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Low power, no ejection charge?

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Senior Space Cadet

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Are there any low power motors that don't have an ejection charge?
I've had several projects in mind that would only work if the nosecone doesn't come off during the flight.
I've considered just having the engine eject out the back, but my understanding is that's frowned upon. I could see someone getting conked with a falling motor.
 

KennB

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Estes made an A10P and D11P motor. You may be able find some of them around.
Look at the old Estes Scout design; it retained the motor and vented the ejection pressure. The motor shifted aft and allowed for tumble recovery as opposed to ballistic recovery.
Booster motors will create some pressure at burn through but venting may be enough.
For black powder motors, if anyone suggests removing the ejection charge or filling the end of the motor casing with epoxy (and someone will), don't fly a motor with either of those modification at a NAR launch.
You may be able to find some low power composite reload motors that you could build without the ejection charge.
 

Zeus-cat

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I have a few rockets that spit the used motor. You can't spit a motor in a competition, but your club may allow it for sport flying. Another option is to eject the motor in a pod and have a streamer or chute bring the pod down.
 

Senior Space Cadet

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Are there any low power motors that don't have an ejection charge?
I've had several projects in mind that would only work if the nosecone doesn't come off during the flight.
I've considered just having the engine eject out the back, but my understanding is that's frowned upon. I could see someone getting conked with a falling motor.
I thought about venting it. Wasn't sure if it was a good idea or not. Sounds like it is.
 

Senior Space Cadet

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I have a few rockets that spit the used motor. You can't spit a motor in a competition, but your club may allow it for sport flying. Another option is to eject the motor in a pod and have a streamer or chute bring the pod down.
Ejecting the motor with a chute might be possible, but a lot of people warned me about rear ejections and my one experience with it wasn't good.
 

samb

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BP motors with the -0 delay have neither delay grains or ejection charge. There is a certain amount of pressure generated at the aft end of the propellant grain when the flame front breaks through that would need to be vented to ensure your nose cone stayed put.
 

Nytrunner

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Ejecting the motor with a chute might be possible, but a lot of people warned me about rear ejections and my one experience with it wasn't good.
But if you want to recover the model safely (and it isn't a glider/helicopter) rear-eject may be the only way to go that retains the nose.
 

beeblebrox

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Fill end of booster motor with epoxy. Perfect for my cluster duck outboard motors, no need to vent and no need to eject them...
 

Scott_650

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Are there any low power motors that don't have an ejection charge?
I've had several projects in mind that would only work if the nosecone doesn't come off during the flight.
I've considered just having the engine eject out the back, but my understanding is that's frowned upon. I could see someone getting conked with a falling motor.
Not to discount your safety concerns but an expended 18mm BP motor casing weighs roughly half an ounce. Not that I care to get bonked by one falling at a decent percentage of terminal velocity but the chances of being injured are about zero.

A possible solution is a tethered retainer like Centuri/Semroc used/uses on The Point https://www.spacemodeling.org/jimz/kc-13.htm
 

shockie

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Are there any low power motors that don't have an ejection charge?
I've had several projects in mind that would only work if the nosecone doesn't come off during the flight.
I've considered just having the engine eject out the back, but my understanding is that's frowned upon. I could see someone getting conked with a falling motor.
eject the motor with a streamer and yell heads up!
 

shockie

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Not to discount your safety concerns but an expended 18mm BP motor casing weighs roughly half an ounce. Not that I care to get bonked by one falling at a decent percentage of terminal velocity but the chances of being injured are about zero.

A possible solution is a tethered retainer like Centuri/Semroc used/uses on The Point https://www.spacemodeling.org/jimz/kc-13.htm
unless it hit🤕 you in the eye while you was looking up.....
 

Antares JS

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which is a violation of NFPA 1122 and the NAR Model Rocket Safety Code....ask me if I care? No I don't
Not if it's an Aerotech composite motor. Aerotech has endorsed the practice of removing ejection charges from their single-use motors, so it's a manufacturer-approved modification and violates no rules.
 

jrap330

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Are there any low power motors that don't have an ejection charge?
I've had several projects in mind that would only work if the nosecone doesn't come off during the flight.
I've considered just having the engine eject out the back, but my understanding is that's frowned upon. I could see someone getting conked with a falling motor.
The answer is YES...Booster engines....has a zero on the end as in A6-0, B6-0 etc.
 

Cape Byron

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Ejecting the motor with a chute might be possible, but a lot of people warned me about rear ejections and my one experience with it wasn't good.
Are you talking about a rear-eject motor pod with chute for the rocket and pod, or just ejecting the motor? I've had good experiences with the former; great for rockets with fragile fins.

 

shockie

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Not if it's an Aerotech composite motor. Aerotech has endorsed the practice of removing ejection charges from their single-use motors, so it's a manufacturer-approved modification and violates no rules..
you got a weblink to that? I believe you. I thought they had approved modifying the delay train, I didn't know they had also approved removing the ejection charge. When I posted that I was thinking primarily of Estes BP motors...
 

