Flight Termination Unit

We designed the FTU (Flight Termination Unit), pictured above, to comply with the FAA regulation that “An unmanned free balloon must be equipped with at least two payload cut down

systems or devices that operate independently of each other.”  Our tow cut down mechanisms include the balloon popping, and the FTU separating our payload from the balloon.

We decided to use a simplified FTU system in order to save time, allowing us to be prepared for launch window.  The FTU itself consists of a 9V battery, an Arduino, a relay, and a small length of nichrome wire.  To protect the FTU, we encased the battery, Arduino, and relay in a styrofoam block.  

Our FTU would work by using the delay function to set a timer, then setting a pin to high on the Arduino.  That pin led to the relay, opening a circuit from the 9V battery through the nichrome wire to ground.  The nichrome wire was wrapped around the line above the parachute and below the balloon.  Included below is a video demonstration of the FTU cutting through the same type of cord we used to secure the balloon to the payload.

Written by: David Juenemann