DALLAS — Today, in 1996, a US-Russian Joint Commission began technical interchange and research on supersonic transport technologies.

The end of the Cold War gave way to an unprecedented opportunity for the US (NASA) and Russia (Tupolev) to collaborate in a joint aeronautical flight research program. Former US Vice President Al Gore and Russian Prime Minister Chernomyrdin chaired the Joint Commission on Economic and Technological Cooperation.

Jock Lowe, a former Concorde pilot, gives us a backdrop of what was to come after the Cold War era regarding supersonic transport (SST) research. In an interview for a BBC Future article on Tupolev's SST, Lowe said: "The thesis was, up to that point, that the faster the aircraft, the more successful it was. With fighter planes like the MiG-21 and the American F-104 already capable of flying at twice the speed of sound, supersonic travel seemed a possible, if challenging, task."

NASA-US HRS Program

At the time, NASA and US commercial aviation industries were heavily involved in a High-Speed Research (HSR) program further to develop Supersonic Transport (SST) aircraft technologies.

The goal of the HSR program was to rearticulate the US in a leadership position toward developing a second-generation SST aircraft. 

In Russia, Tupolev's Aircraft Design Bureau had proposed as early as 1990 that a TU-144 SST could be used as a flying test bed supporting NASA's HSR program. 

Greenlit by the Joint Commission, a team of senior NASA and US industry aviation specialists developed a prioritized battery of flight experiments with a corresponding senior squad from the Tupolev design office. The goal was to understand what modifications had to be made to the TU-144 to conduct the experiments. 

These activities were the genesis of the TU-144LL Supersonic Flying Laboratory used in the joint research program. But before we delve into the research carried out with the test-bed aircraft, we will examine its initial history.

The Tupolev TU-144 Supersonic Transport

Soviet aeronautical engineer Andrei Nicholayvich Tupolev (1888) was responsible for the design of many Russian aircraft.

Tupolev, the director of the Tupolev Design Bureau and the general designer for the TU-144, was known for pioneering aircraft designs. After he died in 1972, Andrei was succeeded by his son, Alexei. Like many great technological feats during the Cold War, politics was at the heart of the TU-144's inception.

Andrei and Alexei Tupolev were present on December 31, 1968, for the maiden flight of a prototype Tu-144, which became the world's first supersonic aircraft. The TU-144 was designed initially as a supersonic transport for service in the Russian airline industry.

On November 1, 1977, a TU-144 flew from Moscow to Alma-Ata, Kazakhstan, making its first passenger flight. Seventeen TU-144s were manufactured, including a prototype and five D models. Due to its design failure and a high-profile disaster at the 1973 Paris Air Show, the type was later known as the Soviet Union's flawed rival to Concord.

What makes the US-Russian Joint Commission's technical interchange interesting from a historical point of view is that 30 years earlier, as Lowe puts it, there was "an international race between the TU-144, Concorde and the American designs made by Boeing and Lockheed."

The TU-144LL Test-bed

And so, in the fall of 1996, NASA, a team of US aircraft and engine manufacturers, and Russia's ANTK n.a. A. N. Tupolev began using the Russian TU-144 D supersonic jet as a flying laboratory. 

Data collected by six experiments aboard the TU-144LL and two ground experiments would be used to develop technologies for a proposed second-generation supersonic passenger jet. 

As for the aluminum-titanium alloy and steel flying spear, the modified TU-144LL used for the HSR flight program had slightly different specifications than a production model. The wingspan of the LL was 88 feet and 7 inches (27.0 m), and the overall length was 196 feet and 10 inches (60 m). 

The typical takeoff weight of the TU-144LL was 440,000 pounds (200,000 kg), and it held 224,800 pounds (102,000 kg) of fuel. If used as a passenger aircraft, the TU-144LL could carry 140 passengers 3,508 nm (4,040 miles/6,500 km), cruising at maximum speeds. 

The type was powered by the then-new Kuznetsov NK-321 turbofan engines, rated at more than 55,000 pounds of thrust in full afterburner.

High-Speed Research Flights

As part of NASA's HSR Program, a US aerospace team contracted with Tupolev to use the modified TU-144 D transport aircraft to conduct supersonic experiments. All test flights would be performed in Russia from Tuvolep's facilities at the Zhukovsky Air Development Center outside Moscow. 

Boeing led the US team of researchers for the TU-144LL project, with help from McDonnell Douglas Corp., Rockwell, Pratt & Whitney, General Electric, flight deck partner Honeywell, and more than 70 major subcontractors.

For the program's first phase, 27 research flights of the TU-144LL were conducted over a two-year period with apparent ease. According to NASA, "The grace and beauty of the airplane masked the very extensive amount of effort that was required by Tupolev to re-engine it for the research flights." 

However, the work ahead was not easy. Developing, implementing, and operating an instrumentation system that could measure nearly 800 parameters required by the experiments was difficult. The six thousand-mile distance between the US experimenters and the airplane did not make the instrumentation task any easier. 

Regardless of these challenges, the test flights were carried out successfully. Researchers compared full-scale supersonic aircraft flight data with results from models in wind tunnels, computer-aided techniques, and other flight tests.

Furthermore, three evaluation flights at subsonic and supersonic speeds accomplished by US pilots in September 1998 underscored US participation in the flight program. 

Two NASA pilots, Robert Rivers of Langley Research Center, Hampton, Virginia, and Gordon Fullerton of Dryden Flight Research Center, Edwards, California, gained hands-on experience with the operation of a truly historical airplane that, albeit rife with problems, was now an updated test-bed for advanced technologies.

Program Results

By March 1998, the Joint Commission had already recognized the program as "a model for US and Russian government-business partnerships in the development of advanced technologies." 

According to NASA, the experiments' propulsion, aerodynamic, structural heating, structural acoustics, ground effects, handling qualities, and operating environment data were "eagerly assimilated into the program's information database."

Thus, the TU-144LL program was successful for the US HSR program and the Joint Commission. Of the 27 flights conducted, seven and two ground-based experiments yielded conclusive flight data that enhanced the supersonic flight information available to US and Russian aeronautical engineers. 

The specifications of the flight test experiments can be found in NASA's factsheets.

End of the US HRS Program

The Russian federal economy was still severely depressed after the Cold War due to political change in Russia following the collapse of communism, which depreciated its global position in HRS research and development.

In the end, after four more data collection flights in the spring of 1999, the cancellation of the US HSR program marked the end of the joint US-Russian research project. According to NASA, the program was ended mainly because an economically viable SST could not be "envisioned near enough to further justify US industry's commitment."

Upon completing all of the joint HRS Program's programmed objectives, the TU-144LL aircraft was consigned to idleness and later relegated to being seen at the MAKS International Air Show at Zhukovsky International Airport (ZIA).

Featured image: A view of the front of the Tu-144, with the distinctive retractable mustache canards deployed and a drooping nose. Photo by Christian Volpati, GFDL 1.

Articles sources/reproduced excerpts: NASA.gov, Past Projects: TU-144LL Flying Laboratory; High-Speed Research - The Tu-144LL A Supersonic Flying Laboratory FS-1996-09-18-LaRC September 1996; BBC FUTURE; theaviationgeeksclub.com.

https://airwaysmag.com/boeings-supersonic-dreams/