Sunday, November 20, 2016

Belated: LDRS - June 2016 launch report

I haven't felt much like blogging in recent months.  Could you tell?  Well I'm attempting to catch up now so I suppose that's something... onward and upward.

LDRS was conveniently hosted by at Lucerne Dry Lake this year in June.  The San Diego club carved out a cozy little portion of the parking area a couple of rows back on the east side.  East side represent!  Mark Treseder was kind enough to shoot photos of the event using my camera and they're on Flickr if you'd like to glimpse into the recent past.
     I've wanted to fly Der Red Mix mark II fully loaded for some years now and this third flight seemed like a great time to try.  My aging Flip Mino HD's battery gave up the ghost unbeknownst to me until I was prepping the flight.   As such I have only ground-based slow-mo and hand-held iPhone 6s slow-mo footie but it's still sort of a good time:

You might recall that I took some airframe damage at the top of the tube, patched that at home, then spent literally hours on the playa sanding the tube interior and nose cone shoulder trying to make the nose cone fit.  In the end I got close enough but still had to use 2" wide Gorilla tape to create a gap at the top of the shoulder so the base would fit and move properly during ejection.  You can see the [tape] gap between the two 8 decals in this liftoff shot,  That did, however, shift the CG north a bit thus adding bonus stability margin (Photo Mark Treseder):
Skidmarks remain my personal motors of choice for this clustered/air-start vehicle so I stocked up on a central 2304K815 as the ground-start motor.  As always I got the thing moving up and away with this single motor before attempting to ignite subsequent motor pairs.  Once off the ground I use both Raven 1 and Raven 3 altimeters in series to theoretically fire 2x 543I297 then 2x 305H226 then 2x more 305H226.  For this third flight I set the air-start delays to 0.1s to maximize seamless titanium amazingness but noted two problems: 1) Only one of the I297s fired and 2) The gaps between motor pairs was more like 1-2 seconds.  I still have no idea what happened with the I297 pair's delay since the capacitor should have been fully charged at that point but all the other motors fired at some point.  If you look at the graph links below you'll see that the second pair of H226 motors were staggered unintentionally.  Also the missing I297's ematch had fired so I suppose this was a rare time when a pyrodex pellet missed its spark:
     Here are the data from the altimeters and both four-phase (really 5-phase) graphs look quite interesting (average altitude: 4,925' AGL) :
Oh and I forgot to mention that deployment bags rock!  The previously documented damage to DRM mark II was cause by an unnecessarily steep launch angle mandated by the RSO.  I was not interested in a second set of repairs and remembered that I have a couple of Rocketman deployment bags in storage.  I used to think of them as parachute blast protectors back when I was using black powder for direct ejection.  I have since moved all my large rockets to the CD3 CO2 system so melting/burning is no longer an issue.  Remember that the primary function of a deployment bag is to gradually and gently allow a parachute to inflate thus eliminating the shock of unhindered inflation.  I'm happy to report that zero incremental damage was done to my semi-fragile repairs on this flight so I'm all over deployment bags once again.
     I had planned a second flight but, despite significant amounts of work on the Madcow Rocketry Mega Cowabunga, I could not pull that one together.  Thanks for hanging in despite the protracted gap.

No comments: