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, we're going to build a replacement.
+
+To increase stability, the main airframe tube length will be extended from
+the original 4.5 feet to approximately 8 feet. The expected increase
+in stability should allowing a reduction in nose weight, increasing safety.
+It should also make recovery system loading less arduous on the rail. Of
+course, this means the rocket will be closer to the length of an upscaled
+Nuke Pro Maxx rather than the original Lil Nuke.
+
+For main deployment, the ARRD is being 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 will 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 will be
+vented to allow apogee ejection gasses to flow from the charge cups on the
+leading edge of the fin can to push the nose off without push up on the
+main in its deployment bag.
+
## 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
[Kloudbusters](http://kloudbusters.org/)
[Airfest 24](http://kloudbusters.org/airfest/) in Argonia, Kansas, USA,
on Saturday, 1 September 2018. The motor was a 6-inch "O" built by James
-Russell using his well-known "Russell Red" formula. Due to a slightly larger
-than optimal nozzle throat, the motor burn was a bit longer and average thrust
-a bit lower than expected... but a side-effect was a 9-10 foot brilliant red
-flame tail that was awesome to see! The rocket hit about Mach 0.6 on the way
-to 8068 feet above ground, and was recovered safely. Weather-cocking due to
-wind caused the airframe to have a residual speed at apogee of nearly 60 meters
-per second, so not surprisingly there was some modest zippering of the top of
-the airframe. It also seems clear that the ARRD failed to retain the deployment
-bag, as the main chute deployed a few seconds after apogee. The stress at
-deployment tore the strap off the deployment bag, and the deployment bag was not
-recovered. Some minor re-design of the deployment sequence seems indicated
-before future flights. All in all, though, this was an outstanding group
-effort, a lovely flight, and a huge crowd-pleaser!
+Russell using his well-known "Russell Red" formula. The total launch mass
+was about 205 pounds on the rail. Due to a slightly larger than optimal
+nozzle throat, the motor burn at 7.7 seconds was a bit longer than expected,
+pushing the airframe with an average acceleration of only 2.89 G to a
+maximum speed of Mach 0.6 on the way to 8068 feet above ground.
+
+Weather-cocking due to wind caused the airframe to have a residual speed at
+apogee of nearly 60 meters per second, so not surprisingly there was zippering
+of the top of the main airframe tube. It also seems clear that the ARRD
+failed to retain the deployment bag, as the main chute deployed a few seconds
+after apogee. We had some difficulty with the ARRD during assembly on the
+rail, so this wasn't terribly surprising. Recovery was completely safe with
+the nose descending under 2 5-foot mil-surplus chutes, and the bulk of the
+airframe descending under a 28-foot mil-surplus chute.
+
+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.
+
+ - 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 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!
projects / web / gag.com / blobdiff