The smallest composite staging system

[Funkworks]

I’ve been there and done it with staging BP motors, so I’m now starting to look into staging composite motors. Here’s what I have in mind:

• 2 APCP motors.
• Lowest power possible. I’m totally fine with 2 small Aerotech D motors.
• Lowest altitude possible. I couldn’t care less about altitude. I just want a safe, successful build.
• Debating between a simple timer and direction sensing (not the first one to debate this, huh?).
• Don't mind if it takes a entire year to build and to fund.

Until I’ve read this entire forum section, any suggestions for kits, parts, information sources and the current status of safety concerns are welcome.

 

[BDB]

I've been working on MPR staging using a scratch-built BT-60 sustainer with a BT-70 booster. I've been using an F50 in the booster and electronically lighting a C11 in the sustainer.

It's honestly been a little frustrating. If I could start the project over, I would have started with a BT80. It just makes it easier to fit everything in. The other issue is that the altimeter that is used for staging often has a minimum safe altitude before it will light the sustainer. The F50 barely gets my rocket to that minimum in my setup. You could get staging to work at any altitude with a simple timer (in essence that's what BP-BP staging does--there is no way to prevent sustainer ignition), but I wanted to learn how to use the safety lockouts, and that has proven to be limiting.

I haven't had the time to mess with this much lately. Hopefully I can make another staging attempt at a launch next weekend. But I've started to suspect that electronic staging might be a "go big or go home" scenario.

 

[mikec]

My first experience with staging was a scratchbuilt scale Argo D-4 Javelin with a 29mm F or G in the first stage and an E20 in the second stage (and eventually, another E20 in the third stage). The second stage was 1.9 inches in diameter. I wouldn't go a lot smaller than that just because it's hard to get it all to fit.

I used a Raven for staging, with an altitude lockout. Orientation sensing is, IMHO, overkill for a project of this size.

 

[Thorfire]

The eggtimer quantum is relatively inexpensive, and has velocity and altitude lockout. I should fit in a 29mm tube. I like Wi-Fi arming from a distance instead of inches away.

 

[Wallace]

How 'bout Quest q-Jets?

 

[Charles_McG]

Cris talks about testing the Quantum in an Estes Mongoose during development. D20-D11, if I recall correctly. But the smaller you go, the harder it gets to fit everything - the igniter wires included.

I've done BT55- but it's tight. And it doesn't take much altimeter/battery/tracker/battery weight before you need a G booster to get the stack to the minimum speed and altitude that the Quantum likes.

 

[vcp]

Just looking for simple acceleration trigger + time for LPR/MPR staging in something smaller than bt60, no other whistles & bells. What's the minimum battery for a single BP ignitor?

 

[gfunk]

I have used the SimpleTimer with good success. https://www.apogeerockets.com/Electronics-Payloads/Staging/Simple-Timer-for-Staging

 

[cerving]

Just looking for simple acceleration trigger + time for LPR/MPR staging in something smaller than bt60, no other whistles & bells...

The problem with a simple timer, even a G-triggered one, is that they don't have any safeties. If you arm it then lift the rocket up on the pad a few inches and drop it, it might go off in your face. If your rocket goes unstable, it's still going to fire, possibly sending the sustainer into the ground (bad) or the flight line (waaaay worse). At a minimum, there should be some kind of altitude-based arming, preferably with qualifications such as altitude-at-time or velocity-at-time. There are several altimeters that satisfy this criteria.

 

[Jmhepworth]

ACPC staging is far more complex than black powder. But it’s worth it. Watching drag separation and then the separation charge is magical. The wait for the sustainer to light seems to always be longer than it is. And then having all the altimeters put out chutes at the right time is very rewarding. You’re going to want to move up to bigger rockets, so you might as well do it right with smaller ones. I wouldn’t worry about orientation but I would use at least an altitude check. I use a Raven in staging, but plan to use a quantum in the one I’m building next.

Joe

 

[Ez2cDave]

Watching drag separation and then the separation charge is magical.

Joe

How does one prevent premature Drag Separation of a 3-Stage APCP rocket ?

Dave F.

 

[Nytrunner]

Stage drag analysis, fit checks, and (if needed) shear pins

 

[Ez2cDave]

Stage drag analysis, fit checks, and (if needed) shear pins

That's all fine on large rockets, but what about small, 18mm, minimum-diameter rockets ?

Dave F.

 

[Nytrunner]

Stage drag analysis and fit checks. Same as the big boys

Heck, if using ****** one's thin wall fiberglass, may even be able to stick a nub of a shear pin in.

but what about small, 18mm, minimum-diameter rockets

I thought we were talking composites here. BP ignition can kick off a skilled friction fit.

