Water supply

Buran had a Water Supply System (SVO) that consisted of the Potable Water System (SPV), designed to provide drinking water to the crew, and the Process Water System (STV), intended to supply water to the thermal control and hydraulic systems.

The bulk of the potable water on Buran was to be produced as a byproduct of the fuel cells, which use oxygen and hydrogen to generate electrical power. Before ending up in one of two reservoirs inside the crew compartment (one prime, one back-up), the near-distilled water passed through a cleansing unit filled with hydrogen gas and then through another unit where it was enriched with silver ions. The water was extracted from the reservoirs via a manually operated pump and then passed through a cooling device or a heater. It could be used either for drinking or for preparing food. A 10-liter back-up supply of potable water was to be pumped into Buran before launch.

Process water was needed for the flash evaporators of the Thermal Control System and the hydraulic system. It was stored in four separate units containing four 25 liter tanks each, giving a total capacity of 400 liters. Since Buran needed this water for cooling during launch, some 370 liters were pumped into the tanks on the ground, with the fuel cells being capable of supplying an additional 30 liters during the final countdown and ascent. During on-orbit operations the STV collected additional water from the fuel cells, dumping overboard any excess supplies. The process water was distilled and saturated with silver ions. It was pushed out of the tanks with compressed air [18].