Tupolev Tu-144

The Tupolev Tu-144 (NATO name: "Charger'") was the first commercial supersonic transport aircraft (SST). It was one of only two SSTs to enter commercial service, the other being Anglo-French Concorde. The design, publicly unveiled in January 1962, was constructed in the Soviet Union under the direction of the Tupolev design bureau, headed by Alexei Tupolev.

The prototype first flew on 31 December 1968 near Moscow, two months before the first flight of Concorde. The Tu-144 first went supersonic on 5 June 1969, and on 26 May 1970 became the first commercial transport to exceed Mach 2. The frequent comparisons to Concorde led to the Tu-144 being known as "Concordski" in the West.

A Tu-144 crashed in 1973 at the Paris Air Show, delaying its further development. The aircraft was introduced into passenger service on 1 November 1977, almost two years after Concorde. In May 1978, another Tu-144 (an improved version, named Tu-144D) crashed in a test flight while being delivered, and the passenger fleet was permanently grounded after only 55 scheduled flights. The aircraft remained in use as a cargo plane until 1983, by which point a total of 102 commercial flights had been completed. The Tu-144 was later used by the Soviet space programme to train pilots of the Buran spacecraft, and by NASA for supersonic research.

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 close similarity in appearance of the Tu-144 to the Anglo-French supersonic aircraft, there were significant differences in the control, navigation and engine systems. The Tu-144 lagged behind Concorde in areas such as braking and engine control. Concorde utilized an electronic engine control package from Lucas, Tupolev was not permitted to purchase it for the Tu-144 as it could also be used on military aircraft. Concorde's designers used airliner fuel as coolant for the cabin air conditioning and for the hydraulic system (see Concorde for details). Tupolev installed additional equipment on the Tu-144 to accomplish this, increasing the weight of the airliner.

Andrei A. Tupolev continued to improve the Tu-144 with upgrades and changes on the Tu-144 prototype. 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 such conical camber, and they added a simple but practical device: two small retractable canard surfaces, one on either side of the forward section on the aircraft, to increase lift at low speeds. Moving the elevons downward in a delta-wing aircraft increases the lift, but also pitches its nose downward. The canard cancels out this nose-downwards moment, thus reducing the landing speed of the production Tu-144s to 315 - 333 km/h, still faster than that of Concorde. The NASA study lists final approach speeds during Tu-144LL test flights as 315 - 335 km/h, however these were approach speeds exercised during test flights specifically intended to study landing effects at maximum possible range of speeds, regardless of how hard and stable the landing can be. As to regular landings, FAA circular lists Tu-144S approach speed as 329 km/h, as opposed to Concorde's approach speed of 300 km/h, based on the characteristics declared by the manufacturers to Western regulatory bodies. It is open to argument how stable the Tu-144S was at the listed airspeed. In any event, when NASA subcontracted Tupolev bureau in the 1990s to convert one of the remaining Tu-144D to a Tu-144LL standard, the procedure set by Tupolev for landing defined the Tu-144LL "final approach speed... on the order of 360 km/hr depending on fuel weight." Brian Calvert, Concorde's technical flight manager and its first commercial pilot in command for several inaugural flights, cites final approach speed of a typical Concorde landing to be 287 - 296 km/h. The lower landing speed compared to Tu-144 is due to Concorde's more refined design of the wing profile that provides higher lift at low speeds without degrading supersonic cruise performance – a feature often mentioned in Western publications on Concorde and acknowledged by Tupolev designers as well.

Design
Along with early Tu-134s, the Tu-144 was one of the last commercial aircraft with a braking parachute.

Engines
Although studies showed that turbojet engines are highly desirable for supersonic airliners, none were available. The Tu-144 prototype was therefore originally fitted with the inefficient Kuznetsov NK-144 turbofan engines and consequently suffered from higher nacelle drag. While this permitted early test flights, it did not permit cruising at Mach 2 without afterburner. A maximum cruising speed of 2430 km/h (Mach 2.29) was obtained with the afterburner. This meant that while Concorde could supercruise (maintain supersonic flight without using its afterburners), the Tu-144 could not. Later work on the Tu-144S resolved this shortcoming. The turbofan engines suffered from heavy fuel consumption, and hence a limited range of about 2500 km, far less range than the Rolls-Royce/Snecma Olympus 593 turbojet powered Concorde.

The Tu-144S model, of which nine were produced, featured the Kuznetsov NK-144F turbofan engines that offered better fuel efficiency over the original engine. The four engines each had a maximum afterburning thrust of 200 kN and each had separate inlet ducts in each nacelle and variable ramps in the inlets, giving a cruising speed of 2000 km/h (Mach 1.88). This also gave it a longer range of 3080 km, but still less than half the range of Concorde.

