Radio Tag Launch Systems

For the missile to radio tag Nessie:

We initially had the idea of having a thruster powered torpedo within a cylinder shell with the tag (glow stick). This would carry the tag to Nessie across the ten feet distance easily. Do to my lack of experience with how to seal a water proof a rotating shaft we decided to go with a water proofed pump motor from the ROV In A Box kit. All we would have to do is seal the batteries, a relay, whatever switches to release and turn on the motor in side a waterproof container, and take care of the tag with a magnet.

While building the housing it became apparent that it was going to be very difficult to mount the motor to the 1.5 inch PVC without a 2.5 inch diameter pipe to couple with. There are no PVC pipes in that diameter and it would take several days to special order some from the local plastic shops. What worked very nicely is actually a soup can. Creme of Mushroom soup can. It has a diameter a little larger then 2.5 but it is the inner lip found on the top of all cans made this such a perfect mount for the motor. The lip on the can met perfectly with a lip on the motor thus preventing the motor from shooting out of it's hold. A simple hose clamp kept the can with the PVC housing for the electronics and from here all that is left is the radio tag holder. I tried to make this holder out of an old 2 liter soda bottle, but it was too short to hold the 6 inch tag, magnet, and mount to the PVC and I was NOT going to drink all that soda again! At this point the design was getting complicated and annoying. We would need multiple switches to release the missile, turn on the motor, and turn it off again. In addition, the weight buoyancy was going to be very difficult, so partway through the difficult building process, I looked at it and knew there had to be a better way and went back to the drawing board.

Rubber Band powered helicopters: requires 2 straws and a rubber band. Why not use the same technique for the underwater missile

We can wind the rubber band on the surface and use a simple switch to release towards Nessie in the water. No batteries, no waterproof housing, no heavy bulky motors; this is a much simpler design. We prototyped this and it worked so now we are perfecting the shape and buoyancy for a better journey to the mythical beast.

We threw our missile as hard as we could and it only went 3 feet in the water. It shape was so awful and non-hydrodynamic, there is no way it'll work. So going back to the design board we came up with a much more hydrodynamic design. We used Easter eggs to create a nice curve for the nose cone and the end of the missile. They actually work very well because they come in so many different sizes it is easy to find the perfect match. Though it is a little difficult to do find some Easter eggs in the middle of June.

Currently there is a piece of surgical tubing for the rubber band. We thought this would be better than a rubber band because it holds a larger amount of potential energy with fewer turns. We can only spin the Propellers eight times before it get difficult to hold back. However this also means that the missile will only have eight to ten turns for propulsion and they are all used up within the first two seconds of release. This will not work, not unless we have an incredibly awesome dynamic shape and weight. We are going to switch to a long rubber band that can contain more like 50 to 75 turns. That way we can have propulsion for the entire flight and not only during the first two seconds. Right now, the missile does not fly straight, and the weight is not well distributed. During it's flight, the missile spins erratically, detracting from its propulsive power. We are going to add fins to stabilize its flight and come back and test it.

List of things to do:

  • get a long rubber band and implement it
  • put on fins
  • distribute weight
  • test test test