16 Rocket Semi-Simultaneous Launch Controller

[LydaRA]

As has already been said, there are _MULTIPLE_ power disconnects involved before ANYONE (Scouts or adults) are allowed on the field.  If it is safe to wire up a rocket while the stock Estes controllers sit on the table, but the removable keys in my pocket at the pad--then how is it unsafe for this proposed system to sit disarmed with the removable keys in my pocket at the pad? 

And if someone is dumb enough to flip the power switch to the Pad Box at all, then the strobe and siren go off.  Show me how a stock commercial control gives that warning?

We have electricians in our Council.  We have been consulting with the local NAR and Tripoli chapters.  Seems like a launch control system can be as well safety-reviewed before acceptance in the same way we commission professional review of our climbing towers and COPE elements by authorities in that field.

If I were going rogue, I wouldn't be taking the time to ask for other opinions on even the simplest of electronics that I learned as a 13 year old Red Cross volunteer building motor wheelchairs and handicap adaptations.  "The only dumb question is the one that goes unasked until _after_ something goes wrong." 

But thanks to all for your concerns....and even more for any and all _constructive_ guidance shared.

[jonpaul]

Perfect, good luck....Check liability insurance (:-:)

j

[LaserSteve]

 Take lessons from the elevator design folks and the railroads, who use failure resistant relay logic in such a way that springs and gravity in the relays take things to failsafe states.   It is OK for the processor to enhance the event with audio, warnings etc,  but final launch authority should come from the ladder logic. If you have your hand on the dead man's switch, it is OK for the processor to close a final launch relay after the countdown, provided you have a full field  of view. .   Odds of a powered up processor failing in a 10 second countdown are low if it has demonstrated to you in some way that it's program is running before you trust it and manually gate it into the circuit.   Odds of it failing indeterminate at startup or just setting there in the sun are high out in the field.   Odds of it being latched up from conducted  EMF from the coil of a  large relay or a two way radio are are high for example.

I'd also read up on the concepts of "Cockpit Resource Management", if I were writing  the launch procedures.  You'll see why in a minute.

In my day job I'm senior technician  for a large portion of a university.  I'm also an Eagle, class of 1988.   My rocketry days are long ago, but I still remember the basics.

This is where I state I'm not a licensed  Professional Engineer in the State of Ohio, nor anywhere else in the world.  I'm just an old technician with lots of experience.  My advice is just that, advice, and it is only worth the electrons it is transmitted by.  There is the required disclaimer.

So lets more or less define what the CPU is going to do for you.  Then we can proceed.  Does the processor select which rocket will launch?   We are firing one at a time, not a Salvo?

How are you going to test if an ignitor is properly hooked up?  Ie the well designed  Ballistic Galvanometer  function used in blasting..

What else do you intend for the microprocessor to do?

Would it not be more appropriate for the processor to characterize the flight, ie show the potential  effects of  the prelaunch wind, predicted ballistics , measure time of flight etc? Just throwing out the idea of other uses that could enhance education.

One other thought.    If I were doing this, the Launch  Safety Officer  would have a firing handle in his hand as a dead man's switch, and the Scout would have a firing handle in her/his hand* for the actual firing.  The Scout then has a launch checklist, as does the safety  officer.  They have to concur to launch and both turn keys before the scout activates the trigger switch. .  The Scout's firing switch could activate the CPU for the countdown, warnings etc, but the LSO's firing handle is doing the safety functions and made the final decision to energize the interlock relay(s).  (*Scouting is Co-Ed now in the US)

BTW, "Fire" is not a valid command, nor should it be used.   See the last scenes of " The Bedford Incident" movie   on Youtube.   Lots of learning opportunities here for the scouts as to the "how and why".

I was going to avoid mentioning the rocket incident on the carrier, but it did cross my mind.

Steve

[Stray Electron]

This is NOT "rocket science" ... here is the circuit!

Battery...fuse......master safety key switch ....master bus...individual firing switches ....cables ....rocket ignitors.

Bon Chance,

Jon

  I agree.  One of the first things that I learned and one of the most important was "KISS", "Keep It Simple, Stupid!". 

    That's a Golden Rule when it comes to safety critical circuits. Everything that you add to the circuit lowers reliability and is an added safety risk.

   You can use optocouplers and added contacts on the relays (and separate power supplies) to operate any bells and whistles but the basic control circuit should be keep as simple as reasonably possible.