The final Tu-144D model of which six were produced was powered by the Kolesov RD-36-51 turbojet. This gave the Tu-144D the ability to cruise at a comparable speed to Concorde at 2124 km/h (Mach 2.0). The new engines also gave the Tu144D a much longer range, more than double the original model at 6500 km. Plans for an aircraft with a range in excess of 7000 km range were never implemented.

Espionage against and influence of Concorde
The development of the Tu-144 is closely related to industrial espionage against the French company Aérospatiale, which was developing Concorde. Sergei Pavlov, officially acting as Aeroflot's representative in Paris, was arrested in 1965 and was in possession of detailed plans of the braking system, landing gear and the airframe of Concorde. Another agent named Sergei Fabiew, arrested in 1977, was believed to have obtained the entire plans of Concorde prototype in the mid-1960s. However, these were just early development versions and would not have permitted the USSR engineers to come up with their own aircraft, but could have served as an indication of the work of Concorde design team. An espionage theory involved the Anglo/French Concorde team, who knew that the Soviets were planning to steal the plans, and therefore put into circulation a set of dummy blueprints with deliberate design flaws.

Production
A total of 16 airworthy Tu-144s were built: The last production aircraft, Tu-144D number 77116, was not completed and was left derelict for many years on Voronezh East airfield. There was at least one ground test airframe for static testing in parallel with the development of prototype 68001.
 * the prototype Tu-144, registration number 68001
 * a pre-production Tu-144S, number 77101
 * nine production Tu-144S, numbers 77102 to 77110
 * five Tu-144D models, numbers 77111 to 77115.

Although its last commercial passenger flight was in 1978, production of the Tu-144 did not cease until 1984, when construction of the airframe was stopped and left partially complete.

Operational service


The Tu-144S went into service on 26 December 1975, flying mail and freight between Moscow and Alma-Ata in preparation for passenger services, which commenced on 1 November 1977.

The passenger service ran a semi-scheduled service until the first Tu-144D experienced an in-flight failure during a pre-delivery test flight, crash-landing, on the 23 May 1978 with two crew fatalities. The Tu-144's 55th and last scheduled passenger flight occurred on 1 June 1978.

An Aeroflot freight-only service recommenced using the new production variant Tu-144D ("D" for Dal'nyaya – "long range") aircraft on 23 June 1979, including longer routes from Moscow to Khabarovsk made possible by the more efficient Kolesov RD-36-51 turbojet engines, which also increased the maximum cruising speed to Mach 2.15.

Including the 55 passenger flights, there were 102 scheduled flights before the cessation of commercial service.

Later use


The Tu-144 programme was cancelled by a Soviet government decree on 1 July 1983 that also provided for future use of the remaining Tu-144 aircraft as airborne laboratories. In 1985, Tu-144D were used to train pilots for the Soviet Buran space shuttle. In 1986–1988 Tu-144D No. 77114, built in 1981, was used for medical and biological research of high-altitude atmosphere radiological conditions. Further research was planned but not completed, due to lack of funding.

Use by NASA
In the early 1990s, a wealthy businesswoman, Judith DePaul, and her company IBP Aerospace negotiated an agreement with Tupolev, NASA, Rockwell and later Boeing. They offered a Tu-144 as a testbed for its High Speed Commercial Research program, intended to design a second-generation supersonic jetliner called the High Speed Civil Transport. In 1995, Tu-144D No. 77114 (with only 82.5 hours of flight time) was taken out of storage and after extensive modification at a cost of US$350million, designated the Tu-144LL (where LL is a Russian abbreviation for Flying Laboratory, Letayuschaya Laboratoriya, Летающая Лаборатория). The aircraft made a total of 27 flights during 1996 and 1997. Though regarded as a technical success, the project was cancelled for lack of funding in 1999.

This aircraft was reportedly sold in June 2001 for $11M via an on-line auction, but the aircraft sale did not proceed. Tejavia Systems, the company handling the transaction, reported in September 2003 that the deal was not signed as the replacement Kuznetsov NK-321 engines from a Tupolev Tu-160 bomber were military hardware and the Russian government would not allow them to be exported.

In 2003, after the retirement of Concorde, there was renewed interest from several wealthy individuals who wanted to use the Tu-144LL for a transatlantic record attempt, despite the high cost of a flight readiness overhaul even if military authorities would authorize the use of NK-321 engines outside Russian Federation airspace.

The last two aircraft remain at the Tupolev production plant in Zhukovsky, Nos. 77114 (the Tu-144LL) and 77115. In March 2006, it was reported that both aircraft would be preserved, with one erected to a pedestal near Zhukovsky City Council or above the Gromov Flight Research Institute entrance from Tupolev avenue.

