From: Bdale Garbee Date: Mon, 20 Apr 2009 06:16:54 +0000 (-0600) Subject: writing about first TeleMetrum flight X-Git-Url: https://git.gag.com/?p=web%2Fgag.com;a=commitdiff_plain;h=4d765045edb282559c4202c6c6b0ef58f8f983fd writing about first TeleMetrum flight --- diff --git a/bdale/blog/posts/TeleMetrum_First_Flight.mdwn b/bdale/blog/posts/TeleMetrum_First_Flight.mdwn new file mode 100644 index 0000000..a611c95 --- /dev/null +++ b/bdale/blog/posts/TeleMetrum_First_Flight.mdwn @@ -0,0 +1,77 @@ +[[!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!