Electronics for Staged Rockets

[Bruce]

I want to get into flying staged composite motors and am looking for advice on electronics.

I'd like to start with a minimum diameter 29mm rocket, so if the board was small, rather than larger, that would be a plus.

Having dual deploy would be nice, but an integrated tracker is not necessary as I want that part to be separate.

I'm looking for something that is simple and as safe as possible.

I certainly don't want to ignite the sustainer if the booster has tilted over too far after launch. What method(s) are used to detect the angle?

What other lockouts are the most helpful?

 

[TimothyG]

I started with eggtimer products to keep things cheap through the learning experience. Worked great for me so far. I don't feel a need for tilt lockout and it is NOT required for two-stage flights despite some of the misinformation put out about that. I do altitude and velocity lockouts based on a percentage of what the simulation says I will be at when I stage. I plan on continuing to do these two lockouts for gradually larger and larger projects.

 

[H_Rocket]

Right now the front runner is the Altus Metrum Easy Timer. If you want to be more sophisticated and have a multi function device, the Raven by Featherweight is a good candidate.

 

[cerving]

I want to get into flying staged composite motors and am looking for advice on electronics.

I'd like to start with a minimum diameter 29mm rocket, so if the board was small, rather than larger, that would be a plus.

Having dual deploy would be nice, but an integrated tracker is not necessary as I want that part to be separate.

I'm looking for something that is simple and as safe as possible.

I certainly don't want to ignite the sustainer if the booster has tilted over too far after launch. What method(s) are used to detect the angle?

What other lockouts are the most helpful?

Actually, you're better off starting with a bit larger rocket, 54mm or larger in diameter. Something like the PML Quantum Leap or a Madcow/RW Double Shot is a good starter. The reason is that with the smaller rockets it can be very challenging to get all of the electronics in the AV bay, and to get the wiring to the sustainer motor. It's much easier with a larger rocket. You will definitely want tracking, and it would be nice if you could fit deployment redundancy into the sustainer; you don't really need it for the motor ignition, because if for some reason it doesn't light then your sustainer is just going to come down normally, and you can use the motor for the next try.

 

[n27sb]

Last year I built a 24mm two stage to go after Tripoli's F impulse staged record.
https://www.rocketryforum.com/threads/f-impulse-2-stage-tripoli-altitude-record.160579/
Before the build I received a lot of help from this forum.
Cris at Eggfinder has a nice article on his site.
http://eggtimerrocketry.com/wp-content/uploads/2018/06/Eggtimer_Quantum_Airstart_Manual.pdfThe article is mostly about his Quantum but it goes into details required for most staging.

I ended up using Apogee's "Simple Timer" and it worked well. Altus had not yet released the Easy Timer.

I like Cris's choice of going bigger in diameter first time around.

Here are more details on my build.
https://www.rocketryforum.com/threads/f-impulse-24mm-2-stage-md-rocket.159884/

 

[Jmhepworth]

My entrance into high power staging was a Wildman Junior with a Raven. I can’t imagine going smaller. Installing the conduit for the sustainer is tight. Really tight. There’s enough room in the sustainer av bay for redundant electronics. Not in the interstage coupler.

 

[cerving]

My entrance into high power staging was a Wildman Junior with a Raven. I can’t imagine going smaller. Installing the conduit for the sustainer is tight. Really tight. There’s enough room in the sustainer av bay for redundant electronics. Not in the interstage coupler.

In the booster, you can usually go single-deploy and use motor-eject for the backup. Since you're talking Level 1 motors, you'll be fine on the booster with single-deploy, and it's unlikely that you'll need a tracker on the booster either. (Yeah, famous last words...)

 

[Jmhepworth]

In the booster, you can usually go single-deploy and use motor-eject for the backup. Since you're talking Level 1 motors, you'll be fine on the booster with single-deploy, and it's unlikely that you'll need a tracker on the booster either. (Yeah, famous last words...)

Cris, I like redundant ejection whenever I can make it fit. In the booster, I use single deploy with the motor as backup. I still add an RF tracker to the booster shock cord, just so I will not need it. And I usually put a GPS in the nose cone and a backup RF tracker on the shock cord of the sustainer. Redundancy all over the place.

 

[Bruce]

Is this an accurate summary?

Altus Metrum Easy Timer $80 .8" board size, gyro-based tilt limiting

Apogee Simple Timer $88 .9" board size, fixed 45 degree tilt limit

Eggtimer Proton $70 1.125" board size, Barometric vs Accelerometer altitude qualification for off-axis detection

 

[Titan II]

Missile Works RRC3 .925 Info in the manual

 

[rocketace]

Featherweight Raven V4 $160 .79" board size, Burnout & Baro vs time limit. And can also run your drogue/main charges.

