Libeň Gas Tank

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The Libeň gas tank towering on a hilltop above Palmovka is indisputably one of the distinctive dominants of the surroundings, not only due to its exceptional location but mainly thanks to its spherical form and distinctive silver paint. Although the former gas tank is generally well-known, it is one of those Prague 8 monuments that the people are rather ignorant of and the fortunes of which often remain hidden to uninitiated persons.

The idea of the construction of spherical gas tanks emerged for the first time in the second half of the 19th century but in terms of technology similar plants could be built only in the 1920s. The basic advantage of this type of gas tank lay in the fact that gas could be stored there under relatively high pressure, which resulted in a significant increase in capacity with a relatively small built-up area.
The firm charged with the construction of the first Czechoslovak spherical gas tank was Vítkovické horní a hutní těžařstvo, while the riveted structure was manufactured by ČKD, Prague, in 1931.

The Libeň gas tank with a diameter of 20 metres and capacity of 4,189 cubic metres was riveted together from 14 mm thick metal plates; it was supported by eight double legs anchored in a round concrete base. It could store up to 12,567 cubic metres of lighting gas at an operational positive pressure of 0.3 Mpa (i.e. 3 atm.). While the gas tank itself was erected on the hill above Palmovka, the respective pumping and regulation station was built on the hill’s north base. The two structures were interconnected with a dual pipeline for gas intake and offtake and a long staircase for technical staff. The ceremonious commencement of operation took place in July 1932.
According to the original plans a network of similar equalizing gas tanks was to be created around Prague but this intention never came to existence. The 1930s and ‘40s represented one of the peaks of the Libeň gas tank fame. As a single structure on a bare rise it fulfilled not only the function for which it was designated by its nature but in a way, also symbolized industrial Libeň. Its distinctive location in the countryside, clear visibility from afar as well as the magic attractiveness of a huge spherical body contributed to the enormous popularity of the gas tank as a source of inspiration for representatives of the then avant-garde.

For long decades, the gas tank was portrayed in paintings, drawings and graphics of painters and other visual artists (František Gross, Václav Sivko, Vilém Heiter, Josef Šíma, Cyril Bouda, Jan Konůpek) and often became an object of attention of photographers, both renowned (Miroslav Hák, Josef Sudek, Tibor Honty, Václav Chochola, Josef Ehm) and amateur. It has even found a place in writing – there surely aren’t many gas tanks in the world that have been mentioned in poetry (Josef Škvorecký: “Libeň Gas Tank Blues”). Unsurprisingly enough, it gripped the attention of Bohumil Hrabal but can also be found in the work of an author who is generations younger – Miloš Urban. The Libeň gas tank is mentioned even in a broadside ballad by Vlasta Burian.
While the importance of the gas tank as an objet d’art continued practically without interruption, the term of its use in the sense of its original purpose was significantly shorter. The gas tank was severely damaged by shooting from a German gun during the Prague Uprising at the very end of the Second World War. A grenade smashed through the southern part of the jacket, made a hole approximately half a metre in diameter in it and exploded inside. Fortunately, the gas tank had been almost emptied by that time, so no explosion happened. Nevertheless, it took many hours for the rest of gas to burn out. Machine gun bullet holes in the supporting legs still bear witness to the fact that the gas tank was a tempting target.

When the war ended, the gas factory was not interested in repairing the gas tank, probably also because its concept had become outdated. Yet, the time of its greatest, although paradoxically hidden, fame was still to come. In 1947, a delegation of British scientists visited the then Aeronautical Research Institute in Letňany (LVÚ, now the Aeronautical Research and Test Institute, a.s. – VZLÚ). A more or less chance note passed on the way to the Letňany institute gave rise to the idea to use the former gas tank as a vacuum reservoir for a wind tunnel. In 1949, after all the unavoidable formalities were settled and the gas tank transferred to LVÚ, the hole in the jacket was mended and the ball underwent internal pressure tests.
The principle of the designed wind tunnel lies in its connection to a vessel, in which underpressure to the ambient atmosphere is created via exhaust. Upon opening the valves, atmospheric air is sucked through the wind tunnel piping. Thanks to appropriately shaped channels it is possible to obtain an accelerated flow with a velocity several times faster than the speed of sound. Then, a reduced-scale model of e.g. an aircraft is placed in another part of the tunnel called the measuring space, in which power effects initiated by the flowing air are measured on the model. The findings obtained in this way are applied in the design and development of real aeroplanes. Tunnels of this kind are characterised, among other things, by a noticeable sound effect created by the fast flow of air into the air vessel.
The laboratory of high-speed aerodynamics gained importance not only for the Czechoslovak air industry (jet aeroplanes such as L-29 Delfín, L-39/59 Albatros and their modifications were tested here) but also for domestic manufacturers of blade machines, above all turbines. During the fifties, it was even decided to plant poplars around the entire area for reasons of confidentiality and the premises were strictly closed to the public for several decades.

Today, the establishment’s focus is practically the same but testing models of complete aeroplanes or their wings has given way to the verification of aerodynamic profiles of single parts, e.g. probes for measuring the flight speed, propeller profiles etc. In addition to experimental research the laboratory quickly develops flow modelling via computer simulations and thus makes it possible not only for experts in aerodynamics but also for mathematicians and theoretical physics to make their mark in the field. Nevertheless, the gas tank, for which the word “koule” (ball) became accepted usage among VZLÚ employees, is still the imaginary centre of the establishment. And it is precisely this ball that, after a relatively short career in the gas industry, has been in the employ of aircraft and industrial research.
Thus, when a strange drone lasting several seconds reverberates through the streets around Palmovka from time to time, it’s not an airliner landing in the distance as the first impression may suggest. Yet, in a way, the sound is quite close to flying – and to high-speed flying in particular.