This is a little experimental project that undertook, just for a bit of fun, to assess the feasibility of firing rockets from a moving RC airplane. Here is how I did it, just in case you are interested. As mentioned below, however, it is essential you understand the legal situation where you live before carrying out something in any way similar. Remember, stay safe, stay legal and have fun with what you make.
Step 1: Understanding What's Legal
On there own, both commercially available model rockets and Radio Control (RC) airplanes are perfectly legal in most places. However, putting them together is not looked on so favourably in most places. If you're in the USA, you cannot try this as it is outlawed by the FAA and AMA. This project was carried out in the United Kingdom where it is legal. Check out the UK CAA guidelines here: https://bmfa.org/Info/Know-the-law
Step 2: Making the Rockets
The rockets were built around 'C' motors bought locally from a model store. They're simply made from paper and foam board for the fins. They're very light and very powerful (and not explosive or harmful, if used responsibly). They also include a launch tube that fits around a guiding wire to ensure that the rocket takes off in a straight line. The igniters are electronically fired and are the ones that came with the rockets.
Step 3: Remote Firing
To make the rockets fire remotely, the initial idea was to have an electromechanical switch made from a servo and two contacting terminals that would complete a circuit which fires the rocket electronically. This would essentially allow me to fire a rocket remotely using a channel on my transmitter. Neat huh!
I built a proof-of-concept version the evening before the first tests. As you saw, if you checked out the video, the switch failed. I hadn't used an amp meter or any other device to test it. As a result, I had the disappointment and anticlimax of the rocket not going off when I told it too. Not to worry though! I'll go back over this and see if I can get it to work on a bench test using a small battery and a few resistors and LEDs or something. If this doesn't work, there are some independent remote switches you can buy, but I would be more comfortable using something that I can physically see when the terminals are disengaged!
Step 4: Ground Tests
The backup battery lead which connected the voltage straight into the electronic igniter did its job. This first launch (pictured below) saw the rocket impact the floor which affected its course. After it bounced back into the sky, the missile veered over and into the trees to the right in a fairly straight line. It's for this reason that I believe that the rockets are actually quite a stable design. A previous test that saw a fifth rocket launched vertically backs this up as that one was also very aerodynamically stable (and seriously quick).
Step 5: Conclusions of the Tests
In all, the results of the tests are fairly promising. The rockets fly well (unless they impact the floor or a bunch of trees) and can be launched from a rail underneath a plane such as this one above. However, as mentioned, I think I may downgrade them to being smaller motor sizes for the flight tests.
Thank you for reading! Article written by James Whomsley If you'd like to, subscribe to my YouTube channel, Project Air, for future videos of this nature.