Zeus-cat
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The weather reports were for winds in the 5-6 mph range so I really wasn't planning on launching the RFD II (Rockets For Dummies II) until Friday when winds were forecast to be 2mph or less. This rocket can hit 1,300 to 1,400 feet on an E9 so I like to launch it high only in calm weather. She is a simple three fin design using Semroc LT115 heavy tubing with an altimeter bay just behind the nose.
Anyway, I got home from work and the air seemed dead calm so I decided to load up my high flying rocket with an E11-5J. I didn't have a lot of time so I was a bit rushed. It had never flown on an Aerotech motor before, but I decided to take a chance with it. Twentyone flights on Estes C6-3 to E9-6 motors. It flies great on an E9 so hopefully it would go higher on the E11 which has 10% more total thrust.
Even though I was rushed I loaded the motor very carefully. I always load Aerotech reloads very carefully. I've had this particular motor for a long time so I inspected it carefully and decided it was good. I scraped the delay grain just a little to make sure it would ignite. The motor grain looked great so I left it alone. Another motor from this same bag resulted in severe damage to my Launch Pad Anubis and my first Perfectflite altimeter when I got a very long delay. A fifteen second flight and the ejection charge went off at 16 seconds. I may have gotten grease on the delay as that was my very first launch of an Aerotech reload. I have been very careful not to get grease on anything that didn’t need it since then.
I got out to the field and realized I grabbed the wrong launch rod as well as forgetting my spacer for using standard 24mm motors in the long E9 motor mount. I drove the 10 minutes back home. It only took me a minute to find the launch rod, but I couldn’t ind the spacer. I finally remembered that I had just ordered a new E9 motor mount from Semroc; it included a spacer! I grabbed the new spacer, but it won't fit in my well used motor mount. It binds up just half an inch in. I pull and pull and it finally comes out - with a cracked fin as an added bonus. The crack is just on the trailing edge and isn't real bad. I don’t have time to glue it or even mix up 5 minute epoxy. An E11 is a pretty tame motor so I decide the fin should be fine in flight. A hard landing might bust it, but I'll take the chance.
I finally remember where the spacer is and get it (mental note – make more of these stupid things from used D12s or E9s). The spacer slides in smooth as silk. It took 20 minutes to do all of this. 10 minutes back to the field. It was just starting to get dark so I knew I had at most 10 minutes or so before I had to call it quits.
Of course now I can't find my Aerotech igniter clip. I have to do the masking tape thing on the igniter. Of course rushing to get the tape on I end up pulling out the igniter. Erghh!
By now I should have realized that the rocket gods are telling me to go home, but I decided to defy them.
I finally get everything hooked up and hit the launch button. Nothing. I've got continuity, why isn't this working? The clips must be touching and shorting together. I go adjust stuff. Hit the launch button again. Nothing. Go adjust stuff again. Hit the switch again. Nothing. Oh wait, you are staring at the power ready light not the continuity light. D’oh. They are not even the same color moron. You did it that way on purpose so you wouldn’t get confused.
Wait, there was just a puff of smoke and a crackling sound just as you released the launch button that last time. Hit the switch again and hold it. More smoke and then finally the RFD II lifts off. Two feet off the rod and the rocket wobbles sickly to the left. Oh great, the motor has decided to give up. Then just as it appears it will fall to the ground the motor roars to life again and the rocket shoots upward at an angle belching black smoke.
I grab my binoculars to try and watch it, but I can't find the smoke trail. I go back to the Mark I eyeballs and watch the smoke trail climb into the darkening sky. I lose sight of the rocket, but immediately head in the direction it flew. About 10 seconds later I hear a poof high above me. The deployment was late, but still well above ground. The recovery system is three feet of Kevlar thread tied to the motor mount with two feet of 1/4" elastic tied to a 50X3 inch streamer. Even deploying at speed the rocket should be OK - if I can find it. And even if the streamer rips away I’ll probably lose a fin at most; this rocket has crashed before and survived with only minor damage.
I keep walking, making sure to avoid the horse droppings in the horse show rings. I keep walking hoping to hear the soft beep of the altimeter. There is no one else out here except two people and a horse and they are now well behind me. It is very quiet. I listen for the altimeter, but hear nothing. I reach the end of the mowed grass and look out into the weeds. They are sparse and only a foot tall at the most. The rocket is nearly three feet long and bright yellow with black trim. The streamer is orange. If it is nearby I should be able to spot it. I have 10 minutes of decent light left before I have to call off the search and come back tomorrow before work.
