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 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!