1. Field of the Invention
The present invention relates to aeronautics. More specifically, the present invention relates to systems and methods for refueling vehicles in flight.
2. Description of the Related Art
The use of unmanned air vehicles (UAVs) for various military and civilian applications is rapidly expanding. A typical UAV flight has three parts to its mission: 1) it must be launched from a support base and fly to an area of operation; 2) it must loiter in its area of operation while performing its intended functions; and 3) it must fly back to its support base and land while carrying sufficient spare fuel to account for unforseen delays such as unfavorable headwinds.
At takeoff, a UAV must carry sufficient fuel for all three phases of its mission. It is often the case that mission parts 1 and 3 will each consume as much fuel as mission part 2, which is the useful portion of its total flight.
If a UAV can be refueled in-flight in its area of operation, a substantial increase in utility may be achieved. Hence, there is a growing need for a system or method for refueling UAVs in flight to allow the UAV to remain on-station for extended periods without consuming time and fuel to return to its support base.
Unfortunately, currently, it is generally not feasible for UAVs to be refueled from conventional manned tanker aircraft. There are two primary reasons. First, most UAVs are much smaller and fly slower than conventional manned tankers, which have been designed to refuel large jet-powered aircraft. It is necessary that the tanker have a flight performance roughly comparable to the UAV in order to perform close formation flight during refueling operations. Specially constructed tanker aircraft will generally be required to refuel most UAVs.
Second, aircrews of manned tanker aircraft are unwilling to permit unmanned aircraft to fly in close formation for safety reasons. During manned refueling operations, skilled pilots are in control of both the tanker and receiving aircraft. There is considerable danger to the human crews in both aircraft should any collision occur during the extremely close formation flight. Pilots of both aircraft place a very high degree of trust in the skill and competence of the other pilot. They are unwilling to rely on the response of robotic unmanned vehicles that may not be able to react to unforeseen problems. An unmanned tanker aircraft will generally be required for in-flight refueling of UAVs.
Hence, a need remains in the art for a safe and cost-effective system or method for refueling a UAV in flight.