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Any ideas on staging for a 3 stage project?

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WDG

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I made a 2 stage rocket (4" Talon with home made 2-stage similar to how Wildman is doing his Eagle Claw 2-stage). I was pretty happy with how it worked, but I used a timer for second stage ignition. I like the timer in that it can easily light 3 e-matches off a single channel (and has 3 channels) and timing is virtually infinite (from .3 seconds to something like 2 days). It was also small, inexpensive and well built. However, setting the time portion is a pita. To do so you have to press and hold a momentary position button for the desired time. (I started to make a device using the output of another industrial timer in flicker mode to set it, but still have not finished that.) Besides being a pita to set, the timer has some built in problems. It initiates via a g-switch. So my set time has to equal to my booster (first motor) burn time and then coast time. Well, that whole +/- 20% burn time most commercial motor mfg's publish and hand setting the timer can be a little iffy. But it worked well on my 2 stage. Going to a 3 stage I certainly don't want to use a timer initiated at lift off to light the third stage - way too many variables in there.

One idea I had was to stick with the timer (but finish my device for accurately setting it). For the middle stage the timer initiated by the g-switch at lift off would light the second motor. I could use one of the other channels to power up the sustainer timer. So now I still have the same guessed timing thing for each stage but not compounded from second to third stage.

The other idea I have is to simply use a break wire-ish technique for the booster and sustainer. On my 2-stage I used a Molex connector with the barb removed for electrical connection between sections of the rocket. I am happy with how that worked. So I could have a 2 wire connector that pulls apart between booster and second stage. That connector would be providing "coil" voltage to a solid state relay that has Normally Open (NO) contacts going to the power supply to that igniter. So at separation NO becomes NC and poof. I would do the same thing between the second stage and the sustainer. The only delays I would have would be the time for the motors to come up to pressure.

A third idea would simply be a modification to the second idea. Instead of the break wires letting a set of relay contacts close to the igniter they would initiate a timer. Then I could add some delay. For second stage I don't really want to push it on the delay and am OK with no delay. But on the sustainer, that thing will be moving pretty quickly. I almost have to have some delay in there.

Now, besides the basics I just covered, I want to ensure safe operation. That means each altimeter must be able to do its thing regardless of the conditions. (I don't want the 2nd or 3rd stage to light while I am recovering the rocket.) I don't want any of them to light if the thing is not going vertically upward. I have thought about mercury switches. Has anyone used a mercury switch for a safety kill switch on something like this? If I used something like that I would have it power a latching relay to hold it in the desired (open to igniter) state. But what does a mercury switch do at high G acceleration? I'd hate to have a really hard hitting first stage and get nothing out of the next stages because the switches splashed at take off. Whatever I do, I will certainly need to do some safe, but in air testing. Maybe I will try a mercury switch and have it set to stop a clock or fire a smoke grain at apogee or something benign in another rocket.

BTW, right now I am not worried about redundancy of staging ignition. If it works it works. But if it doesn't work, I want all my chutes to come out, etc. So no one gets hurt and so I can try again. The first stage will not go supersonic, but the second and third stage will. So mach lock and what happens if a stage fails to light and the second and third altimeters are still in mach block mode is a big concern. I guess a way to get a little more time for an event in a failure mode is to have at least one redundant altimeter set with a very low main event. I have seen rockets coming in ballistically only to have the main pop out at a couple hundred feet before impact. I think as far as bad crashes go, that is worse than a straight in lawn dart (because now you have a rocket landing flat at 600 mph rather than straight in). As far as safety goes it just plain sucks. Remote emergency charges may be in order.

I may not respond right away to any comments, but I will certainly read any/all comments made. This is also a project that is mostly n the , "I wonder..." stage. Family, work and other things in life tend to limit my time available for rocketry.

Thanks,
 
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JDcluster

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highpowerrocket

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Having done a few 3-stage flights (1/4 scale Black Brant XI) I would like to emphasize a few safety tips: 1) The second stage and sustainer must have altimeter based recovery in the event those motors do not light, 2) Sustainer ignition must be based on a timer that uses a pull pin circuit to detect first stage separation before detecting second stage ignition (that starts the timing for sustainer ignition), 3) Finally, the rocket must be launched away from any people. The rocket projected flight path and recovery area must be in a clear zone. If the winds make this impossible then do not launch.

