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Another newb electronics/ deployment question

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Trenman

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Ok forgive my ignorance but I've never had a rocket that was more than cardboard and plastic. I am building my 38mm mongoose and have ambitiously (for me) decided that I want to include an avionics bay so I know how high and fast my rocket will fly. I've gone with a single deployment with a main chute out of the nose cone which frees up the rest of the body tube for a simple ( Missiletech RRg2?) altimeter. My question is since the tube will now be stuffed with an avionics bay, the ejection charge on my Pro38 reload
will be ineffective so how do you get the chute to open up? Please advise and thank you all kindly in advance. L
 

MaxQ

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I believe that you meant to say the MissileWorks RRc2....

If the altimeter you are using does not have a barometric pyro device to trigger an ejection charge at ether apogee and/or a preset main opening altitude, then yes, you would have to rely on a motor ejection charge with a delay selected to open as near to the apogee as possible before the speed builds up, or you could end up zippering the airframe upon parachute deployment.

You need to put the parachute behind (aft ) of the altimeter...to benefit from the motor ejection charge.
I would place the altimeter in the forward section of the airframe..in front of the airframe where the parachute is packed and inserted. Depending on how the kit was designed or built so far, you may have to cut the body tube and install the altimeter bay with the back end acting as a tube coupler. The picture "apogee deployment" shows the concept:



You might consider going dual deployment since this rocket will probably go pretty high, and a high altitude/low opening is probably what you would want. The Missile Works altimeter you mentioned has that capability.

You may have to cut the body tube in more than one location to do it and have screw in retention to hold the section of body tube to the altimeter bay.

Here are some diagrams and the home web page has links to old articles and all manner of high power rocketry stuff:

http://www.info-central.org/?article=291
 
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BRC

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I am just a newbie myself, but couldn't he simply screw on or friction fit the cone and pack the chute and harness in the aft section and await the engine to deploy the chute, with the E-bay secured (screws) into the payload section so its all just one piece..? Just like in your diagram, the apogee deployment instead of a streamer, but the chute..??
 
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JoeG

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I am just a newbie myself, but couldn't he simply screw on or friction fit the cone and pack the chute and harness in the aft section and await the engine to deploy the chute, with the E-bay secured (screws) into the payload section so its all just one piece..? Just like in your diagram, the apogee deployment instead of a streamer, but the chute..??
Sure. If all he wants to use the altimeter for is gathering data that will work fine.

He will still need to mount it and add the equalization hole/s and set it up just as if it were deploying the recovery system other than the ejection charges. I would use the dual deploy and make use of the electronics.........and maybe save a looong walk. Just my two cents.

Yes the rocket will probably work fine with a motor ejection as you suggest.
 

BRC

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Sure. If all he wants to use the altimeter for is gathering data that will work fine.

He will still need to mount it and add the equalization hole/s and set it up just as if it were deploying the recovery system other than the ejection charges. I would use the dual deploy and make use of the electronics.........and maybe save a looong walk. Just my two cents.

Yes the rocket will probably work fine with a motor ejection as you suggest.
I'm in the same boat !! I too built an Alt Bay for an EZI-65 but will wait for a Level 2 attempt to use it... I hope to launch next weekend for my level 1...:)
 

blackjack2564

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Motor eject will not work on high performance rockets like a Mongoose if using large motors. The motor will fire the charge before you reach apogee during the coast. The delays are not long enough.

Flying smaller motors using motor eject will be fine.


Sound like your trying to drive a Ferrari before learning to ride a bike, though.

I would suggest building something similar out of cardboard and flying smaller motors with electronic deploy, then applying lessons learned to the 'goose.

That's a mighty expensive toy to learn on.
 

Trenman

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Motor eject will not work on high performance rockets like a Mongoose if using large motors. The motor will fire the charge before you reach apogee during the coast. The delays are not long enough.

Flying smaller motors using motor eject will be fine.


Sound like your trying to drive a Ferrari before learning to ride a bike, though.

I would suggest building something similar out of cardboard and flying smaller motors with electronic deploy, then applying lessons learned to the 'goose.

That's a mighty expensive toy to learn on.

Yes assuming I do it incorrectly. I am the type to aim for the top and build build build until I am sure I do it right. If it takes me two months to build, check, check again and triple check my rocket Im good with it. Although new to MPR and HPR I am not new to rockets. I have confidence that if I take my time and ask the right questions this will be just fine. I have decided to place the avionics in the top below the nose cone in a sealed bay (from ejectae) and decided to use a single deploy parachute in the middle of the body. At this point id rather successfully gather data and try to mess with ejection charges etc on future projects. I have no expectations for height or speed though clearly I am curious. Once I master how to do it CORRECTLY, then I will aspire for more. Until then thanks for the helpful tips. I will post my build once the components arrive. Cheers.
 

Trenman

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My "Supersonic Stinger"





Front View




Back View





Tried to make an Av bay out of spare carbon however it wont be enough to fit the RRC2. Its a nice piece however and I like the paint job so ill keep it around for potential future need. Either way the idea persists: The Av bay will be upfront.




The single deploy parachute will sit here




And here is a pic of my fins up close. I know I need to sand the fillets I just haven't gotten to it yet...or the engine bay...or the parachute... or the....
 

DAllen

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Tried to make an Av bay out of spare carbon however it wont be enough to fit the RRC2. Its a nice piece however and I like the paint job so ill keep it around for potential future need. Either way the idea persists: The Av bay will be upfront.
Well then you probably can't use a baro-based alt. I donno about the RRC2 but I know PF alts need to be 3x the body diameter away from things like transitions, nose cones, fins, etc. They need smooth airflow over the sampling holes in order to function properly. Did you glue in the coupler mid body or can you still place a e-bay there? If so, are you going to go dual deploy with this bird and the ebay in front and if you are, how?

Plus, I think if the alt bay is upfront that will make it a little more challenging to install a tracker on this bird. Most of the time when I see this bird fly people invariably use a tracker because of it's small, hard to see airframe.

Just curious...

-Dave
 

Trenman

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I dont have any certs so ill use a Pro38 G1 motor. I will assemble the RRC2 which just arrived into the altimeter bay in the front on the nose. I will ensure smooth airflow and understand that I need certain size vent holes per the volume of my rocket. I will use single non computerized deployment for my first electronic rocket. So why bother with the RRC2? I want to know my height and altitude, and build an AV bay which is all new to me. Once I realize my errors I can refine and begin on a new, more complex project :eek:)
 
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