Tu-144 Charger Design
The official basis of the first generation SST (SST-1) building designated as Tu-144 was Resolution of Council of Ministers of the USSR, 1963 and Decree of the same year. TUPOLEV Design Bureau was given a task to design and build SST with cruise flight speed of 2300-2700 km/h, operational range at supersonic speed with 80-100 passengers on the board was prescribed to be 4000-4500 km; in accelerated version with additional fuel tanks carrying 30-50 passengers - 6000-6500 km/h. Operation from I-st class airfields at normal take-off weight of 120-130 tons.
The Chief Designer and Manager was Alexey Tupolev. Tu-144 aircraft conception and future layout was originated under his leadership and with best aviation science specialists involved. Later on the Tu-144 aircraft Project was managed by Y. Popov and B. Gantsevskiy. Soon the Tu-144 Project became one of main and priority subjects of the Design Bureau and of the whole Ministry of Aircraft Industry for the nearest decade.
In 1966-1967 Tupolev was going to build 5 Tu-144 machines (two machines were intended for structural tests). In view of the technical complexity of obtaining maximal flight range, work was divided into two steps: at the first step operational flight range was to be 4000- 4500 km/; at the second step the Tu-144 aircraft had to reach flight range of 6500 km. By-pass turbofans with reheat chamber was prescribed for the Tu-144 aircraft. Design Bureau im. N. Kuznetsov undertook creation of turbofans for the SST that were designated as NK-144 having take-off thrust of 20000 kg thrust and Specific Fuel Consumption equal to 1.35-1.45 kg/kg thrust h at cruising flight.
It should be noted that the Tu-144 project progress was mainly affected by the successes of engine manufacturers. This choice was not self-evident. It was more reliable and cheaper and allowed flights within more wide range of altitudes and speeds in comparison with simple turbojets. Possibility to have small fuel consumption at cruising speed and consequently - ensured the required flight range. It was not a surprise both for TUPOLEV specialists and for Ministry of Aircraft Industry.
During the design of the Myasischev SST there were results showing that it was quite realistic to obtain suitable supersonic flight range if engines with Specific Fuel Consumption not more than 1.2 kg/kg thrust hour were used. Prototype of such engine was built in the 1960s in the USSR - it was non-afterburning turbojet "16-17" (take off was 18000 kg thrust, Specific Fuel Consumption at cruising flight was 1.15 kg/kg thrust hour) which was designed in Design Bureau-16 named after P.Zubtsov. English and French designers of the "Concorde" chose an intermediate way and selected reheated turbojet Bristol "Olymp" 593 with non-high reheating and with Specific Fuel Consumption = 1.327 kg/kg thrust hour at afterburning (afterburning takeoff is 17200 kg thrust).
Unfortunately the work on the heavy SST at Myasischev Design Bureau was terminated. Thus in early 1960s in the USSR development of powerful economically efficient nonafterburning turbofans temporarily was stopped (Design Bureau-16 was switched to solid rocket engines. As a result by the beginning of the Tu-144 aircraft designing the TUPOLEV Design Bureau had to undertake a technical risk by selecting the NK-144 engines.
In 1964 it was decided to resume works on economically efficient powerful nonafterburning turbojet for SST: in Design Bureau-36 under P. Kolesov they started to design RD-36-51 turbojet for Tu-144 aircraft with maximal take off equal to 20 000 kg thrust and estimated Specific Fuel Consumption of 1.23 kg/kg thrust hour at supersonic cruise.
The Tu-144 aerodynamic layout was defined mainly by long flight range at cruising supersonic speed at required stability and controllability and prescribed take-off and landing characteristics. Basing on promised Specific Fuel Consumption of the NK-144 at the first step of designing the task was to reach Kmax=7 at cruising supersonic flight. According to economical, technological and weight aspects M=2.2 was assumed. In the course of the study of the Tu-144 aerodynamic arrangement several tens of approaches were considered. First "normal" arrangement with horizontal tail. It was rejected since such tail contributed up to 20% to total amount of aircraft drag. "Canard" arrangement was also rejected due destabilizer affect on main wing. Finally they decided in favor of low-wing arrangement - "tail-less" aircraft with ogival double-delta wing (the wing was defined by two triangle airfoils with strake edge sweep angle of 78° and 55° along rear basic portion) provided with four afterburning turbojets installed under the wing with vertical tail was installed along longitudinal axis and with retractable tricycle landing gear.
