Will a 2-stage rocket ignites on deployment charge?

Usually when you see a 2-stage rocket, they expect you use a "special" motor for the bottom stage, one that doesn't have a delay for the deployment and also has the black powder (and not some "clay buckshot") at the deployment end. I've read elsewhere that not only does the method not have a delay, it also burns hotter when it burns through, which is part of why it ignites the 2nd stage...

My question is, if one were to use a lower-stage motor that is a traditional motor with a delayed ejection charge, would it ignite the second stage? (I know there's a secondary issue of the rocket wanting to go off at an angle if you have too long of a delay, but let's assume a short delay before the rocket has decelerated much, let's say 3 seconds or less)

and if it doesn't ignite the 2nd stage, does anyone know of a mechanism to trigger an igniter based on the prior stage's ejection charge? (My best thought to date was to trigger a relay based on a broken electrical connection when the lower-stage breaks away).

it will light the second stage but like you said it may be hard to have a safe flight without the rocket falling to the side.

The traditional motor will not light the upper stage because of the clay cap over the ejection charge. The times I've seen the aftermath of a mis-loaded booster/upper stage motor combination, the clay from the traditional motor plugs the nozzle of the booster motor that is mis-positioned in the upper stage.

I'm not sure of the formulation but the ejection charge is a different formulation than the black powder mixture that produces the thrust. A proper booster motor will contain all thrust formulated powder. When it burns through it is still producing some thrust and the hot gases will ignite the upper stage motor (remember vent holes if you are going to gap stage).

You don't indicate where you are from but various black powder booster motors (B6-0, C6-0, D12-0, etc.) are readily available in the US. If you are in some other country, someone from there should be able to give you better guidance.

I've not heard of any mechanical way to use an ejection charge to start an upper stage. It doesn't sound like it would comply with the NAR Safety Code in the US.

Kenn, I'm in the US, but I haven't been able to find what I'm looking for. I'm looking for a composite DX-0 (where X is small, 10 or less) motor in an 18mm casing (which is what I can't find).

My thought was similar to yours about the clay causing trouble (in addition to possibly preventing ignition), but I wanted to hear it from others without inducing the thought. I do have a work-around for that, which would be to put a blocker in between the bottom stage and the 2nd stage, so that the clay won't get in there, but then I'd *definitely* need a way to ignite the upper stage with some other mechanism besides the burn through of the 1st stage.

KennB said:

It doesn't sound like it would comply with the NAR Safety Code in the US.

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I definitely wouldn't want to do something unsafe. Could you be more specific in what you see me doing that would be trouble for the NAR safety code?

KennB said:

The traditional motor will not light the upper stage because of the clay cap over the ejection charge. The times I've seen the aftermath of a mis-loaded booster/upper stage motor combination, the clay from the traditional motor plugs the nozzle of the booster motor that is mis-positioned in the upper stage.

I'm not sure of the formulation but the ejection charge is a different formulation than the black powder mixture that produces the thrust. A proper booster motor will contain all thrust formulated powder. When it burns through it is still producing some thrust and the hot gases will ignite the upper stage motor (remember vent holes if you are going to gap stage).

You don't indicate where you are from but various black powder booster motors (B6-0, C6-0, D12-0, etc.) are readily available in the US. If you are in some other country, someone from there should be able to give you better guidance.

I've not heard of any mechanical way to use an ejection charge to start an upper stage. It doesn't sound like it would comply with the NAR Safety Code in the US.

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when I first started out in rocketry I didn't know about the delay so I put a b6-4 and an a10 something in my Estes solar flare and the second stage lit just fine with the B6-4 although the rocket had started to turn onto its side everything worked as it was supposed to.

kencraw said:

Kenn, I'm in the US, but I haven't been able to find what I'm looking for. I'm looking for a composite DX-0 (where X is small, 10 or less) motor in an 18mm casing (which is what I can't find).