A local Zhukovsky newspaper reported that Tupolev offered to restore a Tu-144 (possible No. 77116) to flying condition for the 2014 Winter Olympic Games in Sochi, to transport the Olympic flame and take part in an air show. Given the time in storage, the history of this aircraft and the claims that hull No. 77116 believed to have been dismantled for metal, this report seems unlikely.

Early flights
Early flights in scheduled service indicated the Tu-144S was extremely unreliable. During 102 flights and 181 hours of freight and passenger flight time, the Tu-144S suffered more than 226 failures, 80 of them in flight. (The list was included in the Tu-144 service record provided by the USSR to BAC-Aérospatiale in late 1978, when requesting Western technological aid with the Tu-144, and probably incomplete). A total of 80 of these failures were serious enough to cancel or delay the flight.

After the inaugural flight, two subsequent flights, during the next two weeks, were cancelled and the third flight rescheduled. The official reason given by Aeroflot for cancellation was bad weather at Alma-Ata, however when the journalist called the Aeroflot office in Alma-Ata about local weather, the office said that the weather there was perfect and one aircraft had already arrived that morning. Failures included decompression of the cabin in flight on 27 December 1977, and engine exhaust duct overheating causing the flight to be aborted and returned to the takeoff airport on 14 March 1978.

Alexei Tupolev, Tu-144 chief designer, and two USSR vice-ministers (of aviation industry and of civil aviation) had to be personally present in Domodedovo airport before each scheduled Tu-144 departure to review the condition of the aircraft and make a joint decision on whether it could be released into flight. Subsequently, flight cancellations became less common, as several Tu-144s were docked at Moscow's Domodedovo International Airport..

Typical flight details
Tu-144 pilot Aleksandr Larin remembers a troublesome flight around 25 January 1978. The flight with passengers suffered the failure of 22 to 24 on-board systems. Seven to eight systems failed before takeoff; given the large number of foreign TV and radio journalists aboard the flight, and also some other foreign notables aboard, it was decided to proceed with the flight in order to avoid the embarrassment of cancellation.

After takeoff, failures continued to multiply. While the aircraft was supersonic en route to the destination airport, Tupolev bureau's crisis center predicted that front and left landing gear would not extend and that the aircraft would have to land on right gear alone, at the aircraft landing speed of over 300 km/h. Due to expected political fallout, Soviet leader Leonid Brezhnev was personally notified of what was going on in the air.

With the accumulated failures, an alarm siren went off immediately after the takeoff with sound and volume similar to that of a civil defense warning. The crew could not figure a way to switch it off and the siren stayed on throughout the remaining 75 minutes flight. Eventually the captain ordered the navigator to borrow a pillow from the passengers and stuff it inside the siren's horn. Luckily, all landing gears extended and aircraft was able to land.

The final passenger flight of Tu-144 on around 30 May 1978 involved valve failure on one of the fuel tanks.

Suggesting low confidence of the Soviet decision-makers in Tu-144 is also the fact that only one route was ever used, with flights limited to once a week, despite having eight Tu-144S certified aircraft by the time passenger service commenced in 1977 and a number of routes suitable for supersonic flights. Booking was limited to 70–80 passengers a flight or less, well below the Tu-144's seating capacity, despite waiting lists. Over its 55 scheduled flights, Tu-144s transported 3,194 passengers, an average of 58 passengers per flight. With officials being acutely aware of the aircraft's poor reliability and fearful of possible crashes, Soviet decision-makers were purposefully limiting flight frequency to the absolute minimum possible that still allowed them to claim regular service, and also were constraining passenger load to minimize the impact and political fallout of a possible crash.
 * Limited routes

Airframe test failures
The most serious problem with the aircraft was discovered when two Tu-144S airframes suffered catastrophic failures during laboratory testing just prior to the Tu-144 entering passenger service. This data is included as a chapter in Firdlyander's memoirs and mentioned by Bliznyuk et al. The problem, discovered in 1976 its return flight in June 1971 from a tour to Salon Aeronautique coming back to Moscow via East Berlin and Warsaw.

In retrospect, the most fatal design decision for Tu-144 was the decision to assemble it from large machined blocks and panels, many over 19 m long and 0.64 to 1.27 m wide. While at the time, this approach was heralded as an advanced feature of the Tu-144 design program, it turned out that large whole-moulded and machined parts contained inconsistencies in the alloys structure that cracked at stress levels below what the part was supposed to withstand. Once a crack started to develop, it spread quickly for many meters, with nothing to stop it. In 1976 during repeat-load and static testing at TsAGI (Russia's Central Aerohydrodynamic Institute), a Tu-144S airframe cracked at 70% of expected flight stress with cracks running many meters in both directions from their origin.

