Leaner Meaner Machine - two-stage modular rocket w/ 2-4x 18" BT50 body tubes.

[BigMacDaddy]

So one of the non-scale (semi-scale) scratch builds I have done over the last couple of months was a Mean Machine inspired rocket that was modular and could use from 2 to 4x 18" sections of BT50 (leaner) with quick disconnect parts. I made these two stage (meaner) with a simple booster setup that I had first used with mini-engines on a rebuilt Mini Mean Machine. I decided to make the fins the same size as the Mean Machine fins since they were not so large anyway.



Initial launch with 3 sections and C6-0+C6-3 was successful (although the booster was struggling a bit). I made a revised version with both 24mm and 18mm booster sections (I have not launched w/ 4 sections but was thinking of doing a 4-section D12-0+C6-3). I also revised the quick-disconnects to use 4x tabs instead of 2x to make the rocket straighter.

 

[BigMacDaddy]

Here is the maiden launch. It was a bit windy so I launched into the wind so I could actually recover the rocket. This worked well (also only one of my chutes deployed but it was still plenty) and I could recover the rocket. Made the mistake on my 2nd launch of the night thinking I did not need to launch into wind and also had some bad luck in that both chutes fully deployed and it drifted to never-never land. The fully primed rocket in front of my kitchen cabinet in the pics above is the new / rebuilt unit (the unpainted one on the ground is one I lost - those tubes were flimsy anyway, one bent on landing and I had to swap it out with the extra tube - another benefit of modularity).

 

[BABAR]

very nice!

yup, a C6 in the booster is definitely gonna struggle with a big rocket with all the extra finnage needed for a booster, you will love the D12-0. Your may have had a real problem with the C6 had you primed and painted it, the weight does add up,

how much do the plastic parts add to the mass?

I have done modular rockets with couplers. I do a “base” tape wrap around the ends of the body tubes, then in the field when I put the rocket together, a tape layer across the joints. The base layer allows me to pull the connecting tape off without pulling off the paint or worse, delaminating the tube. The base layer can be cellophane tape (doesn’t interfere with look of paint or decals, if present.). I usually use Mylar tape cuz it’s shiny and colorful.

looking forward to the D12 flight report.

tip. At least for your next flight, go with an A8-3 (or A8-5 if you can find one) on the sustainer. Since the sustainer is already “up to speed” at ignition (as opposed to standstill start on the pad) you will still get plenty of altitude. A8 motors also have a larger nozzle so easier/more reliable for black powder staging. Also the lighter A8 motor increases stability both because it has less impact on CG AND because with less mass, the rocket gets off the pad faster.

for the most part with staging, you are just doing it cuz it’s cool, if your really WANTED more altitude you’d build a minimum diameter smaller bird with a QJet D in it. Especially for small fields, low impulse sustainers give the same amount of fun without either a long walk or (as you unfortunately encountered) a lost rocket.

I ALWAYS go with the lowest sustainer motor I think I can get away with (even sometimes using and adapter to downsize a motor diameter) for first flights, for precisely the reason you encountered. If my computer sim or mind sim is wrong, or for some reason the lug catches on the rod, the problem with black powder staging is THERE IS NO TILT LOCKOUT! So if it weathercocks or for some other reason it ain’t pointed straight up at staging, the rocket is going to go either straight in some off vertical direction or WORSE it will arc over and come down under power. Going with a smaller sustainer motor doesn’t PREVENT this, but if the rocket is going to do something bad, I’d prefer to have it do so with an itty bitty motor than a big motor.

once you have proven the design, if you want to max out the stack, go for it, but you may need a bit of nose weight to counter the extra motor mass.

and I am lazy, I don’t want to have walk so far to go git it.

 

[BigMacDaddy]

very nice!
...
I ALWAYS go with the lowest sustainer motor I think I can get away with (even sometimes using and adapter to downsize a motor diameter) for first flights, for precisely the reason you encountered.
...
and I am lazy, I don’t want to have walk so far to go git it.

Thanks very much! Good advice about smaller sustainer engine. I have younger kids and so far they have been good chasing after my rockets -- although with the lost rocket I had to yell to make sure my 6-year-old did not go across a road to try to follow it. Also a couple of times they have threatened to make me go get the rockets so need to gauge the mood...

 

[BABAR]

Also a couple of times they have threatened to make me go get the rockets so need to gauge the mood...

LOL, not that I am comparing your kids to my dog (who barks at launches during the countdowns, it is the only time she EVER barks at all), Lucy the yellow Lab. But she is really a RINO (Retriever In Name Only.). Throw the ball once, she’ll get it. Twice, she’ll still get it. Third time, she just looks at you as if to say, “Hey, if you don’t want it, I ain’t gonna go after that thing again!”

 

[BigMacDaddy]

In case it is interesting -- Here is recovery of first launch (one parachute was tangled):



And here is the 2nd launch (which was lost due to wind, both parachutes opening, rod whip, etc...

