CERG July 2005

Date 07/10/05

The July 10^th CEG Ex launch was a great day. Since I was going to fly three rockets today, I got going early due to the excitement I had. The drive up to the launch site was uneventful but with a slight overcast and the sun behind the clouds was at least the drive cooler than usual. I was the first to arrive at the launch site and so I started setup of the equipment. Since I had prepped all three rocket the night before, it was nice that I did not have to rush trying to remember what I needed to do the get the rockets ready to fly.

As some people showed up, I got my first rocket loaded up on the pad. Epic-One is one of my smaller 29mm rockets. It was loaded up with a DW red formula that I have not tested before. I know it had flown on several occasions at a certain Kn so I was not too worried. Well with red formulas known to be a little hard to get started, this motor proved no different. After a couple of igniter's and a couple of chuff's like is was going to start. The next try ,it looked like it was going to go but never fully came up to pressure. It slid up the rod a few times about a foot and then the ejection charge went off. So much for that flight. I took it off and set it aside to load up the next rocket, my son’s Thorax rocket. Upon investigation later at home when I was cleaning out the motor cases, I noticed that the grains did not completely burn. They were only about half burned. Then I noticed that there was no O-ring on the nozzle and by the burn marks on the side, I realized that as the motor was trying to coming up to the pressure was blowing by the side of the nozzle as well as the throat and just could not get enough pressure to lift off. Ok, just goes to show you that even the night before prep does not always pan out.

Thorax is a rocket my son designed and built (with some help from me of course). It is a light weight 38 mm 2.65 inch rocket with the Purple Nurple formula I tested a couple of weeks ago. I really like this formula for several reasons one of which is the color. This was a 38mm motor ejection which I have working in the 29mm size, but I have not tested on the 38mm yet. I was however confident that the method I was using in the 29mm would work for the 38mm so I said lets push the button. Again a bit of a bugger to light, (I had several igniter's that just where not working) but it finely lit. The delay was set for about 15 seconds and the countdown 3...2...1 after some smoke and a little flame it took off the pad. It kinda whipped off the rail and fish tailed a bit. As the burn continued (2.5 seconds total) it straitened out. As time when on I was counting and 15 seconds came and went. We heard a small pop, but no chute and it kept coming down...yes you guessed it, all the way in without a chute. It hit hard. So hard the 14 inch plastic nose cone was all the way in the ground. It took a white to kick it out of the ground. Keep in mind this was only a 4 lbs rocket. The main body tube (fiberglassed) looked like an accordion in the first half of the tube. One nice thing is the fin can took very little damage. I just need to cut out the old coupler and epoxy in a new one and the it will be good as new. So investigation on this mishap when I got home reviled another mistake of the ejection charge. The charge did go off, but when I cut off the top of the couple tube, I saw what looked to be like black powder mixed with the shavings from just cutting it open. I poured the mix in a pile and lit it with a torch and poof. Yep, it was black powder. Then I looked closer and found out what had happened. I had only used one piece of masking tape and small piece of paper towel to keep the black powder in place. I usually use two pieces of tape one going each way over the top and then another piece to wrap around the outside. I don’t know why I only used one piece other that I forgot because I got called in for dinner and when I came back out continued on with putting the rocket together. So with the rocket laying in the sun before launching, the tape must have let go and allowed most of the powder to pour out of the well. At that point there was not enough BP to separate the rocket during flight. Well the rocket will be an easy fix.

The last rocket was Johnny Bravo. It was loaded up a the same purple formula that flew in Thorax. This is a 54mm 5 grain case with a 1 inch tracking grain. After a couple of igniter's on this motor it lit and took to the sky. With a great flame and nice shock wave that could be seen and about a 4.5- 5 second burn time, the rocket was off and running. We heard a flare of the motor (seems to be characteristic of this formula) and then someone thought they heard the drogue ejection charge but no drogue chute. Then a few seconds later I heard a high speed deployment of the main chute. And then it was just there hanging in the sky. The drogue chute came out when the main did. Upon arriving at the site where it landed Johnny didn’t look too bad. I was expecting a huge zipper and the main to be all torn up. After assessing the damage the only two issues were the main chute (that I made) had a small tear up one the lines which is an easy fix and a small zipper in the lower tube which is an very easy replacement was the only damage. Wow. Johnny could be flying again in a week or two.

Don’s was the only other rocket to fly as a few others were not able to make it up. Don had the rocket already prepped and Ed worked on setting up the motor and filling the tank. Once the motor was prepped they load the rocket on the rail and got everything set. Don armed the camera and the electronics and the counted started. The AN grain started and the injector cap popped and away the rocket went strait as an arrow. There where a few puffs of smoke that looked like something might have happened, but it was just the rest of the AN grain coming out the back. This was a wax and asphalt mix with a few other things mixed in. The deployment of the chutes was perfect and the rocket was on it way home. With a camera on-board the hope where high so some great video footage. Turns out the camera turn off just before lift off.

Hind site always has a double meaning. Things that get missed like O-rings or tape for simple operations that look bad and cost time, effort as well as money helps us to learn things to hopefully never forget our past mistakes. You can bet that I won’t forget to use more tape or take apart motors that have been together for a while. All in all it was a good day to fly. It was a bit hot with no clouds, a slight wind and it is starting to dry out, but there was still a lot of green which is unusual for the grasslands. Thanks to those few new people who came out to watch and the regulars who came to fly. Still a bad day launching rockets is way better than a good day at work.

Videos from our day.

Johnny Bravo - Johnny Bravo flies on a 54mm MBR Purple Nurple motor. (mpeg1 1.9 meg)
Thorax - My son's first high power scratch built rocket on a 38mm MBR Purple Nurple motor. (mpeg1 1.2meg)
Don's Rocket - Another great flight with Don's and Ed's wax/asphalt hybrid motor. (mpeg1 2.2 meg)