Back in 2010, the U.S. Army has ordered three LEMV (Long-Endurance Multi-intelligence Vehicle) UAVs from Northrop Grumman, for $173 million each. Now this project has been cancelled and the one LEMV that was built has been sold back to the main developer (a British firm) for $301,000. The army spent nearly $300 million on the project so far and sold the LEMV back to the manufacturer to make it possible to keep work on the concept going. The hope is that current problems with LEMV will be fixed at developer expense and enable the army to buy a version that works.
The original 2010 project called for LEMVs to be designed, developed, tested, and delivered by 2013. All the development was to be accomplished within 18 months. Northrop Grumman thought that by using an old aircraft research project it could get all the design, manufacturing and testing done in time. The army wanted LEMV to provide radar and photo coverage of large areas in Afghanistan, for extended periods. LEMV would do it better and cheaper than existing UAVs. LEMV would use existing UAV sensors and communications and would basically act like a Predator or Global Hawk but with more cameras.
LEMV was based on the existing (and tested) Hybrid Air Vehicle (HAV), which was an aerodynamic blimp built to transport cargo. HAV looks like a flattened blimp, a wide airship with much better handling qualities. Using some of the HAV technology the LEMV was to be an unmanned blimp that could carry 1.1 tons of sensors, stay aloft for 21 days at a time, supply 16 kilowatts of power for sensors, and move at up to 148 kilometers an hour at 6,400 meters (20,000 feet) altitude. This was high enough to avoid most ground fire and to add further protection, the outer skin of the LEMV was made with Kevlar cloth, the same material used in bullet proof vests.
What killed LEMV for the army was the inability of the developer to control the weight of the aircraft. When LEMV took to the air for the first time in 2012 it was 10 tons too heavy, which reduced mission time from 21 days to 6 days. There were some other design problems, but the key one, that is still not solved, was the excessive weight. Northrop Grumman believed that advances in materials and automated flight controls made these aerodynamic blimp UAVs practical. But, so far, no one has created a commercially viable example of the concept for carrying cargo. The problem is always weight and lifting capacity or, in the case of LEMV, the ability to carry enough fuel to keep the blimp aloft as long as required.
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 avoided most of the handling problems because the aircraft would only land once every three weeks. The LEMV would be able to lift up to 5 tons, with most of that being fuel for the 21 day mission. The original weight and design calculations proved inaccurate and that killed the project.
LEMV 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. Northrop Grumman thought they had found the sweet spot (the time when the first commercially viable products can be built and the highest profit margins are available) and that they could turn HAV into LEMV. No one on the army side checked the numbers to determine what the real risk was and so the army eats a $300 million miscalculation. Selling the prototype back to the developer simply recognizes that timing is everything and that eventually the right time for LEMV will arrive.