   One of these days I'll have to tell the story of how one of my coworkers nearly got crispy-crittered while test firing a Bomarc missile!  Long story short, he was standing behind one when it ignited prematurely. He jumped over a safety barrier and wasn't badly injured but got scorched real good!

[Stray Electron]

How are you going to test if an ignitor is properly hooked up?  Ie the well designed  Ballistic Galvanometer  function used in blasting..

  They make MUCH better ones today.  I own a 4314 Digital Ignition Tester made Vahalla Scientific.  It's basically 4 wire Ohmmeter that is guaranteed not to output more than limited amount of current. I don't remember the numbers but in the microamp region. OK, I had to go look it up, the test current is 10uA in the standard version.

[james_s]

   FWIW If I were the BSA I would never allow you to use a home designed and built launch controller in any of my events regardless of the bells and whistles that it includes, PERIOD!

   Everything benefit that you have named could be accomplished on a traditional style launch controller controlled by manual switches and not controlled by some kind of uProcessor.

  "length of control cables can be sourced as cheap commodities at Walmart, BestBuy, wherever."

  If you insist on a controller like this then go buy one of the commercially built firing boxes that are made for use in pyrotechnics (i.e. Fireworks) shows. They have the ability to synchronize to music and other external events and are designed to handle up to thousands of firing circuits.

   Designing a launch system, particularly one that is intended to control multiple simultaneous launches, to use cheap Walmart-grade components is the worst idea that I've heard so far today!

Seems a bit hyperbolic I think. We're talking about model rockets weighing a few tens of grams here, not armed ballistic missiles or sticks of dynamite. It's important to be safe, but you don't need to go overboard. I remember the official Estes launch controller I had when I was a kid and it was nothing more than a cheap molded plastic housing with a leaf switch pushbutton molded into it, the "key" was a metal wire that when poked into a hole, bridged a pair of contacts. A small incandescent lamp wired across the button served to indicate the system was armed and had a complete circuit. Some of us didn't even have the proper launch controller and we got by using a bundle of cheap speaker wire and just touched the ends to the terminals of a 6V lantern battery to launch the rocket. All this talk about mil spec switches and aircraft relays, come on, the official systems that have been around for decades are built like cheap kids toys, they *are* cheap kids toys. As long as people are following reasonably safe practices, an uncommanded launch is more of a "whoops!" event, not "OMG call 911 and bring in the FAA accident investigation team and the ATF!". Let's keep things in perspective here.

[jonpaul]

What exaclty linits the rocket charge when used in the proposed igniton systme?

Could they try larger and larger rockets over time?

Can the grains of propellent be linited to <10 or migh it be 50g? 500G? 5kG?

Regardless of size the use of a pyrotechnic propellant can always   cause injury.

j

[Syntax Error]

Cool project 

I would add a loud claxon. One that indicates to the whole field that the range is hot. Or safe. This could be any electric claxon or even a scavenged truck horn.

The claxon can only be operated under the command of the designated Range Boss - who has a hivis jacket with that on. And everyone defers to the Range Boss.

Also, a GoPro camera on the launch pad to film the rockets launch in closeup. Which is going to look cool on YouTube for your public outreach

Happy firing.

[james_s]

The engine sizes readily available to hobbyists limit it. Most of them come in 4 basic sizes, A, B, C and D, with a range of thrust and ejection charge delays for each. There are larger engines which are available to serious hobbyists but you won't find them in the average hobby store and they are used by a whole different group of people.

Bottom line is the official launch controllers that are sold alongside the rocket kits are cheap toys. They're built with the quality of a 99c trinket from China.

https://estesrockets.com/product/002220-electron-beam-launch-controller/
https://estesrockets.com/product/002221-astron-ii-launch-controller/


There are also rules and regulations, they limit the weight and materials the rockets can be made of (no metal, no sharp edges, etc) and mandate using off the shelf engines, no homebrew stuff. These are kids toys, I remember building several of them when I was age 8-14 and launching them with my friends in a vacant lot near the house I grew up in.

[LydaRA]

Cool idea.  Some parent in the group often uses a smartphone to film launches for their child/den.  We should get the film for camp use.

