Staging on a Two Stage Rocket with Minimum Diameter Rocket

[Alan Offer]

Goodevening everyone,

I'm currently stuck on the interstage design that I will use for my two stage rocket that will attain an altitude of 38km. The rocket is a 4inches Minimum Diameter rocket with a O3400 for the Booster and a N1100 for the sustainer, both from Cesaroni.

My first idea was to offset the upper stage motor so it can fit in the lower stage. Then the lower stage ejects the upper stage with some ejection charges and sheer pins and the sustainer uses an Head End Ignition system to ignite.

Can someone tell me if that system is reliable or is there a better option for a more efficient and safe system ? Any other suggestions are welcome also

Thank you and have a great evening,

Alan Offer from IMF.Rockets

 

[rocketryfanatic]

Goodevening everyone,

I'm currently stuck on the interstage design that I will use for my two stage rocket that will attain an altitude of 38km. The rocket is a 4inches Minimum Diameter rocket with a O3400 for the Booster and a N1100 for the sustainer, both from Cesaroni.

My first idea was to offset the upper stage motor so it can fit in the lower stage. Then the lower stage ejects the upper stage with some ejection charges and sheer pins and the sustainer uses an Head End Ignition system to ignite.

Can someone tell me if that system is reliable or is there a better option for a more efficient and safe system ? Any other suggestions are welcome also

Thank you and have a great evening,

Alan Offer from IMF.Rockets

My suggestion is just rely on drag separation. No need to shear pin the booster to sustainer, no need to have a charge between the too. The more you over think the plumbing the easier it is to stop up the drain.

Head end ignition over complicates things. You can use thin 2 conductor ribbon wire and run that down the side of the motor to connect to the ignitor.

 

[Alan Offer]

My suggestion is just rely on drag separation. No need to shear pin the booster to sustainer, no need to have a charge between the too. The more you over think the plumbing the easier it is to stop up the drain.

Head end ignition over complicates things. You can use thin 2 conductor ribbon wire and run that down the side of the motor to connect to the ignitor.

Thanks for your suggestion. How can I be sure that the rocket will separate at the right moment and will it work if the upper motor is offset and plugged in the lower tube ?

When you say two ribbon wire, you mean along side the external diameter of the body tube ?

 

[rocketryfanatic]

Thanks for your suggestion. How can I be sure that the rocket will separate at the right moment and will it work if the upper motor is offset and plugged in the lower tube ?

When you say two ribbon wire, you mean along side the external diameter of the body tube ?

In my experience of staging, keep in mind I have never done a min diameter sustainer. For me I have always had a interstage coupler go up inside the sustainer. Using the motor as coupler you have to figure a way to eliminate the thrust ring on the commercial motor. Generally, for staging once the booster has burned out and by drag they separate without a charge. Sometimes depending when the electronics fire the sustainer your booster can get cooked a little if your firing it right away. In common since to me I would think drag separation would work in the same way.

Yea, the ribbon wire runs down the motor tube next to the airframe. I have never done a min diameter sustainer in 2 staging but if I did that is the route i would entertain first.

 

[rocketace]

Here is an example of the flat copper ribbon. Also, I would definitely not use shear pins. For separation, I am planning on drag separation, but I do have a 0.2g charge as back up, that will fire 1 second after motor burn out.

 

[Egoldee]

Goodevening everyone,

I'm currently stuck on the interstage design that I will use for my two stage rocket that will attain an altitude of 38km. The rocket is a 4inches Minimum Diameter rocket with a O3400 for the Booster and a N1100 for the sustainer, both from Cesaroni.

My first idea was to offset the upper stage motor so it can fit in the lower stage. Then the lower stage ejects the upper stage with some ejection charges and sheer pins and the sustainer uses an Head End Ignition system to ignite.

Can someone tell me if that system is reliable or is there a better option for a more efficient and safe system ? Any other suggestions are welcome also

Thank you and have a great evening,

Alan Offer from IMF.Rockets

How much experience do you have with electronic staging? My suggestion is to learn what you are doing before you attempt a project like this.

Anyways best of luck with this and any other future projects.

 

[rocketryfanatic]

How much experience do you have with electronic staging? My suggestion is to learn what you are doing before you attempt a project like this.

Anyways best of luck with this and any other future projects.

I agree 100% with your statement but sometimes just send it as long as all the math and stuff check out. You could test and retest over and over and your ultimate goal might not happen.