Later the same year, a Tu-144 was subject to a test simulating heat and pressure conditions during a flight. The Tu-144 was placed in a hyperbaric chamber and heated to 130 - 150 C. Contraction and expansion happen because of the cooling during ascent and descent, heating during supersonic acceleration and cruise and because of the pressure change from high altitude (low outside pressure causing the airframe to expand) to ground-level pressure (causing it to contract). The airframe cracked heavily and in a similar way as during TsAGI load testing.

While fatigue cracks are normal in aircraft, the usual occurrence is that a crack develops slowly and stops once it reaches the end of the panel of which larger parts are assembled. Thus an aircraft could fly with a minor crack for an extended time, until it could be fixed. The Tu-144 design was the opposite of standard practice, fostering a higher incidence of non-uniformities in alloy structure leading to crack formation and allowing a crack to develop fast and for many meters. Academician Fridlyander, leading Soviet metallurgist and long-term collaborator of Tupolev since mid-1940s through the 1990s, concludes his account of the Tu-144 program: "Airplane (the Tu-144) was doomed as soon as the decision was made to compose it of large monolithic fragments machined of large metal panels, this created its antipode, an unsafe, damageable design". However, the Airbus A-380 has large sections of wings and fuselage panels made with computer-controlled milling machines from a solid aluminum slab.

Decision to go back to passenger service
The Soviet leadership made a political decision to enter the Tu-144 into passenger service in November 1977 despite receiving testing reports indicating that the Tu-144 airframe was unsafe and not airworthy for regular service. Aeroflot appears to have thought so little of the aircraft that it did not mention it in its five-year plan for 1976–1980. However, it was not the airline executives' decision and Aeroflot reluctantly put the Tu-144 into passenger service on 1 November 1977.

Though the decision to cancel the Tu-144S passenger service came a few days after the Tu-144D crashed during the test flight on 23 May 1978, this crash was regarded as the last straw over mounting concerns about the reliability of the Tu-144. Even the fact that the technical reason for the crash was specific to the Tu-144D fuel pump system and did not apply to the Tu-144S did not help. The decision to pull the Tu-144S out of passenger service after merely 55 flights is thus more likely to be attributable to high incidence of failures during and before the scheduled flights.

Cabin noise
One problem for passengers during flights was the very high level of noise inside the cabin. The noise came partially from the engines and partially from the air conditioning and the aircraft skin cooling system. Unlike conventional aircraft, this cooling system was absolutely vital for supersonic cruise to cool off the aircraft skin, prevent it from overheating and losing structural integrity. Heat generated by intense air-to-surface friction in supersonic flight is passed to the coolant (cabin air, in case of both the Tu-144 and Concorde) and subsequently discharged via heat exchangers to the fuel stream right before it is pumped to the engines. Unlike Concorde, the Tu-144 cooling system was very noisy. Passengers seated next to each other could have a conversation only with difficulty, and those seated two seats apart could not hear each other even when screaming and had to pass hand-written notes instead. Noise in the back of the aircraft was unbearable. Alexei Tupolev acknowledged the problem to foreign passengers and promised to fix it.

Seeking outside aid
There were unprecedented Soviet requests for Western technological aid with the development of the Tu-144. The request was made despite obviously not helping to foster Soviet technological prestige, which was one of the key purposes of the Tu-144 programme. In 1977 the USSR approached Lucas Industries, a designer of the engine control system for Concorde, requesting help with the design of the electronic management system of the Tu-144 engines, and also asked BAC-Aérospatiale for assistance in improving the Tu-144 air intakes. (The design of air intakes' variable geometry and their control system was one of the most intricate features of Concorde, contributing to its fuel efficiency. Over half of the wind-tunnel time during Concorde development was spent on the design of air intakes and their control system.) In late 1978 the USSR requested a wide range of Concorde technologies, obviously reflecting the broad spectrum of unresolved Tu-144 technical issues. The list included de-icing equipment for the leading edge of the air intakes, fuel-system pipes and devices to improve durability of these pipes, drain valves for fuel tanks, fireproof paints, navigation and piloting equipment, systems and techniques for acoustical loading of airframe and controls (to test against acoustic fatigue caused by high jet-noise environment), ways to reinforce the airframe to withstand damage, firefighting equipment, including warning devices and lightning protection, emergency power supply, landing gear spray guards (aka water deflectors or "mud flaps" that increase engine efficiency when taking off wet airstrip). These requests were denied after the British government vetoed them on the ground that the same technologies, if transferred, could be also employed in Soviet bombers. Soviet approaches were also reported in British mainstream press of the time, such as The Times.

Compressor disc failure in 1980
On 31 August 1980, Tu-144D (77113) suffered a compressor disc failure in supersonic flight leading to further destruction of airframe structural elements and onboard systems. The crew was able to perform an emergency landing at Engels-2 strategic bomber base. On 12 November 1981, a Tu-144D's RD-36-51 engine was destroyed during bench tests, leading to a temporary suspension of all Tu-144D flights. One of the Tu-144Ds (77114, aka aircraft 101) suffered a crack across the bottom panel of its wing.

