A control valve for controlling flow of fuel from a fuel tank to a rocket engine having a valve body longitudinally displaceable between open and closed positions of the control valve, a piston rod secured in the valve body, and a piston secured to the piston rod. The piston is subjected to a pressure gas in a first control chamber to displace the piston to the open position of the valve, against the action of a spring which urges the valve to the closed position. A locking rod is operated by the pressure gas and carries a locking member for engaging in a groove in the piston rod in the open position of the valve. A switching disk is secured on the locking rod and is subjected to the pressure gas in a first gas chamber to displace the locking member from the groove. The switching disk is provided with a control hole for throttled passage of the control gas to the first control chamber to displace the piston with a slight delay to the open position of the valve against the action of the spring. When the first gas chamber is de-pressurized control gas in the control chamber flows out through the control hole in the switching disk. Pressure gas is supplied to a second gas chamber which acts on the locking rod to keep the locking member out of contact with the piston rod.