Similarly, we launch once and wait for "all down," & "range clear" commands.  Then we ask each Scout to stand with their rocket where it landed.  We call them a "living scatter-plot."  A chance to discuss more math, science...  "We all started on the same rods, pointed the same way--why did we end up scattered across the field?"  "Since the winds above the treeline pushed us left, let's point the next launch a little more to the right."  Then we reload and launch a second time.  Then compare where the plot has everyone standing this time.  Reinforce the safety with "We corrected our aim, but still don't control winds aloft.  Most importantly, even if not dead-centered--do you see why we rope off such a LARGE roped-off range (much larger than Estes calls for)--in an even larger open field?"  I keep a log count of on-range, off-range, & lost (gust can sometimes put us into trees).  And can confirm despite hundreds of launches per day, we can usually count the "lost" on one hand!  That's better than many NAR/Tripoli launch days!

Anyway, would _LOVE_ to get photos by drone or such of the "living scatter-plots" to send home souvenirs to help the children remember the lessons.  We let them take home their rockets (minus engines)....but that's a thing.  Let's give them a selfie!

[LydaRA]

Yep, each Pad Box will have a local buzzer and flasher to warn of power on the igniter supply bus.

And the first Pad Box will have a pike with a larger strobe and louder horn.  Warns the whole field of countdown initiation.  (Kind of like the pike on copiers to let the entire office know a customer order may have just been faxed in to be handled...)

[LydaRA]

Yep.  We have been using the stock Estes controller safely for years.  This will be even safer, yet increasing throughput.  The _only_ way I'd increase throughput is with increased controls!

And indeed, _policies_ help.  As said before, like our rifle, pistol, shotgun ranges....we do not allow ammo brought in from outside.  The camp provides our known & proven choice of ammo.  We have only ever flown A and B engines--and usually just 1/2A! 

The Scouts build their rockets.  But they only observe as the range staff load the engines ourselves.  Neither the ready engines nor the used engines ever leave the range and RSO's control!  Ready engines are kept locked in an ammo can until actually being loaded.  Spent engines are collected in a large pail of water and stirred to dissolve to inert any remnants.   (Yes overkill, but we are modelling responsible behaviors.)

[Gyro]

Insurance issues aside, I'm actually heartened to find somebody trying to do it properly - certainly compared to rocket launcher project threads that have come up in the past.

[LydaRA]

Thanks, Gyro!

The year before I took over the rocketry range, I was just an observer with my fourth grade son.  Although I was already a shooting instructor and on my way to formal NRA RSO.  But I was an observer, so _tried_ to hold my tongue and let my child learn from another volunteer...  That is _UNTIL_ the guy left the launchers' removable keys on the table by the launchers--and the Scouts--as he went out to the pads and started rewiring?!?!?  I _HAD_ to shout out to my boys: "Sit down at the back of the tent.  We are not blowing this guy's fingers off.  He is literally wrapping his fingers around gun powder to setup your rockets.  There will be no excited little fingers fidgeting with either the controllers or the safety keys."

After that session, I excused myself to go talk with a Shooting Sports Committee friend.  We agreed that although rocketry was not under Shooting Sports in the national guide, NAR and common sense says rocketry should run with the same discipline as any other range!  They backed my play, and the volunteer was reassigned to a station better suited to their temperament.  That night, SIX of us (Camp Director, Program Director, Quartermaster, Shooting, an Electrician who ran rockets in years prior, & myself) and a Scout all met to re-enact and re-imagine how the station should/could run.  We looked at field (other stations or campsites adjacent), facilities (tents, roping, red flags, etc.), equipment (controllers, keys, rods, covers, etc.), range countdown & commands, educational speaking prompts....ALL of it.  We then played RSO & Scout participants, and acted it all out start to finish until ALL were satisfied.

I have been running the station in the years since.  Still enjoying what everyone had to contribute, still "paying it forward" to the next generation--and still insisting upon God's own discipline on my range!  "I've never had to meet a Mom with their child at the ER--and I'm not going to start today!"

[Stray Electron]

  Bravo for you.  It's good to see someone that still takes the time to teach boys how to use guns and some life skills in general, particularly in an organization like the Boy Scouts that has taken so much public abuse in the past few years. Scouting and model rocketry are both about dead in this area. I tried to get my son into scouting some years ago and basically we had to start our own troop with no guidance or help from the BSA. None of us really knew what we were doing and it soon fizzled. The few scout troops that are left in this are don't do any camping or anything of that sort, they've all become Social organizations that have food drives for the poor, visit nursing homes and other PC events. My BIL was a scout master for an out of town troop and I found some good camping gear including a NIB gasoline fueled Coleman camp stove and I tried to donate all of it to his troop and I was prompted informed that his troop didn't Go camping! And that the BSA do not allow their scouts to handle anything with gasoline!  I bought model rocket kits for all of my nephews but no one was really interested and I don't think that any of them every built any of them. America will soon be a non-technical country from everything that I see with today's youth. My son is the same, he's now in his mid 30s but the ONLY thing that interest him are computer games! He literally has NO life away from a computer and he has ZERO technical skills.

