Doongara – the next generation of thermal line cutters.

Smith and Williamson, the Oregon based tech company who developed the Boomerang controllable balloon valve, are now marketing their next product, the Doongara thermal line cutter. We first covered ‘off the shelf’ thermal line cutters for balloons in 2014 with the modified Zlog 7 from Hexpert. This was based on the original Zlog 7 gps data logger with a relay activating a nichrome wire thermal cutter. The device was effective but large and clunky; requiring two 9v batteries. One 9v battery for the gps data logger and the other for the line cutter. Given it’s weight and size though, it was hard to place close to the balloon line above the parachute. Doongara overcomes the issue of size and weight by relying on a barometric pressure sensor, thus requiring only a single AA cell for power. It also comes with a unique set of nylon cord to simplify the cut down process.

Here is some more information about Doongara from the Smith and Williamson web site:

Doongara is powered from a single AA battery and cuts line based off of user-programmable settings: elapsed time, barometric pressure, and/or rate of pressure change. Features include:

Tandem Demo
Small Tandem Balloon
  • Integrated sensors with on-board data storage:
    • Barometric Pressure, Temperature
  • Redundant burn-wires
  • Battery heater
  • Duration >3 hrs
  • Light-weight at less than 40g, including battery

Single Doongara Applications:

  • Single DoongaraCut-away “tow” balloon for Constant Rate Descending Flights
  • Drop a sonde or ballast during flight
  • Terminate a conventional flight at a specific pressure altitude
  • Separate from balloon remnant after burst

Tandem Doongara Applications:

  • Tandem DoongaraCut-away “tow” balloons and terminate for Level Horizontal Flights
  • Cut-away “tow” balloons and terminate for Stepped Vertical Flights



Smith and Williamson have been kind enough to give us a Doongara to test fly. So we will be using it to drop a simple secondary payload from a primary payload. We will also attempt a tandem flight using the Doongara to separate the tow balloon.


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