My thought was similar to yours about the clay causing trouble (in addition to possibly preventing ignition), but I wanted to hear it from others without inducing the thought. I do have a work-around for that, which would be to put a blocker in between the bottom stage and the 2nd stage, so that the clay won't get in there, but then I'd *definitely* need a way to ignite the upper stage with some other mechanism besides the burn through of the 1st stage.



I definitely wouldn't want to do something unsafe. Could you be more specific in what you see me doing that would be trouble for the NAR safety code?

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Composite motors can NOT lite upper stage motors.
But a Black powder booster motor can ignite a composite upper stage, the old North Coast used to have a kit that did that.

kencraw said:

Kenn, I'm in the US, but I haven't been able to find what I'm looking for. I'm looking for a composite DX-0 (where X is small, 10 or less) motor in an 18mm casing (which is what I can't find).

My thought was similar to yours about the clay causing trouble (in addition to possibly preventing ignition), but I wanted to hear it from others without inducing the thought. I do have a work-around for that, which would be to put a blocker in between the bottom stage and the 2nd stage, so that the clay won't get in there, but then I'd *definitely* need a way to ignite the upper stage with some other mechanism besides the burn through of the 1st stage.



I definitely wouldn't want to do something unsafe. Could you be more specific in what you see me doing that would be trouble for the NAR safety code?

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Here is a 18mm D10 composite motor: https://www.valuerockets.com/product_details.aspx?pid=2&itemid=1

There do not seem to be any 0 delay or plugged variations, but my understanding is that for some composites you can "drill" the delay away and/or remove the ejection charge. You would need someone else's advice on whether/how to do that. And you may not even need to do it, because it seems like if you light the second stage, it will leave the booster behind before the ejection charge fires. My understanding also is that composites are not used to light second stages directly, so you are not going to find a composite booster that is designed to light a second stage.

I believe what you are looking for is a way to "airstart" the second stage using an accelerometer. I've never done it myself, but was looking for some info on it a few weeks ago. The accelerometer senses the loss of acceleration when the booster burns out and uses an on-board battery to light an igniter in the second stage motor. Do a search for "air start" or "airstart." I think the device I was looking at is the RRC3: https://www.missileworks.com/avionics

I think the thing you described of having a relay trigger when the booster stage pulled away is called a "pull pin," and from what I remember when looking it up is that pull pins are banned under NAR rules for safety reasons (probably accidental pulling of the pin lighting the motor at inopportune times).

Keep in mind, I've never done any of this myself, so you would want someone else to verify it!

conman13 said:

when I first started out in rocketry I didn't know about the delay so I put a b6-4 and an a10 something in my Estes solar flare and the second stage lit just fine with the B6-4 although the rocket had started to turn onto its side everything worked as it was supposed to.

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I've heard of people accidentally putting in motors in the wrong order (C6-7 to C6-0) and basically shooting the rocket back at the ground. The ejection charge can light the other motor, although it might not do it reliably (not sure if unreliable in this case is a bad thing or not).

I could see that happening. In this case what the OP is asking to do isn't really possible or safe for that matter. Depending on the size of the rocket your best option would be to use an -0 ejection charge or use a timer to ignite the second stage.

conman13 said:

I could see that happening. In this case what the OP is asking to do isn't really possible or safe for that matter. Depending on the size of the rocket your best option would be to use an -0 ejection charge or use a timer to ignite the second stage.

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Yep. A timer or accelerometer is the way to go. (Or so I say, having never actually done either myself)

jazzviper1 said:

Composite motors can NOT lite upper stage motors.
But a Black powder booster motor can ignite a composite upper stage, the old North Coast used to have a kit that did that.

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I think you've got that backwards there. A composite ejection is capable of lighting a BP upper stage, but a BP booster can in no way light a composite motor up the nozzle, then up to the top of the grain and get things going properly.


You can also use timers/altimeters to electronically ignite staged motors.... that'd be the way I'd go about it.

Most composite motors burn from inside out the entire length of the motor. Black powder motors burn from the bottom up.

