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FIGURE D-4. SPECIFIC ENERGY CALCULATION.
Propulsion - Hovering
The ability to take-off and land vertically can provide added operational benefits, such as being able to operate from a forward arming and refueling point with manned assets or from other unimproved areas. DARPA currently has several joint programs with the Army developing vertical take-off and landing UA. These include the small OAV and MAV ACTD, which are pursuing ducted fan aircraft with the ability to hover and fly in forward flight efficiently, as well as the much larger A160 advanced unmanned helicopter program. Other aircraft, such as the RQ-8 Fire Scout are also being developed for a VTOL capable UA. A goal of the small UA DARPA programs is to field aircraft with the ability to "Perch and Stare.” Conceptually, this would enable the UA to land in a place that it can observe the scene where enemy activity is of interest. The purpose of this capability would be for the small UA to observe movement (change detection) and notify the human user by sending a picture of the object that has moved (changed). This reduces the fuel required to operate and increases the time on station significantly and eliminates the users need to "watch" the video screen. This concept does not need to send pictures unless requested or movement is detected, which would further reduce power consumption and increase endurance.
Aircraft Structures
Mission, environment and intended aircraft performance attributes are key drivers for UA structures in the same sense as for manned aircraft. At one end of the “UA spectrum” aircraft such as the Finder and Dragon Eye diminish the need for durable structures. This is contrasted with Global Hawk class UA where individual airframes are planned to be in the Service force structure for periods comparable to traditional manned systems.
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