Here is why I might try my Estes Saturn V on a D12-0 ... help
 

Hi Folks. This is my first time posting.

The big question is will a D12-0 booster have enough "oompph" to eject the 'chutes??

I will lay out the scenario with data and supporting video. All of these shots in the vidoes were with D12-3 motors

(#1) Beautiful first flight before paint and decal. 448 g (15-3/4 oz) with engine
https://youtu.be/ZQ4WOqvZe5Y

(#2) Not so great flight after paint and decal. 456 g (16-1/8 oz) with engine
https://youtu.be/sS_xpEk-9HU

(#3) Even worse. Shaved off 4g down to 452 g (16 oz) with engine
https://youtu.be/bPoxUuf8MMk

(#4) Made some measurements, estimations and calculations and determined the Cg was too close to the Cp. So I added a weight into the nose. 490 g (17-1/4 oz) with engine. Cg around 17 inches from base. Cp estimated to be 13.4 inches from base. Slightly better flight.
https://youtu.be/AZapV6Vs1qw

Based on #4, it looks like apogee is right when burn is done so I was thinking a D12-0 would minimize the amount of drift back down before ejection.....the catch though is the D12-0 would have to have enough force to eject the 'chute and nose stage.

Thoughts?

I am debating about holding the rocket in my hand and firing to see if it will eject in a low-er risk environment, but that would probably violate some sort of NAR code. How can I fix it in place such as on my sawhorse without messing up the finish?

E15-4. That's the motor everyone espoused many years ago. I still have one I bought back in 2000 for the Saturn-V kit I also bought that year. The kit has never been started, but if I ever git'er'done , I'll have the motor for it :)


Don't do that. It's potentially dangerous - you could get burned. You'd feel awful if it went awry.


Buy another launch rod - ie, a steel rod from the hardware store - and mount it to the sawhorse, then slide the rocket over it. Then put a clamp on the rod just above the launch lug. I have a small pair of Vise-grips that would be a perfect clamp :) Make sure the blast won't hit anything - rig a deflector if you need to.

HTH.

Doug

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I don't know how you built it, but it is way too heavy. I can fly on D12-3's all day with no problems. Since it is so heavy, you only have one solution without modifying the rocket. Fly it on composite motors. Aerotech makes E15-4 and E20-4 single use motors and E18-4 reloadables that will overcome the added weight. Doug didn't specify, but he means the Aerotech motor I'm talking about. Estes used to make an E15 but they were very prone to CATO and were longer than the D12 casing.

That said, build another one with considerably less glue so you can fly it in those same small field locations on a D12-3. ;)

Doug Sams - great suggestion. I can mock that up real easy and safe. Thank you. I'll repor back with results

tbzep - I confess I did glue the $%{+ out of it. I used those molding oldies aftermarket nose and farings that added weight but strength. lesson indeed learned.

I'd use an E engine in a heartbeat but when I look at the launches (see videos themselves if you like) I'd be concerned it'd still be unstable. I did my best on the Cp-Cg thing

Think I might have to simply retire it on the shelf...if this D12-0 scheme does not work

Thanks

The E15 will stomp the heck out of it compared to a D12. You can add all the nose weight you need to get the CG where it needs to be and it will still jump off the pad. You will need a decent size field compared to the D12, though. Unless it means something special to you, fly it on those composites when you have a big enough field. Build another one completely stock to fly on D12-3's on small fields. It makes a great demo, pretty much coasting to a stop and ejecting the chutes at apogee when flown in calm conditions. If you want to get a little creative, build it with a removable mount and play around with 18mm clusters. It can be flown on 4 B6-2's, 3 C6-3's, or 4 C6-5's with great results. Each cluster listed is slightly more powerful than the previous, giving you the ability to fine tune your model for the field size.

The one thing no one has mentioned here is do NOT use a D12-0! There is no ejection charge in -0 motors - they are meant to be used in the lower stage of multi-staged rockets only.

I always flew mine with a cluster of 2 or 3 D12-3 hanging out the back of the primary motor mount. You could simply piston launch it With a D12-3. With a D12-0, add about 1/2g 3F BP.

Jerry

cite:

http://v-serv.com/usr/kits/pistonlaunchedmicroc.htm

I was thinking the same thing SEL was: no ejection charge. How could that possibly work?

It will eject to some extent, but it won't forcefully enough to have successful recovery on all models. Bob Kaplow used zero delay in SuperRoc before it was quickly outlawed. I wouldn't try it on a model that I spent a lot of time making look good.

Remember that the propellant breaks through before all of it is burned. Hot gases and small bits of BP blow forward to ignite the upper stage. This can sometimes create enough pressure to blow a nosecone, but sometimes it isn't enough to get the recovery system to follow. Centuri's Pass-port staging system was designed to vent the pressure so it wouldn't pop stages apart before ignition.

Hi Everybody - Thanks for all of the input. I did a static test of a D12-0. Not so bad, but not super. Video below

https://youtu.be/Llk70IAVhSY

On what basis was it outlawed?

Teach those kids to countdown to ZERO!

Thanks Jerry. Will do. :)

Based on a ruling that the motor was not used as the manufacturer intended.



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You obviously don't care whether the Saturn gets banged up!

That makes a lot of sense. I've long since lost track of the number of things I've learned here.

More glue is not better, contrary to popular belief... It adds weight not strength.

Lesson learned, hopefully...

Later! OL J R

True, but -0 motors blow through the thinking propellant disk at near full combustion chamber pressure, which CAN potentially eject something, theoretically.... It's strong enough that countermeasures of some sort are usually necessary to slow stage separation, like taping motors together or vent ports to exhaust the gases from the blow-through...

The problem is most rockets are traveling their fastest at burnout which will strip the chute in a normal rocket...

Still not the ideal solution to his problem IMHO but theoretically it COULD work...

Later! OL J R

You're a little late there, buddy.



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Exactly...

Not sure if the exact chamber pressure on a D12-0 but probly in the neighborhood of 80-100 psi... As the motor burns the propellant slug holds this pressure in the casing between the burning propellant slug back face and the nozzle inner end and nozzle hole, which is constantly expelling gas to create thrust. When the slug of propellant burns thinner and thinner till it's a disk, at some point it shatters from the chamber pressure behind it, instantly creating another much larger outlet for the pressurized flaming gas, that being the front of the motor case. This blows burning chunks of BP from the shattered disk forward, igniting the second stage. The chunks of burning propellant move slower than the expanding hot gas, which arrives first and can blow the stages apart before the burning particles ignite the upper stage, hence "pass-port" or other gas vent designs, or taping the motors together so they hold together until the upper stage motor repressurizes the booster motor case between the two nozzles, at which point the tape becomes the weak link and ruptures, allowing the pressure to blow the stages apart...

The problem is the volume of gas and speed it's delivered is smaller than that from a fast-burning BP ejection charge... Might not be enough to elect the laundry, especially from a large tube with large volume...

That and ZERO delay between thrust and "ejection"...

Later! OL J R

Better late than never... Posting as I read the thread rather than read all the way thru the post...

Later! OL J R

My concern on the D12-0 would be charring of the relatively thin stuffer tube and over coming the base drag of the transition while in flight.I personally wouldn't try it on a dare.