Transformer was intended to demonstrate a lightly armored vehicle that could fly four people from ship to shore then drive on and off road, lifting off to fly over ambushes or IEDs -- and highly automated so piloting skills would not be required.
Lockheed Martin and Piasecki Aircraft were selected to build the Transformer demonstrator, but DARPA could not get the services interested in a flying jeep. The team had a trump card, however -- in their design the flight module could separate from the ground vehicle and operate independently. And so Ares was born.
Video: Lockheed Martin Skunk Works
An unmanned aircraft with modular payload and ducted-fan vertical take-off and landing capabilities would not seem as "DARPA-hard" as a flying jeep, but Lockheed's Skunk Works says the challenge is in the flight controls. The Ares will use the same "dynamic inversion" control laws that blend vertical and forward flight controls in the F-35B -- but where the STOVL JSF has multiple overlapping aerodynamic and propulsive control effectors, the Ares has just the tilting ducts, variable-pitch fans and exhaust vanes -- and the ducts generate lift that depends not only on tilt angle but also fan pitch/duct flow.
But if you think the morphing of Transformer into Ares is a cop-out, then El Segundo-based Advanced Tactics (AT) is keeping the original fly/drive concept alive with its Black Knight Transformer prototype, which is set to fly this month, funded by the U.S. Army with Congressional special-interest money and supported by the Marine Corps Warfighting Laboratory and Air Force Research Laboratory.
Black Knight is a 4,000lb vehicle with eight 110hp gasoline aero-engines directly driving fixed-pitch proprotors for VTOL and forward flight and a Volkswagen engine driving the rear wheels via an automatic transmission for on- and off-road operation. Nine engines may seem a bit extreme, but is the result of using a multicopter architecture that is well established in the small VTOL UAV market.
A multicopter configuration provides simplicity – the fold-out engine/proprotor units are modular, redundant and field-replaceable, while direct drive and digital control of individual engine/proprotor speed provides flight control while eliminating the complex transmission, articulated rotor head and tailrotor of a helicopter. Turbodiesels, turbines or even electric motors could be used.
The vehicle is fly-by-wire and drive-by-wire, to be flown by an experienced pilot or operated autonomously in flight mode and driven like a car in ground mode.
The design can be modular – the drive section could be removed to increase payload as a UAV, or replaced with a boat or amphibian hull for operation from water. AT received a U.S. patent (8,646,720) in February for a version of the concept able to carry payload modules or vehicles on a “flatbed” airframe. The engine/proprotors are carried on support arms that allow one or more of them to tilt fore-and-aft or side-to-side for control and propulsion.