Design of a Simple Mechatronic Device for Measuring Launch Velocity of Paper Stomp Rockets

Photo of Bryant Davis, Vanya Davydychev, Will Moore, Clyde Sheble Students: Bryant Davis, Vanya Davydychev, Will Moore, Clyde Sheble

Sponsor: The University of Texas at Austin

Date: Spring 2012

Requirements:
The velocity sensor must have errors less than ±5%, and preferably much lower. In addition, the sensor must be accurate for velocities up to 50 m/s, and the device must be durable enough to last over 1,000 launches, with a battery life of greater than 10 hours. Constraints on the solution require that the sensor not significantly alter the rocket's flight path or interfere with the distance the rocket travelsTo ensure affordability; the product should cost only a few tens of dollars.

Problem:
Paper stomp rocket launchers are used by kids at the Austin Children's Museum to demonstrate the concepts of projectile motion. In order to enhance the educational value of the device and to allow measurement-based experimentation, the team designed an inexpensive device that can accurately measure the initial launch velocity of the paper stomp rockets as they leave the launch apparatus.

Solution:
The sensor system developed by the design team consists of an ATMEGA microcontroller, an infrared light emitting LED, and an infrared detecting photodiode. The user is given instructions to make the rocket out of paper with a zebra pattern printed on it. The emitter shines on the body of the rocket as it passes, and the sensor sees an oscillating signal due to the different light-scattering properties of the zebra stripes. The microcontroller determines the frequency of this signal, and calculates the velocity, which is output to an LCD display. The sensor is mounted to the launch apparatus by embedding it in a PVC tube connected to the base of the launch apparatus and running parallel to the rocket's launch path.

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Photo related to Design of a Simple Mechatronic Device for Measuring Launch Velocity of Paper Stomp Rockets project
Photo related to Design of a Simple Mechatronic Device for Measuring Launch Velocity of Paper Stomp Rockets project
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