Two-Stage Question

Just wondering, placement of electronics for lighting second stage. Do people place them in the booster or the second stage.

I was thinking of placing mine in the booster just because of space concerns and am aware of the problem of separation prior to second-stage ignition, but figure I can mitigate the problem. If I can't, then the electronics in each stage will do their job of deployment.

Second stage

2nd

Booster - DD altimeter and separation electronics
Sustainer - DD altimeter + sustainer ignition

2nd Stage.

On my Double Shot build i ran length of break line from near retainer thru the centering rings to allow the ematch wire to run to the DD eBay.

Look at this link pages ~3~7 for a way to do it https://www.wildmanrocketry.com/Instructions/2%20stage%20final.pdf

I have mine in the sustainer to ignite all stages.

The boosters are recovered by parachute using motor ejection.

I hear there are very long drill bits, lol. I should have given that more consideration when I was building my Double Shot. I don't know how well retrofitting some sort of conduit will work, especially where the aft centering is located.

Thanks for the replies everybody.

robbdm said:

2nd Stage.

On my Double Shot build i ran length of break line from near retainer thru the centering rings to allow the ematch wire to run to the DD eBay.

Look at this link pages ~3~7 for a way to do it https://www.wildmanrocketry.com/Instructions/2%20stage%20final.pdf

Click to expand...

Here are a few ideas.

On my MD two-stagers, I use some conduit wire for routing the separation charge and igniter wiring. This stuff used to be called Gecko wire, but there's another name now. It's possible to take off the wear layer such that it can be made very thin.

The three problems I normally cite for putting the electronics in the booster are, (1) limited ability to control the flight profile, (2) pulling out the igniter too quickly, and (3) having the sustainer motor "toast" the booster and/or cato when it lights. By controlling the flight profile, I mean that you can't separate the booster and then coast for a while before lighting the sustainer. This might mean that you have to light the sustainer with minimal coast. However, I have come to believe that you might not lose much altitude if the two parts coast together for a while. If the rocket doesn't have a tendency to drag separate, which you can calculate, then you won't lose much if any altitude.

In order to avoid (3), it would be nice to separate the booster and fire the sustainer igniter at the same time (so that the booster is separated before the sustainer actually lights). I would figure out a mechanical approach to allow the parts to separate without pulling out the sustainer igniter.

Jim

hball55 said:

I hear there are very long drill bits, lol. I should have given that more consideration when I was building my Double Shot. I don't know how well retrofitting some sort of conduit will work, especially where the aft centering is located.

Thanks for the replies everybody.

Click to expand...

Oh, didn't know you've already built... I did purchase a 12" - 1/8 bit from home depot to clear a drop of epoxy from end a tube on one my two stages... maybe they have other bits.

The challenge will be get a straight set of holes and tube in the small gap pass the retainer, etc post build. Maybe an external tube that you can pop in the wire back in the vent hole and you can drill a new hole above the retainer.

This rocket would definitely have a tendency to separate being a 4" booster and a 54mm second-stage. Thanks for your input.

JimJarvis50 said:

Here are a few ideas.

On my MD two-stagers, I use some conduit wire for routing the separation charge and igniter wiring. This stuff used to be called Gecko wire, but there's another name now. It's possible to take off the wear layer such that it can be made very thin.

The three problems I normally cite for putting the electronics in the booster are, (1) limited ability to control the flight profile, (2) pulling out the igniter too quickly, and (3) having the sustainer motor "toast" the booster and/or cato when it lights. By controlling the flight profile, I mean that you can't separate the booster and then coast for a while before lighting the sustainer. This might mean that you have to light the sustainer with minimal coast. However, I have come to believe that you might not lose much altitude if the two parts coast together for a while. If the rocket doesn't have a tendency to drag separate, which you can calculate, then you won't lose much if any altitude.

In order to avoid (3), it would be nice to separate the booster and fire the sustainer igniter at the same time (so that the booster is separated before the sustainer actually lights). I would figure out a mechanical approach to allow the parts to separate without pulling out the sustainer igniter.

Jim

Click to expand...

hball55 said:

This rocket would definitely have a tendency to separate being a 4" booster and a 54mm second-stage. Thanks for your input.

Click to expand...

Might be getting a little off track, but don't assume drag separation would occur just because of the size difference. The masses of the two parts are important too. I have a 4"x3" two-stager and also a 4"x4". It seemed logical to me that the 4"x3" would be more likely of the two to drag separate, but when I went through the calculations, it was the other way around.

Jim

No worries about getting off track . . . I started the thread and won't complain. The booster is around 9 ounces heavier than the second-stage.