[wizard69]

I somewhat agree with others, this seems like going overboard and a liability issue.  This especially if nobody on the team has an engineering background.   However I have no idea how the BSA are insured.  You might have coverage if something goes wrong or you might not, I’d ask for an answer in writing.   In the end when it comes to their kids parent always look for somebody to blame besides the kid. 

Now all of that being said, a little over 45 years ago I built my own little launch station for model rockets.   A side thought is that this could be very educational all on its own.   In any event except for the housing almost everything was salvaged from something and due to money I keep it simple. 

In my case I ran it off a tractor battery as that could be driven to a near by field.  Some things to consider:
1.  The wire used to set off the igniter is basically expendable and will often be destroyed at blast off.    Effectively you want the igniter wire to get hot very fast so you want to assure low impedance throughout the power circuit.
2.   Low impedance is good but there is a catch, your alligators can short at launch and this can be bad if you don’t have some sort of protection.   A  lead acid battery can supply  hundreds of amps making a mess of your project real quick.   
3.   I seem to remember having a method of checking continuity, but that was so long ago I don’t remember how I did it.  It had to be simple though because I had little to work with. 
4.    A decent auto supply store will have some of the hardware required.  Jumper cables can supply you with battery terminal sized alligators, fusible links or standard auto fuses and sockets. Not to mention relays, switches and other parts.  Of course you can go to an electronics supplier like Digi-Key


This post is putting me into a bit of a funk as I just realized I have no idea what happened to that launch controller.  However I remember it being absolutely fun to build.   Fun is one reason why I think it would make a great project for Boy Scouts and of course you learn a bit.     You still have the liability issue so considering the other activities scouts engage in there must be a way to a BSA approved launch controller.   Considering the educational potential you would think that a national level solution could be had.   

[NiHaoMike]

Perhaps a good design for a rocket launcher kit would be based on actual explosive triggering equipment? Basically a generator with a mechanism to spin it using a handle and a switch to dump the energy of the spinning rotor all at once:

It's hard to imagine any fault that can cause an unwanted activation aside from someone operating the unit when they're not supposed to, but that can be prevented by adding a provision to lock the handle with a padlock.

[LydaRA]

As I have alluded to above, this will be well-reviewed before accepted into camp use.  BSA insurance covers us as long as we stay within guidance.  For Rocketry, BSA defers to NAR for guidance.  I have already opened discussions with the local NAR chapter, and reviewed their local equipment.  They use a custom control system built somewhat similar to my proposals: from custom PCB (although not Arduino), commodity cables (CatX & AC extension cords), car battery, and high-power relays (automotive).   So our liability should be covered by the same as how we have climbing tower, pool, etc inspected by authorities in their fields.

I would hope that this might become a prototype for others to use, across BSA and elsewhere.  (Same as how our local COPE & Climbing Standard Operating Procedures are good enough that they are studied, referenced, and spread by the larger BSA.)

[LaserSteve]

I'll do a rough schematic  drawing this evening.

Steve

[LaserSteve]

Affordable modular switches come from here:

https://www.automationdirect.com/adc/shopping/catalog/pushbuttons_-z-_switches_-z-_indicators/22mm_plastic#

You select the switch body, the actuator and the modular contacts for "build a switch" . We use 22 mm bodies at work as they are student proof and ultra reliable.   Their 22 mm high brightness  blue and green led  indicators work in a fairly bright room, with day light streaming in. . They will also custom print you the key legends for cheap.

McMaster Carr also has nice modular switches.

Don't forget the "missile switch" switch guard for arming toggles:

https://www.sparkfun.com/products/9278

We do use the above at work as well.  There are many vendors.

We like the "twist to release" style of E-Stop:

https://www.automationdirect.com/adc/shopping/catalog/pushbuttons_-z-_switches_-z-_indicators/fuji_electric_22mm_(ar22_series)/emergency_stop_pushbuttons_illuminated_-a-_non-illuminated/ar22v0r-01r

Steve

[wizard69]

i remember those days and for an independent launch of a single rocket I agree  100%.   the problem is that this isn't a back yard event and more so there is the desire to add automation to the launch.    Not one rocket but multiple rockets, all of these things require rethinking safety.

