in a controlled manner without failure also the rods must be sized to permit the unpressurized cable to be spooled onto a reasonable size spool the primary design load for the pressurized cable is compression in service the pressurized cable will buckle in a controlled manner without exceeding material strength and strain allowables the elastic energy stored in the buckled configuration provides a thrust vector which is applied to the well tool individual composite rods are usually sized to a diameter of between about 0 1 and about 0 5 inches the number of rods used in a pressurized cable will depend on the size of the cable and usually varies between about 5 and about 200 rods the cable itself usually has a diameter of between about 2 and about 20 inches the membrane which forms the inner surface of the pressurized cable may be formed of a plastic material such as mylar or a rubber material either synthetic or natural the membrane must be sufficiently flexible to form a flattened member when unpressurized and have sufficient strength to react the pressure used to hold the composite rods against the outer protective sheath of the cable when the membrane is inflated since the composite rods are to be maintained in a spaced relationship to each other it is preferred that the surface of the membrane in contact with the rods have a.