Work on the aircraft and the complex of the project “138” began in the OKB A.N.Tupolev in 1962, as a logical continuation of the work on the project “128A”. In the course of choosing the aircraft, the plan went in three directions: minimal changes with respect to the original Tu-128 layout, while maintaining the fuselage layout using a new wing and using completely new layouts. The second option was worked out in more detail. The Tu-138 carrier aircraft retained the general layout of the Tu-128, the power plant was based on the use of VD-19 engines, the aerodynamics were improved due to the new aerodynamically clean wing with a smaller relative thickness and a new shape in plan. Unlike the Tu-128, the main landing gear with wheels on the 138 aircraft retracted to the root of the wing and partially to the fuselage.
The aircraft was to be used for two Tu-138-60 and Tu-138-100 systems. In the first case, the Smerch-A radar and K-60 type missiles were installed on the machine, in the second case the Groza-100 radar and K-100 missiles. The possibility of using missiles of the K-80 (R-4) type of the Tu-28-80 (Tu-128S-4) complex was provided. Modernization of the carrier aircraft, new radars and missiles were to significantly expand the capabilities of the complex to intercept high-speed targets. For example, the maximum speed with missiles increased by 800 km/h, the time of barrage was increased, takeoff and landing characteristics improved, the ranges of detection and capture of radar targets and the range of missiles increased.
During the design of the “138” aircraft, aerodynamic studies were carried out on the models, which showed that it was not possible to obtain the necessary aerodynamic quality in the cruise subsonic mode of flight due to the significant increase in the fuselage VD-19 (the aircraft and the new radars had a larger diameter). This called into question the achievement of the required range and duration of flight, which was one of the most important requirements for the interceptor. With the new thin wing, the runway performance also deteriorated. Various ways to refine the draft were suggested to address the problems encountered. They wanted to introduce the in-flight refuelling system “Konus”(Cone), the system of blowing the boundary layer from flaps and LE flaps or to achieve improvement of aerodynamic quality of the wing due to suction of the boundary layer. However, all these measures either weighted the structure or significantly reduced the economy of the power plant by bleeding air to the blow-off system. By the mid-1960s, it was decided to carry out further work in the OKB on the path of modernization of long-range interception systems using a variable wing sweep design, which was carried out in the project “148.” With the commencement of work on this complex, all work on project “138” was terminated.
In 1963, the OKB worked out several variants of the “138” aircraft, based on unconventional layout schemes, in particular offering delta-wing-free and duck schemes. In addition to the VD-19 engines, the “138” aircraft considered the possibility of using RD-36-41 that were a further development of the VD-19.
|Dimensions & Weight|
|Wing Span, m||17,53|
|Overall height, m||7,78|
|Take-off weight, kg||normal||45000|
|Engines||2 Turbojet RD-19|
|Max speed at altitude, km/h||2400|
|Interception range, km||subsonic||2100|
|Barraging duration, h||4,5|
|Practical ceiling, m||18000|
|AA missiles||4 K-60 or K-80||4 K-100 or K-80|
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