The work on the T-4 project ("article 100") began in 1961. The military set the task of developing a new air arm capability for "reconnaissance, search-and-destroy missions on small-size, mobile and fixed offshore and onshore targets," with a flight range of 7,000 km. The USSR held a tender among the aircraft design bureaus, with the design submitted by the Sukhoi design bureau winning against the bids by the design bureaus of Yakovlev and Tupolev. The T-4 gained a competitive edge with its high cruise speed of 3,200 kph, which, according to expert estimates, promised to render it much less vulnerable to air defence threats. The development of the aircraft was authorised in the government's resolution of 3rd December 1963. The project was headed by Deputy Designer General N.S. Chernyakov.
The T-4's conceptual design passed preliminary design review in June 1964, with an Air Forces mock-up committee review held in February 1966. Detailed design was undertaken jointly with the MKB Burevestnik engineering design bureau, with the Tushino machine-building plant (TMZ) appointed manufacturer of prototype aeroplanes in November 1964.
The specification requirements provided for high-quality Mach 3 cruise performance. A joint programme with CAHI produced comprehensive fundamental research into the aerodynamic performance of aircraft models, which made it possible to select the required configuration. The design was based on a tailless, flying wing concept with a low margin of pitch stability and small-size canards used for the aircraft pitch trim. It featured a double-delta wing, with a sharp leading edge and middle surface deformation.
It took a massive research effort to develop the powerplant configuration, which was finalised as a version with underbelly air intakes and so called bath configuration of 4 engines. It featured the USSR's first supersonic mixed-compression variable air intake with auto start for design Mach 3.0. Under a special T-4 project, the Design Bureau of P.A. Kolesov developed a RD36-41 turbojet to support a Mach 3 extended flight capability.
Each of the T-4 systems, given their heavy-duty aircraft operation requirements, had to be extensively researched by the designers to come up with a required number of adequate new solutions. For example, the T-4 featured, for the first time in Soviet practice, a quadruple redundancy fly-by-wire system, an auto-throttle, a hydraulic system with operating pressure of 280 kg/cm 2, a trailblazing fuel system with turbine driven pumps, a liquid-nitrogen-based inert gas system, and othe innovations.
A major challenge was to develop a design and a combination of materials to enable operation at high process temperatures of 220 to 330˚C. The airframe was engineered using mostly titanium and steel, the development of technology to enable their application in the aeroplane design being the focal point of the effort of the Sukhoi designers and technologists working on the T-4 project. They had to develop a great number of pioneering engineering processes such as automatic through-penetration welding, automatic buried-arc welding using sheet add-on, chemical milling of titanium alloys, and others. The new technologies were tried out under a comprehensive programme to develop new types of materials and coatings, and test full-scale structural specimens. The powerplant, aircraft systems and equipment were tried out by the Design Bureau jointly with its subcontractors under a large-scale programme for R&D and testing of various models, stands and flying laboratories (FL). For example, the wing shape development was conducted using a special-purpose Su-9-based 100L FL built and operated jointly with FRI.
The aircraft's purpose-designed equipment included a NK-4 navigation system and an Okean avionics suite integrating a Vykhr fire control system, Rapira recon system, Otpor defence system and Stremnina radio communications system. The aircraft's principal armaments were specified as 3 Kh-45 aeroballistic missiles under development at the MKB Raduga engineering design bureau. The Kh-45 rocket had an estimated range of 550-600km and cruise speed of Mach 5 to 7.
In the T-4 project, nearly all the aircraft's main blocks, systems and assemblies could claim the merit of invention; a total of 208 inventions were implemented by the Sukhoi designers, and taking into account the inventions used in developing assembly components and units, the number was nearly as high as 600. Not a single aircraft built by that time in the USSR could boast such a great number of proprietary developments!
The building of the first flying prototype of the aircraft (art. "101") was completed in the autumn of 1971, and in December 1971 the aeroplane was moved to the FRI airfield. The maiden flight of the prototype took place on 22nd August 1972, its crew composed of pilot V.S. Ilyushin and navigator N.A. Alfyorov. The flight tests went on till 19th January 1974, with a total of 10 flights completed over that period and Mach 1.36 achieved at a height of 12,000 m.
In the period 1966-74, TMZ assembled 4 T-4 airframes: one for static (art. "100S") and three for flight tests (art. "101", "102" and "103"). The work-in-process inventory included a number of assemblies produced for 3 more machines. In 1974, MAI suspended the work on the T-4 project. Officially, the project was scrapped in accordance with the government's resolution of 19th December 1975.
T-4 was used as a platform in 1968-70 by Sukhoi bureau to develop a design for an upgraded missile carrier T-4M with a variable sweep wing, and in 1970-72, a further design, the T-4MS (art. "200"), was produced in competition with the design bureaus of Myasishchev and Tupolev for development of a strategic dual role strike aircraft.