Development
The RQ-170 Sentinel was developed by Lockheed Martin's Skunk Works as a stealth UAV. Journalists have noted design similarities between the RQ-170 and previous stealth and UAV programs such as the RQ-3 DarkStar and Polecat. It is a tail-less flying wing aircraft with pods, presumably for sensors or SATCOMS, built into the upper surface of each wing. Few details of the UAV's characteristics have been released, but estimates of its wingspan range from approximately 65 feet (20 m)[ to between 75 feet (23 m) and 90 feet (27 m).
The "RQ" designation indicates that the RQ-170 Sentinel does not carry weapons. Aviation Week's David A. Fulghum believes that the UAV is probably a "tactical, operations-oriented platform and not a strategic intelligence-gathering design".
The USAF confirmed the "grainy photos of a gray, flying-wing-typed unmanned airplane near Kandahar Airfield" in relation to the discussion of the RQ-170 Sentinel on 4 December 2009.[3][7] A USAF colonel subsequently commented that RQ-170 is separate from the MQ-X program, which has yet to determine stealth or powerplant requirements, and thus the Sentinel will not replace the MQ-1 Predator and MQ-9 Reaper drones currently in service.As of May 2011, the US Military had not released any statements concerning the Sentinel since December 2009.
Design
The RQ-170 has a flying wing design containing a single (as yet unknown) engine and is estimated by Aviation Week as being approximately 66 feet in wingspan. Its takeoff weight is estimated as being greater than the RQ-3 DarkStar's, which was 8,500 pounds. The design lacks several elements common to stealth engineering, namely notched landing gear doors and sharp leading edges. It has a curved wing planform, and the exhaust is not shielded by the wing. Aviation Week postulates that these elements suggest the designers have avoided 'highly sensitive technologies' due to the near certainty of eventual operational loss inherent with a single engine design and a desire to avoid the risk of compromising leading edge technology. The publication also suggests that the medium-grey color implies a mid-altitude ceiling, unlikely to exceed 50,000 feet since a higher ceiling would normally be painted darker for best concealment. The postulated weight and ceiling parameters suggests the possible use of a General Electric TF34 engine or a variant in the airframe.
On the basis of the few publicly-available photographs of the RQ-170, aviation expert Bill Sweetman has assessed that the UAV is equipped with an electro-optical/infrared sensor and possibly an Active Electronically Scanned Array (AESA) radar mounted in its belly fairing. He has also speculated that the two fairings over the UAV's wings may house datalinks and that the belly and above wing fairings could be designed for modular payloads, allowing the UAV to be used for strike missions and electronic warfare.
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