Is ejection charge strong enough to eject capsule?

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PAL9000

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Hi. My brother and I are building a rocket that will eject a capsule containing an egg. We plan on attaching the capsule to the bottom of the nose cone, which will fall free of the rest of the rocket using its own parachute.
We aren't sure if the ejection charge will be strong enough to push out the capsule+nose cone along with the other main parachute (plus wadding paper).
The rocket is two BT-80 body tubes coupled together.
We have attached details of the rocket.
Do you think an E12-6 motor will eject the capsule+nose cone, or is the rocket too long for the ejection charge to travel 28 inches to eject that combined mass (130.6g)?
Thank you!
 

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NAR29996

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Hi. My brother and I are building a rocket that will eject a capsule containing an egg. We plan on attaching the capsule to the bottom of the nose cone, which will fall free of the rest of the rocket using its own parachute.
We aren't sure if the ejection charge will be strong enough to push out the capsule+nose cone along with the other main parachute (plus wadding paper).
The rocket is two BT-80 body tubes coupled together.
We have attached details of the rocket.
Do you think an E12-6 motor will eject the capsule+nose cone, or is the rocket too long for the ejection charge to travel 28 inches to eject that combined mass (130.6g)?
Thank you!
I'd use a stuffer tube to reduce the volume that you need to pressurize. IOW, Increase the length of the motor mount tube until it reaches the coupler.
 

gna

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I'd use a stuffer tube to reduce the volume that you need to pressurize. IOW, Increase the length of the motor mount tube until it reaches the coupler.
+1
I would use another centering ring on the motor mount tube near the end. How is the main parachute attached to the rocket body? I don't see a shock cord. Also, what are you using for fins? It says "cardboard," but I'm guessing that's not right.

I think an E12-4 might be a better motor choice.
 

Zeus-cat

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I'm not sure an E12 will provide a safe flight. Two BT-80 tubes and an egg means this will be a heavy rocket for an E12.
 

gna

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I think it will be fine. I threw together something similar in OR, using Estes tubes and nosecone, and it seems to be fast enough off the rod. I figured 42" 3/16 rod. I also used 1/8 balsa for the fins.

If it were my rocket, though, I would make the fins a bit bigger so it's stable without the load. I'd worry that they wouldn't have enough force to counteract the weight if it got off track. I'd probably make them TTW and paper them, too.
 

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gna

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Here's an edit, with larger fins and tabs, stuffer tube up to coupling and centering ring butted up to bottom of coupling, It flies OK on an E12-4, both with and without the payload.
 

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RocketTree

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Reduce the internal volume as much as possible, and it should be fine. Might also be important to keep deployment speed as low as possible. If you get really ambitious, determine the charge pressure with online calculator. The charges are usually powerful in the BP motors.
 

gna

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Little late to reply, but I had some BMS BT-80 around, so I ordered a nose cone and built a variant of the rocket. No coupler needed. Longer motor tube, 3 centering rings, papered the fins, through the wall fin tabs. Decided a payload bay would be useful, so made the top 6" into one:
IMG_4037.jpg
 

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Culprit

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Little late to reply, but I had some BMS BT-80 around, so I ordered a nose cone and built a variant of the rocket. No coupler needed. Longer motor tube, 3 centering rings, papered the fins, through the wall fin tabs. Decided a payload bay would be useful, so made the top 6" into one:
View attachment 463134
A little off-topic, but as a guy who enjoys bird photography, I love your paint scheme and the rose-breasted grosbeak decal. Nicely done.
 

gna

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Thank you.

I like birds, so I have been painting my builds to reflect color schemes and putting bird decals/stickers on some of my rockets. I have a Goldfinch and a Chickadee. Working on a Blue Jay and a Cardinal. I just bought a Loc IV and think I should paint it black and call it the Raven.

At one time I had a scale model of the Skylark sounding rocket, too, but it got treed...
Goldfinch.jpg


Maybe should have picked a more delicate rocket for the Goldfinch...
 

BABAR

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Thank you.

I like birds, so I have been painting my builds to reflect color schemes and putting bird decals/stickers on some of my rockets. I have a Goldfinch and a Chickadee. Working on a Blue Jay and a Cardinal. I just bought a Loc IV and think I should paint it black and call it the Raven.

At one time I had a scale model of the Skylark sounding rocket, too, but it got treed...
View attachment 463193

Maybe should have picked a more delicate rocket for the Goldfinch...
You may want to go with Ostriches, Kiwis, Chickens, Turkeys, and other birds that don’t home in on trees.
 

BABAR

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Oh yeah, definitely Emus.
 

BABAR

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Lol
All the flightless birds
Though I've turkeys in trees.
I’ve seen turkeys everywhere. Especially at Walmart.....
 

PAL9000

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Thank you for the advice. The E12 motor turned out okay. We had two successful flights with good capsule ejection and safe landing for the eggstronauts. There was a capsule parachute problem on a third flight and the eggstronaut didn't make it back.
 

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gna

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Hope it wasn't too messy. Will it fly again, with a fresh volunteer?
 

gna

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He needs a spacesuit-- a ziploc bag will do nicely.
 
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