Just wanted to share some of the work we have been doing with with LaunchPoint Technologies on their hybrid-electric DJI S1000. They developed the genset using their advanced Dual Halbach Array generator and a custom-designed rectifier/controller. This controller also allows the generator to start the engine remotely via a switch on the transmitter. The genset maintains a nominal 6S voltage and provides enough power for hover while the downsized battery absorbs the power spikes of climb and sporty maneuvers. The battery also allows the vehicle to fly quietly on electric power only for several minutes.
We have been supporting their effort by converting the S1000 to fly with on a Pixhawk controller (AC 3.4), setting up the control channels, tuning, etc. In addition, we are doing some custom Arducopter coding to communicate with the genset over CAN bus. The genset controller sends genset status (cell voltages, temperatures, engine RPM, fuel quantity, etc.) over CAN bus which can be read by the Pixhawk and sent over telemetry to the GCS. Starting and stopping the engine in flight will also be over CAN bus (currently using PWM RC passthru). This community has been very helpful in this endeavor.
Why gas? On a per mass basis, gasoline contains about 240 times more energy than a LiPo battery. Accounting for the energy conversion losses (more losses with the genset than all-electric), gasoline contains about 12 times more usable energy than batteries. And finally, accounting for extra mass of the genset components, this results in about 3-5 times longer flight times. For the S1000, that means we can expect flight times of 45-75 minutes. As we further optimize the system and reduce mass, we will likely see over 2 hours.
Here is a video of the maiden flight from last week. The integration of the system onto the S1000 hasn’t been perfected yet, we are just working on the proof of concept at the moment. We flew without a payload, but there is weight margin to carry one.
This work is being funded under a NASA SBIR contract.