SLU Physics - Thrust of Estes Model Rocket Engines

Thrust of Estes Model Rocket Engines
Carrie McTague

Abstract:

Two methods were used in this project to measure the thrust of model rocket engines. The first method used Estes A8-3 engines to launch a model rocket. The distance traveled by the launch rocket was recorded using a Pasco Smart Pulley, a Computer Base Laboratory, and a TI-85 calculator. The velocity and acceleration were calculated from the distance data and an average and maximum acceleration were determined. Using the average acceleration the average thrust of the A8-3 engine was calculated to be between 4.6N and 6.2N. While Estes records a value of 7.70N for the average thrust of the A8-3 engines, giving a percent difference of 20% - 50%. The second method of measuring model rocket engines involved the firing of Estes 1/2A6-2 and A8-3 engines onto a strain gauge interfaced with an oscilloscope. The oscilloscope displayed a voltage verses time graph which was calibrated to measure thrust as a function of time. From the results of the strain gauge maximum thrust and total impulse could be calculated. The maximum thrust for the 1/2A6-2 engine was calculated to be 13.95±3.0N, 14.26±3.4N, and 15.04±3.4N, where Estes records a value of 8.5N, giving a percent difference of approximately 50%. The maximum thrust of the A8-3 engine was calculated to be 14.88±3.5N, 21.7±4.8N and 21.45±4.9N, where Estes records a value of 13N, giving a percent difference of 14% and 50%. The total impulse of the 1/2A6-2 engines was calculated to be 1.35±0.013N•s, 1.52±0.015 N•s and 1.55±0.015 N•s, where Estes records a value of 1.25 giving a percent difference of 8% and 20%. The total impulse of the A8-3 engine was calculated to be 2.57±0.024 N•s, where Estes records a value of 2.5 N•s, giving a percent difference of 3%. Little consistency was observed between the results from this lab and Estes. However, a consistency among engines, especially those from the same packaging, were observed.

For more information, contact Dr. Catherine Jahncke:

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