The Tupolev Tu-155 was developed from Tu-154, and Tu-155 was used for an alternative fuel testbed. This is the first experimental airplane in the world operating on liquid hydrogen.
The Tu-155 first flew on 15 April 1988. It used hydrogen as fuel, and, later liquified natural gas (LNG).
Liquefied natural gas (LNG) is widely available, at least threefold cheaper in Russia than aviation kerosenes, and also significantly improves flight performance. It is straightforward to store and handie, and less fire/explosion hazardous even than today’s kerosenes. After years of laboratory work an civil transport aircraft was selected for use as an LNG flight test-bed.
To flight-test an LNG system ANTK Tupolev bailed back a Tu-154 (serial No 85035), and replaced the No 3 (starboard) engine with an NK-88, fed with LNG by a completely separate fuelsystem. The NK-88 is a derivative of the Kuznetsov NK-8-2 turbofan, with thrust unchanged at 20,945 Ib (9,500kg). The main tank, of 10ft 2in (3.1m) diameter and 17ft 81/2in (5.4m) long, is of AMG6 aluminium alloy, with a 50mm (2in) lagging of foamed polyurethane. The NK-88 engine has a dedicated two-stage centrifugal pump driven by a bleed-air turbine. LNG comes in at -152° C and is passed through a heat exchanger to convert it to gas. The engine combustion chamber is able to accept either this supply of LNG or, on command, to switch to the kerosene supply normally used for the other engines.
Range of TU-155 is 1,616 miles (2,600km) on LNG only, or 2,051 miles (3,300km) on combined LNG and kerosene. Eventually the Earth’s store of petroleum will run dry. It is pointless to say ‘More keeps being discovered’. The world’s aircraft will then have no alternative but to switch to another fuel, and LNG is the obvious choice.
Only one TU-155 was produced. More than 70 flights were made in all. The airplane was demonstrated in Nice (France), Berlin (Germany) and Prague (Czech Republic). It is retired and currently stored in the Ramenskoye Airport near Zhukovskiy.