I have a short attention span. I'll take up a hobby for a decade or so, and move on to something else. I'm pretty much to the point of moving beyond rocketry, but there are two projects I must accomplish before I do.
When I got back into rocketry in 2003, I flew the composite motors included with the Initiator kit I bought. They were OK, and sure had more kick that the BP motors I flew as a kid. I took to the internet, and learned about high power rocketry. Well, now. Some pretty cool stuff. Watched the Discovery special. OK...
I was especially excited when I read about the Aerotech hybrid motors. I soon learned that they were pretty much a thing of the past, even at that point, but there were other designs of hybrid motor out there. I was also immediately intrigued by the electronics available. I decided that I was going to be a hybrid guy. I've stuck with that through Levels 1-3. Out of my 168 high power flights, two were APCP.
Six of those flights were by a rocket with a 2-motor cluster of Skyripper Gs. One (sort of) flight was by a K-to-H staged bird. The cluster has flown pretty well – 5 out of six successful flights, plus three aborted launches. The staged flight did not end well.
The two projects I want to complete successfully are a K powered cluster, and a successful staged flight. This thread will be about the construction and eventual flight of the clustered rocket. I've been noodling this project for three years, trying to figure out how to pull all the pieces together to make it work, and still maintain the necessary safety requirements.
I had originally intended to make a 3-motor cluster in a 5.5” airframe, but it would have left me traveling a great distance for a single launch – the sims put it up well over 14K, which is beyond many waivers here in the east. My final design is for two Contrail Ks (54mm x 48”
in a 4” (nominal) airframe. Clearly you can't stuff two 54mm tubes in a 4” airframe, so the motor tubes will extend beyond the walls of the airframe. Kind of a 'cheeky' design. Overall length will be just over 7 feet, with a weight of 19 pounds ready to go and full of nitrous. Motors will be 2 x Contrail K321, which will give an installed impulse of right around 3200 NS.
Clustering hybrids is not simply a matter of hooking up an extra igniter. I use U/C hybrid motors, and these have a fill line that is severed by the ignition process. Problem is if only one motor starts, the second will still have its fill line attached, with potentially disastrous results. Some sort of method to physically cut the lines is indicated.
Add to that my pique about a certain nationally known launch director dissing hybrids, claiming they 'slow down a launch' because of the time they require to fill. I figure if I have to set up a cutter, I might as well run the vent lines through it, with some method of closing them off, so I can fill the thing on the pad, in advance, then simply push the button when the time came.
So, there’s the project. A hybrid cluster. The rocket itself is pretty straightforward, thought the design is 'all out the front' deployment, and will utilize a unique method of chute containment/release. The ground support equipment is far more complicated. There will be an air storage tank, with pneumatic cylinders to activate a guillotine cutter to sever the fill/vent lines, and N.O. pneumatic valves to close the vent lines when the motors are full. There will be all the usual solenoids and tanks to manage nitrous flow, with a burst diaphragm added in case of an accidental system over-pressure. There will also be an electrical system that will control all of the pneumatic features. Designing a control system that will do the job, and FAIL SAFE has been a challenge.
I've finally acquired the last of the pneumatic devices necessary to make that happen, so am ready to actually begin construction. I've ordered the phenolic tubing necessary, the rest of the bird I'll make from materials I already have on hand.
I'm looking to put this into the air late summer '13.
Kevin O
When I got back into rocketry in 2003, I flew the composite motors included with the Initiator kit I bought. They were OK, and sure had more kick that the BP motors I flew as a kid. I took to the internet, and learned about high power rocketry. Well, now. Some pretty cool stuff. Watched the Discovery special. OK...
I was especially excited when I read about the Aerotech hybrid motors. I soon learned that they were pretty much a thing of the past, even at that point, but there were other designs of hybrid motor out there. I was also immediately intrigued by the electronics available. I decided that I was going to be a hybrid guy. I've stuck with that through Levels 1-3. Out of my 168 high power flights, two were APCP.
Six of those flights were by a rocket with a 2-motor cluster of Skyripper Gs. One (sort of) flight was by a K-to-H staged bird. The cluster has flown pretty well – 5 out of six successful flights, plus three aborted launches. The staged flight did not end well.
The two projects I want to complete successfully are a K powered cluster, and a successful staged flight. This thread will be about the construction and eventual flight of the clustered rocket. I've been noodling this project for three years, trying to figure out how to pull all the pieces together to make it work, and still maintain the necessary safety requirements.
I had originally intended to make a 3-motor cluster in a 5.5” airframe, but it would have left me traveling a great distance for a single launch – the sims put it up well over 14K, which is beyond many waivers here in the east. My final design is for two Contrail Ks (54mm x 48”
in a 4” (nominal) airframe. Clearly you can't stuff two 54mm tubes in a 4” airframe, so the motor tubes will extend beyond the walls of the airframe. Kind of a 'cheeky' design. Overall length will be just over 7 feet, with a weight of 19 pounds ready to go and full of nitrous. Motors will be 2 x Contrail K321, which will give an installed impulse of right around 3200 NS.Clustering hybrids is not simply a matter of hooking up an extra igniter. I use U/C hybrid motors, and these have a fill line that is severed by the ignition process. Problem is if only one motor starts, the second will still have its fill line attached, with potentially disastrous results. Some sort of method to physically cut the lines is indicated.
Add to that my pique about a certain nationally known launch director dissing hybrids, claiming they 'slow down a launch' because of the time they require to fill. I figure if I have to set up a cutter, I might as well run the vent lines through it, with some method of closing them off, so I can fill the thing on the pad, in advance, then simply push the button when the time came.
So, there’s the project. A hybrid cluster. The rocket itself is pretty straightforward, thought the design is 'all out the front' deployment, and will utilize a unique method of chute containment/release. The ground support equipment is far more complicated. There will be an air storage tank, with pneumatic cylinders to activate a guillotine cutter to sever the fill/vent lines, and N.O. pneumatic valves to close the vent lines when the motors are full. There will be all the usual solenoids and tanks to manage nitrous flow, with a burst diaphragm added in case of an accidental system over-pressure. There will also be an electrical system that will control all of the pneumatic features. Designing a control system that will do the job, and FAIL SAFE has been a challenge.
I've finally acquired the last of the pneumatic devices necessary to make that happen, so am ready to actually begin construction. I've ordered the phenolic tubing necessary, the rest of the bird I'll make from materials I already have on hand.
I'm looking to put this into the air late summer '13.
Kevin O
Last edited:
