Short delay
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bobkrech
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What are you trying to do?
There should not be a need for such a short delay on any stable rocket that I can envision. A rocket on a B engine that could utilize a 1 second delay would weigh about 8 ounces and would have an apogee of only 36 feet. The maximum velocity would be less than 40 ft/sec and it would likely to be unstable.
Did I miss something?
Bob Krech
There should not be a need for such a short delay on any stable rocket that I can envision. A rocket on a B engine that could utilize a 1 second delay would weigh about 8 ounces and would have an apogee of only 36 feet. The maximum velocity would be less than 40 ft/sec and it would likely to be unstable.
Did I miss something?
Bob Krech
Maelstrom
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Although I have not had opportunity to test-launch it yet, I have a rocket that should separate into 3 pieces from the ejection charge and my goal is to simulate a CATO. SO, I'd really like a short delay A motor that will 'detonate' in plain view. Although the shortest delay I've seen is 2 seconds and with a B motor.
So I guess I need to find a balance that keeps it stable, and as close to the ground as possible but allow for ejection before the rocket starts to freefall.
Ideas?
So I guess I need to find a balance that keeps it stable, and as close to the ground as possible but allow for ejection before the rocket starts to freefall.
Ideas?
bobkrech
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This is a possible solution, but it is an RSO's nightmare. You would have to prove that a safe recovery would occur before I would let you launch it at our launches.
In a 4.6 ounce rocket, a B6-0 at burnout is moving at 87 fps and has reached about 40 ft altitude. With a 4 ft launch rod, the launch velocity is 39 fps so the rocket is aerodynamically stable.
In theory, you could put some BP on top of a B6-0 to effectively have a zero delay ejection charge. This would "CATO" or "disassemble" your rocket. All components would have to be designed for tumble recovery since you would strip off a parachute or streamer at the deployment velocity.
This solution could work.
Bob Krech
In a 4.6 ounce rocket, a B6-0 at burnout is moving at 87 fps and has reached about 40 ft altitude. With a 4 ft launch rod, the launch velocity is 39 fps so the rocket is aerodynamically stable.
In theory, you could put some BP on top of a B6-0 to effectively have a zero delay ejection charge. This would "CATO" or "disassemble" your rocket. All components would have to be designed for tumble recovery since you would strip off a parachute or streamer at the deployment velocity.
This solution could work.
Bob Krech
A
Austin
Estes had such a rocket for 18mm motors and as a matter of fact, it was called a "CATO". I have one in my collection and did not plan on building it, but the principle is the same. It flies on B6-0 and C6-0 motors, uses a piston ejection and it comes down on streamers and a parachute.
For more info, go to - https://www.dars.org/jimz/estes/est2071.pdf
Carl
For more info, go to - https://www.dars.org/jimz/estes/est2071.pdf
Carl
powderburner
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I don't think you need to add any loose BP on top of the booster motor, the blow-through (normally used for staging) should be powerful enough to trigger any necessary deployment, if not too powerful.
As for:
This is a possible solution, but it is an RSO's nightmare. [/QUOTE]
Yes, the rocket's design sounds a little unconventional, but if the components will recover safely, what's the big deal? (Am I overlooking something?)
bobkrech
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Carl
Just goes to show there really nothing new under the sun.
Powderburner
Right about the possibility to not have to use BP, particularly if you use a piston as Carl noted previously with the ESTES CATO.
I tend to be conservative. I know how to design a rocket to look like it CATOED (even more so than the ESTES kit), but I'm not sure that everyone can do it correctly. If I were the RSO and the builder could answer the recovery questions to my satisfaction, then it would fly, otherwise it wouldn't. My safety questions and concerns are two-fold.
In the solution I proposed, there is a relatively high (disassembly) velocity near the ground so it is important that the pieces slow down and tumble recover. While a commercial kit will be proven safe by the manufacturer, a scratch-built may not have been flown before. As RSO I would want know how the rocket comes apart inflight and what the recovery expectations are.
Also it is important to only use A or B motors to keep the velocity low. There is always a temptation to use bigger motors which if the design were unstable, could prematurely disassemble at low altitude and high velocity under power and then you have a burning motor to contend with. As RSO I would like to know the CG/CP relationships of the model.
Bob Krech
Just goes to show there really nothing new under the sun.
Powderburner
Right about the possibility to not have to use BP, particularly if you use a piston as Carl noted previously with the ESTES CATO.
I tend to be conservative. I know how to design a rocket to look like it CATOED (even more so than the ESTES kit), but I'm not sure that everyone can do it correctly. If I were the RSO and the builder could answer the recovery questions to my satisfaction, then it would fly, otherwise it wouldn't. My safety questions and concerns are two-fold.
In the solution I proposed, there is a relatively high (disassembly) velocity near the ground so it is important that the pieces slow down and tumble recover. While a commercial kit will be proven safe by the manufacturer, a scratch-built may not have been flown before. As RSO I would want know how the rocket comes apart inflight and what the recovery expectations are.
Also it is important to only use A or B motors to keep the velocity low. There is always a temptation to use bigger motors which if the design were unstable, could prematurely disassemble at low altitude and high velocity under power and then you have a burning motor to contend with. As RSO I would like to know the CG/CP relationships of the model.
Bob Krech
