NOT TO BE LEFT BEHIND

Lockheed Martin's newly unveiled Polecat unmanned aerial system demonstrator is designed to explore the aerodynamic characteristics of the tailless flying wing design at higher altitudes than attempted to date, and possibly feed technologies into future aircraft for the U.S. Air Force.

The company's Advanced Development Programs sector, commonly called the Skunk Works, had been rumored to be working on a secret unmanned aerial system (UAS) project for years. And, company officials are lifting the veil in an attempt to quell critics who have said Lockheed Martin has been too focused on its manned fighter business--with multibillion-dollar F-22 and F-35 programs--thereby neglecting future opportunities with unmanned systems.

With the Polecat prototype, the company is aiming at Boeing's and Northrop Grumman's turf--developing combat UAS for the U.S. military and, possibly, the U.S. Navy's yet-to-bedefined Broad Area Maritime Surveillance program.

Skunk Works, noted for rapid prototyping and such technological feats as the high-flying U-2 and speedy SR-71 reconnaissance aircraft, selected a tailless "Horton" wing design first used by Germany in World War II. Without vertical structures and a tail, the 90-ft. wingspan vehicle is inherently low-observable but it has not been "coated" with radar-reflecting materials because it is not expected to fly operationally.

A new "twisting strut" inside the Polecat's wings is designed to flex in air and improve the laminar flow over its swept wings, propelling the UAV to high altitudes. Aircraft such as the straight-winged U-2 have traditionally behaved like gliders but lack a survivable design. "No one has ever developed in this configuration a high lift-to-drag ratio, and we are going to do it higher than anyone has done it," says Skunk Works Executive Vice President Frank Cappuccio. The engine inlets (see the cover photo) are designed to deflect radar energy away from the engines, masking some signature, although Frank Mauro, Lockheed Martin's director of unmanned systems, admits more work is needed to improve low observability.

Intended to soar to a 60,000-ft. altitude and higher, Lockheed Martin has two main mission areas in mind for Polecat: the Air Force's yet-to-be defined Long Range Strike (LRS) system and a next-generation intelligence, surveillance and reconnaissance aircraft. So far, the flying wing has not flown that high. Mauro says the B-2's 45,000-50,000-ft. operating area is the Horton's ceiling to date. "The air gets pretty thin above those levels. Our main objective is to determine how effective that wing concept is at that altitude so we'll have better data if we should [develop] something that requires that design." Cappuccio says that in the coming months engineers are devising sensors for Polecat that are part of a contrail suppression system. Contrails often give U-2s away despite altitude. So, Skunk Works wants to detect conditions conducive to contrails and avoid these areas.

During its first two flights at the Nellis Test Range, Nev., last year, Polecat reached 15,000 ft., a limit set by the portion of the range where it was flying. Officials are now moving operations to another area of the proving ground. Cappuccio, who unveiled Polecat to the media during a briefing at the Farnborough air show last week, says high-altitude flights are expected as soon as September.

Powered by two FJ44-3E Williams International engines, Polecat has a 9,000-lb. gross takeoff weight. A bay nestled between the two engines can accommodate 1,000 lb. of sensors or weapons. Skunk Works is negotiating with various sensor makers for potential demonstrations, possibly conformal radar arrays. Cappuccio adds that he wants to experiment with conformal antennae on the vehicle.

Engineers designed Polecat using 98% composites, aside from landing gear, avionics and engines, and it consists of fewer than 200 parts--all to bring costs down. They used an innovative, low-temperature composite curing process for the vehicle. Normally cured at 350F in an autoclave, the new technique relies on a 150F curing process that eliminates the need for investing in autoclaves. The composites are then post-cured. These are further iterations of processes used in the F-22, F-35 and Joint Air-to-Surface Standoff Missile programs.