I walk out 20 feet into the weeds. I scan the area with my binoculars. What’s that over there? Hmmm, it’s yellow. It doesn’t look right though. That can’t be my rocket.
I keep walking in that general direction since no direction is better than another. Twenty seconds later I take another look through the binoculars. Uh oh, that color looks right, but that does not look like a rocket. My rocket should be about 3 feet long and straight. That is not 3 feet long and it clearly isn’t straight. I walk over to the object and sure enough there lies the carcass of my RFD II. Well, the booster section anyway. The nose, the streamer and my altimeter bay are missing. I pick up my old friend and she is clearly DOA. The first 6 inches are now an accordion. There is a nice crease just above the upper launch lug; which means half the body tube is destroyed. One of the fins is missing, probably the one I cracked earlier. There really isn’t enough left to salvage. My Aerotech motor casing is still there, so at least I have that. But where is the nose?
I look around and maybe 100 feet away is a long strip of orange. With the carcass in hand I walk over to the orange object. There is my nose cone and altimeter bay sticking nearly straight up after lawn darting into the grass. The orange streamer is still attached. The altimeter is beeping out the altitude – 879 feet. At least that seems to have survived. I pull the nose out of the ground. It is only painted balsa and it looks fine except for a little mud.
Initial Post Mortem: The Perfectflite Alt15K altimeter survived with no damage. I downloaded the data and it showed that apogee was right around 9 seconds. The ejection occurred 12.5 seconds into the flight or 3.5 seconds after apogee. The rocket was moving at approximately 100 feet per second at deployment. The streamer was intact. The elastic was intact. The 100 pound Kevlar thread failed. All three strands appear to have snapped just above the motor mount. I will cut apart the rocket later to see exactly what happened.
Of all the reasons for a crash the last one I would have suspected was a failure of the Kevlar shock cord. Another oddity; the descent rate of just the nse was 53 feet per second with the full streamer. The entire rocket typically dropped at 35 feet per second on the same streamer.
Epilogue: The nose, altimeter and the altimeter bay will fly again. I will build a new booster and the RFD III will soon take to the sky on its maiden voyage - assuming the rocket gods say it is OK to launch.
Anyway, I got home from work and the air seemed dead calm so I decided to load up my high flying rocket with an E11-5J. I didn't have a lot of time so I was a bit rushed. It had never flown on an Aerotech motor before, but I decided to take a chance with it. Twentyone flights on Estes C6-3 to E9-6 motors. It flies great on an E9 so hopefully it would go higher on the E11 which has 10% more total thrust.
Even though I was rushed I loaded the motor very carefully. I always load Aerotech reloads very carefully. I've had this particular motor for a long time so I inspected it carefully and decided it was good. I scraped the delay grain just a little to make sure it would ignite. The motor grain looked great so I left it alone. Another motor from this same bag resulted in severe damage to my Launch Pad Anubis and my first Perfectflite altimeter when I got a very long delay. A fifteen second flight and the ejection charge went off at 16 seconds. I may have gotten grease on the delay as that was my very first launch of an Aerotech reload. I have been very careful not to get grease on anything that didn’t need it since then.
I got out to the field and realized I grabbed the wrong launch rod as well as forgetting my spacer for using standard 24mm motors in the long E9 motor mount. I drove the 10 minutes back home. It only took me a minute to find the launch rod, but I couldn’t ind the spacer. I finally remembered that I had just ordered a new E9 motor mount from Semroc; it included a spacer! I grabbed the new spacer, but it won't fit in my well used motor mount. It binds up just half an inch in. I pull and pull and it finally comes out - with a cracked fin as an added bonus. The crack is just on the trailing edge and isn't real bad. I don’t have time to glue it or even mix up 5 minute epoxy. An E11 is a pretty tame motor so I decide the fin should be fine in flight. A hard landing might bust it, but I'll take the chance.
I finally remember where the spacer is and get it (mental note – make more of these stupid things from used D12s or E9s). The spacer slides in smooth as silk. It took 20 minutes to do all of this. 10 minutes back to the field. It was just starting to get dark so I knew I had at most 10 minutes or so before I had to call it quits.
