The Tupolev which flew on hydrogen 32 years ago

How Tupolev made history with the Tu-155

Suddenly, a tremor seems to cross Europe. France, Germany and the European Union have announced in recent months that they will invest billions in hydrogen infrastructure By 2030, Europe wants to develop a hydrogen passenger plane. This source of energy has the potential to make all of our energy consumption climate neutral. This approach is not entirely new. A hydrogen jet plane took off from the ground as early as the 1980s – in the Soviet Union.

Hydrogen plane

Hydrogen should be used more and more in aviation. France, for example, plans to fuel the Airbus A320, the widely used short and medium-range jet, with hydrogen by 2035. The development of such a green passenger plane still faces many obstacles. But Airbus has made a decision: the next generation of commercial aircraft should run on hydrogen.

Instead of passengers seats

But there are also downsides: due to its significantly lower energy density, hydrogen requires much more space than fossil fuel. It also needs to be laboriously cooled in order to stay liquid to save space. Soviet developers tackled these issues anyway. The aircraft with registration number CCCP -85035 has a large hydrogen tank in the rear part of the passenger cabin. It took up about a third of the space there. A total of 30 additional systems were integrated into the aircraft so that it could run on hydrogen. Tupolev converted the CCCP -85035 to the technological support Tu-155. In this role, it made aviation history: on April 15, 1988, the Tu-155 was the world’s first hydrogen-powered airliner to take flight.

Five years in advance

When news of the Tu-155’s successful maiden flight circled, a nervous whisper crossed the professional world west of the Iron Curtain: while in Europe the most abstract considerations in this direction were in the air, challenging time, the Russians did it, with liquid hydrogen: bringing an airliner to fly. The Tu-155 is a hybrid; only one of its three Kuznetsov NK-8 engines – they are now called NK-88 – is actually powered by hydrogen. Nevertheless, the project had made a strong impression in the West.

Hydrogen and natural gas

In the period that followed, the Tu-155 took off from Schukowski on more than 100 test flights. However, he only did part of it with hydrogen: from January 1989, Tupolev was mainly testing natural gas as a substitute for kerosene, available cheaply and in large quantities in the Soviet Union. Unlike today, the fact that the tests were carried out with hydrogen was based less on ecological than economic reasons. The idea was that crude oil could become scarce by the early 2010s at the latest – and kerosene therefore expensive. Hydrogen, on the other hand, can be produced relatively inexpensively using nuclear power.

The problem with volume

However, Tupolev engineers already faced two central challenges at the time: on the one hand, hydrogen can only be stored in liquid form with a reasonable footprint, but it needs constant cooling: at least minus 253 degrees Celsius. In contrast, liquid hydrogen provides three times more energy per kilogram than kerosene, but it takes up four times the space. That’s why it has to be stored under high pressure, which in turn requires cylindrical or spherical tanks – and these can no longer be housed in the wings as with fuel.

Big projects at Tupolev

In test mode, Tupolev solves the problem of space in a pragmatic way: the cabin of the Tu-155 has no seats, instead, apart from the test equipment, there are whole batteries of tanks of ‘hydrogen or natural gas. Engineers must also adapt three dozen other systems and components in order for the project to succeed. A production version of the Tu-155, the Tu-156, was already in planning. It provided for the storage of tanks in the rear third of the cabin, separated from the passenger area by a pressure bulkhead – very similar to what Airbus is currently considering with two of its three hydrogen airliner projects.

Back to the future?

The Tu-156 will never be produced, although tests with the Tu-155 are quite promising. Although there are even efforts between the German and Russian representatives to continue to jointly research hydrogen propulsion. After several visits to the west – in 1990, for example, the Tu-155 was invited to the ILA in Hanover – the project fell behind schedule.
In the decades that followed, the Tu-155 rotted in Schukowski. Sad.