Space Grant Consortium - University of Wisconsin - Green Bay

entire rocket assembly was too far forward. In order to compensate, weight was placed in
nosecone, around the threaded rod. This stabilized the fully assembled stack, but over-stabilized
the dart. In spite of this, the decision was made to fly in this configuration and the launch was a
success. However, the dart noticeably arced into the wind and considerable altitude was lost.
Nevertheless, the basic concept was proven to be viable: the booster-dart junction provided clean
separation and recovery devices deployed properly.
Version II: Drag Coefficient Test Flight Because of the overstability of “Green Bean,” the
drag coefficient of the rocket could not be determined from the Midwest Power flight. Version II
was built as a second attempt to gather data. This version focused on the drag coefficient of the
booster and dart while they remain in contact.
To get the data, the booster and dart from Green Bean were simply screwed together at the joint
between the two. Recovery devices were deployed with motor ejection only, and the flight
computer was used only for gathering data. The flight was technically a success because the
rocket was recovered with no damage. However, a spiraling flight path (caused by the dart’s
inability to rotate) rendered the data useless for the purposes of finding the drag coefficient.
Version III: 1.5-inch (38mm) Dart Following the drag coefficient test flight, it was decided that
we should attempt to fly with a smaller diameter dart. Due to the decreased cross sectional area,
a dart of this diameter was expected to gain about 1200 feet of altitude.
Similar in many respects to the 2.1-inch dart, the 1.5-inch dart included a number of changes and
improvements. The stability problem from Version I was corrected by re-evaluating the fin size.
The booster was also rebuilt and reduced in size to minimize its weight. The airframe was also
lengthened in order to provide the necessary volume to store a small parachute and the necessary
fire blanket and shock cord.
The booster was designed so that either dart (2.1-inch or 1.5-inch) could be flown
interchangeably. Changing darts only requires that the transition section be removed and the
alternative size of transition be riveted on.
Unfortunately, the test flight of this design was not successful. A major malfunction occurred at
approximately 500 feet, immediately following powered flight, and resulted in the loss of the
rocket. The cause of the failure was insufficient venting of the parachute chamber. As the dart
flew higher into the air, the pressure outside the rocket dropped while the pressure inside
remained constant. The pressure difference was sufficient to push the nosecone out of the
airframe, deploying the parachute. The parachute deployed while the rocket was moving at
maximum velocity and was immediately torn off. The damage to the dart was irreparable.
However, the booster was recovered in fair condition and both the fin can and transition were reuseable.
Despite this failure, it should be noted that the flight was aerodynamically stable even
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