Economic inefficiency
Finally, the higher oil prices of the 1970s were starting to catch up with the Soviet Union. Much later than in the West, but since the late 1970s, commercial efficiency was starting to become a factor in aviation development decision-making even in the USSR. The Tu-144 disappeared from Aeroflot published prospects, replaced by the Ilyushin Il-86, a jumbo jet that was to become the Soviet flagship airliner.

In the late 1970s, Soviet insiders were intensely hopeful in conversations with Western counterparts of reintroducing Tu-144 passenger service for the 1980 Moscow Olympic games, even perhaps for flights to Western Europe, given the aircraft's high visibility, but apparently the technical condition of the aircraft weighed against such re-introduction even for token flights.

As discussed by Moon, economic efficiency alone would not have doomed the Tu-144 altogether; continuation of token flights for reasons of political prestige would have been possible, if only the aircraft itself would have allowed for it, but it did not. The Tu-144 was to a large extent intended to be and trumped as a symbol of Soviet technological prestige and superiority.

Cessation of Tu-144D production
The decision to cease Tu-144D production was issued on 7 January 1982, followed by a USSR government decree dated 1 July 1983 to cease the whole Tu-144 programme and to use produced Tu-144 aircraft as flying laboratories. A formal decision to cease the Tu-144 programme was in all likelihood related, to an extent, to the generational change in the Soviet leadership and departure of those officials who had strong individual commitment to the Tu-144 and stakes in the project, and corresponding change in the bureaucratic balance. The Tu-144 fared worse after the death of Minister Petr Dementiev on 14 May 1977, but the last bureaucratic straw must have been Brezhnev's death on 10 November 1982.

In retrospect it is apparent that the Tu-144 suffered from a rush in the design process to the detriment of thoroughness and quality, and this rush to get airborne exacted a heavy penalty later. The rush is apparent even in outward timing: the 1963 government decree launching the Tu-144 programme defined that the Tu-144 should fly in 1968, so it did indeed fly on the last days of 1968 to fulfill government goals set five years earlier. (By the way of comparison, Concorde's first flight was originally scheduled for February 1968, but was pushed back several times until March 1969 in order to iron out problems and test components better). Unlike Concorde development, the Tu-144 project was also strongly driven by ideologically and politically motivated haste of Soviet self-imposed racing against Concorde; Aleksei Poukhov, one of Tupolev's designers, reminiscences: "For the Soviet Union to allow the West to get ahead and leave it behind at that time was quite unthinkable. We not only had to prevent the West from getting ahead, but had to compete and leapfrog them, if necessary. This was the task Khruschev set us... We knew that when Concorde's maiden flight had been set for February or March, 1969, we would have to get our plane up and flying by the end of 1968."

The introduction of the Tu-144 into passenger service was timed to the 60th anniversary of the Communist revolution, as was duly noted in Soviet officials' speeches delivered at the airport before the inaugural flight – whether the aircraft was actually ready for passenger service was deemed of secondary importance. Even the outward details of the inaugural Tu-144 flight betrayed the haste of its introduction into service: several ceiling panels were ajar, service trays stuck, window shades dropped without being pulled, reading lights did not work, not all toilets worked and a broken ramp delayed departure half an hour. On arrival to Alma-Ata, the Tu-144 was towed back and forth for 25 minutes before it could be aligned with the exit ramp. Equally telling is the number of hours spent on flight testing. Whereas Concorde had been subjected to 5,000 hours of testing by the time it was certified for passenger flight, making it the most tested aircraft ever, total flight testing time of the Tu-144 by the time of its introduction into passenger service was less than 800 hours. Flight testing time logged on the prototype (68001) was 180 hours flight testing time for the Tu-144S till the completion of state acceptance tests was 408 hours; service tests till the commencement of passenger service were 96 hours of flight time; altogether totalling 756 hours. It is unclear why the Minister of Aviation Industry and the Minister of Civil Aviation did not endorse the protocols of state acceptance tests for four months after the tests completion. One reason could be the change of the guard – Minister Dementiev, who was one of the chief backers of Tu-144, died a day before the tests completed (something Gordon fails to notice) – but it might also had something to do with aircraft reliability record uncovered during the tests that was no better than the subsequent dismal service record.

External factors contributing to project cancellation
Fridlyander points out that in addition to the Tu-144, Tupolev's bureau had to work on other projects, including the Tu-154 passenger aircraft and the Tu-22M bomber. Despite large and high-priority resource investment in the Tu-144 development programme and the fact that a large part of the whole Soviet R&D infrastructure was subordinated to the Tu-144 project, parallel project development overwhelmed the bureau causing it to lose focus and make design errors. (Design errors affected not only the Tu-144, but the Tu-154 as well). The first batch of 120 Tu-154s suffered from wing destruction due to excessive structural load and had to be withdrawn.

