The Effect Of The Drag Force
On A Model Rocket Flight
Stacey Marie Benson '00
 "Space Cadet" Benson |
Abstract:
In our previous studies of the height achieved by model rockets, we have found that our simple model used to predict the height is inadequate; the drag force must be taken into account. We present the results of a study of the thrust of Estes1 model rocket engines and the drag coefficient of model rockets. In order to accomplish this we have divided the study into two components. In the first part we determined the thrust and impulse of Estes model rocket engines. In the second part we determined the drag coefficient of the rocket and the thrust of the engine. Two types of rocket engines were tested: 1/2A–6 and A8–3. For the A8–3 engines the average trust was measured to be 3.00 ± 0.38 N, and for the 1/2A–6 the average thrust was measured to be 4.32 ± 0.38 N. These are well below the Estes' reported averages. However the measured impulses are in excellent agreement with Estes' published data. The measured A8–3 impulse is 2.36 ± 0.07 Ns as compared with Estes' data of 2.5 ± 0.25 Ns and the 1/2A–6 has a measured impulse of 1.24 ± 0.3 Ns as compared with Estes' prediction of 1.25 ± 0.125 Ns. The next step in the research process was to determine how the drag coefficient influences rocket flight. To accomplish this we digitized a videotape of the rocket trajectories for both types of engines. We developed a model describing the height of the rocket as a function of time that included the drag force of the air. We fit the mathematical model to the trajectory data and determined the average thrust of the launched rocket engines and the drag constant, k, to be 0.00131 kg/m. This value for k is three times higher than the expected values found in the literature. However, the thrust values obtained using this model fell within the 10% variance claimed by Estes.
1Estes is the leading manufacturer of model rocket engines.
For more information, contact Dr. Catherine Jahncke:
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| © | St. Lawrence University | Department of Physics |
| Revised: 25 Jun 03 | Canton, NY 13617 |