Of 5 Black Brant XI launches 2 suffered "anomalies". One was a CATO in one of two first stage motors (the onboard video is impressive). The other was a failure of the second stage motor to ignite. Here is a report on that flight:

http://www.spaceportrocketry.org/pdfs/Anatomy of a Successful Failure.pdf

A 3-stage flight is challenging but rewarding. Good luck.

http://home.roadrunner.com/~highpowerrocket/
 

Marsman

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Have you looked at the Parrot or Raven altimeters?
 

JDcluster

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The G-Wiz LCX & possible the HCX has the ability to ignite the second or third ( on or the other with the LCX) stage without getting confused. You will have to program it through your computer properly to get it to work. I've seen the ARTS units do this as well.




JD
 

WDG

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Having done a few 3-stage flights (1/4 scale Black Brant XI) I would like to emphasize a few safety tips: 1) The second stage and sustainer must have altimeter based recovery in the event those motors do not light, 2) Sustainer ignition must be based on a timer that uses a pull pin circuit to detect first stage separation before detecting second stage ignition (that starts the timing for sustainer ignition), 3) Finally, the rocket must be launched away from any people. The rocket projected flight path and recovery area must be in a clear zone. If the winds make this impossible then do not launch.

Of 5 Black Brant XI launches 2 suffered "anomalies". One was a CATO in one of two first stage motors (the onboard video is impressive). The other was a failure of the second stage motor to ignite. Here is a report on that flight:

http://www.spaceportrocketry.org/pdfs/Anatomy of a Successful Failure.pdf

A 3-stage flight is challenging but rewarding. Good luck.

http://home.roadrunner.com/~highpowerrocket/
Thanks for the good advice. One thing that I plan to do to ensure safety is to have all connectors between stages be unique. Before I get to the launch the wire harnesses will be in place and basically make it idiot proof to mix outputs.

I do plan to use drag separation at least on the first stage motor. That allows the booster to drop off as soon as it changes from providing thrust to drag. The sustainer will need to be secure enough to not separate at the same time.
 

WDG

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Have you looked at the Parrot or Raven altimeters?
The G-Wiz LCX & possible the HCX has the ability to ignite the second or third ( on or the other with the LCX) stage without getting confused. You will have to program it through your computer properly to get it to work. I've seen the ARTS units do this as well.




JD
I really want to keep the electronics simple and easy to use in the field. I am not saying anything bad about any product, but I have witnessed more than one person messing with programming the ARTS2 at the range. Also, once you remove its umbilical cord you just have to hope you did everything right. There is a pretty nice looking altimeter, the MARS A4 that seems pretty appealing. The other thing with being laptop dependent is that I have the chance to have dead batteries, forget needed cables, get sand, dirt, etc into the laptop. I know of one person who used the MARS altimeter at a launch and really liked it. I know one person's experience is not overwhelming proof of quality. In general, I like the approach of this unit. I definitely need to do more homework.

My biggest safety concern is preventing accidental ignition if something goes wrong and successful deployment of chutes in the event of a problem. For instance, let's say the booster works as planned, drag separation occurs - booster will coast a bit, then come down as planned. Let's say the second stage did not ignite. The altimeter in the second stage is set on mach lock to avoid bad things when that motor lights. The third stage doesn't light because there was no separation to close the ignition circuit. But what if I want it to separate for recovery? I don't want to throw out the laundry and then have a motor light (which I have seen before). The thing - still in mach lock coasts for a bit, arcs over and starts coming in hot. It has at least 2 deployment charges, 2 unburned motors (one with igniter in place) and both altimeters in mach lock. Hopefully safe distances prevent it from hitting anyone as it lawn darts. But now things go every which way. I don't want the 3rd stage motor - likely a K250 - to lawn shark. On my 2 stage I had mach lock set so that if the second stage didn't light it would still be in mach lock - so I simmed the the sustainer with no motor. It seemed that it would still be pretty high (but 4 or 5 seconds past apogee) by the time mach lock went off and it deployed. I was not totally comfortable with that but it seemed reasonably safe. With a 3 stage I do not want to leave anything to chance. If it works - great, but if it doesn't work, I don't want to hear the LCO screaming for everyone to run for cover. (I'd also like to be able to try again with the same rocket.)
 

