Last year I launched a high altitude balloon to take near space pictures. You can see some here - Launch « I Can’t Believe it’s Not NASA

My wife is quite thrilled with my DIY space program

I’m in the process of building for my next flight and one of the pieces I would like to incorporate is a system that will drop my payload if needed and perhaps later on; be used to ignite a small rocket motor at altitude. The system needs to work at extreme temperatures (as low as -70c) and in a near vacuum)

It recently occurred to me that I might be able to use a light weight laser to do this!

For the next flight I was thinking of using one as the release mechanism if needed. The laser would simply point straight up at my balloon and pop it if required.

I have designed and built some simple circuitry that I can control from my gumstix computer and that will allow me to control a relay.

I’m looking for:
A laser that will be cheap; I might not get it back
Lightweight!
Powerful enough to pop a balloon and perhaps light off a small rocket motor.
A simple example circuit (it seems there are some prebuilt boards out there)
And any other general thoughts / suggestions recommendations

Thanks!

If you use a dark colored balloon you wouldn't even need all that much power. I would recommend using a blu-ray, since they tend to burn better than other colors of the same power output. I laser that would have plenty of power to do what you need and will will be cost effective is a 6X blu-ray diode. They run about $60 for the diode. That along with the module and driver would be about $80 on the high side. You can get them in either the buy/sell/trade or group buys section here on the forum.

For an example circuit, search the forum for "DDL driver" or "LM317 driver"..

Sounds like a cool idea. you've got some amazing pics on your site there!

6x Bluray + flexdrive + aixiz module

The balloon will be white. I've already got it.

You'll need a considerable amount of power to pop a thick white balloon, unless you color a part of it black and shine the laser there to pop it. You will need to focus just about any hobbyist laser to a point to reliably ignite rocket fuel. I would suspect it might be easier to use two lasers, one for each function.

is this like a hot air balloon ? or weather balloon ? if it is ur gonna need a powerful laser to burn a whole in the balloon

That's a really cool project...

Will a diode laser function well at those temperatures (-70c)?
I would suggest coloring part of the balloon black and using a >2W 808. They are cheap for the power and you can use simple and cheap driver circuits to run them.
I'm not sure 200mW of violet is enough to pop a thick balloon in those conditions.

If you do use a laser, I would suggest you put it in a decent heatsink and then insulate it from outside.

I'm not exactly sure how the balloon will act at -70 degrees... I don't think it will "pop" at those temperatures. I heard that the will freeze and then shatter.

--Hydro15

I'm pretty sure it won't take much to pop the balloon. The latex is so delicate and thin you can't touch it with your hands. You have to use gloves and a sheet on the ground to inflate the thing. Its a helium balloon. I don't think a hot air balloon will make it to 120K feet

It does shatter as you can see here -http://icbnn.files.wordpress.com/2009/01/left-img_1156.jpg

Is a laser from a DVD burner pretty much my best bet for high power and low cost? Maybe a link to a suggested diode for sale?

I think ive read "not" 100% sure but a balloon filled with helium is much harder to pop
that one filled with reg air from our lungs lol

Isn't a spike on a spring, or solenoid with a sharp tip a more effective solution? Laser diodes aren't rated to work at -70, and you may run into issues with focus or the coldness of the environment literally sinking heat away from the laser spot. You can get small pyrotechnic "caps" which are used on-stage, which detonate off a straightforward 12v signal, though they're only one-use. I suspect they'd be more reliable at this temperature and altitude, and I think you can get ones which don't require external oxygen. Another alternative is a big, thin coil of wire to act as a heating element and burn through the balloon, or light a det-cord for the rocket motor.

True i dont think you are going to get a laser to work at -70c

This ^^

If you're going to use a laser in those conditions you need to be VERY weary of condensation, at -70 ice and condensation may form on the laser diode rendering it useless.


EDIT: As suggested above, a solenoid or " caps " would be better.

I'd go with a small blasting cap, or a solenoid that requires less power to operate, along with an piece of high-resistance wire in the rocket fuel to ignite it. In a pinch, you could maybe go with the old trick of the 9V battery and a piece of steel wool, though separated by, say, a sheet of paper or something from the fragile balloon.

Good luck with your space program, and don't get shot down. A friend of mine did...

-70 how do you expect the laser to heat up the ballon enough to pop it? i would reccomend a servo motor and a needle and as for lighting a rocket motor in a near vacuum, you may have some combustion issues with no oxygen. For once i would not reccomend using a laser! blasphamy!haha

This is ridiculous. Are charlie and thunderbird the only sensible people here?

I'm just saying any laser module/diode/driver would be too expensive for a (potentially) one-shot application, like this one, especially when there are better ways to deal with the situation, from cheaper materials and equipment, even if it's not that professional, and looks MacGyvered. If it works, it's good, even if it's dirt cheap.

It seems to me that at the current juncture everyone is in agreement that an electro-mechanical means would be best. You have different ideas?

^ Electrical rocket/fireworks ignitors, indifferently if commercials or self-made ..... one sticked on the surface of the balloon, another in the rocket end (ofcourse )

more cheap, much more light, more effective in these conditions of operation.

^That's by far the best and simplest idea I've seen yet...

Damn yeah. I don't know anything about fireworks igniters, so it didn't even occur to me that he could use them too...

definately....thats your best choice....and they weigh almost nothing.

but don't they require a 12V battery to ignite? that would be pretty heavy. or there are other variants that make do with less...

This coldness will have big influence on battery.
It's important to choose special batteries.
Standard batteries freeze at about -20, -30.

i don't believe so, i had one when i was a kid, the toy rockets, and i think it jsut used a couple of AA batteries,

you can get the same effect by busting the top of a christmas tree light and filling it with gun powder....hook it up to a AA battery and it will ignite.