The airframe structure was mainly made of common aluminum alloys. The wing was defined by symmetrical profiles and had complex twist in two direction: longitudinal and lateral. This resulted in the best flow about the wing at supersonic speed. Furthermore this twist contributed to improvement of longitudinal trimming under said conditions. The entire rear edge was provided with four-pieces elevons per each half-wing. The wing has multi-spar structure with powerful skin made of continuous aluminum alloys plates, central wing and elevons were made of titanic alloys. The elevons sections were activated by two irreversible actuators. Rudder was deviated by means of irreversible boosters and was defined by two separate sections. Aerodynamic arrangement of the fuselage were chosen in view of obtaining minimal drag under supersonic conditions. Aiming at this the aircraft structure was made more complicated.
Characterizing feature of Tu-144 aircraft became lowerable, well glazed nose fuselage in front of cockpit which provided good view at large take-off and landing angles of attack inherent to the airplanes with wings of small aspect ratio. The nose fuselage could be lowered or hoisted by means of hydraulic drive. When designing the deflectable non-pressurized portion and its components Tupolev managed to preserve a smooth skin in interfaces between the movable portion and pressurized and the rest fuselage surface. Engine nacelle form was mainly defined by arrangement considerations and requirements to reliable functioning of powerplant. Four turbofans NK-144 were disposed under wing close to each other. Each engine was provided with its own air intake ; two adjacent air intakes were tied together in a common unit. Under-wing air intakes were flat and were provided with horizontal ramp.
Under supersonic conditions airflow can be decelerated in three oblique shock waves, in normal terminal shock wave and in subsonic diffuser. Each air intake operated by automatic control system which could change ramp position and by-pass flap depending on NK-144 engine setting. Engine nacelle length was defined by engine size and TsAGI and TsIAM requirements to air intake duct length needed for normal functioning of the engines. It should be noted that contrary to "Concorde" engines design where it was done as a single process, NK-144 engines engine nacelles with air intakes were designed in two mainly independent processes which led to resizing the engine nacelles and further to many lack of co-ordination in operation of engines and air intake system.
The braking system was supposed to be introduced at landing at the expense of reverser; reverser was planned to be installed on two outer engines (reverser system was not developed which resulted in operation of prototype and production machines with drag parachute). Main landing gear were retracted into wing, nose leg was retracted into forward fuselage space between two air intakes. Small wing height required reduction of wheels dimensions. It resulted in using twelve-wheeled bogie with rather small diameters of wheels. The main fuel resource was kept in wing integral fuel tank. Forward integral wing fuel tanks and additional tail integral fuel tank served for aircraft balancing.
Main activities on selecting of optimal aerodynamic configuration of Tu-144 aircraft were headed by G.A.Cheryomukhin, powerplant optimization was performed by B.Voul department. In Tu-144 aircraft many principle approaches of remote control system. In particular signals of stability and controllability were tried out in longitudinal and azimuth channels. Under certain conditiona said activities made it possible to perform flight at static instability. The Selection of the concept of Tu-144 aircraft control system was mainly the work of G.F. Naboitshikov. L.Rodnianskiy made a substantial contribution to creation and development of this principally new control system.
The pilot cockpit was designed according to requirements of up-to-date ergonomics. It was designed for four seats: two forward seats were intended for pilot and co-pilot, flight engineer was seated behind them, the forth seat was intended for engineer - experimentor in the first prototype. Further the flight crew was supposed to be limited by three pilots. Cabin interior arrangement and finishing of Tu-144 aircraft cabin were state-of-the art level, the most new finishing materials. Flight and navigation equipment was the best of our native avionics: perfect autopilot and airborne computer could maintain heading automatically. Pilots could see in instrument panel display where aircraft was at certain moment and how many kilometers are left to destination point. Approach was performed automatically at any time of a day under severe weather conditions etc. - all these represented a serious break-through for Soviet aviation.
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