A disaster valve for downhole use in a gas or oil well is built into a unitary housing having a wireline running tool connector at one end and a control package at the other end. In the center of the housing, a ball valve (in one embodiment) or a piston and cylinder valve (in another embodiment) is arranged to be operated by a new and improved mandrel driven by a motor for rotating a feed screw. The housing includes passages and parts configured so that the lower end of the housing lies along the axis of the tubing to enable a peripheral fluid flow, coaxially around the housing. Near the valve, the fluid is diverted from the peripheral flow into an axial flow. The valve controls the fluid flow at the point where the peripheral flow converts into the axial flow. During catastrophic conditions, a quick release feature enables the valve to be driven to a closed position under spring tension.