Question: strengthening a Nike Ajax

Any advice on how deep (calibers) to nest a 54mm tube up inside a 3" tube?

I'm starting to build my quarter scale Nike Ajax (single stage) This is a 4" dia Nike booster to a 3" dia Ajax. The rocket should end up just over 8ft and fly on 54mm motors. The two components will separate for transport but I'm trying to decided how deep into the Ajax the central tube should extend. The 3" Ajax tube serves as recovery gear compartment for the whole rocket so I need as much volume as possible.

My question, is how deep, in calibers, should the 54mm tube extend up into the 3"Ajax tube? This is rocket separates for transport. Recovery separation is at the nose cone. This 3" tube is 30" overall, minus half an e-bay at the top, so I have 27" for the 54mm tube and recovery gear.

To add more strength, this 54mm tube that extends out of the Ajax will have two centering rings and LOC coupler/stiffy that fits just inside the top of the 4" Nike booster. Screws/tee-nuts will hold the two together for flight. The 54mm tube has a very thick wall coupler that fits into the upper end of the 54mm motor tube proper in the Nike booster.

Rocksim 8.0 file included for perusal. Of course, it's a rough drawing at the moment.

Thanks for any advice or help

Moe

View attachment NikeAjax_QuarterScale.rkt

After looking at your file, I;m not sure where you are breaking the rocket for drogue deploy. That aside, this is how I would approach the booster to sustainer attachment.

From the bottom of sustainer boat tail, going toward the nose of rocket.....
..a centering ring flush with the bottom of boat tail....one at the top of boat tail that would be a coupler bp with mm hole in it. It would rest on top of boat tail and slide into airframe, keeping everything aligned. Finally a third CR 1 1/2 caliper [or 4.5 in.] from top of boat tail. All with the 54mm tube running down the center. This should give you a very rigid connection point, and leave plenty of room forward for recovery gear. I would also foam the boat tail to make it as rigid as possible. Where is your attachment point for recovery shock cord?

I cannot tell how you connect the MM tube with this 54mm extension or if you do. How far back into the booster all this goes?

If the sustainer and booster remain attached during recovery, I would use a coupler sub-assembly with the transition, CR's , 54mm tube etc. that would remain attached to the sustainer,for travel, but slip into booster airframe and over the MM tube, and held in place with removable rivits or pem nuts, etc for flight.

I'm not sure how you are going to separate the rocket for DD, so this is the best I can do at this point.
I have always been fascinated, with the Nike's and hope to build a 2 -stage some day similar. Have been collecting all the data and reference materials on these things for quite awhile. Good luck on this project!.

Blackjack - thanks for taking the time to reply and your input. My Rocksim file may not sufficiently "explain" the separation point.

The rocket is not dual deploy; the nosecone is the separation point for recovery; the anchor point will likely be the top of the 54mm tube in the Ajax...likely a 1" wide piece of strap kevlar anchored to/around the tube below the top 54mm centering ring ala PML for their piston system (with a gap between the ring and tube for the strap kevlar.

For extra longitudinal stability, the 54mm tube from the Ajax is joined with a long length of thick-walled tube sanded to fit into the 54mm tube in the Nike. Since I'm planning on single event deployment, the 54mm tube in the Ajax will be capped to seal the recovery bay. This is seen below in the 2nd photo. The tube was temporarily positioned for the photo.

At this point, I'm thinking about going with 2 calibers within the Ajax bottom. I'm getting some 3" coupler tube with a recent order so I can make a between the centering rings, similar to the coupler shown in the attached photos that goes into the top of the Nike booster. That Nike coupler is shown in three of the photos below. There are six 10-24 tee nuts already installed in the coupler for machine screws to hold the lot together during flight. Of course, the holes are already drilled in the Nike booster as well.

The boat tail is shown in the photo below with internal glassing. I can try to foam the inside before mounting the Ajax tube permanently. It is not load-bearing per se and the three interstage struts mount to it so they'll provide some strength to it as well.

If I want to have two deployment events I can always attach my ChuteTamer to a main chute for the second event.

A two-stage Nike Ajax would be very cool...I'm a little intimidated by that for this project!

Thanks again, Moe