MPR Booster Recovery?

[GL-P]

I'm building a 3x24mm to 3x18mm two stage rocket. How do I put a recovery system that doesn't interrupt the ejection charge going to the top 3x18mm motors?

The booster needs a chute cause it's big! (36" long!) so I can't do tumble recovery.

First time large two stager, pls help!

 

[WiK]

I had the same problem on High on BP, in the end I added two strap-ons to the side of the booster which use D12-3's. And more power can only be a good thing

Phil

 

[MetMan]

Originally posted by GL-P
I'm building a 3x24mm to 3x18mm two stage rocket. How do I put a recovery system that doesn't interrupt the ejection charge going to the top 3x18mm motors?

What diameter tube are you using? If you can get two more 24mm tubes in the booster you can use your 3 24mm booster motors along with 2 24mm motors with short delays to deploy parachutes.

If not enough room in the booster, you could go with side pods on your booster with short delay motors. This gives you the advantage of being able to use a bigger tube (BT55 or 60) to use larger chutes.

Hope this helps...

MetMan

 

[MetMan]

Originally posted by GL-P
The booster needs a chute cause it's big! (36" long!) so I can't do tumble recovery.

You aren't planning to use gap staging, are you? A gap of ~30" is a long way to try to stage across...

 

[hokkyokusei]

Originally posted by GL-P
I'm building a 3x24mm to 3x18mm two stage rocket. How do I put a recovery system that doesn't interrupt the ejection charge going to the top 3x18mm motors?

The booster needs a chute cause it's big! (36" long!) so I can't do tumble recovery.

First time large two stager, pls help!

Why do you want an ejection charge going to the upperstage motors?

 

[MetMan]

Originally posted by hokkyokusei
Why do you want an ejection charge going to the upperstage motors?

I assumed he meant the hot gas and burning particles from the -0 motors to ignite the sustainer motors...

 

[hokkyokusei]

Perhaps a combination of booster motors and motors with ejection charges could be used. To both ignite the upper stage, and deploy a recovery system for the booster, perhaps via rear ejection?

The gap descibed is longer than I've seen staged successfully before.

 

[GL-P]

It's a 2.14" tube. How long should it be with around 3xD12s and higher impulse motors to do proper gap staging? I'm thinking I could glue a 38mm tube down the side to allow the ejection charges to ignite the top with out having the dang chute in the way till the ejection charge forces the two pieces apart.

Would a 38mm tube with a chute not symetrical in the tube affect flight performance?

 

[hokkyokusei]

Are you using the booster motors to ignite the sustainer motors?

It's not the hot gases that ignite the sustainer motors, but the small burning particles. You need to be careful if thoes particles need to travel around corners to get to the sustainer motors - that's basically how baffles work.

 

[MetMan]

GL-P,

Check out this article on gap staging:

https://www.apogeerockets.com/education/how_to_multi-stage.asp

A gap of about 12" is the most you want to try to get reliable staging. The key is venting the top of the booster near the sustainer so the cool gas can get out of the way of the booster motor blow through.

To illustrate my suggestion about using short delay motors to deploy ejection, check out my Project Omega:

https://www.rocketreviews.com/cgi-bin/rvwbuild/rvwbuild.cgi?descon14/omega.html

Hope this helps.

MetMan

 

[GL-P]

No worries. This was an after school build. It was meant to be a single stage rocket but after I realized I could make a 2 stager, I wondererd what it would take to convert it. I'll keep it single stage!

Thanks guys! I plan ahead next time!

 

[Mad Rocketeer]

Here's a thought I just had. You could attach a line to a chute in the booster, then hook a peg on the other end. You could then arrange a hole in the lower end of the sustainer (just be careful not to provide an alternate escape for the sustainer's ejection charge). The peg would be inserted in the hole when preparing the rocket for flight. As the booster is pushed away by the sustainer's ignition, the line would cause the booster's chute to deploy, then the peg would be pulled out of it's hole.

This would be tricky in three ways though.

One: The peg tightness would have to be just so. It would have to be tight enough to get the booster chute pulled out but loose enough to pop out once the chute's free.

Two: The line and the chute would be in a perfect position to get scorched. That could probably be handled be creative positioning of the motor mount tube and the coupler.

Three: The tug of the plug could cause a "tip-off" effect. I.e., the sustainer could be turned a bit in its flight at the point of plug separation. This might be offset by using more than one plug or by using three lines that end in a sleeve (rather than the plug) which encircles the end of the sustainer's motor mount tube. The sleeve would slide off in a way that would be much like the booster itself sliding off.

This could be a fun thing to try and a nice challenge, but the solutions that use extra motors (with delays and ejection charges) are doubtless more reliable and practical.

Another way would be to use a timer and an ejection canister (as in dual deployment systems) to handle the booster's chute ejection.

You could even do a rear ejection from the booster, triggered by a burn string across the front of the booster's motor. That way, the same particles that ignite the sustainer (or the sustainer's motor) would burn the burn string. Thus, the sustainer would ignite, kicking the booster away, and the booster would (at approximately the same moment) kick out its parachute (or streamer) via a spring (or something similar).

Let your thoughts run wild! Have fun! Get really creative!