Originally the Kuznetsov NK-8 turbofan, engine of the IL-62 airliner, was used as basis for the design of the engine for the first SST. After many upgrades and more than a thousand test-hours, the new engine became a reality as the Kuznetsov NK-144, a 2 spools turbofan engine with 14 compressor stages, 3 in the low pressure area and 11 in high pressure zone. Four of these engines put into the air the first SST history on 31 December 1968 and became the Tu-144 in the first passenger aircraft to exceed Mach 2.0.

In spite of these achievements, the NK-144 did not fulfil with the expectations placed on it. A best performance in fuel consumption was required if the Tu-144 wanted be used in long routes. After the accomplishment of a big number flights test, the Specific Fuel Consumption was established in 2.23 kg/hr and the range of flight of the aircraft resulted limited to 2,920 km, too far than the expected and desired for an airliner.

Looking for a better performance, the NK-144 engine was upgraded to the NK-144A model, an improved version used in Tu-144S with better features. The Specific Fuel Consumption was reduced to 1.81 kg/hr making possible a longer range of flight, but these engines still had a big problem. The new Tu-144S model was bigger and heavier than the prototype and it was necessary to keep afterburners on to maintain Mach 2.0 speed, producing a high consumption of fuel.

Because the limitations of the engine NK-144 were known since was decided to use it, was in the late sixties when was took the decision to develop a new engine for the Tu-144. A new manufacturer was chosen for that task, the company was Kolesov and the new engine was the turbojet RD-36-51A. First test with these new engines in Tu-144 were made in 1973 when the aircraft CCCP-77105 was re-engined with them. After 1978 the aircraft production was made with this engine and the new model was called Tu-144D. The RD-36-51A was a turbojet engine with 2 fans and 14 compression areas. Thanks to a low Specific Fuel Consumption of 1.26 kg/hr the Tu-144D finally reached the foreseen range and desired performance for a SST.

When in 1993 Tupolev and NASA signed an agreement to use a Tu-144 as a testbed for research experiments, the engines RD-36-51A is no longer manufactured and needed replacement. For to fit the new engines in the aircraft the nacelles were re-designed, because they were longer than previous model. After the upgrade the aircraft was designated as Tu-144LL Flying Laboratory.

The selected engine was the low bypass turbofan NK-321, an improved version of the engines of the bomber Tu-160. This new engine had 3 spools and 12 compressor stages, 5 in the low pressure area and 7 in high pressure zone. All flights test were performed over Russian territory because that engine model was catalogued as military secret. Those engines transformed the Tu-144 in an excellent tool for the accomplishment of the targets of the experiments.

A common point in all engine models used in the Tu-144 is that all they were equipped with a reheat system or afterburners. This is a system that injects fuel directly into the jet pipe downstream of the engine, producing its inflammation and providing an extra thrust to the aircraft needed in take-off or when Mach 2.0 speed is wanted.

Another common feature of all engines of the Tu-144 was the absence of thrust reverses, this converted the Tu-144 in one of the latest airliners that used parachutes as brake to stop after the landing. A double drag parachute was deployed from a conic structure under the tail of the aircraft just in the moment when she touches the runway.

The use of this brake system was necessary if the Tu-144 wanted to stop after the landing in the 1,900 meters that allow it to operate in the main airports of the world. In addition of the drag parachute, the Tu-144 was equipped with a system of hydraulically powered carbon brakes that help in the task of to stop the aircraft after the landing.

Equipping the Tu-144 with thrust reverses was always a goal for the Tupolev designers. When they were asked about that possibility they answered it was planned to install them in the two outer engines (number 1 and 4) in future versions of the Tu-144. In the left picture (from aircraft CCCP-77115) it's possible to see reverse levers on the throttle of engines 1 and 4. This shows that the Tu-144D model was very close to be equipped with a thrust reverse system.

In the Tu-144 each engine was provided with its own air intake, even after the installation of double separated nacelles in the pre-production aircraft. Originally the four engines NK-144 were mounted side by side but, due to problems with vibrations and high cabin temperature, the next models of Tu-144 were two separate nacelles holding two engines each, both positioned near the centre of the aircraft in order to guarantee the longest possible air intakes.

These long air intakes holds inside the necessary ramp system for to reduce the speed of the airflow at all speeds up to Mach 2.0 down to a level suitable for the engines. A more sophisticated ramp system would have allowed a reduction in the length of the air intakes.

Inside the air intakes an internal horizontal ramp varies from an up position at speeds below Mach 1.25 to full down at Mach 2.0. Three shocks are produced in the inlet during supersonic flight in order to slow the inlet flow to subsonic speeds. Each air intake was operated by automatic control system which could change ramp position and by-pass flap depending on engine setting.