Laser target-finding, self-reloading multi-shot rotary rocket launcher.
This side view of the rocket launcher reveals most of its key features. On top of all sits the feeder mechanism, which consists of a reservoir for up to five rockets and a feeding motor that delivers them into the launch bay.
The close-up shot of the feeder mechanism shows its functioning. Rockets get inserted at the yellow arrows, and sit in a vertical slot (first two missiles). Below is a cross-shaped assembly that rotates, grabbing one rocket at a time (third rocket) and placing it in the launch bay (fourth rocket).
The stepper motor (based on Robert Munafo's design) makes exactly one rotation with each impulse. The yellow bush gets pulled up by a rubber band. The motor gets turned on just enough time to make half a turn, then it's put in float mode, and the rubber band completes the turn. The red and green gears are 2:1 reduction stages. So, for each turn the motor makes, the blue cross-shaped assembly makes exactly 1/4th of a turn. The rockets fall between two of the cross's arms, so exactly one gets moved at a time. This ensures a precise movement without the need for control sensors.
The other main characteristic of the rocket launcher is its ability to locate targets autonomously. This is done using a custom-made laser sensor (original design by Philippe Hurbain), that returns an impulse when its laser light gets reflected directly back into its photocell. Using reflective targets and a rotating sensor, the target finding task is made easy.
These are the targets. They are covered with retroreflecting tape. This tape has the property of (unlike normal mirrors) reflecting any incoming light directly back to the source, in this case, the laser sensor. You can see this in the first picture, where the camera's flash gets bounced back just the same. The second picture shows the laser sensor's light. The black panels are just to make the targets slightly larger and therefore easier to hit, as the aim is not 100% exact.
The target finding task is accomplished using the Technic turntable at the bottom of the structure. It has a rotation sensor made out of a polarity switch (which short-circuits with each 1/4 turn, making it look like a touch sensor closing) to limit the sweeping range.
The original idea was to make the whole robot capable of tilting the launcher, allowing it to shoot down targets at variable distances. However, this brought numerous problems:
Last but not least, a video showing the rocket launcher in action. Click the link at the end of this page for a high-resolution version of the video (640x480).
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