an energy - absorbing bumper system features a variably controllable valve which is responsive to impact conditions . the initially closed valve opens upon maximization of the pressure reading upon the bumper , and maintains the same open setting during such period of pressure maximization . during the succeeding period of pressure declination from maximum , the valve undergoes ongoing adjustment of its open setting so that the reaction force of the bumper remains constant . the valve closes when the pressure falls abruptly toward zero , thereby avoiding or curtailing an unwanted rebound effect . conventional bumper systems are dependent upon adaptation of size and / or number of fenders in order to suit different marine vessels in terms of energy absorption ; by comparison , the inventively “ smart ” bumper system is readily adaptable to diverse marine vessels .