Adrian A

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My biggest safety concern is preventing accidental ignition if something goes wrong and successful deployment of chutes in the event of a problem. For instance, let's say the booster works as planned, drag separation occurs - booster will coast a bit, then come down as planned. Let's say the second stage did not ignite. The altimeter in the second stage is set on mach lock to avoid bad things when that motor lights. The third stage doesn't light because there was no separation to close the ignition circuit. But what if I want it to separate for recovery? I don't want to throw out the laundry and then have a motor light (which I have seen before). The thing - still in mach lock coasts for a bit, arcs over and starts coming in hot. It has at least 2 deployment charges, 2 unburned motors (one with igniter in place) and both altimeters in mach lock. Hopefully safe distances prevent it from hitting anyone as it lawn darts. But now things go every which way. I don't want the 3rd stage motor - likely a K250 - to lawn shark. On my 2 stage I had mach lock set so that if the second stage didn't light it would still be in mach lock - so I simmed the the sustainer with no motor. It seemed that it would still be pretty high (but 4 or 5 seconds past apogee) by the time mach lock went off and it deployed. I was not totally comfortable with that but it seemed reasonably safe. With a 3 stage I do not want to leave anything to chance. If it works - great, but if it doesn't work, I don't want to hear the LCO screaming for everyone to run for cover. (I'd also like to be able to try again with the same rocket.)
I totally agree about being concerned about timer-only motor ignition. If something goes wrong with the flight, a simple timer will simply ignite your upper stage motor no matter which way it it is pointed, including the ground or the flight line. The Raven altimeter is designed for high-performance, multi-stage flights (as well as simple flights), and has 4 separately-programmable outputs. I used it in my my 3-stage 38mm attempt at BALLS this year. The deployment logic can be set up so that a motor ignition is inhibited until the rocket reaches a user-specified altitude prior to a user-specified time. That way you can be sure that the rocket is roughly on the planned trajectory before motor ignition occurs. You can set up other channels to deploy your recovery gear at apogee and at your main deployment altitude, regardless of whatever else happens with your flight.

I'm about to start flight testing on a firmware upgrade (rev 1.5) that has a new burnout counter capability that won't get fooled by short-duration thrust dropouts (including hybrid flights) or delta-V from separation charges.
 

JDcluster

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The ARTS is immune to Mach & doesn't need a lockout as do most of the Baro. only based altimeters. I'd most likely program mine the night before. If you try & do it at the field then it's already too late in the game ( in my book any how).
Things get way too hectic & that's where allot of things go wrong very quickly.

I also remember reading that if the G-Wiz detects apogee before the timer delay expires that it will fire the apogee charge & not the staging igniter(s).


JD
 

highpowerrocket

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Let's say the second stage did not ignite.
That's why a timer (for sustainer ignition) with a pull pin circuit will help. The timer will not begin to look for second stage ignition until after the first stage separates (pull pin event). If second stage ignition does not occur after the pull pin event then the timer will never activate and the sustainer motor will not ignite. If the second stage and sustainer have altimeters (that activated after liftoff) then all of the chutes will deploy.

Unfortunately MissileWorks no longer makes the PET2. You might look at the Xavien X-FiST if you want to try this method.
 

WDG

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I totally agree about being concerned about timer-only motor ignition. If something goes wrong with the flight, a simple timer will simply ignite your upper stage motor no matter which way it it is pointed, including the ground or the flight line. The Raven altimeter is designed for high-performance, multi-stage flights (as well as simple flights), and has 4 separately-programmable outputs. I used it in my my 3-stage 38mm attempt at BALLS this year. The deployment logic can be set up so that a motor ignition is inhibited until the rocket reaches a user-specified altitude prior to a user-specified time. That way you can be sure that the rocket is roughly on the planned trajectory before motor ignition occurs. You can set up other channels to deploy your recovery gear at apogee and at your main deployment altitude, regardless of whatever else happens with your flight.

