Tupolev Tu-144
The Tupolev Tu-144 is a Soviet supersonic passenger airliner designed by Tupolev that operated commercially from 1975 to 1983, including 1977–1978 passenger service.
The Tu-144 was the world's first commercial supersonic transport aircraft with its prototype's maiden flight from Zhukovsky Airport on 31 December 1968, two months before the British-French Concorde. The Tu-144 was a product of the Tupolev Design Bureau, an OKB headed by aeronautics pioneer Aleksey Tupolev, and 16 aircraft were manufactured by the Voronezh Aircraft Production Association in Voronezh. The Tu-144 conducted 102 commercial flights, of which only 55 carried passengers, at an average service altitude of and cruised at a speed of around . The Tu-144 first went supersonic on 5 June 1969, four months before Concorde, and on 26 May 1970 became the world's first commercial transport to exceed Mach 2.
Reliability and developmental issues restricted the viability of the Tu-144 for regular use; these factors, together with repercussions of the 1973 Paris Air Show Tu-144 crash, projections of high operating costs, and rising fuel prices and environmental concerns outside the Soviet Union, caused foreign customer interest to wane. The Tu-144 was introduced into commercial service with Aeroflot between Moscow and Alma-Ata on 26 December 1975 and starting 1 November 1977 passenger flights began; it was withdrawn less than seven months later after a new Tu-144 variant crash-landed during a test flight on 23 May 1978. The Tu-144 remained in commercial service as a cargo aircraft until the cancellation of the Tu-144 programme in 1983. The Tu-144 was later used by the Soviet space programme to train pilots of the Buran spacecraft, and by NASA for a supersonic research programme from June 1996 to April 1999. The Tu-144 made its final flight on 26 June 1999 and surviving aircraft were put on display in Russia, the former Soviet Union and Germany, or into storage.
Background
Given the vast size of the Soviet Union, supersonic travel was seen as economically feasible, especially for government employees travelling between Moscow and Siberian cities. Flying was the only practical alternative to week-long rail journeys, and supersonic transport could significantly cut travel times. While the idea of SSTs was controversial in the West due to noise and environmental pollution concerns, the Soviet Union planned to continue with their development, largely for its long Siberian and Central Asian routes. With ample airspace, flight corridors were likely to avoid built-up areas. Even if international landing rights were not granted, the Tu-144 could still be used for domestic and regional flights.Aeroflot, the flag carrier of the Soviet Union, had an extensive network of interconnected airfields and increasing international reach, with hopes of extending flights to Sydney, Australia. Initial estimates suggested that 20 Tu-144s would suffice for Aeroflot's domestic and international needs.
Given the geopolitical climate during the Cold War period, the Soviet Union was intent on not just matching, but surpassing Western advancements, particularly in aerospace technology. The idea of the West getting ahead and leaving the Soviet Union behind was unthinkable. The directive from Nikita Khrushchev, the leader of the Soviet Union at that time, was clear: not only prevent the West from getting ahead, but also compete fiercely, even to the extent of leapfrogging their technological advancements, if necessary.
The aircraft was seen as a formidable challenge to the United States' dominance in the field of civil aviation.
Development
The Soviet government published the concept of the Tu-144 in an article in the January 1962 issue of the magazine Technology of Air Transport. The air ministry started development of the Tu-144 on 26 July 1963, 10 days after the design was approved by the Council of Ministers. The plan called for five flying prototypes to be built in four years, with the first aircraft to be ready in 1966.Despite the similarity in appearance of the Tu-144 to the Anglo-French supersonic aircraft, there were significant differences between the two aircraft. The Tu-144 is bigger and faster than the Concorde. Concorde used an electronic engine control package from Lucas, which Tupolev was not permitted to purchase for the Tu-144 as it could also be used on military aircraft. Concorde's designers used fuel as coolant for the cabin air conditioning and for the hydraulic system. Tupolev also used fuel/hydraulic heat exchangers, but used cooling turbines for the cabin air.
The Tu-144 prototype was a full-scale demonstrator aircraft with the very different production aircraft being developed in parallel. The MiG-21I I = Imitator was a testbed for the wing design of the Tu-144 but came too late to provide inputs for the first prototype. The findings of the MiG-21I led to the completely redesigned wing of the following aircraft. While both Concorde and the Tu-144 prototype had ogival delta wings, the Tu-144's wing lacked Concorde's conical camber. Production Tu-144s replaced this wing with a double delta wing including spanwise and chordwise camber.
They also added two small retractable surfaces called a moustache canard, with fixed double-slotted leading-edge slats and retractable double-slotted flaps. These were fitted just behind the cockpit and increased lift at low speeds.
Moving the elevons downward in a delta-wing aircraft increases the lift, but also pitches its nose downward. The canards cancel out this nose-downwards moment, thus reducing the landing speed of the production Tu-144s to.