The rushed introduction to service of poorly tested aircraft happened previously with another Tupolev project that had high political visibility and prestige: the Tu-104 passenger jet liner that was the first successful passenger jet airliner in service (the de Havilland Comet 1 was not considered successful because four of the original nine aircraft crashed). In a decision-making similar to the Tu-144 story, the Soviet government introduced the Tu-104 into passenger service before satisfactory stability and controllability of the aircraft could have been achieved, despite the fact that during high-altitude and high-speed flights the aircraft was prone to longitudinal instability, and also that at high altitudes, it had a narrow range of angle of attack separating the aircraft from stalls. These problems created the preconditions for spin dives, that happened twice before the Tu-104 was eventually properly tested and the problem was resolved.

This politically motivated rush, along with the fact that the project was essentially ideologically motivated rather than driven by intrinsic needs of the Soviet society, and with general technological insufficiencies of Soviet industrial base, contributed to the final undoing of the Tu-144 project. (Alexander Poukhov, one of the Tu-144 design engineers who subsequently rose to be one of the bureau's senior designers, estimated in 1998 that the Tu-144 project was 10–15 years beyond the USSR's capabilities at that time).

Moon suggests that subordination of available Soviet R&D resource allocation to the Tu-144 programme significantly slowed down the development of other Soviet aircraft projects, such as the IL-86 wide-body jet, and stagnated Soviet aviation development for almost a decade.

After project cancellation
After ceasing the Tu-144 programme, Tu-144D No. 77114 (aircraft 101 or 08-2) carried out test flights between the 13–20 July 1983 to establish 13 world records registered with the Fédération Aéronautique Internationale (FAI). These records established an altitude of 18200 m with a range of loads up to 30 tonnes, and a sustained speed of 2032 km/h over a closed circuit of up to 2000 km with similar loads. The note about loads, does not hold much significance as payload was compensated fuel load reduction to maintain the same overall takeoff weight and the records for a closed circuit length, suggest that the aircraft was only carrying a partial fuel load.

To put the numbers in perspective, Concorde's service ceiling under a typical Transatlantic flight payload of 10 tonnes is 18290 m, and this is higher than the record set by the Tu-144D. According to unverified sources, during a 26 March 1974 test flight a Concorde reached its maximum speed ever of 2370 km/h (Mach 2.23) at an altitude of 19415 m and during subsequent test flights reached maximum altitude of 20700 m. It is unclear why Tu-144D's maximum achievable altitude would be lower than Concorde's even regular flight altitude given that Tupolev's data claim better lift-to-drag ratio for the Tu-144 (over 8.0 for Tu-144D vs Concorde's 7.3–7.7 at Mach 2.x) and the thrust of the Tu-144D's RD-36-51 engines is higher than Concorde's Olympus 593 engines.

Concorde was originally designed for cruising speeds up to Mach 2.2, but its regular service speed was limited to Mach 2.02 to reduce fuel consumption, extend airframe life and provide a higher safety margin. One of Tupolev's web site pages states that "TU-144 and TU-160 aircraft operation has demonstrated expediency of limitation of cruise supersonic speed of M=2,0 to provide structure service life and to limit cruising altitude".

Neither Concorde nor the Tu-144 are limited in their maximum speed by the airframe drag, nor by the engines' thrust. They are limited by the airframe heating and structural integrity of their similar aluminium alloys. The Tu-144 prototype (airplane No. 68001) may have had an edge since about 15–20% of its parts were built of titanium. Indeed, the Tu-144 No. 68001 briefly achieved a maximum speed of 2443 km/h (Mach 2.26) during one of the test flights on 25 May 1970. However the use of titanium for production Tu-144's was radically cut down and the Tu-144S/Tu-144D were built almost entirely of aluminium alloys with titanium and stainless steel used only for the leading edges, elevons, rudder and under-surface of the rear fuselage (which was heated by engine exhaust, since Tu-144 engines were located close to the fuselage).
 * Use of titanium:

Given that the alloys used for both airplanes are almost identical and the thermodynamics of their critical edges is similar, the speeds achievable by each aircraft, while maintaining the same level of structural safety, would be about the same. The Tu-144S may have had an edge with its higher fuel consumption, as this fuel doubled as a heat discharge medium, allowing for more airframe cooling.

