firing of the first charge blew the altimeter end-cap off, leaking enough gas to the other end to eject the main.  

Speculation is rampant.  Opinions are welcomed.

Jimmy Yawn
Recrystallized Rocketry