Aurora Flight Sciences has flown its Excalibur experimental vertical takeoff and landing unmanned combat aircraft. The subscale proof-of-principle aircraft made its first hover at Aberdeen Proving Grounds in Maryland on June 24 and Aviation Week has the story, with exclusive pictures and video (here).
Photos: Aurora Flight Sciences
The 13ft-long, 10ft-span Excalibur is a half-scale version of a VTOL UCAV designed to carry a 400lb weapons payload - four Hellfires - at speeds up to 400kt. The aircraft is the testbed for a hybrid turbine-electric propulsion system which combines a tilting 700lb thrust-class turbojet and three 12kW battery-powered lift fans.
Full-size UCAV (Concept: Aurora)
Aurora had hoped to fly Excalibur last last year, but diverted resources to completing development of its GoldenEye 80 ducted-fan VTOL tactical UAV. Although AATD and ONR have supported the program, Aurora conducted the first hover flight on its own funds.
The company plans to complete initial hover-phase testing at speeds up 20kt, but is looking for funding to modify the vehicle for medium-speed flights up to 40kt, which will involve making the aerodynamic control surfaces active. If it can secure funds, Aurora plans to build a second demonstrator for high-speed testing - one that can retract the lift fans, retract the gear and tilt the engine down.
Art: Aurora
I wonder if this configuration also shields the jet intake from direct radar detection, it kinda looks it does.
Great post Graham!
Granted, the large Mule UGVs aren't doing much (yet), but their little Packbot brothers are doing some real neat stuff.
The Eagle Eye was a too complicated piece of flying kit, too expensive and suffering from (among other things) tiltrotor transition difficulties, or so I'm told. Give the Osprey another few years to really mature and tiltrotor VTUAVs will return eventually. I hope.
This jet/electric fan VTOL approach hasn't been tried before, and I always applaud new aerospace experiments, as it would make for a more smoother flight with the usual higher speed and altitude advantages.
What *is* going to make the tests interesting is that "flip-over" transition once in flight - I don't really see why they bother, looks like the take-off configuration would fly just as well.
Yes, fan-in-wing has been done before, but it needed complex ducting or shafting. Tilt-rotor needs rotating nacelles and cross-shafting. This needs wires, and there is geater freedom of location for the fans.
Transition may be an issue, but we have fly-by-wire these days. Also, having the lift fans provide 30% of vertical lift may help during transition.
Batteries are heavy, but battery and motor techology is advancing faster than jet engine technology. Will a set of electric lift fans be any heavier than a shaft-driven lift fan, three-bearing nozzle and roll posts?