In the beginning of 70s military leadership of Soviet Union had a great interest in laser weapon development. Laser equipment was planned to put in space platforms, stations and aircrafts.
All the built units were based on stationary sources of energy and didn't meet the requirment of military space - full autonomy. This also didn't allow designers to carry out rigorous test. The government of the USSR ordered the Navy to test and work out autonomy. Laser gun which was figured in all documents as MSU (powerful propulsion unit) was decided to be installed to a ship.
In 1976 Sergey Gorshkov, a chairman of Navy approved rebuilding of landing ship 770 SDK-20 to experimental ship called project 10030 "Foros". It was planned to test here "Akvilon" - a laser complex which targets were optical-electron units and opponent ship crew.
Process of rebuilding lasted for 8 years. Ship's hull needed to be imroved because of "Akvilon" huge size and weight. At last in September of 1984 ship OS-90 "Foros" joined The Black Sea Fleet of the USSR.
Indeed, a lot had been changed in the ship's hull. Traps were replaced by stem and bow section, 1,5 metre wide board bulge were formed, additional storey was built as 1 module with all equipment and rooms, a crane of 100 tonne carrying capacity was installed. To lower the level of noise all living and service rooms had sound-absorbing isolation. Cofferdam (a narrow horizontal or vertical section separating neighbouring rooms) also emerged for this purpose.
"Akvilon" complex was installed very carefully. A great attention was paid at designing of its bearing.
In October of 1984 first successful tests of "Foros" were carried out in Feodosiya. It was the first time in history of Soviet Navy when low flying missile had been promptly found and destructed by laser beam.
But there were some disadvantages - the attack lasted for several seconds and preparations took more than 24 hours. Efficiency output was very low - about 5%. No doubt that scientists gained experience of using laser in the battle. But dissolution of the Soviet Union and following economic crisis stopped the experiments.