A tank especially suitable for use as a fuel or oxidizer tank in spacecraft is divided into two tank spaces by a membrane. A liquid is stored on one side of the membrane and a pressure gas is stored on the other side of the membrane. The pressure gas is to drive the liquid out of the tank. The membrane is made of a polymer material and is held by a spring ring in a recess on the outer wall of the tank. The spring ring has a substantially C-shaped cross-section to exert elastic spring holding forces on the membrane in the recess.