In the 1980s and early 1990s the Northrop Corporation was busy developing and testing three aircraft with stealth features, Tacit Blue, B-2 Spirit, and YF-23, stealing some of the spotlight from Lockheed when it came to stealth aircraft development. However, the long-term aftermath of the failure of Operation Eagle Claw in April 1980 prompted the creation in 1987 of the US Special Operations Command (SOCOM) to handle the operation of aircraft specifically tailored for special operations, so Northrop felt keen to look at applying low observables to a notional special operations aircraft.
Northrop made its first foray into special operations aircraft design to in April 1990 when it envisaged a design study for a special operations transport in response to an announcement by DARPA in January of that year soliciting "Research in Technologies Supporting Special Operations/Low Intensity Conflict" (SO/LIC). The design, known internally as the SO/LIC Mission Oriented Combat Aircraft (SMOCA), had a planform inspired by the Tacit Blue, namely in having highly tapered straight wings and a V-tail. The air vehicle itself was called the Special Operations Tactical Air Carrier (SOTAC) while the crew capsule was known as the SMOCA Air Vehicle Enclosure (SAVE). The initial SMOCA concept was powered by two turbofans and measured 65 feet 3 in (19.89 meters) long with a wingspan of 75 feet (22.86 meters), a height of 19 feet (5.79 meters), a mission radius of 1,726 miles (2,778 km), and a payload of 15,000 lb (6,804 kg). Super STOL (SSTOL) performance would be achieved with the use transverse-thrust lift augmentation (span-wise blowing of engine bleed air across the flaps and control surfaces to re-energize the detached airflow). An alternative SMOCA design drew upon the more rigorous edge alignment design seen on the B-2, and engine exhaust was discharged through thin, rectangular ducts ahead of the inboard flaps. It measured 87 feet 4.4 in (26.63 meters) long with a wingspan of 90 feet (27.43 meters) and a height of 25 feet 3.96 in (7.72 meters).
By November 1990, the SMOCA had evolved into an aircraft with a full perimeter chine, low-mounted intakes, and two fixed horizontal stabilizers with elevators controlled pitch. The final SMOCA design, which resembled the B-2 from the side, was powered by two 17,000 lb (78.62 kN) thrust General Electric F404 turbofans buried in the fuselage on the sides of the cargo bay, and it measured 51 feet 8 in (15.75 meters) long with a wingspan of 64 feet 6 in (19.66 meters) and a height of 11 feet 1 in (3.38 meters). Gross weight was 50,400 lb (22,961 kg) with a radius of 1,150 miles (1,852 km), and the wingspan allowed for the SMOCA to be stowed aboard a carrier without the need for wing folding. The SMOCA was envisioned by Northrop for use as a basic airlifter, gunship, covert infiltration/exfiltration aircraft, or special ops transport.
Even before it conceived its final SMOCA design, Northrop unveiled a number of Special Operations Forces Transport (SOFTA) designs for a special operations transport drawing heavily on B-2 design strategies such as edge alignment for low observability. The "baseline" and "preferred" SOFTA designs took the form of an edge aligned trapezoidal flying wing with a wingspan of 100 feet (30.48 meters), a length of 75 feet (22.86 meters), and a height of 16 feet 3 in (4.96 meters), and both were powered by four tip-driven lift fans (covered by doors during horizontal cruise) for vertical takeoff and landing and four cruise turbofans. Cruise speed was 345 mph (556 km/h), and payload was 4,500 lb (2,041 kg), with upper and lower rear cargo doors enabling access to the cargo bay and allowing for in-flight cargo and special forces to be rapidly deployed when the aircraft was hovering. The "preferred" SOFTA design differed from the "baseline" design in having the fixed engine inlets above the chines, and the "baseline" and "preferred" SOFTA designs had a low-altitude mission radius of 1,150 miles (1,852 km) and a range of 2,762 miles (4,440 km). An alternative SOFTA design, measuring 53 feet (16.15 meters) in length with a wingspan of 71 feet (21.64 meters) and 12 feet 2 in (3.71 meters) in height, retained the four tip-driven lift fans but had four F404 cruise turbofans and two turbine-driven aft fans, and it had a smaller payload bay measuring 6 ft x 6.5 ft x 15 ft (1.83 m x 1.98 m x 4.78 m). In all three designs, the wingtips were capable of being folded upwards for carrier storage.
Despite being interesting designs, none of Northrop's stealthy special operations transports would reach the hardware stage. Given that these proposals were conceived amidst the end of the Cold War and the unraveling of the Soviet Union, it is likely that US defense budget cuts in the post-Cold War context precluded the US Air Force from contemplating a contract award for the SOFTA program that would have enabled one or more aircraft manufacturers to proceed with building SOFTA prototypes.
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