Variants

 * Tu-144 – (izdeliye 044 – article 044) The sole prototype Tu-144 aircraft
 * Tu-144 – (izdeliye 004 – article 004) Six re-designed production aircraft powered by Kuznetsov NK-144A engines in widely spaced nacelles, and re-designed undercarriage
 * Tu-144D – (izdeliye 004D – article 004D)(D-Dahl'neye – long-range) Production Tu-144 aircraft powered by Koliesov RD36-51 non after-burning engines. One aircraft converted from Tu-144 CCCP-77105(c/n10031) and five production aircraft (CCCP-77111 [c/n10062] to CCCP-77115 [c/n 10091]) plus one (CCCP-77116) uncompleted
 * Tu-144DA – Projected improved version of the Tu-144D with greater fuel capacity and therefore longer range increased up to 7500 km
 * Tu-144LL – One Tu-144D aircraft (CCCP-77114 [c/n10082]) converted to a flying laboratory with four Kuznetsov NK-321 afterburning turbofan engines and re-registered RA-77114. The first flight took place on 19 November 1996 with the 27th and last flight on 28 February 1998

Proposed military versions
Early configurations of the Tu-144 were based on the unbuilt Tu-135 bomber, retaining the latter aircraft's canard layout, wings and nacelles. Deriving from the Tu-135 bomber, early Tupolev's design for supersonic passenger airplane was code-named Tu-135P before acquiring the Tu-144 project code.

Over the course of the Tu-144 project, the Tupolev bureau created designs of a number of military versions of Tu-144 but none were ever built. In the early 1970s, Tupolev was developing the Tu-144R intended to carry and air-launch up to three solid-fueled ICBMs. The launch was to be performed from within Soviet air space, with the aircraft accelerating to its maximum speed before releasing the missiles. The original design was based on the Tu-144S, but later changed to be derived from the Tu-144D. Another version of the design was to carry air-launched long-range cruise missiles similar to the Kh-55. The study of this version envisioned the use of liquid hydrogen for the afterburners.

In the late 1970s Tupolev contemplated the development of a long-range heavy interceptor (DP-2) based on the Tu-144D also able to escort bombers on long-range missions. Later this project evolved into an aircraft for electronic countermeasures (ECM) to suppress enemy radars and facilitate bomber's penetration through enemy air defenses (Tu-144PP). In the early 1980s this functionality was supplanted with theatre and strategic reconnaissance (Tu-144PR).

The dimmer civil prospects for Tu-144 were becoming, the more Tupolev tried to "sell" the aircraft to the military. One of the last attempts to sell a military version of the Tu-144 was the Tu-144MR, a project for a long-range reconnaissance aircraft for the Soviet Navy intended to provide targeting information to the Navy's ships and submarines on sea and oceanic theaters of operations. Another proposed navy version was to have a strike capability (two Kh-45 air-to-surface cruise missiles), along with a reconnaissance function.

The military was unreceptive to Tupolev's approaches. Vasily Reshetnikov, the commander of Soviet strategic aviation and subsequently, a vice-commander of the Soviet Air Force, remembers how in 1972 he was dismayed by Tupolev's attempts to offer for military use the aircraft that "fell short of its performance target, was beset by reliability problems, fuel-thirsty and difficult to operate.

Reshetnikov goes on to remember: "The development and construction of the supersonic airliner, the future Tu-144, was included in the five-year plan and was under the auspices of the influential D.F. Ustinov (then Soviet minister of defence and confidant of Brezhnev, who represented interests of defence industries lobby in opposition to the military) who regarded this mission as a personal responsibility – not so much to his country and people as to 'dear Leonid Il'ych' (Brezhnev) whom he literally worshipped, sometimes to the point of shamelessness... Yet the supersonic passenger jet was apparently not making headway and, to the dismay of its curator, it looked like Brezhnev might be disappointed. It was then that Dmitry Fedorovich (Ustinov) jumped at someone's bright idea to foist Aeroflot's 'bride in search of a wedding' on the military. After it had been rejected in bomber guise, Ustinov used the Military Industrial Commission (one of the most influential Soviet government bodies) to promote the aircraft to the Strategic Aviation as a reconnaissance or ECM platform, or both. It was clear to me that these aircraft could not possibly work in concert with any bomber or missile carrier formation; likewise I could not imagine them operating solo as 'Flying Dutchmen' in a war scenario, therefore I resolutely turned down the offer."

"Naval Aviation Commander Aleksandr Alekseyevich Mironenko, followed suit."

"Ustinov could not be put off that easily. He managed to persuade the Navy C-in-C (admiral) S.G. Gorshkov who agreed to accept the Tu-144 for Naval Aviation service as a long-range reconnaissance aircraft without consulting anyone on the matter. Mironenko rebeled against this decision, but the commander-in-chief would not hear of heed – the issue is decided, period. On learning of this I was extremely alarmed: if Mironenko had been pressured into taking the Tu-144, this meant I was going to be next. I made a phone call to Aleksandr Alekseyevich, urging him to take radical measures; I needn't have called because even without my urging Mironenko was giving his C-in-C a hard time. Finally Ustinov got wind of the mutiny and summoned Mironenko to his office. They had a long and heated discussion but eventually Mironenko succeeded in proving that Ustinov's ideas were unfounded. That was the last time we heard of Tu-144."

