All-electric multi-rotors have very limited duration when carrying heavy payloads. Fifteen minutes of flight time is typical as the payload approaches the mass of the aircraft. Several companies have developed serial hybrid (gas-electric) multirotor aircraft in order to extend flight time. This approach suffers from several drawbacks including low efficiency (~15%), poor flame-out redundancy, low power-to-weight ratio, and difficult payload integration due to the large on-board range extender. In response to these shortfalls we have developed a new type of multi-rotor which combines parallel and serial hybridization. The result is a much higher conversion efficiency compared to typical range extenders while retaining the ability to distribute propulsion. The system also has a much higher power-to-weight ratio as the powertrain mass is lower. Data from our proof-of-concept parallel hybrid indicate flight-time improvements of over 3X compared to serial hybrids, and 7X compared to all-electric. The unique characteristics of the parallel hybrid enable flight critical systems to be extremely reliable due to intrinsic redundancies.
There are many government and commercial applications for parallel hybrid technology. These range from wild-land firefighting, unmanned logistics for military support, ship-to-shore, agriculture, and urban air mobility applications. As UTM evolves and BVLOS UAS missions become commonplace, the need for high efficiency, high payload, long duration platforms will drastically expand. The initial target market for our technology is wild-land firefighting, where critical logistics gaps currently exist.
This proposal focuses on enhancing the reliability of our prototype aircraft by enabling seamless failover to electric propulsion and implementing a fuel injection system. These enhancements will prepare our technology for SBIR Phase II where we will optimize powertrain efficiency and bring our product to a beta test stage with our first customers.
Our technology matches well with the UTM project where loiter capability, long duration, and heavy payload mission profiles will be useful as UTM evolves. It is also a good fit for the Advanced Air Vehicles Program (AAVP) which explores fuel efficiency and intrinsic safety, both of which are key to Parallel Hybrid Multi-rotors. Finally, the Transformative Aeronautics Concepts Program (TACP) is also a good fit as our parallel hybridization design will be transformative in terms of power-to-weight ratio, hybrid efficiency, and reliability.
Non-NASA applications include extended flight time and increased carrying capacity of UASs for direct fire suppression, fire suppression support, search and rescue, disaster relief, unmanned logistic for military applications, commercial transport of goods, agriculture, long range inspection, off-shore logistics/inspection, and improved capabilities applicable to UAM such as hybrid air-ambulances.