DIY radio control for rocket

[bearcreek]

What do I need to attach to my radio to ignite a rocket attached to my plane while flying? Could I use a servo relay wired to a standard Estes ignitor?

[BushmanLA]

What do I need to attach to my radio to ignite a rocket attached to my plane while flying? Could I use a servo relay wired to a standard Estes ignitor?


You will put your eye out kid!!




That being said, the way I did it was to use a small microcontroller to watch for the appropriate PWM signal from the receiver and then activate a relay that connects the estes igniter to a 9V battery.

Here is some info on how I did it for the XPort, I have one setup for regular receivers but haven't posted any info on the web for it yet.

http://www.pasqualy.com/xport/

[bearcreek]

cool plane! Do your missiles fly straight in the horizontal direction when mounted under the wing? I was thinking it may be better to add a stabilizer to the rocket to improve horizontal launch.

[Malc C]

I remember some discussion on this subject many years ago when someone showed a video of some rockets being fired from a Piccolo indoor model helicopter ! The concept was the same as bushman, using a PIC to act as an RC switch to turn on the ignitor.

The rockets never flew straight, the recoil nearly always took the Piccolo out - but it looked like fun :) With a larger heli the recoil could be absorbed and it would provide a more stable platform. (wasn't there a video on Youtube of some guys firing a shotgun from a 60 sized heli ?? )

However, there was some discussion on the Ikarus form as to the laws in different countries regarding launching live rockets from model aircraft, which if I remember lead to some heated discussion.

[bearcreek]

Yeah, I can imagine how much recoil that would be. One interesting aspect of a rocket is that it does not push directly against the airplane, but of course the propellant may interfere with the flow of air around the plane.

[BushmanLA]

There is essentially no recoil because the thrust of the rocket is not pushing against the aircraft since the launch rail is slung under the wing.

The launch rail is only about 5 inches long compared to the normal 3 feet or so that you would use when launching from the ground. This length is required for the rocket to build up enough airspeed for the fins to keep it stable.

If the aircraft is already moving 20 or 30 miles per hour the rocket has enough air speed to stay fairly straight even off a short 5 inch rail.


Here is my first setup on the underpowered aircraft.
http://www.pasqualy.com/XPort/100_3730sml.jpg

an outbound rocket..
http://www.pasqualy.com/XPort/rocket00.jpg


Here is the new rail on my glow trainer, I haven't had a chance to try it out yet though...
http://www.pasqualy.com/FPV/100_0573sml.jpg

[BushmanLA]

Oh yeah, these are the rockets I'm using.
http://www.estesrockets.com/products.php?number=1888

You can find them in a 2 pack for about 7 dollars if you don't buy the kit that comes with the launch pad etc.

They are just the right size, and no assembly required other than mounting the motor.

[Brandano]

simple but hackish way, if you can afford the weight? Attach a servo to a rotary switch.

[jeffs555]

Why not just use an ESC for a brushed motor?

[bearcreek]

That second picture from your video camera looks really nice. Like a space shuttle launch.

[BushmanLA]

Why not just use an ESC for a brushed motor?


Would probably work just fine, just make sure you have lots of dead band in the middle so you aren't leaking current through the igniter. Also make sure the ESC can handle the draw that the typical rocket igniter requires.

[Brandano]

Why not just use an ESC for a brushed motor?
Because with switches you can pretty much ignore current issues, and can arrange for firing more than one rocket on a single channel. With a rotary switch you can wire some 10 or so, depending on the switch layout... would make for some great FFAR runs :)

[mjsas]

I used a simple 15 Amp FET to fire automotive air bags. I would think an air bag has about the same size igniter as a rocket. This was controlled by a DIY radio system made from a cordless phone.