Have you ever had a -0 motor display an ejection charge?

[RocKen]

Hi Everyone,

I just flew a new pack of 2 Estes D12-0 motors last week and both seemed to have a distinctive "pop" after burnout. The second actually had motor ejection out of the rocket (custom cup rocket made for ejecting of motor casing; however I was testing it without ejection). Has anyone ever heard of this happening? I'm sure these were -0s...they even had the red label on them and they were new recent purchase 2-packs.

Unfortunately I'm not sure I can locate the spent casings...the first was thrown into the trash/mixed with other spent motors and the second was ejected in flight.

Note: I really LOVE Estes products; however I seem to be having a spate of issues recently...notable was a Blast Off pack which only included A8-3s when it should have been an assortment of A/B/Cs and it's been a week contacting them about this. Before that was another Blast Off pack with C6's with what seemed like excessive ejection charge (blew apart 2-3 rockets - one of them into 5 pieces another into 4). I'd rather not bother them about yet another issue for now.

 

[Zebedee]

Edit - I guess I was wrong. Learn something new every day Apologies for the mis-info.

 

[RocKen]

Thanks for the clarification...

 

[rharshberger]

-0 motors dont have ejection charges, however the gases from the burning propellant can be quite forceful.
Check out Emma Kristal's video from Naram a couple of years ago about what happens when BP booster motors burn through.

 

[RocKen]

I thought I read somewhere that they didn't have an ejection charge; however I can see how the burn through can cause similar to an ejection. Thanks!

 

[RocKen]

Ah! I just remembered why I didn't expect the -0s to have an ejection charge...I had flown a Quest Probe as well as Rocketarium Vorticos (regular and Mega) multiple times in the past month and they both have motor reco's of -0s. The earlier flights on B6-0s and C6-0s didn't have any distinctive/loud pop or motor ejection. Even some of the earlier D12-0s I flew didn't have any type of loud noise; however that last pair of D12-0's were loud and one was quite forceful...really shot out the motor.

 

[RocKen]

Just to be clear, from Estes 2015 catalog: "Engine types ending in '0' have no time delay or ejection..."

Also here are my recent -0 engine launches this month as a baseline for comparison to the experience first mentioned (these are the ones I tracked...I may have had a few more I didn't):
Date Rocket Name Kit Name Motor(s)
2015-03-01 Rocketarium Mega Vortico Rocketarium - Mega Vortico (Kit) D12-0
2015-03-08 Rocketarium Mega Vortico Rocketarium - Mega Vortico (Kit) D12-0
2015-03-09 Rocketarium Mega Vortico Rocketarium - Mega Vortico (Kit) D12-0
2015-03-10 Rocketarium Mega Vortico Rocketarium - Mega Vortico (Kit) D12-0
2015-03-10 Rocketarium Mega Vortico Rocketarium - Mega Vortico (Kit) D12-0 (loud pop)
2015-03-13 Rocketarium Vortico Rocketarium - Vortico (Kit) B6-0
2015-03-15 Monsters University Art Cup Rocket II (Scratch Build) D12-0 (loud pop, motor ejection)
2015-03-13 Rocketarium Mega Vortico Rocketarium - Mega Vortico (Kit) D12-0

rharshberger - Thanks for the info! I'll look for the vid.

Best regards
Ken

 

[Micromeister]

-0 motors have NO delay or ejection charge added PERIOD. They are Casing and Press BP Propellant grain only.

That said the Burn-thur and After burn as the remaining BP burns once it breaks thru the forward Grain end can have enough gas pressure to blow off a Nosecone if these gases are passing thru a small tube and/or short distance. But and I MEAN But! -0 motors Can NOT be relied on to deploy a standard run of the mill recovery device. It can be used to Seperate strap-on boosters, and deploy small streamers or chutes on engineered Scale models.
Hope this clarifies the question.

 

[shreadvector]

Using a booster motor in an open top tube, like in a flying saucer, will allow the hot gasses to come out the top with little or no sound.

Using the booster motor inside a closed tube will capture the hot gasses inside until the motor POPs out of the tube or the stage POPs off of the bottom of the multi-stage rocket.

If you hold you mouth open and exhale you will not make a POP.

If you close your mouth with your finger inside, pressurize your mouth, and flick your finger out you will make a POP sound.

And you do not have an ejection charge in your mouth.

 

[RocKen]

That explains the pop in the cup rocket (which had had a plugged end); however not the Mega Vortico which had an open end. Additionally I had flown the MV several times before on D12-0s and didn't hear any noticeable/significant pop. I was surprised by both "pops" for that pair of D12-0s and actually have it on video (although the sound is fairly poor), so it wasn't my imagination and each time I was actually surprised by the loud sound (the cup rocket ejection was almost identical to the C11-3 I had just launched prior).