You need either the delay puck or plug in the top of a composite motor to keep it pressurized and all the thrust coming out the bottom end. If you've ever seen a CATO of a composite motor where the forward closure fails, it looks like a flamethrower out the top of the rocket. It might light the second stage, but it would do it on the pad.

Composite motor staging is done with timers and igniters, similar to dual deploy.

The only end burning composite motor I know of is the Apogee F10-8. IIRC, the ejection charge is held in with a cardboard cap. If you were really driven to try, you could probably remove the cap and ejection charge and drill out the delay. At an 8 second burn, your rocket would be pretty high before it staged.

kencraw said:

I definitely wouldn't want to do something unsafe. Could you be more specific in what you see me doing that would be trouble for the NAR safety code?

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While the NAR Model Rocket Safety Code doesn't address multiple stage rockets directly, item #2 could be used by any RSO to deny the flight of any rocket that isn't using a -0 booster in the first stage.

Based on the certified motor list, there isn't an 18 mm D-impulse -0 booster as a composite or otherwise. As has been mentioned elsewhere in this thread, composites work differently and would be difficult to use and ensure a vertical orientation if it could light the upper stage. Without getting into some complex electronics, it seems that you'll have to work with available black powder boosters.

KennB said:

While the NAR Model Rocket Safety Code doesn't address multiple stage rockets directly, item #2 could be used by any RSO to deny the flight of any rocket that isn't using a -0 booster in the first stage.

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This RSO would and has allowed a composite motor with delay and ejection charge light a black powder second stage. I just need to be reasonably sure it will be pointing up when the staging occurs.

I think you were there the day we let it go. It was one of the early TARC years when they were doing two stages. To be honest, I was skeptical but I remember the flyer convincing us he had done it successfully several times before.

If you use a sufficiently light 2 stage rocket (with unlit sustainer weight included) that would normally use say a -7 delay, then perhaps a D10-4 composite (18mm) is an option to light your BP sustainer motor, if the whole kit would still be going straight up. I'm not saying to try it. I'm just saying its a possibility of getting closer to the answer you're looking for (and close counts in horseshoes and...yep, hand grenades).

Any chance we can see a picture of your design?
Sounds like you are going to a lot of trouble to maintain an 18mm D engine in your booster.

Thanks everyone for your feedback, I had a feeling the answer was going to be an altimeter based ignition of the second stage using a traditional igniter. I can see where some mechanical separation technique will have safety issues without some meaningful fail-safe. It would be really bad news to accidentally separate the stages in one's hand and then have the sustainer ignite in my hand.

As for the altimeter based "airstart" the I have a feeling that's going to be very hard to find for an 18mm body tube. Might have to make something myself... and that will be a HUGE project.

kencraw said:

Thanks everyone for your feedback, I had a feeling the answer was going to be an altimeter based ignition of the second stage using a traditional igniter. I can see where some mechanical separation technique will have safety issues without some meaningful fail-safe. It would be really bad news to accidentally separate the stages in one's hand and then have the sustainer ignite in my hand.

As for the altimeter based "airstart" the I have a feeling that's going to be very hard to find for an 18mm body tube. Might have to make something myself... and that will be a HUGE project.

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Actually, for staging you want a timer. Altimeters fire the first event at apogee and odds are your rocket will be far from vertical when that happens. With a timer you can set it to fire after first stage burnout while the rocket's still going up.

Something like these:
https://www.missileworks.com/pet2
https://www.perfectflite.com/timers.html

Another option to fit the electronics and battery would be to build a larger diameter first stage and make your transition the av bay.

ETA: I googled mid power 2 stage and found this: https://www.apogeerockets.com/downloads/Newsletter289.pdf

It has a tip on installing staging electronics on the outside of a small diameter rocket.

Exactimator said:

Actually, for staging you want a timer. Altimeters fire the first event at apogee and odds are your rocket will be far from vertical when that happens. With a timer you can set it to fire after first stage burnout while the rocket's still going up.

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Or an accelerometer based altimeter.