In late 1976 Northrop was to design, develop and build an experimental reconnaissance-minded stealth aircraft for demonstrating emerging stealth technologies. Under heavy security and an impenetrable veil of secrecy that was common for advanced projects of the period, "Tacit Blue" was born. Testing was conducted out of Groom Lake, Nevada at the United States Air Force's (USAF) secret test facility "Area 51". Because of Tacit Blue's general appearance - deep fuselage, blunt nose, squared wing surfaces - the stealth engineers associated with the project became known as "Whalers" and the prototype was itself recognized as "Shamu".
Despite its early-1980s origins, the aircraft was not officially revealed by the USAF until April 30th, 1996.
Tacit Blue held origins in a DARPA initiative for the USAF under the program name of "Battlefield Surveillance Aircraft-Experimental" (BSAX) . A low-observable air vehicle was to be the focal point of the program and pave the way for future stealth aircraft in service to the United States military at a time when the Soviet Empire remained the last world power to challenge American military might. The new aircraft would be capable of working near contested frontlines with impunity due to its radar-reflecting/absorbent technology which could - theoretically - make it invisible to scanning/tracking systems. Onboard systems would allow for the aircraft to communicate to ground force commanders in real-time, providing vital targeting information.
The fuselage of Tacit Blue took on a slab-sided shape with a chined body. Its nose was blunt and lacked a true cone. Wing mainplanes were seated aft of midships though no horizontal tail surfaces were featured. Instead outward-canted vertical fins were used which added one key stealth quality. 2 x Garret ATF3-6 high-bypass turbofan engines of 5,440lb thrust (each) were installed in the aft fuselage for general propulsion and this engine pairing was aspirated through a single intake opening found along the fuselage spine. Maximum speed was proven up to 287 miles per hour with a service ceiling reaching 30,000 feet. A wheeled, retractable tricycle undercarriage was installed for ground running. The crew numbered one and sat behind a multi-paned canopy showcased at the front of the aircraft. Dimensions included a length of 55.9 feet, a wingspan of 48 feet and a height of 10.6 feet.
Awkward-looking and unimpressive by appearance alone, the Tacit Blue aircraft was known under such names like "Whale" and "Alien School Bus". One of its own designers commented on the Tacit Blue as "...one of the most unstable aircraft man had ever flown...". Because of its inherent instability, the aircraft was given a Fly-by-Wire (FBW) system with quadruple redundancy built in.
Tacit Blue served as a technology demonstrator for its entire operational life and only one air vehicle was ever completed. It reached around 250 hours in the air before being retired in 1985. A decade later, it became a permanent part of the Research and Development Hangar of the National Museum of the United States Air Force in Dayton, Ohio where it remains to this day. Some of the technology proven in the Tacit Blue program went on to be featured in operational platforms like the "JSTARS".