A coupling assembly (10,100, 200) for fluidly connecting first and second spacecraft (S1, S2), the first spacecraft comprising a drive mechanism and the second spacecraft comprising a valve (1, 101, 201) for filling and/or draining the second spacecraft, the coupling assembly (10,100, 200) comprising: a first connector comprising an actuating member (14, 114, 214) configured to engage and open the valve (1, 101, 201) and a coupling member configured to couple to the drive mechanism such that the drive mechanism is operable to exert a torque on the coupling member to rotate the coupling member; a second connector comprising a stop portion and a bore for transferring fluid, the second connector configured to screw on to the valve (1, 101, 201) until the stop portion engages the valve (1, 101, 201); and, at least one lock configured such that, in use, the or each lock is initially in a locked state wherein the coupling member is rotationally fixed relative to the second connector such that operation of the drive mechanism rotates the coupling member and the second connector together such that the second connector is screwed on to the valve (1, 101, 201) until the stop portion engages the valve (1, 101, 201), the actuating member (14, 114, 214) being prevented from moving relative to the second connector to engage and open the valve (1, 101, 201) whilst the or each lock is in the locked state, and wherein the or each lock is configured such that, once the stop portion engages the valve (1, 101, 201), operation of the drive mechanism to exert a torque on the coupling member that is greater than a predetermined torque level moves the or each lock to an unlocked state wherein the actuating member (14, 114, 214) is moveable relative to the second connector to engage and open the valve (1, 101, 201). a first connector comprising an actuating member (14, 114, 214) configured to engage and open the valve (1, 101, 201) and a coupling member configured to couple to the drive mechanism such that the drive mechanism is operable to exert a torque on the coupling member to rotate the coupling member; a second connector comprising a stop portion and a bore for transferring fluid, the second connector configured to screw on to the valve (1, 101, 201) until the stop portion engages the valve (1, 101, 201); and, at least one lock configured such that, in use, the or each lock is initially in a locked state wherein the coupling member is rotationally fixed relative to the second connector such that operation of the drive mechanism rotates the coupling member and the second connector together such that the second connector is screwed on to the valve (1, 101, 201) until the stop portion engages the valve (1, 101, 201), the actuating member (14, 114, 214) being prevented from moving relative to the second connector to engage and open the valve (1, 101, 201) whilst the or each lock is in the locked state, and wherein the or each lock is configured such that, once the stop portion engages the valve (1, 101, 201), operation of the drive mechanism to exert a torque on the coupling member that is greater than a predetermined torque level moves the or each lock to an unlocked state wherein the actuating member (14, 114, 214) is moveable relative to the second connector to engage and open the valve (1, 101, 201).