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The Lockheed Martin P-791 is an experimental aerostatic/aerodynamic hybrid airship, developed by Lockheed Martin. The first flight of the P-791 took place on 31 January 2006 at the company's flight test facility, located at Palmdale Air Force Plant 42. The P-791 has a tri-hull shape, with disk-shaped cushions on the bottom for landing. As a hybrid airship, part of the weight of the craft and its payload are supported by aerostatic (buoyant) lift and the remainder is supported by aerodynamic lift. The combination of aerodynamic and aerostatic lift is an attempt to benefit from both the high speed of aerodynamic craft and the lifting capacity of aerostatic craft.

The P-791 was designed as part of the U.S. Army's Long Endurance Multi-intelligence Vehicle (LEMV) program, but lost the program's competition to Northrop Grumman's HAV-3 design. The P-791 was modified to be a civil cargo aircraft under the name SkyTug, with a lift capability of 20 tons (40,000 pounds) and plans to scale larger.

Airship Roles & Capabilities
The Lockheed Martin p-791 could transport many individuals across various geographical regions. Since this hybrid airship was intended for U.S military purposes, it has the ability to provide American soldiers with vital information through the role of surveillance. In addition, Lockheed Martin continue to construct many p-791 airships with the intent of carrying and distributing large amounts of cargo. Recently, there have been reports stating that the airship was used in Afghanistan, taking part in various arial surveillance missions to aide in combat related issues.

Design/Test Flight/ Features
The p-791 hybrid airship’s helium filled section, is what allows such an aircraft to fly very smoothly. However, this airship still weights more than air. This means that it still takeoffs and lands much more gradually than normal aircraft. When it comes to length specifications, the p-791 is over 40 meters long which is roughly 130 feet. Recently, the p-791 was taken out for a flight test on Janurary 31, flown by Eric P. Hansen. This flight test lasted well over four minutes, where the airship hovered around the Palmdale Airforce Plant 42 airport. When it comes to the design of the p-791, there are various pressurized lobes attached to each other, resembling the same principles of an aircraft wing. The submarine shaped airship lands using its well positioned air cushions replacing the idea of wheels. Fortunately, the added benefit of the air cushions is that they are able to turn in the opposite direction in order to fight against tough wind currents during the transport of heavy equipment. Although the aircraft does not use wheels during taxing, it has its own towing system. Clearly, like many airships, the p-791 is extremely vulnerable to strong winds. The maximum wind speed that the p-791 can handle is just under 10 kts. The airship also has four circular propellers attached to its oval shaped body. Two propellers are identically placed on either side of the tail, while the other 2 are placed on opposite sides of the main body. The structure of the tail components allows for a pivoting movement for pitch controls, such as up or down. Similarly, underneath the airship are four propellers, intended to help with ground performance. It has been reported that these propellers are in fact linked to the air cushion system. The four motors attached on either sides contain gimbal rings that aide in the airship’s collective pitch. Similarly, the p-791’s design resembles another airship, called the SkyCat. Both airships not only resemble the oval-like shaped structure, they both also use aircushions as landing gear.

Specific Characteristics

 * Is able to depart and arrive from various weather conditions, such as solid ice, snow, gravel and tundra
 * Able to transport various cargo that is not possible with other aircraft
 * Is very fuel efficient, as the p-791 burns just under 26% less fuel than an aircraft on average
 * Extremely quiet, which provides an advantage for ground surveillance
 * The four 100 hsp (75kw) two cycle piston engines provide speeds well over 55km (30 knts).