We all know that this forum has been dead for several years, but I know that a lot of people (namely Chuck) want to bring it back, so here is my contribution towards that goal. This is the full story of a project that I began on the rainy Saturday morning of Midwest Power 13 with some friends in Tim’s workshop.
Fresh off the success of SteveH’s BALLS 24 project and with a private waiver in NM from earlier in the year still in effect, we decided that we needed to push it further. He decided on a 5” x 1/8” wall full O motor, and since I blew up my 5” motor in August I decided to do a 114mm mid size O (4.5” x 0.24” wall). A couple months after BALLS, I took a cheap flight down to Dallas where Steve picked me up and we went out to Pat Gordzelik’s ranch to do a weekend propellant mix session. Without any hardware built yet, we decided to mix up 100lbs of propellant of various formulations for a launch date over the MLK weekend in January.
The formula used in this motor is:
56% 200um AP
14% 90um AP
13% 400 mesh AL
December rolled around, and by that time I had no hardware made, no rocket built and the propellant was untested, all that I had were some grains made. To calm my fears about the propellant, I got some ancient 90mic from Chuck and made a 75/6000 and flew it in Princeton. The motor worked perfectly and behaved very close to my predictions.
By the time finals were over, my nozzle, bulkhead, pin rings and nose cone adapter were fresh off the CNC and I was ready to build a rocket. I was going to be trying something pretty ballsy; I was going to glue my fins straight to the case. With a 0.24” wall case and a CE phenolic liner, I was pretty confident the heat soak into the case wouldn’t be so bad as to adversely affect the epoxy. I was worried about the adhesion to the aluminum. The epoxy used was 3M 8115 panel bonding adhesive.
For the tip to tip, I used three layer of 3k carbon with standard aeropoxy and vacuum bagged. This was covered with an ablative coating of aeropoxy and phenolic microballoons.
After the rocket was mostly finished, it was time to pack it up and ship it to Steve’s apartment in Houston where it would meet with it's propellant and the final prep work would be done. I flew into Houston the Sunday before the launch and we spent the rest of the week prepping both of our rockets for flight that weekend.
Here is a picture of all the propellant we planned on flying that weekend ready to be liner bonded on one table.
My grains with funky lengths:
All grains but the top were inhibited at one end and bonded in place to form the representative grain lengths:
The prep work was unbearable at times, luckily there’s a place down the road that sells daiquiri by the half gallon to make those late night prep sessions a little more fun.
The morning of January 16th, 2016 had finally come and it was time to push the button on some O motors. Also in attendance at this private launch were Jerry O’Sullivan and Mitch Guess from the east coast with their O motor project, Randy Appelbaum from NYC flying a 4” carbon rocket with a 98/17.5k that Steve and I made for him at our big mix session, Clay Reynolds from SLC attempting his L3, and John DeMar the one in charge of the site along with his crew from Tripoli White Sands.
With a little help from my friends we were able to get it on the pad that Clay had built for us. (L to R: Steve Heller, myself, Mat Orsak)
My flight was less than nominal. The rocket appeared to have survived the boost. After burnout, the telemetry data had gone silent for longer than it should have. About 20 seconds after burnout, something was heard fluttering in. About 10 seconds after that, a loud boom was heard, this was not a good sign. It was obvious that the rocket had augured in. After everybody was done flying, I went out and searched for a short while before giving up, knowing that it was certainly completely underground and that finding it in the sage brush would be near to impossible. When walking back, I found the graphite exit cone of the nozzle. This was interesting as both mine and Steve’s nozzles were of a similar design and suffered almost the exact failure mode of the unsupported exit cone shearing off mid flight.
Here is the video:
Many valuable lessons were learned in this project that will be applied to future projects down the road, the main one telling me that I am through with full diameter graphite nozzles! The next stop for me rocket-wise is BALLS 25, see you there.