Personally I'd rather see a roll back of what is being attempted here.   The goal is to get scouts involved to have fun and learn a bit.    That can be done via a build of ones own launch controller.    Why there is a need to do a multiple rocket launch controlled electronically is beyond me.

   FWIW If I were the BSA I would never allow you to use a home designed and built launch controller in any of my events regardless of the bells and whistles that it includes, PERIOD!

   Everything benefit that you have named could be accomplished on a traditional style launch controller controlled by manual switches and not controlled by some kind of uProcessor.

  "length of control cables can be sourced as cheap commodities at Walmart, BestBuy, wherever."

  If you insist on a controller like this then go buy one of the commercially built firing boxes that are made for use in pyrotechnics (i.e. Fireworks) shows. They have the ability to synchronize to music and other external events and are designed to handle up to thousands of firing circuits.

   Designing a launch system, particularly one that is intended to control multiple simultaneous launches, to use cheap Walmart-grade components is the worst idea that I've heard so far today!

Seems a bit hyperbolic I think. We're talking about model rockets weighing a few tens of grams here, not armed ballistic missiles or sticks of dynamite. It's important to be safe, but you don't need to go overboard. I remember the official Estes launch controller I had when I was a kid and it was nothing more than a cheap molded plastic housing with a leaf switch pushbutton molded into it, the "key" was a metal wire that when poked into a hole, bridged a pair of contacts. A small incandescent lamp wired across the button served to indicate the system was armed and had a complete circuit. Some of us didn't even have the proper launch controller and we got by using a bundle of cheap speaker wire and just touched the ends to the terminals of a 6V lantern battery to launch the rocket. All this talk about mil spec switches and aircraft relays, come on, the official systems that have been around for decades are built like cheap kids toys, they *are* cheap kids toys. As long as people are following reasonably safe practices, an uncommanded launch is more of a "whoops!" event, not "OMG call 911 and bring in the FAA accident investigation team and the ATF!". Let's keep things in perspective here.

Actually you are underplaying the risks in these "toys".    Toys in quotes because they are in every sense real rockets and thus have all the risks associated with rockets.    Maybe on a much smaller scale but a burn from a model rocket can still send you to a hospital and even a accidental collision with a model rocket can cause injury.

It is sort of like flying model helicopters.    They can be perfectly fun but fly those rotor blades into your neck and you are dead.

In either case though the big factor here is that the BSA is an organization and is the constant target of lawyers and parents that are overly protective of their children.    Believe me there are parents that are just waiting for a reason to bring a law suit against the BSA.    They will do that for just about any reason even if the only impact on their children was a scare from an accident.

Now I can't say I agree with this mind set, I think it is fair to say my parents where the opposite of overly protective.   If you where bleeding you learned to patch your self up and if sprained you walked it off.

[wizard69]

If you have these contacts; I'd work with the NAR and BSA to create a standardized and tested solution for all Boy Scout locations.   Get the design reviewed by qualified engineers and maybe even industry functionaries (such as Estes) that can point out any short comings that may exist.   If there must be programmable devices in the hardware have somebody familiar with safety systems design it and program it.

I'd even consider trying to get industry involvement in the launch controller.   There are still industries that will be willing to support the BSA and it never hurts to ask.    In that regard you might be able to get some donations of either hardware or code.   It would be nice to have everything implemented on a safety PLC for control logic and the rest mounted in a well laid out industrial panel.   Again the goal is to have something that can spur the interest in scouts.   In the end there are as many or more jobs in automation available to scouts as there are jobs in aerospace and frankly right now there is a shortage of engineers and technicians in industry.    So you might find an industry leader that wants to spur interest in youngsters.

By the way, part of the reason I'm concerned about software is that if one doesn't have the right background, programming can introduce faults that might not be easy to find and stay dormant for years.   Just yesterday at work I had a machine dong very strange things due to a combination of hardware and software that was not seen in the prior 10 years.   

As I have alluded to above, this will be well-reviewed before accepted into camp use.  BSA insurance covers us as long as we stay within guidance.  For Rocketry, BSA defers to NAR for guidance.  I have already opened discussions with the local NAR chapter, and reviewed their local equipment.  They use a custom control system built somewhat similar to my proposals: from custom PCB (although not Arduino), commodity cables (CatX & AC extension cords), car battery, and high-power relays (automotive).   So our liability should be covered by the same as how we have climbing tower, pool, etc inspected by authorities in their fields.

