Model Rocket Drag Analysis using a Computerized Wind Tunnel

This NAR Research & Development report describes a series of experiments using a computerized
wind tunnel to determine the drag coefficients of typical model rocket designs. The main goal of
this report is to derive a practical list of drag coefficients to improve the usefulness of existing
altitude prediction software. To verify the accuracy of the data, the predicted altitudes are
compared to actual tracked altitudes for a sample of the models tested (TBD).
The drag measurements were made using a commercially available wind tunnel intended for
experimentation at the high school and undergraduate college level. The design of this equipment
is less sophisticated than a wind tunnel found at a research facility, but is more accurate than the
typical home-made device. As shown in this report, the wind tunnel is tested for accuracy and is
found to be sufficient for the purposes of this report.
Several model rockets were built for each of six series of tests to isolate the major effects on drag:
frontal area, finish, nose shape, body shape, fin cross-section, and launch lug. The resulting table
of drag coefficients represents most of the typical configurations, making it very useful in many
areas of model rocketry. Some applications are: optimizing parameters for maximum altitude in a
competition design; selecting an appropriate motor for the model and field size; and verifying
compliance within the limit of an FAA waiver.
The methods used in this report may prove useful in studying other research topics in the future.
Some of these ideas are discussed further in the last section.