1. Tupolev Tu-104:
While the three major US, European, and former-USSR powers all designed supersonic transports, that of the latter was actually the first to fly. But its development was complicated and it ultimately ended in failure.
Seeking to increase speeds and reduce travel times on scheduled routes, all of which were flown by Aeroflot, the country stepped up to pure-jet technology with its first such airliner, the Tupolev Tu-104, when it first flew in prototype form on June 17, 1955.
The low-wing monoplane, incorporating many of the elements of the military Tu-16 twin turbojet bomber to reduce development time, featured a glazed nose navigator’s station, a 35-degree swept wing mounted with significant anhedral, dual wing root buried, 14,881 thrust-pound Mikulin RD-3 or AM-3 eight-stage, axial-flow turbojets, and quad-wheel main undercarriage units that retracted into wing underside fairings. Although initial capacity was 50, 70-passenger Tu-104As and 100-passenger Tu-104Bs, in five-abreast configurations, followed.
Inaugurated into service on September 15, 1956 on the Moscow-Umsk-Irkutsk route, it severely reduced flying times over the piston types it replaced.
“At the time of its entry into service, the Tu-104 was the only turbojet-powered transport in airline service,” according to John Stroud in “Soviet Transport Aircraft since 1945” (Putnam and Company, Ltd., 1968, p. 199), “the de Havilland Comet 1 and 1A types having been withdrawn from service in 1954. It was not until the autumn of 1958 that BOAC introduced Comet 4s and Pan American World Airways Boeing 707-120s.”
Like the countries in the West, the former Soviet Union believed that a supersonic transport was the next logical development of commercial aviation.
2. Myasishchev M-52:
The foundation for a Russian supersonic transport was laid by the Myasishchev Design Bureau’s M-52 intercontinental bomber. Powered by four Solovy’ev turbojets, two of which were pylon-mounted to the high, swept wings and two of which were attached to their tips, it was intended for at least Mach 2 cruise speeds.
Although the only example ever built publicly appeared in Tuscino in 1961, or a year after the design bureau which had given birth to it was abolished, commercial feasibility studies of it had been commenced. While its high-wing configuration was considered inappropriate for passenger-carrying services and its range was insufficient for such operations, this logic, at least in the Soviet Union, was sounder than may at first be considered, since both the turboprop Tupolev Tu-114 and pure-jet Tu-104 had been civilian versions of, respectively, the Tu-95 and Tu-16 bombers.
3. Tupolev Tu-144:
An all-new supersonic design was clearly needed. Because Myasishchev’s proposal was inappropriate and Ilyushin was preoccupied with rectifying the problems with its Il-62 long-range, pure-jet passenger aircraft, Tupolev, the country’s long established military and commercial manufacturer, was selected to produce it.
The result, the Tu-144, was one of the few aircraft up to this time initially and exclusively designed for commercial operations.
Powered by four 38,500 thrust-pound engines, the aircraft featured a 188.5-foot overall length, an 83.10-foot span of its delta wing, and a 330,000-pound gross weight. Although still only in prototype form and resembling, as expected, Concorde in configuration, there were several differences between the two.
The fuselage, first and foremost, incorporated 18 percent of titanium in its construction to cater to the expected expansion and contraction cycles that resulted from the frictional heat buildup and internal pressurization, and it was wider, with a flatter cabin floor, for five-abreast coach seating. Its single-droop nose, deflecting to the 12-degree position, sported top windows.
In planform, its double-delta wing featured an ogival or s-shaped leading edge and trailing edge elevons, but was devoid of camber or twist with a flat bottom.
Its NK-144 turbojets, grouped in barely separated pairs, were air entered through its six-foot rectangular inlets on the leading edge and stretched across more than 17 feet to its exhaust pipes at the trailing edge.
Undercarriage consisted of a two-wheeled, aft-retracting nose unit and two 12-wheeled, forward-retracting main units mounted outboard of the engine ducts and rotating 180 degrees before settling into their airfoil bays.
First flying from Moscow’s Zhukovsky Airfield after executing a 25-second acceleration roll-which marked the world’s first commercial supersonic flight of any design-the prototype, number 68001, remained airborne for 28 minutes, with its landing gear extended the entire time. Unpressurized, it internally carried flight test equipment.
Although no photographs were released at the time, it is believed that a second airframe, numbered 68002, was damaged during its own flights and a third, 68003, was used for static testing.
Fuel thirsty and range deficient, the type, requiring consistent, 100-passenger load factors to even meet breakeven costs, indicated the need for an extensive redesign of a production version, which more closely reflected Concorde.
Stretched, the fuselage, now with a 215.5-foot length and sporting 34 as opposed to the previous 25 windows, facilitated accommodation of up to 140, and its droop nose, of greater length, introduced side windows.
Two canards, installed on the upper fuselage immediately behind the cockpit, extended out- and forward to improve the aircraft’s low-speed handling characteristics.
The compound swept, full delta wing, 94.5 feet in span, offered variable camber and sculpting and a circular underside.
The engines, with square inlets, were repositioned further outboard and there was greater separation between their pairs, while the main undercarriage units, of shorter length, retracted into them.
Range, with a 33,000-pound payload, was projected as 2,000 miles.
