A Lockheed Martin/Piasecki team will build and fly a new kind of unmanned, vertical take-off and landing (VTOL) aircraft in mid-2015 that will seek to replace helicopters on a wide range of military missions.
The newly unveiled affordable reconfigurable embedded system (ARES) is the result of a dramatic shift in focus of the previously named Transformer TX programme.
Lockheed Martin
The US Defense Advanced Research Projects Agency (DARPA) launched Transformer in 2009 with the ambition of finally creating a feasible flying car, with a diameter in "roadable" configuration no wider than a single-lane road.
Lockheed teamed up with Piasecki – the company that experimented with the VZ-8 Airgeep in the early 1960s – and automotive engineering consultancy Ricardo.
DARPA selected the Lockheed team’s design and a compound auto-gyro proposed by an AAI/Carter Aviation team to begin preliminary studies in 2010. Both teams competed through a preliminary design review, but DARPA selected only the Lockheed proposal to enter a detailed design phase in 2012.
By early 2013, however, DARPA agreed with a proposal from the Lockheed team to abandon the goal of developing a true flying car, says Kevin Renshaw, the programme manager at Lockheed’s Skunk Works unit.
DARPA instead agreed to pursue a flying vehicle that can carry a mix of modular payloads, including small vehicles, cargo containers, sensors or weapons weighing up to 1,360kg (3,000lb).
The newly renamed ARES programme appears substantially based on an existing design concept for a “modular and morphable air vehicle”.
Mike Hirschberg, executive director at the American Helicopter Society, recalls reviewing Piasecki proposals with the design as a consultant to the Office of Naval Research (ONR) and DARPA several years ago.
Indeed, Piasecki received a patent for an ARES-like air vehicle in 2011. It features an “air module” with a wing, tilting ducted fans, engines, drive system and a load-carrying structure to support the payload.
DARPA reopened the design of the air module by dropping the requirement for it to be driven on a single-lane road, Lockheed's Renshaw says. That requirement had limited the diameter of each ducted fan to about 2.44m (8ft), but now the Lockheed team is considering widening the diameter to 3.05m, he says.
The team also is evaluating proposals for the vehicle's two turboshaft engines, which fall within the thrust class of a light twin helicopter, Renshaw says. Lockheed plans to select an engine supplier by the end of the third quarter this year.
Instead of seeking to produce a realistic flying car, ARES is hoping to develop a vehicle that can meet several critical needs.
By offloading the lifting force on to the wing in forward flight, the ARES vehicle should be capable of reaching speeds around 200kt (370km/h) with a full payload, Renshaw says. Most wingless helicopters fly 30-100kt slower with payloads stored internally, and up to 130kt slower with an underslung load, he says.
In addition to higher speeds, the ARES vehicle is designed to be more versatile. Helicopters use a spinning rotor to produce lift and thrust, but the diameter of the rotor disc limits the number of safe landing zones – especially in urban and cluttered areas.
A helicopter in the ARES class requires a 30.5m-wide landing zone, but the ARES’ narrower ducted fans need only half the space to manoeuvre, Renshaw says. A study of landing zones in Afghanistan showed the ARES vehicle would have access to 10 times the number of landing zones than a conventional helicopter, he adds.
The trade-off for that added flexibility is a reduction in fuel efficiency in hover mode, however. While the ARES wing makes the vehicle more efficient in forward flight, the helicopter’s rotor is better for lifting a payload vertically. “A helicopter is more efficient at hover,” Renshaw says.
By design, DARPA’s aggressive approach to technology development produces mixed results. However, Lockheed believes ARES could follow in the footsteps of two of the agency's past successful projects: the Have Blue programme that yielded the Lockheed F-117 stealth fighter, and the advanced short take-off and vertical landing programme that led to the Lockheed F-35B.
Meanwhile, the ONR is developing software for unmanned vehicles to find landing zones autonomously. The goal is to replace the system used to manually direct the Kaman/Lockheed K-Max unmanned helicopter, which has been resupplying remote bases in Afghanistan autonomously for nearly two years.
The ONR’s autonomous aerial cargo/utility system could be combined with a future design evolved from the ARES programme, Renshaw adds.
Source: FlightGlobal.com
