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Filed under: Project-archive — mgrusin at 3:38 pm on Wednesday, September 23, 2009

SPARTAN was an R&D project from Sierra-Nevada Corporation for a tactical military UAV system.  I assisted with several aspects of this project, including design of the onboard power system, flight termination, and problem solving.

  • Power system

A versatile power system was developed all the way from requirements to I&T, which could run the aircraft off either the ultra-fast rotational output of the ducted-fan engine, or in the event of engine failure, on backup batteries.  The system provided regulation and on-off control for payload and critical flight systems.  A bank of status LEDs indicated which power source was in use, and whether all voltages were within acceptable limits.   This system was even adaptable to a customer request to use the generator as a motor to start the ducted-fan engine.

  • Flight termination

Per requirement, flight termination features were built into the power system.  Several channels of servo control signals generated by the power system microcontroller were used to cut off fuel flow to the engine, and release a recovery parachute.  Termination could be initiated by the main avionics system (via either autonomous or direct command), or by a completely separate radio system using a coded signal (the iconic “big red button”).  Logic was built into the system to reduce the possibility of inadvertent activation, while ensuring that the intended signals were promptly applied.

  • Problem solving

In addition to designing an effective RF and DC power-grounding architecture for the aircraft, several black boxes were built to solve issues that were preventing effective flight testing.  These boxes allowed standard radio-control systems to interface with various parts of the aircraft and test fixtures.  At the core of these boxes were microcontrollers programmed to input, process, and regenerate servo actuator signals in real-time.  These signal translators solved several difficult problems in an inexpensive and elegant way.

As these were flight-critical systems, considerable care was given to circuit and code correctness, reliability and speed.  Particularly gratifying was the fact that the onboard power system, based on a four-layer PCB and fine-pitch surface-mounted parts, worked perfectly the first time it was assembled.

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