 

[ksaves2]

I did a modified full sized Mean Machine some years ago. Added epoxy impregnated tubes, larger fins and made it a DD rocket. Only issue was I kept the 24mm motor mount though modified with so it could take a long 10", 24mm research motor casing and has an Aero Pac screw in retainer. The research motor was turned down from thicker tube and a flange (about a 1/4") is left at the end for a thrust ring.
The research motor uses turned graphite nozzles that unfortunately turned into single use ones.
Flown twice, due to fin alignment it goes up with a slight coning action that leads to a tight spiral smoke trail. Looks neat and cuts down on max apogee which is nice for tighter launch sites. I believe that part of the reason for the coning is a slight warp in the long necked tubes. A long necked rocket needs absolutely straight tubes to minimize the effect of coning......;. But in my case, I think the spiral looks great. The rocket flies straight and controlled but the aft end does this little tight spiral thing.

I had the motor cut down as when recovered, it was hotter than Hades and the graphite nozzle became "crumbly". Definitely single use. Couldn't handle it till it cooled as it is a snap ring motor so breakdown was much later. If I recall, the motor sim burned to a little over a second.

I discovered that is the reason there aren't any high l/d 24mm reusable motors out there.

Kurt

 

[BigMacDaddy]

I believe that part of the reason for the coning is a slight warp in the long necked tubes. A long necked rocket needs absolutely straight tubes to minimize the effect of coning......;. But in my case, I think the spiral looks great. The rocket flies straight and controlled but the aft end does this little tight spiral thing.

I had the motor cut down as when recovered, it was hotter than Hades and the graphite nozzle became "crumbly". Definitely single use. Couldn't handle it till it cooled as it is a snap ring motor so breakdown was much later. If I recall, the motor sim burned to a little over a second.

Cool - Sounds like an interesting rocket -- part of my goal doing this was to try to make something that was big like Mean Machine but could fly on 18mm engines. Unfortunately, it got too heavy / draggy for the C6-0. I wish they would release a C5-0 super engine. I have not played around with composite or other non-Estes engines.

I was worried about the straightness of the rocket with the quick disconnects and just raw length. I did a few things to try to make it more rigid / straight like the printed lips on either end of connectors to give a solid surface to press together. Overall I was impressed with how straight the rocket seemed to fly (although have not moved up to D-sized engines yet and have not tried flying the 4-tube version).

I think rod whip was more of an issue than anything with my prior launches. I launched on a 4' rod. but the 3x tube version I launched is over 5' tall (and will be almost 7' tall w/ 4x tubes). I built a new rail-based launch setup partly to help with this rocket. Put micro rail lugs on the latest version of the rocket to help make it launch more vertical off 5' Makerbeam (but might also put bigger buttons to launch off the 6' 20mm rail).

 

[BigMacDaddy]

I realized I never posted the most recent (last?) video of this rocket launching... Launched better off a 1.5m makerbeam rail but I kinda think this rocket may be cursed.

https://www.youtube.com/shorts/3Wk5P1pYk5Q
Parachute did not deploy so rocket was mostly a loss. Easy enough to replace 3D printed parts and make again. However, I realized that:
1) I need to use a bigger booster (it was hard to find this rocket since it had angled pretty substantially with the weak booster before the sustainer fired up) - I made a booster for D engine but this will likely fly too high for my field.
2) I need to do something different for parachute recovery - maybe separate rocket in middle instead of at nose cone.

 

[BigMacDaddy]

So as you can see from the thread above I have struggled a bit with this rocket. The C6-0 in the booster was barely strong enough to launch the 3 body tube version (see videos above) and had little hope with the 4 body tube version. However, I was afraid with a D-engine in the booster that this rocket would go too high for me to get it back (I already lost a 3-body tube version with a pair of C6-0 + C6-5 set of engines in it - simulation below says 10.8m/s off rail and 297m apogee; surprisingly the 4 tube version is the same speed off the rail???).



D-engine booster version is very likely to be lost...



The thread asking "Why clusters..." and my consequent analysis of cost-effective clusters made me realize I could maybe do a 3-mini engine cluster in the booster. They do not quite fit in the BT50 tube I was using for this model but I could go up to a BT55 tube on the booster and use a transition to connect to sustainer. Simulation shows this might work quite well 22.9 m/s off the rail and 162m apogee.

 

[neil_w]

Why not a C11 booster? Also, you can put an A in your sustainer.

 

[BigMacDaddy]

Why not a C11 booster? Also, you can put an A in your sustainer.

Ah... I always forget about C11 engines... That is definitely easier but may not be as much fun...



hmm... 3 mini engine cluster costs $4.63, D engine is $3.60, and C11 costs $2.40 (same as C5). Might be worth the extra couple of bucks to try...

In any case I need to make another AC-Supply order... all my A10-0T engines are spoken for and I do not have any C11s...

 

[BigMacDaddy]

Why not a C11 booster? Also, you can put an A in your sustainer.

I finally got some C11-0 engines so may go back to this rocket...

 

[lakeroadster]

Here's a thought... Following the K.I.S.S. theory, why not use BT-50H and some full-length overlapping C-50's inside, secured with some external sheet metal screws. It'll be hell for stout and help to minimize fuselage damage from handling and mishaps.

Then still use your modular fin can configuration. As you know... there's nothing more humbling than crushed body tubes on a finished rocket.