Relatively low energy density in batteries, 265Wh/kg.
Steady, though not indefinite, battery improvement, flexible configurations, mechanical simplicity, motor power density, combustion independence.
We may be only a decade away from economically competitive subsonic or supersonic electric passenger transport. Beyond breakeven, battery improvements allow continual improvements of range within the same airframe.
The existing situation
Numerous consumer and professional drones have been developed, adapted for racing, harassing cats, and as a video platform. Platform adaptation for policing or war shows haphazard development. Human transportation also shows development, though mostly in the "flying lawn chair" or "flying car" space, rather than as competition for the Pilatus PC-12 or Boeing 737.
The development timeline
Human rated commercial aviation technology has a timescale of around a decade, which is similar to the battery specific energy horizon.
Small scale drones can demonstrate and develop engineering expertise in high speed electric flight. Small scale is less efficient, so scaling up improves range. Uses exist in rapid delivery of cameras, packages, or drone capture nets.
Develop a series of innovative tabletop scale drones which develop the metric of maximum speed. Must run on rechargeable batteries. Produce a steady stream of documentation to spread ideas.
I built, flew, and fatally crashed a drone based on a carbon fiber and 3D printed frame. It was based very loosely on the Stigg 195 concept (https://www.catalystmachineworks.com/products/stig-6-fpv-racing-quad) which at the time held the speed record for small electric drones, at 137mph.
All new 3D printed design, 200mph speed goal. Also, crashing less =D.
Multicopter (154mph in May 2017): https://www.youtube.com/watch?v=HOAcHUmgffE&feature=youtu.be&t=1m
Electric plane (at least 250mph): https://www.youtube.com/watch?v=BC2KPsKwLpY
Glider (dynamic soaring 517mph): https://vimeo.com/213265400
If someone knows of a leaderboard with record progressions for all classes please let me know!
0 - Duplicate current speed record (~200mph)
1 - Demonstrate transonic propulsion surfaces (~500mph)
2 - Demonstrate supersonic horizontal flight (>760mph for >5s)
3 - Demonstrate sustained supersonic flight (>1000mph for >60s)
4 - Suborbital flight - accelerate to 4000mph up to 100k feet - nightmare mode
Can you help me? Get in touch!