Upscale Dilemma

[Hospital_Rocket]

I have completed the Rocksim of a 2X upscale CCEXPRESS and now I need to figure out how to stage it.

Couple of questions:

1) Is it possible to CHAD stage AT SU or RMS motors?

2) If the motors don't but together can you CHAD by creating a channel out of a length of tubing or would it be better to use a piece of thermalite to fire the sustainer?

3) I am considering electronics, however am not sure how. From my reading I would need a plugged booster, and use an e-match to set off an e-match to ignite the sustainer and push away the booster. The only thing is how do you prevent the flame from the sustainer from roasting the booster?

Any thoughts or suggestions would be welcome.

 

[eugenefl]

Just curious, but how far apart will the booster motor be away from the upper stage? You should check out Jason Toft's (jetra2) Terrier/Sandhawk. It features a near 14" BP gap stage!!! 3-18mm motors ignite the upper Sandhawk 24mm motor. Crazy...works though! I think you might be able to get away with gap staging.

To answer your earlier question regarding CHAD staging Aerotech motors, the answer is no. Electronics are a must for composites. Eh...I wouldn't recommend thermalite. What if the rocket goes unstable? Instant wandering sustainer fires off in who knows what direction!

 

[Hospital_Rocket]

About three inches.

Follow on: Can you Gap stage composites? My guess is that I can't for the same reason you can't CHAD them.

 

[sandman]

Can you Gap stage composites?

Nope! Sorry to say...no you cannot stage composites like BP motors.

Not without electronics.

sandman

 

[loopy]

The problem is, AP motors burn from the top down, and require a much stronger ignition source than BP motors. Burning ejection charge particles will never make it to the top of the grain, and if they do, they will never ignite the AP. To stage AP, you need a timer wired to the sustainer motor.

Loopy

 

[Papa Elf]

Also the problem is the design of the composite motors themselfs... they usually don't have a solid bulhead of propellant ahead of the core (usually the core goes all the way to the top of the propellant). Usually there is a huge delay grain there, or a solid bulkhead to prevent the motor from thrusting at both ends... and composite delay grains are so inacurate, they simply can't make a reliable -0 (they have tried, back when thermalite was available).

 

[firemanup]

Please keep us posted with this project i'm very interested.

I started this same project about a year ago.. still have all my notes and I ran into the same problem. At that time having no experience with electronics I ended up letting it go.

The only thing I came up with was clustered motors but then didn't like the added weight I was putting on the rear end of the rockets..

Electronics seemd to be the only way to go from what I could find at the time..

I've not given up on it.. I think I'll probably try again in about a year since i'm planning on getting some experience this year with electronics.

The other issue I had to look at was recovery of the booster section as I was planning on 2.6" body tube and ply fins, tumble recovery with a heavier unit like that was marginal in my head.

With electronics I'd go for drag seperation of the booster, setting the sustainer motor to fire just a second or so after motor burn out.. with a loose fitting coupler sustainer to booster the booster should come right off..

Least those were my ideas last year..

Love the CC Express... it's a fun rocket should look great upscaled..

 

[Missileman]

I had a similar delima when planning a Hercules project.
I have heard that motor separation alone can cause severe damage.
What a I am doing is explosive seperation via a piston.
A 2 event timer is used in the booster.
Event 1 fires a charge that shoots a piston out to separate the stages (this gives a good distance of seperation and the piston keeps hot gasses from damaging your igniter for your sustainer.
1 second later event 2 fires a charge to eject the boosters chute.
The sustainer motor is fired via a normaly closed microswitch witch is held open by the stages being together.
Just some ideas. Many variations of this theme can be thought up.
Good Luck and lets see some pics.

 

[havoc821]

Or you could do this. I am using this on my 2 stage hpr project. I will have a 2 event timer . On one channel will be the igniter, the other channel will be a BP charge. Both will fire at the same time. The BP charge will blow off the booster and the other will iginte the motor. It will take it a split second longer for the motor to light than the BP to light, so the booster should be far enough away when the motor lights. If it is a single event timer, you could do the same except just put the igniter and BP leads on the single channel, but you will have to make sure the timer has enough power to light both things. Hope this helps.