Electronic deploy at very small scale

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smstachwick

LPR/MPR sport flier with an eye to HPR and scale
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Although actually building and flying anything that incorporates electronic deployment is a long way off for me, it seems like something that is involved enough that I should start learning about it sooner rather than later.

Specifically, I’m looking for advice regarding the feasibility of flying very small conventional, whoosh-pop type rockets on plugged motors that were originally designed for gliders and other unusual applications. More specifically, I’m looking at building something for the AeroTech C3.4T and the AeroTech D2.3T, and I may adapt down to an Estes A10-PT as well

I’m also hoping to accomplish this at some point on a larger scale too. The AeroTech F13 and G12 (both 32mm diameter) both come to mind.

Here are my thoughts on the engineering challenges presented by this:

The motors are going to be limited in terms of their thrust at liftoff. They don’t quite match the initial thrust of the Estes C6s we’re all familiar with.

D06E93B4-93B0-4830-A7F7-0497CD68AE9F.jpeg
The difference doesn’t look particularly worrisome to me, but I wouldn’t be doing my due diligence if I didn’t factor it in.

The rocket must be large enough to accommodate the electronics but light enough to clear the launch equipment safely. I’m willing to invest a bit in some custom GSE (a tower, perhaps) if launching from a standard rod is just not going to be feasible.

The rocket is also going to need to be trackable from the kind of altitude that a long-burn C or D will put it at, possibly without the benefit of tracking smoke. I would very much like to get that casing back, so it will definitely be flying with a streamer instead of a parachute.

Here are my main questions:

Is there a particular airframe design or even just a design philosophy/method that works well? I know @Leo and @0011001100 used commercially available kits as the basis for their small-scale dual deploy projects but I have a feeling I’ll need something more specialized to keep the weight down. I’ll be fooling around quite a bit OpenRocket but I figure it’s better to not reinvent the wheel if I can avoid it.

What are the options as far as electronics at this scale? Most of the systems I see people talk about here are for dual deploy, which seems a bit overkill and may eat up weight. For something like this, I think I only need one deployment event.

What am I looking at in terms of GSE? Does going from a standard rod and pad sound feasible, or am I going to need a larger tower/a piston launcher for better clearance speeds?
 
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Eggtimer Apogee, deploys at apogee. Single event. Very small. Very small 1 cell lipo. GSE could be a std rod. Build with cardboard tubes and keep it light. Myself, I like the small maker beams to launch from. Railbuttons,com has micro and mini buttons.
 
Eggtimer Apogee, deploys at apogee. Single event. Very small. Very small 1 cell lipo. GSE could be a std rod. Build with cardboard tubes and keep it light. Myself, I like the small maker beams to launch from. Railbuttons,com has micro and mini buttons.
Good to know.

I had imagined that I’d be shaving tenths of a gram off a BT-20 rocket, ending up with something like an overweight Hi-Flier that would need 10 minutes of GSE setup to get off the ground without parting spectators’ hair, and even then it would disappear and make recovery impossible. At that point I might have just been better off building a glider. Your input is encouraging.
 
Hi Shane, I'd start with the Eggtimer Apogee. Though it's the largest and heaviest of the three systems mentioned above, it will still work fine with B/C/D power and is by far the least expensive at just $15. Makes a nice cheap learning experience. You'll be in a 24mm rocket but with a D you will have to do things to reduce the performance or it will bust our limit at Fiesta Island...C11 should give a nice flight to several hundred feet. Long shiny mylar streamers are just about the best way to find small rockets coming down from high altitudes, and they don't add that much weight either.
 
This hot little number from Boris du Reau does dual deploy and comfortably fits into a small tube. Not sure about the BT stuff but the tube fits the 18mm motors. It's the Micro Alti Duo. 20220506_230557.jpg20220506_230611.jpg20220506_230631.jpg
 
Hi Shane, I'd start with the Eggtimer Apogee. Though it's the largest and heaviest of the three systems mentioned above, it will still work fine with B/C/D power and is by far the least expensive at just $15. Makes a nice cheap learning experience. You'll be in a 24mm rocket but with a D you will have to do things to reduce the performance or it will bust our limit at Fiesta Island...C11 should give a nice flight to several hundred feet. Long shiny mylar streamers are just about the best way to find small rockets coming down from high altitudes, and they don't add that much weight either.
Hey Dave! Good to hear from you on this. Thanks for your input.

After receiving a few polite requests from DART regulars for less power on my larger rockets, I typically fly one impulse class lower than is recommended for any kit that is predicted to break 1000. Do it by the book, you know? I also sim things out now to get an idea of what kind of performance to expect. I imagine having that data on hand would be nice if there ever arise questions about compliance. Some common configurations, like an Alpha III on a C6-7, will shatter our ceiling pretty easily.

Now my Goblin flies on C11-5s, my Hi-Flier XL flies on D12-5s, and my Star Orbiter flies on E16-6s. They’re hot rods, that’s for sure.

I was definitely thinking of this as a TRASD/ROC project to take advantage of more forgiving recovery conditions, but I’ll definitely look into a Mylar streamer. I may not be landing in the water out there, but losing sight of it at altitude is a real possibility.

This hot little number from Boris du Reau does dual deploy and comfortably fits into a small tube. Not sure about the BT stuff but the tube fits the 18mm motors. It's the Micro Alti Duo. View attachment 517427View attachment 517428View attachment 517429
Thanks for that! Another thing to look into, obviously.

Estes has a few standard tube sizes that are well-known, the 18mm inner diameter one is the BT-20. BT-50 is the 24mm inner diameter one, and there is a huge leap up to BT-60 that fits three BT-20s scrunched together ( 20 x 3 = 60).

That provided them with plenty of room for intermediate sizes, BT-55 is pretty common. The numbers go past 60 as well, BT-80 is often used for stubby builds. The numbers are arbitrary but they do scale with diameter, they’re just not always proportionate.

A bunch of other manufacturers make stuff that fits these standard sizes and has these numbers as part of their designations.
 
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Here is a BT-20 size 2-stage dual deploy example:
Estes_Astron_Elliptic_II_DD_E-bay.jpg


Build thread...

Come visit NSL 2022 to watch this rocket fly...
 
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