Airframe Prototype Update

This semester we Mechanical Engineering students had to do a few Critical Function Prototypes, which would help us analyze critical components of the rocket and ensure they worked properly.  The airframe did a little write up of their prototype which looked at the rocket separation.  Here's what they wrote:

Prototype model red is the rest of the airframe, blue is the parachute bay and black is the black powder charge the shear screws can be seen at the tops and bottoms of the drawing

The section separation for parachute deployment is likely the most critical function for safe recovery of the rocket after it has been launched.  To verify the reliability of the separation design a scaled portion of the rocket was made to test the separation method.  The separation design used fastens the two sections together with three small shear screws which are broken when a black powder charge inside of the connection ignites and explodes the two sections apart.  

Prototype of the connection between the motor and the rest of the airframe

The connection after the charge was set off

We calculated that about 6 grams of black powder would be required to shear the screws.  We incorporated a safety factor of 1.5 to ensure that there would be a large enough explosion to separate the sections, so we loaded the test section with 9.5 grams of black powder.  We tested the separation 4 different times, and each time everything functioned perfectly.  One lesson learned is that a smaller safety factor may be used for the amount of black powder because when the videos frames are slowed we observed that the sections separated with excessive force.  

Another critical lesson learned is that little to no debris from the black powder charge will escape into the avionics bay.  This was another critical part of the test because debris or soot in the avionics bay could damage the electronics systems.

Prototype parachute bay after detonation test, very little debris in the chamber

The airframe and avionics teams on the day of the test