Liquid storage system

A liquid storage system, suitably an aircraft fuel tank system, comprises an outer tank 16 for containing a liquid enclosing a liquid storage space 14, and an inner tank 18a, 18b located within the outer tank and enclosing the liquid storage space. A deformable spacing means 20a, 20b associated with the outer tank and the inner tank for maintaining the tanks in a spaced apart relationship. On application of a force to the inner tank, at least part of the inner tank moves relative to the outer tank. The inner tank may define a chamber between a first wall and a second wall. The volume of the chamber is sufficient to allow a shockwave 30 in the liquid in the system, resulting from compression of the liquid by impact of a projectile 24 to be reduced by expansion of the compressed liquid into the chamber. The inner tank may be formed of aramid or para-aramid fibres. The inner tank may be rigid. The spacing means may be elastic.