only considered safe to launch from Terry Lee's launch trailer with 20 feet
of very stiff 1515 rail.
+### Revisions for Version 2 ###
+
+Because the main airframe zippered somewhat on the first flight, and the
+ARRD released at apogee, rather than just repairing the existing airframe
+tube, I designed and built a complete replacement.
+
+To increase stability, the main airframe tube length was extended from
+the original 4.5 feet to approximately 6 feet. This increased stability
+allowing a reduction in nose weight, increasing safety. It means the
+length is more than a strict scaling of the Lil Nuke, but is less than
+the Nuke Pro Maxx.
+
+For main deployment, the ARRD was replaced with a
+[Tender Descender L3](https://tinderrocketry.com/l13-tender-descender-tether),
+which has the advantage that the release mechanism is orthogonal to the
+axis of flight. That seems important when the airframe is this heavy and
+apogee occurs at a non-nominal velocity, as in the first flight.
+
+The original build had internal 1x2 ribs and a baffle yielding a "D" shaped
+main bay with the apogee charge gasses going up the channel without pushing
+on the main deployment bag. For this rebuild, 3 ribs were run the airframe
+length between the 12" airframe and a concentric full-length 8" deployment
+bay, with centering rings on each end. One sector of the rings was
+vented to allow apogee ejection gasses to flow from the charge cups on the
+leading edge of the fin can to the nose, bypassing the main chute bay.
+
## Design / Simulation File
-[mehganuke.ork](/rockets/airframes/MehGaNuke/mehganuke.ork)
+ * Original [mehganuke.ork](/rockets/airframes/MehGaNuke/mehganuke.ork)
+ * Revised [mehganuke-v2.ork](/rockets/airframes/MehGaNuke/mehganuke-v2.ork)
## Construction Log
## Flight Log
+### First Flight
+
The first flight of this airframe was at the
[Kloudbusters](http://kloudbusters.org/)
[Airfest 24](http://kloudbusters.org/airfest/) in Argonia, Kansas, USA,
the nose descending under 2 5-foot mil-surplus chutes, and the bulk of the
airframe descending under a 28-foot mil-surplus chute.
-[Tender Descender](http://www.tinderrocketry.com/l13-tender-descender-tether).
-
The stress at deployment tore the strap off the deployment bag, and the
deployment bag was not recovered. After studying the zipper and thinking
about the main deployment sequence, several changes will be made before the
next flight:
- - The main airframe tube will be replaced with a tube that's a bit
- longer (for greater stability), and has an internal 7.5-8" diameter
- tube instead of the flat baffle to ease main chute deployment.
+ - The main airframe tube will be replaced with a tube that's a bit longer
+ (for greater stability), and has an internal 7.5-8" diameter tube instead
+ of the flat baffle to ease main chute deployment.
- - Switch from the ARRD to the largest [Tender Descender](http://www.tinderrocketry.com/l13-tender-descender-tether) for main deployment
+ - Switch from the ARRD to the largest [Tender Descender](http://www.tinderrocketry.com/l13-tender-descender-tether) for main deployment.
- - Add a TeleGPS to the nose assembly so it can be tracked
- independently, and let it come down under the 2 existing 5-foot
- chutes. Add a third 5-foot chute to be a dedicated pilot for the
- 28-foot main chute.
+ - Add a TeleGPS to the nose assembly so it can be tracked independently, and let
+ it come down by itself under the 2 existing 5-foot chutes. Add a third 5-foot
+ chute to be a dedicated pilot for the 28-foot main chute.
These changes should reduce the chance of another zipper, and reduce the amount
of strap we need to stuff into the bay.
All in all, this first flight was an outstanding group effort, a lovely
flight, and a huge crowd-pleaser!
+### Second Flight
+
+In 2021, the NAR National Sport Launch was held near Alamosa, CO. Doug
+Gerrard planned to be there with his camera-laden launch pad so there was
+the possibility of a highly-documented launch. Since I
+really wanted to fly this project in Colorado and that was a national-scale
+event, plans were made. As a NAR sanctioned event, the motor needed to be
+commercial and not research. Simulations led to the choice of a CTI N3301
+White Thunder which would fit case hardware already on hand. This would
+require fabricating an adapter from the 6" motor mount to the 98mm
+motor, but that seemed easy enough. My thanks to the good folks at
+[Moto-Joe Rocketry](http://moto-joe.com/) for helping me obtain the reload.
+
+Unfortunately, logistics issues prevented flying at the NSL. The second
+flight ended up happening on Sunday, 19 September 2021, at the
+[Tripoli Colorado](https://www.tripolicolorado.org/) Fall Frenzy launch.
+
+In addition to the rebuilt main airframe section and motor adapter, a
+TeleGPS was added to the nose bay. Then, at the last minute, Meh-ga Nuke
+was equipped with two keychain cameras mounted looking up and down.
+
+The rocket was about 145 pounds on the rail of Terry Lee's launch trailer,
+and was flowing with 2 e-matches and a pinch of Pyrodex P in the Tender
+Descender, and apogee charges of 6g primary and "fill the cup"
+secondary. The rocket departed the rail with about 5.5g max acceleration
+on the way to Mach 0.7 and an apogee altitude of 9183 feet. The dual
+deployment process worked as designed, but unfortunately the shround on
+the main tangled, probably due to a hasty repacking of the deployment bag
+during assembly on the rail. Wind pushed the airframe ENE out of the
+optimal landing area and into a "field of rocks", where the higher than
+expected landing velocity of the main airframe and fin can assembly and
+wind drag resulted in cosmetic damage to the fin can and more significant
+damage to the main airframe tube. The nose cone also suffered damage as
+a result of the wind causing the chutes to pull it across rocks.
+
+Both TeleMega boards returned good data logs. The TeleGPS in the nose
+cone wasn't heard during launch and flight (it turns out the unsupported
+antenna wire broke off sometime before landing, perhaps even before
+launch?), but the data recovered from the board shows a clean trace of
+the nose cone's path during flight. Good thing we didn't need the
+GPS to locate and recover the nose cone!
+
+The video from the up-looking camera worked great through apogee, but
+unfortunately the video froze before the main deployed so only audio was
+recorded for the rest of the flight. The down-looking camera video came
+out very well, though! It shows only a couple rotations of the airframe
+during ascent with some great view of the flight line, etc. It also
+captured the nose cone and two 5 foot surplus military parachutes deployed
+at apogee travelling past the main airframe rapidly at apogee. The
+shadow of the nose cone and associated chutes descending independently can
+be seen in the video before landing... and the very violent landing of
+the fin can and main airframe can be clearly seen.
+
+All in all, this second flight was another huge crowd-pleaser and very
+satisfying overall. Particular thanks to Terry Lee for his help
+rebuilding the main airframe and the use of his launch trailer, George
+Barnes IV for his outstanding photos on launch day, and my wife Karen who
+attended the launch with great enthusiasm despite being only a few weeks
+into the recovery from major surgery.
+
+I think the primary lesson learned from this flight is that the design
+of the airframe pretty much guarantees the main airframe tube is going
+to be damaged in each flight. The video proof of what we already
+understood intellectually about the dramatic reversal of direction the
+airframe
+undergoes at apogee when the nose comes off and the drogue chutes deploy
+alone is enough to rip the leading edge of the airframe apart back to the
+first centering ring below the nose shoulder. So, even without landing
+in rocks and being dragged due to high winds by the main chute, we
+probably just need to acknowledge the main airframe is in some ways a
+"single use" design.
+
projects / web / gag.com / blobdiff