Alright gang I found a great webpage with a ton of new info about this project.
HAC News Page
The Defense Dept. is showing interest in two categories of airships--those that can carry large cargo at low altitude, exemplified by the Defense
Advanced Research Projects Agency (DARPA) Walrus program, and those that can operate in high-altitude low-wind conditions and remain on station for
long periods of time. The configuration of the Skunks Works ship indicates it is the former--a hybrid heavy-load carrier.
The speed of the testbed was estimated at about 20 kt. A full-scale version would be able to go much faster, over 100 kt. Lockheed Martin has long
proposed a large transport airship, at one time called the Aerocraft, which was halted around 2000 (AW&ST Feb. 22, 1999, p. 26). That design was about
800 ft. long and was to carry 1-1.2 million lb. at 125 kt. The Skunk Works was one of two contractors to receive one-year, $3-million Darpa contracts
in August 2005 to study Walrus. The second Walrus phase would be a three-year demonstration effort.
The P-791 uses four air cushions as landing gear, located on the outer lobes. Taxiing the vehicle could be like flying a hovercraft, except one with
greater exposure to winds. An advantage of the air cushions is they could be reversed to suck the aircraft onto the ground to resist winds for cargo
operations. Air pressure may also be the best way to spread landing loads into the inflatable structure. It's not clear if there are any devices,
such as wheels, to keep the airship from sliding sideways when taxiing in crosswinds. The craft has a special towing system.
The P-791 appears to have four propellers--two at the tail and two on the sides. The tail units appear to be able to pivot for yaw vectoring, and
it's unclear if the ones on the sides can move. One knowledgeable individual says there are four vectored propulsors used for ground handling, but
it's not clear if these are the main propellers, or separate units perhaps connected with the air cushion system. The rings around the motors may be
shrouds for the propellers and/or gimbal rings for vectoring. Vectored thrust can be useful for lighter-than-air blimps, which lose conventional
control authority as they approach zero airspeed while landing, but a hybrid airship lands with some airspeed that may keep the tail control surfaces
effective. But for control during low-speed air cushion taxiing, vectoring would seem essential.
The P-791 appears similar to the proposed full-scale version of the British SkyKitten, called the SkyCat. They have similar overall shapes--though the
Skunk Works design is wider--and similar propulsion layouts, and both use air cushion landing gear. Perhaps the two programs have people in common.
One of the partner names on the side is TCOM, which makes aerostats and envelopes for airships.
[edit on (1/10/08) by AllSeeingI]