I'm about to start flight testing on a firmware upgrade (rev 1.5) that has a new burnout counter capability that won't get fooled by short-duration thrust dropouts (including hybrid flights) or delta-V from separation charges.
I saw you out at Balls. Unfortunately I did not fly at that event - just came for moral support and to watch. (Oh yeah, I helped take apart a handful of motors and helped carry launch equipment around so I wasn't totally useless.)

I will check into the Raven. How user friendly is the Raven? The confidence in simplicity means a lot to me. The MARSA4 also has burnout detection and does not require any sort of mach locking. There certainly is a lot of cool stuff out now.
 

Adrian A

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I saw you out at Balls. Unfortunately I did not fly at that event - just came for moral support and to watch. (Oh yeah, I helped take apart a handful of motors and helped carry launch equipment around so I wasn't totally useless.)

I will check into the Raven. How user friendly is the Raven? The confidence in simplicity means a lot to me. The MARSA4 also has burnout detection and does not require any sort of mach locking. There certainly is a lot of cool stuff out now.
Dan, it was nice to meet you and thanks for your interest in the Raven.

The Raven's default settings lock out the baro-based deployments automatically based on the accelerometer-derived velocity, so you can just fly it right out of the box without every having to change anything. You can keep flying it and it automatically keeps the most recent 5 flights worth of data. When you hook it up to a computer, the Featherweight Interface Program is an easy-to-use application with nice graphs and an easy-to-use GUI for reviewing the flight data and modifying the deployment settings.

If something goes wrong in your flight, the Raven records a wealth of data available so you can figure out exactly what happened. The continuity of each deployment output is recorded throughout the flight, along with the deployment current and all of the logic that can be used for the deployment control. For example, I have lost continuity in flight due to a loose connection, and another time due to a broken wire, and both events showed up clearly.

Yes, there are quite a few altimeters out there. On the Raven page I have a comparison chart at the bottom that summarizes the full-featured altimeters I know of, including features, size, and list price. I thought I had the Mars4A on there also, but it looks like I need to add it.
 

WDG

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Dan, it was nice to meet you and thanks for your interest in the Raven.

The Raven's default settings lock out the baro-based deployments automatically based on the accelerometer-derived velocity, so you can just fly it right out of the box without every having to change anything. You can keep flying it and it automatically keeps the most recent 5 flights worth of data. When you hook it up to a computer, the Featherweight Interface Program is an easy-to-use application with nice graphs and an easy-to-use GUI for reviewing the flight data and modifying the deployment settings.

If something goes wrong in your flight, the Raven records a wealth of data available so you can figure out exactly what happened. The continuity of each deployment output is recorded throughout the flight, along with the deployment current and all of the logic that can be used for the deployment control. For example, I have lost continuity in flight due to a loose connection, and another time due to a broken wire, and both events showed up clearly.

Yes, there are quite a few altimeters out there. On the Raven page I have a comparison chart at the bottom that summarizes the full-featured altimeters I know of, including features, size, and list price. I thought I had the Mars4A on there also, but it looks like I need to add it.
Adrian, the Raven sounds extremely capable. I think I helped my friend Lou install one in one or more of his rockets. I like the USB hookup (not sure why everyone isn't doing that yet. (Same on PLCs - not sure why that isn't standard.) The comparison chart is very handy. One of the features I see on the Raven that attracted me to the timer I used is the full current output. I use low current e-matches and make igniters with the same, but it is nice to have the power there if I need it. The size, not to mention the price makes the Raven very attractive for the sustainer especially. For my 2 stage I just used motor ejection on the booster (which really limits my choices). Before I start on my 2 stage, I am doing some repair work on my 2 stage and building a 6" 3fin and nose cone rocket.

Thanks for all of your input.
 
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