Design
Along with early Tu-134s, the Tu-144 was one of the last commercial aircraft with a braking parachute. The Tu-144 was not fitted with any reverse thrust capabilities, and so the parachute was used as the sole alternative. A prototype without passenger seats was fitted with ejection seats for pilots.;Materials:
The aircraft was designed for a 30,000-hour service life over 15 years. Airframe heating and the high temperature properties of the primary structural materials, which were aluminium alloys, set the maximum speed at Mach 2.2. 15% by weight was titanium and 23% non-metallic materials. Titanium or stainless steel were used for the leading edges, elevons, rudder and the rear fuselage engine-exhaust heat shield.
Engines
SSTs for M2.2 had been designed in the Soviet Union before Tupolev was tasked with developing one. Design studies for the Myasishchev SST had shown that a cruise specific fuel consumption of not more than 1.2 kg/kgp hr would be required. The only engine available in time with the required thrust and suitable for testing and perfecting the aircraft was the afterburning Kuznetsov NK-144 turbofan with a cruise SFC of 1.58 kg/kgp hr. Development of an alternative engine to meet the SFC requirement, a non-afterburning turbojet, the Kolesov RD-36-51A, began in 1964. It took a long time for this engine to achieve acceptable SFC and reliability. In the meantime the NK-144 high SFC gave a limited range of about, far less than Concorde. A maximum speed of was reached with afterburning. Afterburners were added to Concorde to meet its take-off thrust requirement and were not necessary for supersonic cruise; the Tu-144 used maximum afterburner for take-off and minimum for cruise.The Tu-144S, of which nine were produced, was fitted with the Kuznetsov NK-144A turbofan to address lack of take-off thrust and surge margin. SFC at M2.0 was 1.81 kg/kgp hr. A further improvement, the NK-144V, achieved the required SFC, but too late to influence the decision to use the Kolesov RD-36-51.
The Tu-144D, of which five were produced, was powered by the Kolesov RD-36-51 turbojet with an SFC of 1.22 kg/kgp hr. The range with full payload increased to 5,330 km compared to 6,470 km for Concorde. Plans for an aircraft with a range in excess of range were never implemented.
The engine intakes had variable intake ramps and bypass flaps with positions controlled automatically to suit the engine airflow. They were very long to help prevent surging; twice as long as those on Concorde. Jean Rech states the need for excessive length was based on the misconception that length was required to attenuate intake distortion. The intakes were to be shortened by 10 feet on the projected Tu-144M.
The Kolesov RD-36-51 had an unusual translating plug nozzle as an alternative to a variable con-di nozzle, either of which give the variable area ratio required for the range of nozzle pressures which come from low inlet ram at low speeds to high at Mach 2. A plug nozzle was studied for Concorde but rejected as it was not certain that it could be cooled adequately during afterburner operation. The RD-36-51 had no afterburner.
Airframe
The aircraft was assembled from parts machined from large slabs, many over long and wide. While at the time, this approach was heralded as an advanced feature of the design, it turned out that finished parts contained defects which had not been detected in the raw material. Cracks formed at the defects at load levels below that which the part was expected to withstand. Once a crack started to grow, it spread quickly over many metres, with no crack-arresting design feature to stop it. In 1976, during repeat-load and static testing at TsAGI, a Tu-144S airframe cracked at 70% of the design flight load with cracks running many metres in both directions from their origin.Two Tu-144S airframes suffered structural failures during laboratory testing just prior to the Tu-144 entering passenger service. The problem, discovered in 1976, may have been known prior to this testing; a large crack was discovered in the airframe of the prototype Tu-144 during a stopover in Warsaw following its appearance at the 1971 Paris Air Show. Polish sources say the crack was discovered after the aircraft made an emergency landing due to the failure of both left-hand engines; however, an Aeroflot spokesperson denied the damage and disputed the circumstances of the landing.
Later the same year, a test airframe was subjected to a test simulating the temperatures and pressures occurring during a flight. High skin temperatures of were caused by kinetic heating when the boundary layer air reached during cruise. The Tu-144 was placed in an environmental chamber and heated to simulate the skin getting hot quickly, during acceleration to cruising speed, while the underlying structure took a while to reach its equilibrium temperature. This thermal effect caused internal stresses and the situation was reversed while slowing down and descending. The pressure in the cabin, which caused additional stresses, was changed at the same time as the skin heating to simulate climbing to cruise altitude and then descending. Repeatedly cycling the temperature and pressure, as happened with the aircraft in service, caused fatigue damage and the airframe failed in a similar way to that of the TsAGI load testing.
According to, an aerospace aluminium and beryllium alloys expert, the Tu-144 design allowed a higher incidence of defects in the alloy structure, leading to the fatal in-air breakup of the aircraft in the 1973 Paris Air Show Tu-144 crash. This conclusion was supported by some of the designers involved in the aircraft's development. Vadim Razumikhin wrote that the load factor experienced by the plane at the moment of the break-up was less than the design limit. If the stress tests had been conducted earlier, the disaster may have been averted. Eventually, the airframe was strengthened and the control system was modified to prevent overstressing the aircraft.