Operators

 * Ministry of Aviation Production
 * Aeroflot Soviet Airlines
 * Aeroflot Soviet Airlines

Aircraft on display
While several Tu-144s were donated to museums in Moscow Monino, Samara and Ulyanovsk, at least two Tu-144D remained in open storage in Moscow Zhukovsky.

As of June 2010, two aircraft are located outdoors at LII aircraft testing facility, Zhukovsky (at coordinates 55.56979°N, 38.15565°W and 55.57178°N, 38.1523°W). Previously, they were constantly on display at MAKS Airshows.

Tu-144S, tail number 77106, is on display at Central Air Force Museum of Russia in Monino. Maiden flight was on 4 March 1975, the final one on 29 February 1980. The plane was used to assess the effectiveness of the air-conditioning systems and to solve some problems on the fuel system. It can be considered the first production aircraft, being the first to be equipped for commercial use and delivered to Aeroflot. The first operational flight was on 26 December 1975 between Moscow and Alma-Ata carrying cargo and mail. This aircraft was the first SST to land on a dirty runway when she was retired to Monino. Another Tu-144, tail number 77107, is on open display in Kazan. The plane was constructed in 1975 and was a production model intended for passenger use. However, it was only used during test flights. On 29 March 1976 it made its last flight to Kazan.

TU-144S, tail number 77108, is on display in the museum of Samara State Aerospace University. It made its maiden flight on 12 December 1975, and its final flight on 27 August 1987. Development works on navigation system were made in this aircraft as well as flight-director approach. 

TU-144S, tail number 77110, is on display at the Museum of Civil Aviation in Ulyanovsk. Maiden flight	occurred on 14 February 1977, the final Flight on 1 June 1984. This aircraft was the second of the two planes used for regular passengers' flights on Moscow - Alma-Ata route. In 1977 it flew to Paris to take part in the XXXII Paris Air Show at Le Bourget Airport. This was the last appearance of a Tu-144 in West Europe. CCCP-77110 was the last plane produced of the model Tu-144S, powered with Kuznetsov NK-144A engines. In the first half of 2008 the cabin was open for visits and between August and September was restored and painted in the original Aeroflot livery.

The only Tu-144, tail number 77112, on display outside the former Soviet Union was acquired by the Auto & Technikmuseum Sinsheim in Germany, where it was shipped – not flown – in 2001 and where it now stands, in its original Aeroflot livery, on display next to an Air France Concorde.

Paris Air Show crash
At the Paris Air Show on 3 June 1973, the development program of the Tu-144 suffered severely when the first Tu-144S production airliner (reg 77102) crashed.

While in the air, the Tu-144 underwent a violent downwards manoeuvre. Trying to pull out of the subsequent dive, the Tu-144 broke apart and crashed, destroying 15 houses and killing all six people on board the Tu-144 and eight more on the ground.

The causes of this incident remain controversial. A popular Russian theory was that the Tu-144 tried to avoid a French Mirage chase plane that was attempting to photograph its canards, which were very advanced for the time, and that the French and Soviet governments colluded with each other to cover up such details. The flight of the Mirage was denied in the original French report of the incident, perhaps because it was engaged in industrial espionage. More recent reports have admitted the existence of the Mirage (and the fact that the Russian crew was not told about the Mirage's flight) though not its role in the crash. The official press release did state: "though the inquiry established that there was no real risk of collision between the two aircraft, the Soviet pilot was likely to have been surprised." Howard Moon stresses that last-minute changes to the flight schedule would have disoriented the pilots in a cockpit with notably poor vision. He cites an eyewitness who claims the co-pilot had agreed to take a camera with him, which he may have been operating at the time of the evasive manoeuvre.

Yet another popular Russian theory (even claimed to be the official Soviet version - sources needed) is that the co-pilot has a video camera with him to film the flight. He dropped the camera, and its shoulder belt contacted the electric switcher of trimmer control and engaged it at the wrong moment of time.

Another theory relates to deliberate misinformation on the part of the Anglo-French team. The main thrust of this theory was that the Anglo-French team knew that the Soviet team was planning to steal the design plans of Concorde, and the Soviets were allegedly passed false blueprints with a flawed design. The case, it is claimed, contributed to the imprisonment by the Soviets of Greville Wynne in 1963 for spying. Wynne was imprisoned on 11 May 1963 and the development of the Tu-144 was not sanctioned until 16 July 1963.

Specifications (TU-144D)