Numbered 77101, the first prototype of this extensively redesigned version first flew in August of 1972, while the second, 77102, was the first exhibited in the West at the 1973 Paris Air Show. Its pride was short-lived, however.
During a demonstration flight on June 3, the aircraft made a low pass with its canard surfaces and undercarriage extended, before executing a steep, afterburner-augmented climb. Appearing to experience a stall at 3,000 feet, however, it commenced a dive, abruptly leveling off only a few feet above the ground, at which point the right wing tore off at the root.
Spitting flames from its engines, it rolled and the other wing dislodged itself from the structure. Exploding and plummeting to the earth, it impacted, killing the six crew members on board, eight on the ground, and damaging more than a hundred buildings in Goussainville, France.
Although no official cause was ever found, it was believed that the Tu-144 attempted to land on the wrong runway, beginning a go-around when the error was discovered, which placed it on a collision course with a Mirage fighter. Diving to avoid it, it was subjected to g-forces beyond the airframe’s capacity and too little altitude remained in which to recover. Its structural failure was therefore not attributed to any design flaw or deficiency.
After operating cargo and mail root proving flights between December of 1975 and 1976, the Tupolev Tu-144 entered scheduled service on the 2,400-mile segment between Moscow and Alma-Ata, Kazakhstan, on November 1 of the following year, operating 102 such services with an average of 70 passengers, before they were discontinued on June 6, 1978. The aircraft logged 181 airborne hours, of which 102 were at subsonic speeds.
Despite its extensive redesign, it had failed to rectify its deficiencies. Still excessively fuel thirsty, it was only able to cover the 2,400-mile route with half its payload capability, attained by deliberately leaving half its eats unoccupied, and the cabin noise level, caused by the engines and the air conditioning required to counteract the external, skin friction created heat, was intolerable.
The succeeding Tu-144D, fitted with uprated, more economical Koliesov RD-36-51A turbines, while offering hope when it first flew on May 23, 1978, fared little better. A fire in the left engines, propagating to the fuselage, left insufficient power to reach an alternate airport, causing the aircraft to careen into a field and explode. Of the five crew members aboard, two were killed and three were injured.
Although the type began route proving flights on the 3,480-mile sector from Moscow to Khabarovsk on June 23 of the following year and it covered the distance in three hours, 21 minutes, it never proceeded to scheduled status. The noise, fuel consumption, and range parameters of supersonic flight could not be transcended for commercial operations, leaving the one prototype, the two pre-production, the nine production Tu-144s, and the five production Tu-144Ds as the only testaments to this fact.
4. Tupolev Tu-144LL:
The National Aeronautics and Space Administration (NASA) teamed with US and Russian aerospace industries over a five-year period to conduct a joint international research program to develop suitable technology for an early-21st century supersonic transport that would resolve the obstacles plagued by the three Boeing 2707, Aerospatiale-British Aerospace Concorde, and Tupolev Tu-144 actual and still-borne designs.
Conducted as part of NASA’s High Speed Research (HSR) program and managed by the NASA Langley Research Center, the project was initiated after the June 1994 agreement was signed by US Vice President Al Gore, Jr. and Russian Prime Minister Viktor Chemomyrdin.
Cornerstone of it was the last Tu-144D, constructed in 1981 and sporting tail number 77114, which itself never entered commercial service, but logged 82 hours, 40 minutes during research and test flights. Originally powered by four Koliesov RD-36-51 turbojets, which provisioned it for a maximum Mach 2.15/1,450-mph speed at a 59,000-foot service ceiling, it had a range of less than 2,500 miles.
Modified for the joint program to Tu-144LL Flying Laboratory standard, it was retrofitted with four 55,000 thrust-pound Kuznetsov, afterburner-equipped NK-321 turbofans originally produced for the Tupolev Tu-160 Blackjack bomber, resulting in a Mach 2.3 speed and 3,500 nautical mile range with 224,000 pounds of fuel at a 410,000-pound maximum take off weight.
Other modifications included the addition of thermocouples, pressure sensors, microphones, and skin friction gauges to measure the aerodynamic boundary layer, an emergency crew escape system, and a Damian digital data collection system that replaced the earlier analog one.
The first of the two-phase program, running from June of 1996 to February of 1998, entailed two ground engine and six flight experiments, which required 19 airborne sorties to complete, from the Zhukovsky Air Development Center near Moscow, and involved studies concerning the aircraft exterior surface, the internal structure and powerplant, temperatures, boundary airflows, interior and exterior noise, airfoil ground effect characteristics, and varying flight profile handling characteristics.
The second phase, taking place between September of 1998 and April of 1999, entailed six fights, which not only facilitated greater understanding of the original six airborne experiments, but also provided analysis of fuselage and wind deflections, angles-of-attack, sideslip angles, and nose boom pressures.
Although no bonafide US supersonic airliner designs have been established, with those appropriate for the business jet segment more likely to precede them, these Tu-144LL aerodynamic, structural, acoustic, and operating environment experiments may pave the way for long-range, higher-capacity, economic fight that minimizes ozone layer deterioration, and the ground-experienced sonic boom.
Article Sources
National Aeronautics and Space Administration (NASA) website.
Stroud, John. “Soviet Transport Aircraft since 1945.” London: Putnam and Company, Ltd., 1968.