 

[cerving]

Is this an accurate summary?

Altus Metrum Easy Timer $80 .8" board size, gyro-based tilt limiting

Apogee Simple Timer $88 .9" board size, fixed 45 degree tilt limit

Eggtimer Proton $70 1.125" board size, Barometric vs Accelerometer altitude qualification for off-axis detection

Bruce: Yes, but the Proton is a 6-output flight computer, it will do your separation charge, airstart motor, and dual deployments and you still have two outputs left to play with. Plus, it's remotely programmed and armed via WiFi/browser on your phone, with no apps or Internet.

 

[boatgeek]

Is this an accurate summary?

Altus Metrum Easy Timer $80 .8" board size, gyro-based tilt limiting

Apogee Simple Timer $88 .9" board size, fixed 45 degree tilt limit

Eggtimer Proton $70 1.125" board size, Barometric vs Accelerometer altitude qualification for off-axis detection

Eggtimer Quantum can do airstarts, $40, 0.9" board width. Baro altitude and velocity lockout options for off-axis detection.

 

[Bruce]

Can the Eggtimer TRS do airstarts or staging?

 

[cerving]

No. It's GPS and dual-deploy. No room in the firmware for anything else.

 

[Bruce]

Does the Missileworks RRC3 have tilt or other lockouts to prevent suboptimum staging?

It looks like the Altus Metrum Easy Timer and Apogee Simple Timer have gyro based tilt limiting and all the rest use the barometric, accelerometer and time based information to arrive at the decision of whether or not to ignite the upper stage. Is this correct?

Here's the updated summary with boards in order of size. Corrections and additions would be welcome.


Staging Electronics:

Featherweight Raven V4 $160 .79" board size, Burnout & Baro vs time limit
Altus Metrum Easy Timer $80 .8" board size, gyro-based tilt limiting
Apogee Simple Timer $88 .9" board size, fixed 45 degree tilt limit
Missileworks RRC3 $74 .93" board size, no tilt lockout
Eggtimer Proton $70 1.125" board size, Barometric vs Accelerometer altitude qualification for off-axis detection

 

[boatgeek]

Does the Missileworks RRC3 have tilt or other lockouts to prevent suboptimum staging?

It looks like the Altus Metrum Easy Timer and Apogee Simple Timer have gyro based tilt limiting and all the rest use the barometric, accelerometer and time based information to arrive at the decision of whether or not to ignite the upper stage. Is this correct?

Here's the updated summary with boards in order of size. Corrections and additions would be welcome.


Staging Electronics:

Featherweight Raven V4 $160 .79" board size, Burnout & Baro vs time limit
Altus Metrum Easy Timer $80 .8" board size, gyro-based tilt limiting
Apogee Simple Timer $88 .9" board size, fixed 45 degree tilt limit
Missileworks RRC3 $74 .93" board size, no tilt lockout
Eggtimer Proton $70 1.125" board size, Barometric vs Accelerometer altitude qualification for off-axis detection

Featherweight Raven V4 $160 .79" board size, Burnout & Baro vs time limit
Altus Metrum Easy Timer $80 .8" board size, gyro-based tilt limiting
Eggtimer Quantum $40 .9" board size, Barometric altitude/velocity qualifications for off-axis detection
Apogee Simple Timer $88 .9" board size, fixed 45 degree tilt limit
Missileworks RRC3 $74 .93" board size, no tilt lockout
Eggtimer Proton $70 1.125" board size, Barometric vs Accelerometer altitude qualification for off-axis detection

 

[Bruce]

From this chart,

http://eggtimerrocketry.com/home/altimeters-av-bay/eggtimer-altimeter-comparison/

it looks like the Eggtimer Proton has an accelerometer in addition to the barometric sensor to help decide whether to ignite the upper stage or not. Is this correct?

My understanding is that there are 4 sensors that could commonly be on these type of boards:

1) Timer
2) Barometric altitude sensor
3) Accelerometer
4) Gyro tilt sensor

I assume they all have 1 and 2. Which ones have 3 and / or 4?

 

[cerving]

From this chart,

http://eggtimerrocketry.com/home/altimeters-av-bay/eggtimer-altimeter-comparison/

it looks like the Eggtimer Proton has an accelerometer in addition to the barometric sensor to help decide whether to ignite the upper stage or not. Is this correct?

That is correct.

 

[FredT]

My favorite, by far, is TeleMega. It's not cheap, but oh is it good; 6 pyro channels, tilt detection, remote RF arming with continuity monitoring, GPS tracking, and it talks to you during flight.

I also use Ravens quite a bit. With 4 pyros, you can use just one and you get stage separation, ignition, and apogee and main deployment. They're not as easy to program as TeleMega because it doesn't have explicit tilt detection, but with careful simulation and flight experience, you can do a "how high by when" analysis to program stage ignition lockouts.

