2 Stage Model Rocket feasibility

Hi, I'm an beginneer with Arduino. I've had one for a few months now (having asked for a arduino uno for my birthday) and know the basic layout of its functions an how various sketches work and so forth. An aspiring Aerospace engineer I have been thinking about building a 2 stage model rocket with a ardunio as the timer for second stage engines. I have already experimented with a relay circuit to power the second stage ignitors (using the 5 volt pin, and a digital pin) and it has allowed me to channel the necessary power to light the ignitors, as th ardunio cannot put out enough power to do so (why I am using a relay). So before I start attempting to spend money on parts and so forth I would like any feedback that could help me make this easier, simpler, or maybe if this is even remotely possible. My electronics knowledge is moderate at best. So if I don't understand something you say please bear with me.

Thanks, (also this is my first post on the forums)

The main problem as I see it is getting the current source needed for the ignitor up along side the arduino. Controlling that source is no problem and you can use FETs in place of a relay to make the control lighter. Are we talking about the model rocket motors here that take quite a bit of current for the igniter?

Yes, the ignitors are for estes model rocket engines. They require quite a lot of current. In the ranks of about 4 AA batterys alone to ignite. not including the power source for the ardunio. So yeah, i have serious power issues :disappointed_relieved:

Also, how would i use a FET to accomplish the same feat as the relay?

You need what is known as a logic level n-channel FET, connect the source to ground, the gate through a 100 ohm resistor to the arduino output pin and the drain to your load. Connect the other end of the load to the positive of your power supply and connect the negative of the supply to ground. As simple as that.

Okay, i think i understand that. thank you. But still theres a power issue. would it be viable to go online and look up maybe LiPo batteries or something to that extent?

Yes or look for a lower current ignitor, when I was a kid I used flash light bulbs that I crushed in a vice to get at the filament.

Hm, i have some flash bulbs of similar characteristics. could i use those? what kind of amps would be needed vs the standard ignitors?

Typically they take 300mA, but they are much more fragile than the standard ignitor so I put some home made gunpowder round them.

http://www.amainhobbies.com/product_info.php/cPath/1683_1686/products_id/59816/n/Quest-Q2G2-Rocket-Motor-Igniter-Pack-6?utm_source=Google-Base&utm_medium=cpc&utm_campaign=Product-Feeds&source=google_ext

So would these work? they seem to have a very low current requirment

I've lit 2 of those Quest ignitors, in a 2 cluster configuration (A6-4), with 4 AA batts.

Please keep us posted on your progress as I've been thinking about doing a similar project.

I'm not sure what your timer needs to do, but if it's just doing something after a delay (or doing several things after several delays) you might find it's easier and more reliable to use plain old NE555 timers and a transister to trigger whatever you want to trigger. I suspect that a rocket will be a fairly hostile environment for a microprocessor and the normal boards aren't ruggedised so I don't know how well they'd cope with that. Perhaps the SMD ones would stand up to it better. In any case it's overkill for what you're trying to do.

I know beggar all about rockets, but I'd have expected the second stage to be triggered by the first stage separating, and I'd expect that to be triggered somehow by the expiry of the first stage. Doing it based on a timer somehow doesn't feel like a good way to synchronise the handover to the next stage.

I agree with PeterH; a separation charge can ignite the second stage. We used to build (illegally!) multi stage rockets out of ordinary firework rockets, filling the nozzle of the upper stage with loose fine black powder with very thin tape to hold it in place. The top of the lower stage was similarly doctored. Got some quite impressive results, with no soldering required. :-)

Don't try this at home kids. Go to your friend's home.

I don't know about you but I cannot afford to kill my arduino. Since you just got it for your your birthday I guess you are going to try try not to blow it up, so how are you going to protect and recover it?

What is are your targets for payload and altitude, and what will the maximum g force be?

I don't imagine any well-built Arduino would be troubled by the sort of accelerations likely to be encountered by amateur rockets, assuming all connections are soldered.

AWOL: [sic] Don't try this at home kids. Go to your friend's home.

LOL great idea AWOL, this WILL have to go to every sketch of mine... :D

Cheers,

I don't imagine any well-built Arduino would be troubled by the sort of accelerations likely to be encountered by amateur rockets, assuming all connections are soldered.

saulton7 seems to know what he is about but he also has budget considerations. My rocket attempts were all pretty terminal affairs, with people suggesting home made gunpowder I guess they have had similar experiences. ]:) I would be concerned not so much about about the board itself but how it was mounted, whether or not it would short and if/how it was protected from engine failure.

Arduinos fly in rockets just fine. Yesterday I sent my 4" 10lb Patriot up to 2500' on a J440. It was a bit windy, so I used a smaller motor than I'd originally planned. In the nose was a serial arduino with a radioshield connected to a Garmin GPS18 and a ham radio for tracking. That particular rig not only survived that, but several previous flights to higher altitudes (5000+ ft), including one where the main failed to deploy and it hit the ground (salt, actually, at the Bonneville salt flats) at 50+MPH. That impact bent some pins on the shield because the bulkhead broke loose and tried to go out the side of the nosecone, but it was otherwise undamaged.

Relays are not a good idea in a rocket, as G forces and vibrations beyond a typical relay's ratings may be encountered. Use something solid state, such as a FET like grumpy_mike described.

If the circuit will be anywhere that it can cause the flight to fail unsafely (e.g. fail to deploy a chute because the second stage motor didn't ignite), don't do it.

A pair of CR123A batteries are smaller and provide much more current than four AAs, while providing the same voltage.

If you change igniters, make sure they're compatible with your motor.

but I'd have expected the second stage to be triggered by the first stage separating, and I'd expect that to be triggered somehow by the expiry of the first stage.

That's how it happens on model (e.g. Estes sized) rockets. A special first stage motor burns through the top and lights the next stage.

Doing it based on a timer somehow doesn't feel like a good way to synchronise the handover to the next stage.

Works for NASA - that's how they stage their multi-stage sounding rockets (and deploy payloads, parachutes, etc). High power rocketry also uses timers for staging. As a matter of fact, I just bought a couple of commercial units. Haven't even used one yet, and I'm already planning to make my own, probably arduino-compatible. :)

-j

Hi, Many people use Arduino Pro Mini (which can fit inside a ping-pong ball) for balloon and rocket work;

http://arduino-direct.com/sunshop/index.php?l=product_detail&p=107

Estes ignitors, "electric matches" and EB Caps (Electric Blasting Caps) are made with low-resistance high-current ignitor wires for safety. In this case, with care, the Flashlight Bulb Filament igniter may (with great care) be suitable. It is the favorite of the CellPhoneTerrorist group... Sigh...

Google is your friend; see what others are doing...

DISCLAIMER: Mentioned stuff from my own shop...

I planned on putting the Arduino and other circuits in the nose cone of the rocket, also i have solved the low current ignitor issue, as i found these http://www.amainhobbies.com/product_info.php/cPath/1683_1686/products_id/59816/n/Quest-Q2G2-Rocket-Motor-Igniter-Pack-6?utm_source=Google-Base&utm_medium=cpc&utm_campaign=Product-Feeds&source=google_ext

they should be able to be fired by a couple of digital pins wired together (about 4 i think)

If it were my time and money, I 'd look at what others are using for similar size/design rockets. Unless the rocket is of unusually large size, I can't see the improvement over a very small and simple piece of timed fuse.