To Drogue or not to Drogue etc.?

[Conway StevensParticipant]

I like JW use alot of the same ways in recovery. Most of all my recovery has all been done without a drogue chute. Most times it was with a wide and long nylon custom built streamer. In fact when JW and I were some years back dueling for the K club alt record all I ever used was a streamer followed up by a main chute. worked great to about 15K with perfect recovery many times My choice for a drogue chute on my L3 project was within a weight consideration as well as the rockets over size and air drag. I felt that due to the size and weight and the amount of drag after separation that I wanted a little slower decent that was controlled the way it should so as not to botch up my main recovery. According to my data capture from my on board electronics I ended up while on a drogue chute at about 70 ft per second. About where it should be. I really think that there are more factors that go into choosing to drogue or Not to drogue then you are weighing out.

First off the weight of the rocket itself is fairly light. At a higher altitude a drogue will have more effects on drift and slow recovery. You don’t want to have to much hang time way up high. A good rate of decent at apogee for any rocket like this is about 60 to 75 feet per second. I use shock cords made of either Kevlar or Tubular nylon. I prefer the Kevlar for the burn resistance and strength. Wider is better inside and direct outside the rocket body joint as it will aid in not zippering. Quantum tube is much more durable then most give it credit to. Ive had Quantum tube rockets before (not my personal favorite choice as im a composite guy But stronger then regular Phenolic and cardboard) Ive flown my 4″ PML Endeavour That was Quantum tube on MANY motors. By the time of its retirement I bet close to 50 flights+. The smallest being my L1 cert flight with a H242 and then from every I and J motor in 38mm and 54mm I could throw at it from Kosdon to AT and even some AMW K motors on this very rocket past 2 miles in Altitude and most all flights were dual deply. So quantum is more durable then you think. The key is also how cold or warm it is makes a big difference as to how brittle it can be. The warmer the better. Anyhow. I would not use a drogue I would use a streamer Like I mentioned for your apogee deployment. Placement will vary from rocket to rocket based on weight and drag. Last thing you want is the Booster higher then the mains and have it come crashing though your main chute. I also believe that shock cords should be long. I normally use 3 to 5 times the length of the rocket for one event. On my rocket VDP I ad 25 to 30 ft on each end and on my L3 rocket Full Throttle I had roughly 35 to 40 ft on each event. I believe its better to also have a bit larger main and bing it down quite slow. With your rocket I would deploy the main at 800 to 1000 ft. But all the above is just my opinion and other may think differently.

[Bret PackardParticipant]

Thanks Conway, Bruce, Warren, Mike, John and Chris (hope I didn’t miss anyone) 😛 . As Conway mentioned, I KNOW for a fact that there are more factors involved than I am considering, since this is my first attempt to design a DD recovery. And as Bruce said, I realize that there is a certain amount of trial and error involved. I started out as a physics major in college, and have been flying airplanes most of my life, so I have alot of theoretical understanding of how things should work, but with rocketry, my real life experience is still pretty limited. I watch all you guys fly your big motors and complex recovery systems, that I’m sure you’ve refined over time, and I just wanted to sponge some of that experience. This club is truly awesome from that perspective, not only are people willing to help, but we have so many people that are really pretty extraordinary in their rocketry skills as well.

I’m gonna get down to building this thing and hopefully I can corral one or two of you at the april launch to look it over. I don’t expect it to be perfect (is there such a thing?), but I do want to make sure that the design and construction are thought out and executed well enough to give me a good chance of success. Thanks again for the thoughts.

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