Of course now I can't find my Aerotech igniter clip. I have to do the masking tape thing on the igniter. Of course rushing to get the tape on I end up pulling out the igniter. Erghh!
By now I should have realized that the rocket gods are telling me to go home, but I decided to defy them.
I finally get everything hooked up and hit the launch button. Nothing. I've got continuity, why isn't this working? The clips must be touching and shorting together. I go adjust stuff. Hit the launch button again. Nothing. Go adjust stuff again. Hit the switch again. Nothing. Oh wait, you are staring at the power ready light not the continuity light. D’oh. They are not even the same color moron. You did it that way on purpose so you wouldn’t get confused.
Wait, there was just a puff of smoke and a crackling sound just as you released the launch button that last time. Hit the switch again and hold it. More smoke and then finally the RFD II lifts off. Two feet off the rod and the rocket wobbles sickly to the left. Oh great, the motor has decided to give up. Then just as it appears it will fall to the ground the motor roars to life again and the rocket shoots upward at an angle belching black smoke.
I grab my binoculars to try and watch it, but I can't find the smoke trail. I go back to the Mark I eyeballs and watch the smoke trail climb into the darkening sky. I lose sight of the rocket, but immediately head in the direction it flew. About 10 seconds later I hear a poof high above me. The deployment was late, but still well above ground. The recovery system is three feet of Kevlar thread tied to the motor mount with two feet of 1/4" elastic tied to a 50X3 inch streamer. Even deploying at speed the rocket should be OK - if I can find it. And even if the streamer rips away I’ll probably lose a fin at most; this rocket has crashed before and survived with only minor damage.
I keep walking, making sure to avoid the horse droppings in the horse show rings. I keep walking hoping to hear the soft beep of the altimeter. There is no one else out here except two people and a horse and they are now well behind me. It is very quiet. I listen for the altimeter, but hear nothing. I reach the end of the mowed grass and look out into the weeds. They are sparse and only a foot tall at the most. The rocket is nearly three feet long and bright yellow with black trim. The streamer is orange. If it is nearby I should be able to spot it. I have 10 minutes of decent light left before I have to call off the search and come back tomorrow before work.
I walk out 20 feet into the weeds. I scan the area with my binoculars. What’s that over there? Hmmm, it’s yellow. It doesn’t look right though. That can’t be my rocket.
I keep walking in that general direction since no direction is better than another. Twenty seconds later I take another look through the binoculars. Uh oh, that color looks right, but that does not look like a rocket. My rocket should be about 3 feet long and straight. That is not 3 feet long and it clearly isn’t straight. I walk over to the object and sure enough there lies the carcass of my RFD II. Well, the booster section anyway. The nose, the streamer and my altimeter bay are missing. I pick up my old friend and she is clearly DOA. The first 6 inches are now an accordion. There is a nice crease just above the upper launch lug; which means half the body tube is destroyed. One of the fins is missing, probably the one I cracked earlier. There really isn’t enough left to salvage. My Aerotech motor casing is still there, so at least I have that. But where is the nose?
I look around and maybe 100 feet away is a long strip of orange. With the carcass in hand I walk over to the orange object. There is my nose cone and altimeter bay sticking nearly straight up after lawn darting into the grass. The orange streamer is still attached. The altimeter is beeping out the altitude – 879 feet. At least that seems to have survived. I pull the nose out of the ground. It is only painted balsa and it looks fine except for a little mud.
Initial Post Mortem: The Perfectflite Alt15K altimeter survived with no damage. I downloaded the data and it showed that apogee was right around 9 seconds. The ejection occurred 12.5 seconds into the flight or 3.5 seconds after apogee. The rocket was moving at approximately 100 feet per second at deployment. The streamer was intact. The elastic was intact. The 100 pound Kevlar thread failed. All three strands appear to have snapped just above the motor mount. I will cut apart the rocket later to see exactly what happened.
Of all the reasons for a crash the last one I would have suspected was a failure of the Kevlar shock cord. Another oddity; the descent rate of just the nse was 53 feet per second with the full streamer. The entire rocket typically dropped at 35 feet per second on the same streamer.
Epilogue: The nose, altimeter and the altimeter bay will fly again. I will build a new booster and the RFD III will soon take to the sky on its maiden voyage - assuming the rocket gods say it is OK to launch.
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