Random tidbits Bdale thinks are worth documenting.

Bdale Garbee
bdale@gag.com

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Level 3!
I wrote last month about my failed first attempt to achieve a "level 3" high power rocketry certification. Last week, I learned that one of the commercial altimeters I flew for control of the ejection sequence has a firmware bug, which can cause premature ejection of the main parachute on flights above 10k feet! So it may in fact be the case that everything I did was perfect and I was simply the victim of a bug in software... how ironic!

Yesterday, on my second certification attempt, I was successful!

The rocket I flew this time was based on a Polecat Aerospace ten inch Goblin kit. I incorporated several modifications in my build, including additional fiberglass and carbon fiber reinforcement, and a payload bay in the nose cone. Once again, my wife Karen graced me with a parachute sewn from the Team Vatsaas design, this time a slightly larger one in burgundy and black rip-stop nylon. She incorporated several design tweaks based on her experiences sewing the first one which we'll try to write up at some point, that allowed her to sew this one in less time.

The motor selected was again an Aerotech M1297W reload.

The launch went perfectly, and the ascent was impressive. At apogee, the nose cone separated as planned and the drogue parachute deployed. Unfortunately, when the backup charge fired two seconds later, the main parachute also deployed. That wasn't intended... the main was supposed to deploy much lower, at 1300 feet. Luckily, the winds were light enough that the rocket touched down only about a mile downrange from the launch rail, well within the waiver distance, and was easily recovered without damage.

There are three things I'll consider changing before flying this rocket again. First, the chute size calculator used to design the main parachute seems way off. The actual descent rate was around 32 feet per second, while our goal was 20. Other than that, the parachute performed admirably! Second, the premature deployment of the main at apogee could be cured by replacing the paper taped over that parachute bay with another piston capping the bay and held in with a pair of shear pins. Finally, the hard touch down snapped some of the nylon wire ties holding the batteries in place in the avionics bay. While no damage was done, and reducing the descent rate might prevent it happening again, improving the battery mounting would be an easy upgrade.

For more information, see my project page for this rocket. James Russell took some pictures at the launch, including a great one of the rocket under boost just leaving the launch rail. And Jeff Lane captured video of the ascent and descent.

It was a great flight and a great day, and represents a major milestone in our hobby rocket activities!

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YikStik
As some of you know, the first weekend in October was a big deal for me, because it was NCR's Oktoberfest launch event. My son and I spent the weekend camped out on the prairie with Keith Packard and many of our other friends. Keith successfully went from nothing to a "level 2" high power certification, which was pretty cool. I wasn't quite so lucky.

On Saturday morning, I flew my custom-designed rocket YikStik for a "level 3" certification attempt. The name comes from the word my wife uses to describe lipstick. The rocket was built from a mixture of custom and Giant Leap parts, including 98mm Dyna Wind airframe, a 98-75mm tail cone retainer, and a Pinnacle nose cone. All the centering rings were cut on my 3-axis CNC milling machine, and the fins were custom 7-layer composite layups using plywood, carbon fiber, fiberglass, and epoxy... all vacuum bagged using a kitchen food saver appliance. Painted red, gold, and black, with a custom 8 foot main parachute sewn by my wife Karen from the Team Vatsaas design in red and black rip-stop nylon.

The motor selected was an Aerotech M1297W reload. This is a 75mm diameter motor 66.5cm in length with 2722 grams of propellant yielding 5417 Newton-seconds of total impulse. It was also on sale earlier this year for cert attempts. My simulations said YikStik should have flown to about 14,800 feet above ground level at the NCR north site on this motor.

The launch went perfectly, and the rocket was stunningly beautiful under boost. It disappeared into some high clouds, but we continued to have strong signals from the two tracking transmitters installed in the payload bay behind the nose cone. About the anticipated time after launch, we saw a rocket descending under chute in the distance, and headed in that direction. A few minutes later, we abruptly lost both tracking signals, and that's when things took a turn for the weird.

In hindsight, I think we suffered an apogee deployment of the main chute, and the rocket we saw descending was someone else's. YikStik was designed to deploy a streamer at apogee, then descend fairly quickly to about 1500 feet above ground where a second set of ejection charges would fire to separate the nose cone on a 3 foot drogue parachute that would pull a deployment bag containing the main chute out of the airframe and then pull the bag off the chute. The nose cone, payload bay with the tracking transmitters, and deployment bag would then descend under the drogue chute and the remainder of the rocket would descend under the big chute. In the world of deployment bags, this is called a 'free bag' configuration. With deployment at 1500 feet, the two bits should have landed within sight of each other. But that didn't happen.

It wasn't until late Sunday afternoon, after we had to leave to get Keith to the airport, that some friends finally located the nose cone assembly about 3.5 miles down range from the launch site, over a couple rises and past an area of rough terrain. By then it was cold, windy, and rainy, and so I really appreciated the effort they put in locating the nose, and wasn't too surprised that they didn't immediately see the rest. Since the bulk of the rocket under the main should have had a slightly higher descent rate than the nose cone, I expected to find the rest of the rocket somewhere near a line between the launch rail and where the nose cone was discovered. So last Wednesday I spent about 5.5 hours walking around the area searching... but no luck. Since then, several other people have been out looking for my rocket, including two friends who flew over the area today in a light plane looking down into all the washes. Still nothing.

I posted some signs in the area with a photo of the rocket and my contact info, I hope someone calls eventually. In the meantime, the bulk of YikStik remains missing, and of course I did not achieve a successful level 3 certification.

Lessons learned for next time are that tethering the deployment bag to the main chute instead of flying in a "free bag" configuration might have been a better choice, and it's kind of silly having two tracking transmitters in one of the two pieces of your rocket and none in the other...

Ray LaPanse took some stunning photos of the launch. He will likely post better versions with color correction and so forth at some point, but in the meantime, I've put a few up on my Garbee Rockets web site. She sure was a beauty!

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