From 26705813a7927467b31a1317373660e1c69d88e4 Mon Sep 17 00:00:00 2001 From: Bdale Garbee Date: Sun, 16 Nov 2008 00:01:00 -0700 Subject: [PATCH] post --- bdale/blog/posts/Level_3.mdwn | 61 +++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) create mode 100644 bdale/blog/posts/Level_3.mdwn diff --git a/bdale/blog/posts/Level_3.mdwn b/bdale/blog/posts/Level_3.mdwn new file mode 100644 index 0000000..6236829 --- /dev/null +++ b/bdale/blog/posts/Level_3.mdwn @@ -0,0 +1,61 @@ +[[!tag tags/rockets]] +I [wrote last month](YikStik) +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](http://www.polecataerospace.com/) +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](http://www.vatsaas.org/rtv/systems/Parachutes/Chute.aspx) +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](http://www.aerotech-rocketry.com) +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](http://www.gag.com/rockets/projects/goblin10/) +this rocket. +James Russell took some +[pictures](http://picasaweb.google.com/jamesr2/StealeyMemorialLaunchSiteHudsonRanch) +at the launch, including +[a great one](http://picasaweb.google.com/jamesr2/StealeyMemorialLaunchSiteHudsonRanch#5269066826180657666) +of the rocket under boost just leaving the launch rail. +And Jeff Lane captured +[video](http://cosrocs.org/all%20other%20videos/2008videos/11-15hudson/bdale_L3.mov) +of the ascent and descent. + +It was a great flight and a great day, and represents a major milestone in +our hobby rocket activities! -- 2.30.2