I would hope that this might become a prototype for others to use, across BSA and elsewhere.  (Same as how our local COPE & Climbing Standard Operating Procedures are good enough that they are studied, referenced, and spread by the larger BSA.)

[james_s]

Actually you are underplaying the risks in these "toys".    Toys in quotes because they are in every sense real rockets and thus have all the risks associated with rockets.    Maybe on a much smaller scale but a burn from a model rocket can still send you to a hospital and even a accidental collision with a model rocket can cause injury.

It is sort of like flying model helicopters.    They can be perfectly fun but fly those rotor blades into your neck and you are dead.

In either case though the big factor here is that the BSA is an organization and is the constant target of lawyers and parents that are overly protective of their children.    Believe me there are parents that are just waiting for a reason to bring a law suit against the BSA.    They will do that for just about any reason even if the only impact on their children was a scare from an accident.

Now I can't say I agree with this mind set, I think it is fair to say my parents where the opposite of overly protective.   If you where bleeding you learned to patch your self up and if sprained you walked it off.

I disagree. I was into model rockets for several years up until I was around 15, it was something young kids did, mostly with little supervision. When I was in 7th grade my middleschool had a "airsports" elective and the class projects were a model rocket and a rubber band powered balsa/tissue airplane. We built them in class and then had a launch day where we shot them off from the parking lot and collected them from the athletic field, mind you this was while physical education classes were simultaneously using the field. In the ~20 years that class ran before the teacher retired I don't think there was ever an injury, we were all taught basic safety and nobody got near rockets that were on the launchers ready to go, it wouldn't have mattered much at all if one had launched inadvertently. It just isn't that big of a deal, sure it's possible to get hurt by one, but far more kids were hurt playing sports and nobody is advocating mil spec body armor to play soccer or lacrosse.

[LydaRA]

If you didn't take away from what I said above, we agree: safety trumps all on the range.

So which is more safe: trying to account for SIXTEEN loose launch keys, or ONE Master key? 

I am human, and _have_ had to halt movement to the field, when I realized I had missed collecting a key.  With the RSO being at the table, no one could have inserted that key.  But it was a breach, and safety modelling _required_ we immediately halt and reset.  That was with just ten separate keys.  And any RSO will still be human, so still subject to mistakes.

Thus I have _zero_ interest in expanding the number of individual loose keys & controllers to keep up with.  It just increases the odds of failure.  But in my proposed system, just as in the U.S. nuclear missile systems, there are TWO removable keys in the hands of TWO different people for any launch!  I "only" have to remove the RSO's Master Arm key to safe the entire range--each and EVERY rocket at once.

And if I forgot to remove the RSO's key, what are the chances an excited child--eager to control their own launch--would forget to remove their key?  First consider that ZERO launch keys are handed out until AFTER the first round of rockets are completely wired up--and EVERYONE has left the range!  The keys are in the ammo can with the engines--at the pads...  So appreciable risk does not occur until correcting first-round misfires or wiring up for the second round. 

We could even make the ammo can require the _same_ key as the RSO's Master Arm!  So one could not pull out the engines for the misfire or second round, without _first_ removing the key from the RSO's Box!

MUCH better than relying upon a bunch of loose OEM "keys."  Let's get real, the OEM keys are just metal pins.  When we have broken/lost one, we made replacements by bending simple landscaping pins!  So imagine how "secure" it really is, when so many children have metal picks in their pocketknives...  Do you understand why we always keep a responsible adult at the table to oversee the controllers--even after we collect the "keys???"

Better safety _CAN_ be built into even a "more complex" system!
 

[LydaRA]

Trying to learn KiCAD....still rough, but getting better. Finally enough drafted to share (and drown in the red ink as you all mark it up)... Thanks in advance for constructive criticism!

Showing just two of eight independent parallel igniter sub-circuits. And considering variations....DPDT vs. SPDT....Arduino source current for continuity measurements vs. dedicated constant current source....building driver/relay sub-circuits vs. buying an 8x driver/relay board...

Obviously just focused on the pre-launch continuity tests and one the launch signal handling. There _ARE_ _MULTIPLE_ power discos, removable keys, momentary "deadman" switches, and program logic safety measures as well!