Staged rockets stability

[Scotty Dog]

I dont know why,but it hit me again. I had a thought. Been alot of talk about balancing rockets here lately --cp,cg,nose weight and such. So whats the deal when you drop a stage that weighs,say, between the motor,tube and fins ,8-14 gs off the back of a rocket. That sure throws the CG off . Does it keep stable because of the speed its going at the time it stages???????????And if you scratch a staged rocket how would one (that doesnt have SIM) go about balancing it. Do you do with it all together or just the rocket without the stages. I wonder about this stuff ,ya know!

 

[Rocketman248]

It actually becomes more stable as you drop the booster off. With the booster connected, it's like a single rocket with two sets of fins. Rockets like that generally have a CP that is more forward than one with a single set of fins. Plus, that's a lot of weight in the back. Once the booster falls, you just have a standard rocket with one set of fins and a normal CG.

When balancing, you'll need to find the CP of the whole stack and balance it for that. You also need to find the CP of each stage individually. You want the booster to remain stable by itself, so it doesn't start to tumble immediately following the staging event.

 

[Scotty Dog]

It actually becomes more stable as you drop the booster off. With the booster connected, it's like a single rocket with two sets of fins. Rockets like that generally have a CP that is more forward than one with a single set of fins. Plus, that's a lot of weight in the back. Once the booster falls, you just have a standard rocket with one set of fins and a normal CG.

When balancing, you'll need to find the CP of the whole stack and balance it for that. You also need to find the CP of each stage individually. You want the booster to remain stable by itself, so it doesn't start to tumble immediately following the staging event.

I thought about the factiod of the cp. That would change/move as the shape (and drag?)of the rocket changed. HMMMMMMMM Thanks

 

[mwtoelle]

If you're designing a multi-stage rocket, start with just the upper stage alone and get the CP/CG relationship correct for just the upper stage. Next, add the booster to the sustainer and get the CP/CG relationship correct with both stages together. A good place for more info is the Estes Model Rocketry Technical Manual which includes some basic info on staging and other basic rocket stuff. You can download it here: https://www2.estesrockets.com/pdf/2819_Estes_Model_Rocketry_Technical_Manual.pdf