SpudFiles

Has anyone sucessfully launched a rocket out of a spud gun, then had it ignite/take off in mid air? I think I could wire up a photoresistor to an ignitor circuit so when the rocket leaves the barrel it would launch itself.

Another idea was to use an accelerometer/mercury switch but the first is to expensive and the second is dangerous if it breaks.

I got the idea from stinger missiles which use a small charge to launch the missile away from the operator before the main engine ignites. If you watch a stinger video you can see what I mean.



I am aware that incendiary ammo is against the rules, but this is not incendiary by nature. I intend on parachute recovery, and incendiary means being designed to start fire/use fire to damage. If this is too taboo then delete it, but I think it would look amazing if it could work.

This is a video I found that shows what he is talking about.
You will see the actual slow mo launch showing how it fires at the very end.
Mind the annoying music please. http://youtube.com/watch?v=WJBGV2nHf5U& ... ed&search=

Wouldn't the hot gasses ignite the motor on firing anyway?

Generally no. On lots of model rocket engines you need a flame of pretty high temperature to ignite them.

Alternatively, you could avoid the need for a combustion altogether and just ignite the rocket in a closed tube (though you might have to conjure up some flip-out fins, shouldn't be too difficult).

The Germans used this trick in WW2 with their Puppchen:



This basically took the rocket projectile from the panzerschreck (which was basically an open-ended tube) an put it in a barrel sealed at one end to generate more pressure behind the rocket and thus boost velocity and range.

You could also try using a two stage setup in which the first stage is the booster. Now what I mean by booster is you have a shell with one end closed off and then when the first rocket motor goes off the pressure will build & eventually break the seal sending the projectile flying. After a bit the second stage should go off sustaining the flight. Of coarse one must note that this could be dangerous!

And if you try your idea of the motor igniting after leaving the barrell, the rocket needs to be flying perfectly in the direction you want it to or it will light off and spin and go places where you prob dont want it to go.

Why dont you try a pneumatic launch then an electronic igniter? Just make sure it ignites in the tube on the way out

Just be careful, this is flirting with a DD.

Even though the act excludes, in essence, things designed for recreational use, they could still easily nail you.

Well it doesnt have an exploding device in it so the most damage it could do would be a fire or bodily damage, both overrated anyway.....

I am under the impression that it will have a parachute charge, which is explosive. There is also a limit of 4oz of fuels, etc.

Like I said, it can be inturprited as a legal device, or a DD, it just depends on who you are talking to.

True and I am sure a cop would shit his pants with you standing there with a combustion gun and rockets.

Im sure you could get a rocket to ignite, but personally I wouldnt want gunpowder residue crapping up my barrel/chamber

You wouldn't need a very complex accelerometer for the switch. (And you are right, a mercury switch would be a very bad idea, and wouldn't work anyway.)

A screw as one contact, a piece of tin can (something like a 1/4" x 1") as the other contact. A screw holding one end of the metal down and for connecting the wire. A screw+ bolt on the other end to give the tip some mass. Ta da! Accerometer that'll work great at the G forces of a typical spud gun.

BC Pneumatics wrote:I am under the impression that it will have a parachute charge, which is explosive. There is also a limit of 4oz of fuels, etc.

Like I said, it can be inturprited as a legal device, or a DD, it just depends on who you are talking to.

All true. It's just that if you go by the parachute charge being illegal then all rocket motors are illegal. Still I would be careful it is flirting with trouble!

Also my Idea with the two stage motors was just to eliminate the need for any complex ways of doing it.