Ejection charge containment tube

[LBarron]

Got a question for ya'll...

I like the idea of using a containment tube to confine the blast of plack powder, but I'm confused as to whether or not the tube is closed or open on the end opposite the charge. If it is open it will protect the chute and lines from being burned, and the entire parachute bay will be pressurized. If it is closed, everything will be protected as well and the charge will pressurize a much smaller area. Do people use both methods or is one preferred?

I am building a large rocket (11.5" body tube) and it seems to me that if the containment tube is closed and is located on one side of the parachute compartment the force might cause the two sections to jam at an angle and not separate cleanly. If I use two charges opposite each other I can hope, but not be guaranteed, that they both ignite at the same time. So, maybe the entire compartment should be pressurized?

Ok, enough rambling. Any thoughts or wisdom would be appreciated.

Thanks,
Leland

 

[Rocketmaniac]

Leland,

To answer your question about open or closed..... kind of both...... The Black Powder must be closed up (as in contained in one area......containment tube), but the gases released from the charge must be be able open (separate) the rocket......

Attached is a pic on how I am going to handle the ejection charge on my LOC Expeditor....... It is just a 1/2" PVC cap..... I drilled 2 small holes in the bottom.... In one I put a bolt with a slightly larger head, throught the bulkhead and put a nut on the backside..... thus securing it to the bulkhead...... In the other hole I will run the actual e-match in the electronics bay......

 

[Rocketmaniac]

Oh, to answer another of your questions....... You will need to protecct you parachute and shock cords from the ejection charge..... The methods of this protection include the use of "dog burf", nomex shields, and kevlar shields........

 

[rocwizard]

An 11.5 rocket is going to need a significant amount of powder to deploy your chute/s I would recommend the Safe Eject Ex that can hold up to 20 grams of BP. It is machined aluminum and can hold 2 e-matches. You can get them from Magnum.

P.S. Tell us about your project!!!!!!!!!

 

[Rocketmaniac]

Originally posted by rocwizard
An 11.5 rocket is going to need a significant amount of powder to deploy your chute/s

Eric is right, earlier I missed that very important fact (11.5" rocket)......... I take back the idea of the PVC Cap...... That's fine for 2 or 3 grams of BP, but you will need more to separate a LARGE rocket.........

 

[LBarron]

Thanks for the info guys - that's very helpful. Including that little Safe Eject gizmo. Hadn't seen that before.

My project is a 1/34 scale Saturn V (the prettiest rocket ever!!). It'll be about 10ft tall which is the result of using the 11.5" body tubes. I'll have three chutes for recovery; one drogue, and then one for the main body (stages 1 and 2 of the real rocket) and one for the rest (from the first transition upward). Electronics (two deployment controllers) will be in the 3rd stage (between the two transitions) and the escape tower, which will remain on for flight, will be spring loaded to cushion the landing on the pointy end.

Power will be from five home-made liquid fuel motors, so this project will be in the amatuer/experimental category. I know most people on this forum use solid fuel motors so pardon me if this is boring. I've developed and tested a small motor using gasoline and gaseous oxygen for fuel, and now I just have to refine the pressures, make four more, and then plumb them all together. Should be a piece of cake, huh?

I have no idea when I'll finish it and no idea where I'll fly it, but it's an extremely fun project.

I imagine I'll be back with more questions later....

Thanks again,
Leland

 

[rocwizard]

That sounds like an awesome project! Please keep us updated on how the progress goes. As for where you will fly it, bring it up to BALLS! Being that iti is liquid fueled though, you will have to send some information about the project to the Tripoli BODs for approval to fly it. Mark Clark would be the man you would want to talk to.

HTH

 

[Rocketmaniac]

Originally posted by LBarron
My project is a 1/34 scale Saturn V

WOW, sounds like a great project....... You got any pictures!!!! (we like pic here at TRF!!!!)

 

[LBarron]

Here are a few pic's of what I've done so far....

This is the top section of the rocket - a little dark but you get the idea. It looks a bit crooked cuz the top sections haven't been lined up and attached yet.

(Partially completed Estes Saturn V in the background)

 

[LBarron]

Here's the bottom of the lower transition which will be one side of the main parachute compartment. Two u-bolts so the top will come down straight. The round CR in the middle with the wing nuts is the cover for the electronics tube and has a seal underneath to keep the ejection charge pressure from getting to the electronics.

 

[LBarron]

Cover off the bottom of the electronics tube. I used crimp-on wire connectors so that everything can be removed and stored away from the rocket

 

[LBarron]

Two deployment controllers on a piece of wood that slides out of the tube. I'm using a Missile Works RRC2 for deployment of the drogue and main (800ft) and an Adept DCS1 for a main backup at 500ft. On/off switches are mounted on the body tube so the d.p.'s can be armed when the rocket is ready to go.

That's it for now - I'll post some more when I finish the LES on top of the nose cone.