Kremlin stars

The Kremlin stars (Russian: Кремлёвские звёзды) are the pentagonal luminescent ruby stars, installed in the 1930s on five towers of the Moscow Kremlin, replacing gilded eagles that had symbolized Imperial Russia.

The first Kremlin star was installed on top of the Spasskaya Tower on October 25, 1935. During the next week, another three stars were installed on the Troitskaya, Nikolskaya, and Borovitskaya towers. These stars replaced huge copper two-headed eagles, installed in pre-revolutionary times, which were a part of the Coat of Arms of Imperial Russia.

The body of each star was made of stainless steel and covered with copper plating. The Kremlin stars were decorated with a hammer and sickle on both sides, made of semi-precious stones from the Ural mountains. The installation of the first Kremlin stars did not meet the designer's expectations since the surfaces of the semi-precious stones lost their luster and required re-faceting. In 1937, these stars were replaced with new ones made of ruby glass, in time for the 20th anniversary of the October Revolution. One more star was also installed on the Vodovzvodnaya tower.

The size and the form of each of the five stars were defined proceeding from the height and architectural features of each corresponding tower. The distance between the end points of beams of the star installed on the Vodovzvodnaya tower equals 3 metres (9.8 ft), Borovitskaya tower – 3.2 metres (10 ft), Troitskaya tower – 3.5 metres (11 ft), and Nikolskaya and Spasskaya towers – 3.75 metres (12.3 ft). The bearing construction of each of the Kremlin stars is made of stainless steel and represents a spatial pentagonal star, the points of which have the form of a tetrahedral pyramid. The durability and rigidity of the construction was designed to withstand the maximum pressure of a hurricane wind equaling 200 kgf per square meter (2 kPa). Despite the considerable mass of each star (approximately 1 tonne (0.98 long tons; 1.1 short tons)), they revolve pretty easily as the wind changes its direction. Because of its form, each star always positions itself with its frontal side against the wind. The Kremlin stars are illuminated from the inside by filament lamps so that they could be seen against the sky. Even distribution of light inside the stars is ensured by the refractors, which consist of prismatic glass plates. The power of these lamps (3.7 kW in the stars of the Vodovzvodnaya and Borovitskaya towers and 5 kW in the remaining three) ensures good visibility of the stars day and night. The lamps have a luminous efficacy of 22 lm/W. The 5 kW lamps are 383 millimetres (15.1 in) in length, the diameter of their retorts is 177 millimetres (7.0 in). Each lamp produces a great deal of heat; hence, each star has to be cooled. For this purpose, each tower is equipped with two fans aimed at the star.

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Wikipedia