I've been gathering experience with Eggtimer Protons. 6 pyro channels, remote wireless arming with continuity monitoring. The "deviation" function for stage ignition is promising, I just need more flight experience to feel confident. I think I'll get there, just not there yet.

All provide extensive data logging so when things didn't work the way you thought (and it will), you have data to figure out why.

...Fred

 

[blackjack2564]

What ever you end up with....know your units inside out before using.

99.9% of staging problems/failures are user error.

 

[plugger]

My favorite, by far, is TeleMega. It's not cheap, but oh is it good; 6 pyro channels, tilt detection, remote RF arming with continuity monitoring, GPS tracking, and it talks to you during flight.

I've been gathering experience with Eggtimer Protons. 6 pyro channels, remote wireless arming with continuity monitoring.

...Fred

Fred, please correct me if I'm wrong, but I was under the impression that remote RF arming was no bueno from a TRA perspective? I did it years ago with a TeleMetrum and posted about it here and was told that it was explicitly forbidden by the TRA BoD.

 

[rocket_troy]

plugger,
what was the reasoning behind that?

 

[JimJarvis50]

I agree with most of what Fred said. I don't know his specific procedure for arming, but one important criteria for me is the ability not to have to climb a ladder for arming sustainer motors. I would recommend to anyone engaged in staging to make this a goal in their setup. We use hobby quality (inexpensive) electronics that often are not fully debugged, along with amateur wiring procedures, and the last place you want to be when arming your rocket motor is next to the motor on a ladder.

My favorate approach is a wifi switch in combination with an EasyMega or a Raven or an Easytimer, in combination with an igniter shunt that can be removed from the ground. I can energize the wifi switch with the rocket horizontal, raise the rocket, energize the altimeter remotely, and then pull off the shunt. In the context of this arming procedure, I would not use the Telemega or the Proton because the piece of electronics that fires the igniter would have to be energized before lifting the rocket. I object to that, even though I recognize that those devices were designed for exactly that purpose. Just my opinion, but I want to keep that extra degree of safety.

I haven't used an EasyTimer but I believe it's a pretty good option (assuming it operates as I think it does). It's not just a timer with tilt, but rather, a configurable flight computer than just doesn't have a barometric altimeter. But, it's still possible to use an accelerometer-based altitude check, and tilt or no tilt, an altitude check should always be used as part of the staging logic. As with the other devices, I would use it with a wifi switch and a removable from the ground igniter shunt.

My favorate favorate device for staging is Kate, but she's not going to fit in a 29mm tube.

Jim

 

[plugger]

plugger,
what was the reasoning behind that?

According to Steve Shannon, NFPA 1127.

Here's what he wrote about it in 2018.

Edit: rereading the above thread it appears the Eggtimer Quantum is ok as it is based on the Eggtimer Wifi switch. I suspect the Proton's Wifi is the same.

 

[rocket_troy]

Here's what he wrote about it in 2018.

That appeared (for me at least) to link to something completely different ie. pre-arming electronics before heading out to the pad and relying on the rocket's orientation to keep it safe? Unless the link was pointing me to the wrong post?

TP

 

[cwbullet]

I gues we can get clarity from @Steve Shannon

 

[plugger]

That appeared (for me at least) to link to something completely different ie. pre-arming electronics before heading out to the pad and relying on the rocket's orientation to keep it safe? Unless the link was pointing me to the wrong post?

TP

Sorry Troy, I should explain my comment better. It's specifically in relation to the TeleMega RF arming comment Fred made. With TeleMega and TeleMetrums you have two modes that the fc will boot into dependent on orientation. Boot it horizontally and it's in idle mode. You can change the orientation and nothing happens along any channels. This is also the mode where the fc will accept RF commands to the unit, including rebooting the unit.
When you boot(or reboot) the fc and it senses it's vertical it enters flight mode. The fc also no longer accepts remote commands as the onboard radio enters a transmit only mode.
I can't think of another way RF arming could be accomplished with a TeleMega given my understanding how that device operates.

 

[FredT]

Fred, please correct me if I'm wrong, but I was under the impression that remote RF arming was no bueno from a TRA perspective? I did it years ago with a TeleMetrum and posted about it here and was told that it was explicitly forbidden by the TRA BoD.
[/QUOTE

It wasn't completely banned, but for a time remote arming was limited to devices that were blessed for this purpose by the BoD. That limitation was later lifted.

 

[Steve Shannon]

Actually, remote arming was never prohibited. For a while we required a mechanical disconnect until the rocket was on the range, whether remote arming was used or not.
We no longer require a mechanical disconnect, but devices that control ejection charges or staging must be inhibited (powered down) until the rocket is on the pad.