Senior Space Cadet

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I had other projects in mind, but what prompted this question was my current build, which is a fixed wing jet.
I'm thinking it would be cool if it came in for a space shuttle like landing, rather than using a chute.
Because of the wings, I'm going to need quite a bit of nose weight to get stable flight on launch, and I might need to retain the motor to get the plane to balance right for the glide.
I really need to try and get the wing and fin shapes into Open Rocket so I can make a more accurate calculation on nosecone weight. It's going to take me some time.
The other obvious problem is that, with fixed wing and stabilizers, in order to get the plane to glide right, it's going to want to do a loop on launch.
Given enough safe room, that might be cool, assuming it didn't hit me. If it did one big loop, then glided into a landing, that would be awesome.
You think a spent engine falling to earth is a fire danger?
 

Scott_650

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I had other projects in mind, but what prompted this question was my current build, which is a fixed wing jet.
I'm thinking it would be cool if it came in for a space shuttle like landing, rather than using a chute.
Because of the wings, I'm going to need quite a bit of nose weight to get stable flight on launch, and I might need to retain the motor to get the plane to balance right for the glide.
I really need to try and get the wing and fin shapes into Open Rocket so I can make a more accurate calculation on nosecone weight. It's going to take me some time.
The other obvious problem is that, with fixed wing and stabilizers, in order to get the plane to glide right, it's going to want to do a loop on launch.
Given enough safe room, that might be cool, assuming it didn't hit me. If it did one big loop, then glided into a landing, that would be awesome.
You think a spent engine falling to earth is a fire danger?
Most non-R/C boost gliders are either the parasite style with a carrier rocket or use some kind of Cg shift to glide after apogee - which is where, in your design, ejecting the motor comes into play. My personal opinion is a rear ejected power pod - the engine mount structure with a streamer - would work better than just trying to get the Cg corrected for the glider by ejecting the motor case. You’ll probably have to add weight to the power pod to get a stable boost with the amount of nose weight it could take for a decent glide and a stable boost. If you’re planning on not having some kind of sprung elevator arrangement with the control surfaces held neutral during boost the recovery glide is going to be fairly steep but it’s going to take a fair number of trials to get it trimmed to glide at all. As far as possible fire danger that’s always a risk - lots of suboptimal things from a rocket launch could increase the risk of a fire, a falling expended engine case is just one of several.
 

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I don't think that will glide. Look at glider designs and the wings are fairly large so they generate lift. Your wings look way too small. Also, you should airfoil your wings to create more lift.
 

Bruce

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Fill end of booster motor with epoxy. Perfect for my cluster duck outboard motors, no need to vent and no need to eject them...
It doesn't matter to me one way or the other, but could this possibly be considered by some to be "modifying the motor" and thus running afoul of the safety code?
 

Senior Space Cadet

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I don't think that will glide. Look at glider designs and the wings are fairly large so they generate lift. Your wings look way too small. Also, you should airfoil your wings to create more lift.
That's what I meant by a space shuttle type landing. But the wings are bigger than they look because I'm shooting from the side.
 

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I suggested to you in the beginning, build some kits, now definitely for gliders built a kit or two to help you sort out all design criteria. Boost glides are tricky as your analysis suggest.
I'd like to think I'm far past the kit stage for standard rockets. I've got about a dozen self designed and built rockets that fly fine. My problem is the recovery.
If I found a kit that did something like I'm trying to do, I think I'd buy it.
 

Zeus-cat

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That's what I meant by a space shuttle type landing. But the wings are bigger than they look because I'm shooting from the side.
I am not a glider guy, but a number of people in my club are. Your rocket doesn't look like the ones they fly. Most gliders are long and have big wings. Yours will definitely be a heads up flight the first few times. Good luck.
 

Senior Space Cadet

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Most non-R/C boost gliders are either the parasite style with a carrier rocket or use some kind of Cg shift to glide after apogee - which is where, in your design, ejecting the motor comes into play. My personal opinion is a rear ejected power pod - the engine mount structure with a streamer - would work better than just trying to get the Cg corrected for the glider by ejecting the motor case. You’ll probably have to add weight to the power pod to get a stable boost with the amount of nose weight it could take for a decent glide and a stable boost. If you’re planning on not having some kind of sprung elevator arrangement with the control surfaces held neutral during boost the recovery glide is going to be fairly steep but it’s going to take a fair number of trials to get it trimmed to glide at all. As far as possible fire danger that’s always a risk - lots of suboptimal things from a rocket launch could increase the risk of a fire, a falling expended engine case is just one of several.
Probably too late for this build, but I was trying to figure out a way that the ejection charge would change the angle of the stabilizers. Possibly by the motor ejecting, or simply moving back, thus allowing a spring loaded lever to move into the empty space.
Do you know any kits that work that way?
 

Senior Space Cadet

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I am not a glider guy, but a number of people in my club are. Your rocket doesn't look like the ones they fly. Most gliders are long and have big wings. Yours will definitely be a heads up flight the first few times. Good luck.
Again, that's what I meant by space shuttle landing. It's no sailplane. I've made a few gliders in my time. I don't expect it to rise on a thermal or anything.
 

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