X-Git-Url: https://git.gag.com/?p=web%2Fgag.com;a=blobdiff_plain;f=rockets%2Fairframes%2FMehGaNuke%2Findex.mdwn;h=f0956009df4a6b05081deb9566b8af279ab5eb6d;hp=2aa6ccb2ff2ef3d462d5f14576fb743b78566814;hb=93c02838e7ed81125987a2b7990741d2b68b11b7;hpb=edfe2ece95368b4dd488327e95b51bf3f640ca32 diff --git a/rockets/airframes/MehGaNuke/index.mdwn b/rockets/airframes/MehGaNuke/index.mdwn index 2aa6ccb..f095600 100644 --- a/rockets/airframes/MehGaNuke/index.mdwn +++ b/rockets/airframes/MehGaNuke/index.mdwn @@ -110,9 +110,36 @@ The airframe is configured with two 1515-sized rail buttons, and is really 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 @@ -159,6 +186,8 @@ about 10:36 in. ## 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, @@ -199,3 +228,75 @@ 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. +