P-791, a blimp originally developed as an aerodynamic airship that would be a cheaper way to transport cargo by air. P-791 looks like three normal blimps smushed together to form one wide blimp. The army wants an unmanned blimp that can carry 1.1 tons of sensors, stay aloft for 21 days at a time, supply 16 kilowatts of power and move at up to 148 kilometers an hour.
The U.S. Army wants aircraft manufacturer Lockheed to dust off and spiff up an old aircraft research project, and get it ready for service within 18 months as the LEMV (Long-Endurance Multi-intelligence Vehicle). The old project in question is
The idea of a cargo carrying blimp has been around for over three decades, and the concept is simple. An aerodynamic blimp is a helium filled aircraft, with a rigid, but lightweight, shell that is aerodynamic (like an airplane wing.) Thus the aerodynamic blimp takes off and flies like an aircraft, gaining additional lifting power in the process, and able to carry heavy and bulky cargoes using low power (and low fuel consumption) engines. All past efforts to make aerodynamic blimps practical have failed because these aircraft are still lighter than air vehicles, and difficult to handle on the ground or whenever it's windy. They are also large and bulky compared to conventional transports. But the LEMV version of P-791 avoids the handling problems, because the aircraft only lands once or twice a month. The LEMV would be able to lift up to five tons, with most of that being fuel for the 21 day mission.
Lockheed believes that advances in materials and automated flight controls make these aerodynamic blimps practical. But, so far, no one has created a commercially viable example of the concept for carrying cargo. DARPA believed that the problems were soon going to be solved, and helped keep P-791 development going. Now, LEMV may bring P-791 out of the lab, and onto the battlefield. The army wants LEMV to provide radar and photo coverage of large areas in Afghanistan, for extended period. LEMV would do it better and cheaper than existing UAVs.
This is an example of an evolutionary technology. Engineers (and some tech savvy historians) understand how some of these crazy ideas eventually do become economically practical. The problem is figuring out when the needed technologies will all mature and make it possible to build workable, and commercially self-sustaining, products. Get involved too early, and you spend a lot of money, with little return. Get in too late, and you just end up another competitor in a crowded market. Lockheed seems to sense that the sweet spot (the time when the first commercially viable products can be built, and the highest profit margins are available) is on the horizon, and they may be able to get there first with P-791. If not the P-791, Lockheed, and other aviation firms, have plenty of other blimp type designs available to chase the LEMV contract.