Loadstar 2.5

For the motors involved this just barely qualifies for the MPR section, but since it's an LPR-based design I decided I'd post here anyways.

Last year I built up an Estes Loadstar II kit which I've now got many flights on, both as a single and dual stage. Following the footsteps of others in the "DIY electronics" thread I built an Arduino-based data logging altimiter for it, and the excitement of looking over the resulting data has pushed me to step things up a bit. Work will have me travelling to Yuma, AZ in the next couple of weeks so I've decided to build up a 24mm capable booster stage for it, resulting in a mated stack that I refer to as my Loadstar 2.5.



This will be my first gap-staged rocket, the gap distance being about 6". Because of the length of the booster I designed a spring-loaded compartment on the side of the booster to hold a 9" to 12" chute. A tongue at the bottom and spring pin in the top holds the hatch closed, when the sustainer stages the spring pin retracts allowing the door to fall open and the booster chute to deploy. (No core samples here I hope!) The close-up of the booster below shows the chute hatch open, but not yet tied to the booster. A structure of rings and longruns made of G-10 (or FR-4 for you electronic types) maintains the strength of the booster through the 18mm stuffer tube despite the large hatch. I plan to make up a bridle that will tie the G10 in two places to secure the chute, and have a seperate attachment point for the chute door so nothing is lost.



The booster was designed with 3/32" basswood fins, TTW. My big question on this design is what size vent holes to make at the top of the booster to allow proper staging. I found a build thread on a gap-staged Commanche III where 3 x 5/32" holes were used, my intention was to follow those numbers unless anyone here has suggestions otherwise. (pick1e, if you're reading this a big "thanks" to you for sharing what you did on your Commanche and for posting an after-action report that confirmed that it worked!)

My other question with this design is with the 24mm booster can I still use the standard sized launch lugs on the sustainer, or do I need to put 3/16" launch rod compatible lugs on the booster? Is rod-whip the concern with using small lugs with 24mm motors?

When I get to Yuma I plan to fly the stack on a D12-0 + C6-5. OpenRocket predicts I'll get a little over 1k' out of the stack, I'm looking forward to seeing how close I actually come.

Comments, thoughts, suggestions?

Test flight complete! Sunday morning a had a few hours off work so a couple of us drove up i95 from Yuma to just north of Stone Cabin and let the Loadstar 2.5 do its thing. The gap staging worked perfectly and both booster and sustained recovered without issue. Because of the stiff winds (>10kts) she arced over into the wind pretty good which limited the max altitude to only 850'. I'm still very happy and am looking forward to my next opportunity to fly her. Photos to follow....

Not sure how I missed this thread before, nice work! Cool looking model and upgrade.

Thanks Chadroc.

Here are some photos of the first flight.
Ready for launch:


Launch!


Booster sep, sustainer ignition:


Sustainer accelerating away, booster returning under its chute:


Successful sustainer recovery:

I like the side door/parachute bit. Very nice. I have to ask: It looks like the hatch flying off in the staging photo—is that bugger attached?

Sorry for the delayed answer - I've been traveling again.

Yes, the door is tied on (in two places) to the parachute bridle - I can't imagine having to make another one.



You can also make out the spring-pin that holds the door in place when the booster is mated up to the sustainer.

Pretty darn clever. No extra tubes, pull-strings and/or whatnot to mess with it's trajectory. A fairly elegant answer to recovering what would normally be a ballistic booster. Nice.

This is an old thread to dig up, but I received a few questions on how I implemented the sprung door latch for the chute.

Here's the hatch pin in the interstage coupler bay. The bulkhead at the bottom of this bay is also the top of the parachute bay. IIRC I liberated the spring from a ballpoint pen. The only really tricky part was soldering a brass washer to the (music wire) hatch pin so the spring would have something to push against. The wood block at the top of the interstage coupler prevents the pin from coming out of the assembly. The pin is supported top and bottom with pieces of brass tube so it slides easily.


This next photo shows the position of the pin as if the sustainer were sitting on top of the booster. The hatch pin is pushed down against the force of the spring, forcing the pin through the bulkhead and protruding into the parachute bay area. There's a hole in the top of the parachute bay hatch that this pin passes through to hold it in place. The bottom side of the parachute bay door is retained by a lip that fits inside the booster's skin.


This last shot is just a close-up of the annular parachute bay and the matching hatch. When it's all closed up there's not much room in there, all I can fit is a 12" Estes chute, but the booster is pretty light and that's all it seems to need. You can just make out the lip at the bottom of the chute bay hatch.


I've lost count of how many successful launches I've done on this arrangement. Never early, never late, always immediately following separation 100% of the time. (I guess I'm screwed now!)