Oh well, sorry to beat a dead horse. I'd guess if this was actually an issue other reports would come in. Thanks for everyone's input...very informative!

BTW - I think I have something like a dozen+ D12-0s which just came in the mail so I think I'm set for the next bunch of tests/watch-outs.

 

[bobkrech]

If you take a balloon and pop it with a pin, you hear a bang. The bang is an acoustic wave generated by the sudden release of pressure from the balloon as it ruptures.

A booster motor is simply made from compressed black power. There is no delay column, no black powder and no clay cap or the end of the compressed black powder propellant grain.

As the black powder propellant in a booster burns, the length (thickness) of propellant separating the hot high pressure gases inside the burning motor gets thinner and thinner until it ruptures. While the pressure in the balloon is 1 psi or so, the pressure in the rocket motor is ~ 100 psi. The sharpness and the loudness of the pop released when the booster motor burns out sounds just like an explosion of black powder, and it indeed so large a pressure difference that the initial sound wave is supersonic, just like the sound wave you obtain when a confined black powder ejection charge go off behind a clay cap......

Bob

 

[DizWolf]

-0 motors are boosters.... intended to light a second stage after thrusting.

-P or plugged motors are the ones you'd use in a situation where you want neither ignition of a second stage or ejection.

apparently there's a very limited selection of these nowadays (used to be larger ones)

https://www.estesrockets.com/rockets/engines/plugged-engines

 

[Gus]

-0 motors dont have ejection charges, however the gases from the burning propellant can be quite forceful.
Check out Emma Kristal's video from Naram a couple of years ago about what happens when BP booster motors burn through.

Here is a link to Emma's presentation at NARAM:

[video=youtube;1Nhe5Y78PRQ]https://www.youtube.com/watch?v=1Nhe5Y78PRQ"]https://www.youtube.com/watch?v=1Nhe5Y78PRQ[/video]

 

[RocKen]

Here is a link to Emma's presentation at NARAM:

Thanks Gus and rharshberger! Great video. Does show what can happen on a booster motor and coincidentally it was the 24mm/D12-0 which had the failure.

Has anyone compared the cap on the A/B/C -0s vs. D-0s? I'm wondering if it is uniform thickness across sizes and if so, that would mean that the ones on the Ds are comparatively weaker and more likely to fail given the greater diameter. Given the price of motors now, I'd rather not tear a bunch of them apart to find out. .

Another thought is that there is a possibility that the package of D12-0s I had were dropped at some point and this may have caused a small fracture/stress in the cap, increasing the chances of the failure. I think I had picked that package up at a local Hobby Lobby and it was up on the pegs, so there is a chance of that happening and I'm thinking this is the most likely scenario since a failure of the D (like in the video) can cause quite a noise and explosion similar to an ejection charge.

Thanks!
Ken

 

[jadebox]

Has anyone compared the cap on the A/B/C -0s vs. D-0s?

As Bob noted, there is no cap on a -0 motor.

-- Roger

 

[Gus]

View attachment 258302

As Bob noted, there is no cap on a -0 motor.

-- Roger

Nothing explains it better than Fliskits' Cut Away Model Rocket Motor.

 

[RocKen]

Nice! You're a lot of help here Gus!

I saw the black stuff at the end of the D12-0 and called it a "cap". Do you know what that is? Is it just glue to keep the propellant in?

Eventually I'll get this.

 

[rcktnut]

That black stuff is the black powder/ propellant grain no glue. It is highly compressed into the casing, no glue needed.

 

[shreadvector]

View attachment 258302
Nothing explains it better than Fliskits' Cut Away Model Rocket Motor.

That cutaway is only partially accurate. The nozzle and centerbore on a black powder motor looks NOTHING like that converging/diverging thing that he incorporated. It teaches incorrect information to students.

 

[shreadvector]

One problem we must remember that beginners hear or read "black powder" and they imagine loose powder. It is pressed into the casing at high pressure and it forms a solid "grain" which resembles a stick of chalk but black or dark grey.

 

[tmacklin]

One problem we must remember that beginners hear or read "black powder" and they imagine loose powder. It is pressed into the casing at high pressure and it forms a solid "grain" which resembles a stick of chalk but black or dark grey.

Exactly! One large solid "grain" as opposed to thousands of tiny granules, or "grains". Same material, different form for different purposes.

 

[shreadvector]

https://www2.estesrockets.com/pdf/2845_Classic_Collection_TR-TN.pdf

See the engine section (actually, read all of it and save a copy).