+[[!tag tags/rockets]]
+Today was the season opener for [Tripoli Colorado](http://tripolicolorado.org)
+at their launch site on the buffalo ranch near Hartsel, Colorado. After huge
+snowfalls along the front range of the mountains in the last few days, we were
+a little tentative about going, but it turned out to be nearly perfect flying
+conditions! There was apparently much less snow this week on the high plains
+west of the front range, and by this morning the snow had almost entirely
+disappeared, the skies were clear and blue, and the winds were calm except
+for a few gusty bursts in the afternoon. This launch site is really something
+special, at 8800 feet above mean sea level, in the middle of a huge area of
+wide-open short grass prairie. We love flying there, and today the drive to
+and from the launch site through the snow-covered Colorado Rockies was just
+beautiful!
+
+Son Robert and I flew three rockets today, including his
+[LOC/Precision](http://shop.rocketsbymelissa.com)
+[Lil Nuke](http://shop.rocketsbymelissa.com/product.sc?categoryId=-1&productId=114) with added
+[payload section](http://shop.rocketsbymelissa.com/product.sc?categoryId=-1&productId=159) on an [Aerotech](http://www.aerotech-rocketry.com/) G54W-M reload,
+and our
+[Polecat Aerospace 5.5 inch Goblin](http://stores.whatsuphobby.com/-strse-361/Polecat-Aerospace-5.5"-Goblin/Detail.bok) kit on one
+of the relatively new [Aerotech](http://www.aerotech-rocketry.com/) I245G-M "Mojave Green" green-flame reloads. But by far the highlight of the day was
+flying my [Giant Leap](http://giantleaprocketry.com) Vertical Assault on
+a [Cesaroni](http://pro38.com/) J335 red-flame reload... with
+serial number 1 of [TeleMetrum](http://altusmetrum.org/TeleMetrum) on
+board collecting our first-ever flight data!
+
+From the ground, it looked like a textbook perfect dual-deploy flight, with a
+small drogue chute out at apogee around 4000 feet above ground, and the main
+chute deploying at 700 feet above ground for a beautiful, soft landing only
+a couple minutes walk from the launch rail.
+
+The ejection events were controlled by a PerfectFlite
+[MiniAlt/WD](http://68.178.208.82/cgi/PF_Store/perlshop.cgi?ACTION=enter&thispage=MAWD.html&ORDER_ID=!ORDERID!). The data recovered from it shows a big
+negative spike in the altitude right at apogee, coincident with firing of the
+apogee deployment charge. I have to assume this means the aft bulkhead on the
+avionics bay in the reconstructed coupler section isn't sealing well, and some
+pressure from the apogee deployment charge leaked in to the avionics bay
+"fooling" the altimeter into thinking the altitude was lower for a sample or
+two. Clearly, that needs to get fixed before that airframe flies again.
+
+Further evidence that we had a mighty kick from the apogee ejection charge
+was discovered when we went to clean the motor casing. The Cesaroni reloads
+are packaged in a plastic liner tube that slides into the reusable aluminum
+case. When we pulled the spent reload out of the case, it was significantly
+shorter than when it was loaded, suggesting that the ejection charge forced
+the forward closure on the reload backwards compressing the heat-softened
+plastic. This could be evidence that the reconstructed coupler was slow to
+separate from the booster airframe due to excessive friction?
+
+The flight data recovered from the
+[TeleMetrum](http://altusmetrum.org/TeleMetrum) board looks great until
+apogee, when the data collection stopped. Since I flew firmware that was
+compiled and flashed on the flight line from Keith's latest git commit as
+of this morning, it's entirely possible that there was a software bug that
+caused data collection to terminate at apogee. We'll investigate that. But
+I personally think what actually happened is that we experienced a temporary
+short in the power supply at the time the apogee ejection charge fired. On
+extraction of the electronics sled from the avionics bay this evening, I
+noticed that one of the mounting screws has gone missing. If it wasn't snug
+enough, and vibrated loose during flight, it could have been torn loose at
+the time of the ejection event and shorted something as it rattled around in
+the avionics bay. The screw is now just missing, but may have fallen out
+when we were extracting data on the flight line just after the flight without
+being noticed at the time. So I'm not inclined to worry much about this, at
+least until we can get some more flight data!
+
+Keith post-processed the raw flight data and presented me with a
+[plot](http://www.altusmetrum.org/TeleMetrum/flights/sn1-flight1.plot.ps)
+showing two traces, acceleration and barometric altitude. The data from the
+accelerometer closely matches the published data for the motor we flew, which
+is a really cool result, and my 10-year-old son enjoyed figuring out why the
+rocket showed negative acceleration after the motor burn out but was still
+climbing. (See, there really is some science education hidden in the fun!)
+
+All in all, we had a great time, and it's totally cool to have data from a
+first flight of [TeleMetrum](http://altusmetrum.org/TeleMetrum)! Can't wait
+to fly it again!
projects / web / gag.com / commitdiff