 

[heada]

I thought we were talking composites here. BP ignition can kick off a skilled friction fit.

There are 18mm APCP based motors. I have a 13mm snapring case for APCP based reloads. EX only, but still.

 

[Nytrunner]

There are 18mm APCP based motors.

I'm aware. They also require electronic ignition. Is there a staging computer/timer that fits in 18mm tubes?

 

[Ez2cDave]

I'm aware. They also require electronic ignition. Is there a staging computer/timer that fits in 18mm tubes?

Probably would have to be a simple multiple-event timer, with a G-Switch.

Dave

 

[heada]

I'm aware. They also require electronic ignition. Is there a staging computer/timer that fits in 18mm tubes?

Yes, there are.

 

[Nytrunner]

Yes, there are.

Care to share?

 

[heada]

Care to share?

Nothing commercial that I know of. I made some pre-programmed micro-controller based timers. Fixed time delay that then just discharges a cap to the output. Multiple boards, 1 for each delay from 3 seconds to 7 seconds. Only works with ematches that I make since they're a little extra sensitive with a custom pyrogen. No advanced logic, no safety checks besides power on/power off. g-switch launch detect. Since there is no other safeties besides basic power, I would never even offer them for use to others.

edit: not staging electronics but I have a Featherweight Parrot that does recording and apogee deployment.

 

[Nytrunner]

Since there is no other safeties besides basic power, I would never even offer them for use to others.

Wise. So for the consumer hobbyist, there aren't 18mm MD stagining devices yet. Wonder if featherweight would want to try his hand at the business

 

[heada]

Wise. So for the consumer hobbyist, there aren't 18mm MD stagining devices yet. Wonder if featherweight would want to try his hand at the business

Not sure there'd be enough demand for 18mm MD staging electronics for a commercial product. Might sell a dozen of them over the life of the product. I believe that both Eggtimer and FeatherWeight have devices that fit in 24mm though.

 

[cerving]

Some things in hobby rocketry start small and scale up, and some things start larger and scale down. Electronic staging falls into the latter category, it's actually fairly difficult to do it in 38mm, harder to do it in 24mm, and pretty much impossible to do it in 18mm. My advice to people that want to get started with electronic staging is to get something at least 54mm, so you have a lot of room to work with. It makes things MUCH easier.

 

[Ez2cDave]

Well, "back in the day", before electronic staging, we used Thermalite strands, ignited by the flame from the motor below it.

The burn time could be shortened by sheathing or partially-sheathing the Thermalite. Sheathed Thermalite burns VERY ( extremely ) fast.

BTW - ( gasp ) we lit the motors inside the coupler ( lined with foil or coated with JB Weld ) . . . We did not use Drag Separation or Separation Charges . . . Ah, the "Good, Old Days" !

Naturally, Thermalite is no longer available . . .

Dave F.

 

[Nytrunner]

Is thermalite (when available) or visco allowable under the modern safety codes?

 

[Fattbank64]

I have used the SimpleTimer with good success. https://www.apogeerockets.com/Electronics-Payloads/Staging/Simple-Timer-for-Staging

IMHO the issue with the SimpleTimer is setting the correct delay interval. Inventor couldn't set the proper time int the video. He said one could use a metronome.

 

[Cameron Anderson]

Well, "back in the day", before electronic staging, we used Thermalite strands, ignited by the flame from the motor below it.

The burn time could be shortened by sheathing or partially-sheathing the Thermalite. Sheathed Thermalite burns VERY ( extremely ) fast.

BTW - ( gasp ) we lit the motors inside the coupler ( lined with foil or coated with JB Weld ) . . . We did not use Drag Separation or Separation Charges . . . Ah, the "Good, Old Days" !

Naturally, Thermalite is no longer available . . .

Dave F.

Was also a good way to light any motor...that stuff would ignite dirt.

 

[Ez2cDave]

Was also a good way to light any motor...that stuff would ignite dirt.

 

[BDB]

I don't really want to go down as the safety naysayer, but....

We stage LPR rockets all the time without safety checks. It's not really any different to use a timer for 18 mm and 24 mm composite motors.

 

[Ez2cDave]

I don't really want to go down as the safety naysayer, but....

We stage LPR rockets all the time without safety checks. It's not really any different to use a timer for 18 mm and 24 mm composite motors.

Very true !

A timer is a timer :

(1) It must fit. ( 18mm appears to be difficult, at this time, but I expect that will be solved )
(2) It must be reliable.
(3) It must be able to fire the number of igniters being used, 100% of the time, with "room to spare".

Dave F.