Lockheed Martin Advanced Development Projects has resumed flight tests of its hybrid heavy-load carrying airship concept dubbed the P-791.
The latest flights at the Skunk Works' Palmdale, California site are understood to be aimed at verifying an improved flight-control system that integrates automated pitch and yaw commands. Further flight tests of the proof-of-concept demonstrator are also believed to be planned following renewed signals of interest from the US Department of Defense, as well as from commercial freight companies. The 40m (130ft)-long vehicle uses a lighter-than-air gas, most likely helium, as well as aerodynamic lift to operate.
Powered by four 100shp (75kW) Herth two-cycle piston engines driving ducted fans, the demonstrator is sized to fly at around 30kt (55km/h). Sources indicate a full-size version would be around 200m long, incorporating space for a 50t cargo load. The larger vehicle would also be designed for faster cruise speeds of around 80kt.
Although virtually no design details of the P-791 have been revealed, it is believed the four thrust-vectoring units are fully gimballed, enabling the vehicle to be rotated 360°, and for vertical or near-vertical landings to be accomplished. The P-791 does, however, require a short, if sedate, take-off roll to become airborne, observers say, as the vehicle needs aerodynamic lift to fly. The body of the P-791, similar in concept to the now cancelled US Defense Advanced Research Projects Agency's Walrus, consists of three laterally connected pressurised lobes.
Source: Flight International