[Lil' Nuke](http://shop.locprecision.com/product.sc?productId=114&categoryId=12)
kit.
-So .. how about a stupidly-large upscale of the LOC Lil' Nuke! A meh-ga nuke!
+So .. how about a stupidly-large upscale of the LOC Lil' Nuke! Bdale's
+wife Karen suggested the name, since this is definitely a meh-ga nuke!
## Design Details
-After a bunch of playing around in [OpenRocket](http://openrocket.sourceforge.net/),
-and considering the limits of the CNC equipment at hand, an airframe diameter of
+After a bunch of playing around in
+[OpenRocket](http://openrocket.sourceforge.net/), and considering the
+limits of the CNC equipment at hand, an airframe diameter of
approximately 12 inches was chosen. We can fly high on 6-inch research motors
-(first flight planned to be on a James Russell research red-flame "O" motor), and
+(first flight was on a James Russell research red-flame "O" motor), and
fly low and super crowd-pleasing on fast-burning M motors like the
-[CTI Pro98 M3400WT](http://pro38.com/products/pro98/motor.php) in a suitable adapter.
+[CTI Pro98 M3400WT](http://pro38.com/products/pro98/motor.php) in a
+suitable adapter.
To achieve sufficient stability on an O motor, the nose needs to be pretty
heavy. Simulation suggested that turning the nose out of solid pine would work
logs drying... but trying to turn a nose cone out of one of those was kind of a
disaster! So we ended up asking Dan at
[Python Rocketry](https://pythonrocketry.com/)
-for help, and he delivered an outstanding nose cone for the project!
+for help, and he delivered an outstanding bespoke nose cone for the project!
Because such a heavy nose cone would put significant compression load on the
rest of the airframe, we took notes from Kevin Trojanowski's large rocket
landing. The epoxy used for all fin to ring joints (and most others in the
airframe) was augmented with West Systems 403 Microfibers, yielding very
strong yet light joints. Once the fin can was fully assembled, the fins
-were laminated with laminated with one partial layer of 5.7oz 2x2 twill
-carbon fiber for stiffness, and one layer of tip to tip 6oz fiberglass for
-surface preservation and strength.
+were laminated with with one partial layer of 5.7oz 2x2 twill carbon fiber
+for stiffness, and one layer of tip to tip 6oz fiberglass for surface
+preservation and strength.
Charge cups for primary and secondary black powder charges mount on the
top of the fin can forward ring where they are easy to load before adding
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
is, I think the trick will just be to paint the tube with a thick layer of epoxy
before starting to apply the glass, then be generous when wetting each layer.
-At this point, a lot of time passed, and the airframe wasn't completed until
-early 2018!
+At this point, a lot of time passed, detailed note-taking more or less
+stopped, and the airframe wasn't completed until early 2018!
## Photos
All the photos and video I've collected associated with this project can
be found [here](https://thor.gag.com/index.php?/category/MehGaNuke).
+Kent Burnett's drone video hightlights reel from Airfest 2018 includes
+[video of the launch](https://vimeo.com/295459157#t=636s) starting at
+about 10:36 in.
+
## Flight Log
-The first flight of this airframe was at the [Kloudbusters](http://kloudbusters.org/)
+The first flight of this airframe was at the
+[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