The Tupolev Tu-125 was under developement parallely with 1/3 larger "135" bomber which was to have the similar shapes. These works were in tandem with the Sukhoi T-4 bomber as a competitor. No aircraft were built. This unrealized project sought to develop a new long-range supersonic bomber for the Soviet Air Force. Development commenced in 1958 to replace the newest Tu-22. The "Tu-125" designation was an internal one used by the Tupolev design bureau. Since the aircraft was never built, it never received a military designation.
The draft was initiated after deriving the requirements to Tu-22 successor. The limited success of the Tu-22 led the designers to begin work on a replacement rather early on. One of the options was a 'minimal' modification Tu-22M family. Another (project '125') involved radical changes in the design and passed through several stages. S.M.Yeger's department of Tupolev Bureau was responsible for it. Preliminary calculations had shown that the necessary parameters may be achieved in the case of providing supersonic drag to lift ratio not less than 6 and subsonic one not less than 12.
As the plane "125" (TU-125) had to make a long cruise at high supersonic speeds, the inevitable question arose about the materials used, as the airframe of the traditional aluminum alloys would not satisfy the temperature conditions at these speeds. As the flight would take place under very severe conditions - high temperature and high air flow loads - obviously previously used materials couldn't been used. Titanium and steel structure elements were planned. The new project, "125" (TU-125) became a kind of successor to the version of "106" with 2NK-10 engines.
For the aircraft, according to the developers the most suitable scheme selected was the canard. It was reviewed in several dozen variants of possible arrangements, are analyzed a large number of power plant options on the basis of existing and future engines. It was necessary to create a whole range of complex equipment and weapons systems, able to provide high efficiency of the shock generated by the aviation system. We considered several dozen variants of the possible configurations of the aircraft "125" (TU-125), were subjected to analysis based on many existing and future engine propulsion options.
Work on the aircraft, originally started as a future alternative to planes "Tu-105A" and to some extent the aircraft "Tu-106" gradually evolved into the design impact of strategic supersonic aircraft, on the basic flight characteristics close to another project Bureau of the period - the plane "Tu-135" , but at a third less take-off weight. Since the beginning of the 1960s the work on both projects proceeded almost simultaneously, and therefore their basic layout decisions were very close.
The long-range strike carrier aircraft, optimized for the long flight to the target and to break through the enemy's defense at high altitudes with high supersonic speed, was intended for the application of missile and bomb strikes against land and sea targets. The design was developed in versions: bomber, carrier-aircraft missiles of class "air-surface" or ballistic airborne missiles, reconnaissance aircraft, long-range interceptor and antisubmarine aircraft with low response reaction and designed for rapid destruction of SSBNs.
The first Tu-125 variant was a canard missile carrier powered by pair of turbojets in the rear fuselage with side air intakes. The "125" Project of 1958 had two engines NK-6 or SC-10 (maximum takeoff thrust 23500-24000 kg), established under the wing in the rear fuselage in two nacelles. It was armed with single 4000 kg missile (600 km range), had estimated range 4500-4800 km and a speed 2500 km/h. The severe heat conditions caused wide use of titanium alloys in the airframe.
Extensive wind tunnel studies resulted in excessivly optimistic predictions: at Mach 2.0 the '125' had airdynamic quality 6 (12 at subsonic flight) and afterburning fuel consumption of 1.6 kg/kgf/hour which allowed the required range could be achieved. Later practical experience with the Tu-144 passenger jet revealed that practical fuel consumption better than 1.8-1.9 kg/kgf/hour was unrealistic. Serious doubts were expressed by military concerning about the stability of the unusual layout.
But in the early 1960s Khrushchev called for the deployment be the USSR of land-based strategic missiles. In contrast, Tupolev was working on a single-mode attack aircraft in competition with KB Sukhoi ( T-4 ) and Yakovlev (Yak-35). In July 1962 a scientific and technical council, summed up the contest, and the Tu-135 project was not approved. AN Tupolev, knowing that he will be removed from the contest, gave the command to its design office on the preparation of the terms of the contest of the Tu-125. Since the work on the missile "125" were in Tupolev under different terms of reference, it had a slightly different performance characteristics.
Aircraft under Project "125" in the beginning of the 1960s in general repeated the layout solutions adopted for the aircraft "135". Depending on the type of engine number varied from two to four (2 x 6 or NC-SC-10, 4 x P-15B-300, etc.). The Tu-125 planned extensive use of titanium alloys along with duralumin, and the use of the latest electronic equipment. However, the Bureau did not have enough time to work through the Tu-125 under conditions of competition.
The 1960's brought a change in the strategic planning concepts (infamous Khruschiov's ballistic missile bias) and known shortcomings of the American B-58 resulted in cancellation of the Tu-125. In the second scientific and technical council in September 1962 discussed aviation institutes and military projects. The Soviet Air Force rejected the project and it was stopped. The draft of the Tu-125 did not pass the competition because of its unteseted nature (this had hefty "help" from AS Yakovlev). The technical and technological difficulties associated with the creation of "125" equipment systems and armament of the aircraft played a role also. There is an opinion that one element in the failure of the Tu-125 (and its lrger sibling '135') belonged to A.S.Yakovlev - he was pushing his Yak-35 project. Nonetheless A.N.Tupolev KB tried to solve technical and political problems for a few more years.
But Tupolev's team could be happy: the failure of the project did not result in the bureau 'cancellation' (like happened to V.M.Myasichev). Anyway, the single-regime supersonic bomber concept faded in the mid-1960's. Some historian have the opinion that '125' canard scheme inspired P.O.Sukhoi to create his T-4 ('100') missile carrier, which competed later with the '135' and Yak-35 in a lose-lose-lose contest. The work on this project continued until the mid-1960s up to the moment when military men rejected the tactics of high altitude supersonic attack. Variable geometry layout was under development in many countries, and here Tupolev took a lead among Soviet designers. By the mid-1960s the approach of views on aviation strategic weapons system turned towards the creation of long-range multi-mode shock aircraft, the implementation of which was the creation of missile-bomber with variable sweep wing, the Tu-22M.
|Function||long range supersonic bomber|
|Supersonic cruise speed||3500km/h|
|Ceiling||over target 25000m|
|Armament||Rocket one X-22 missile|
|Dimensions & Weight|
|Wing Span, m||24,7||22,2|
|Overall height, m||10,1||9,55|
|Wing Area, m2||226||226|
|Take-off Weight, kg||125000||110000|
|Number of Engines||2||2||4|
|Engine Type||Turbofan NK-6 or NK-10||Turbofan NK-6?||Turbojet R-15B-300|
|Thrust on afterb per engine, kgs||23500-24000||22480||15000|
|Max speed, km/h (M=)||2700||3500|
|Cruise speed, km/h (M=)||2500-2650|
|Practical ceiling , m||25000||18500-20500||25000|
|Practical range, km||supersonic||4800-6000||4800|
|GM||1 ? Kh-22|
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