A molecular drag vacuum pump configured for pumping a gas stream from an inlet to an outlet, the pump including a high-speed spinning disk or rotor disposed within a housing. A passageway is formed inside the housing adjacent the disk, and gas comes in contact with surfaces of the spinning disk in successive stages, conformable wipers being disposed adjacent the spinning disk to direct the gas stream to the successive stages. The disk can be powered by an integrated motor, comprising permanent magnets associated with the disk and cooperating coils associated with the housing. The wipers can include parallel ridges on a contacting face to facilitate creation of a conformable fit with the rotor. Seal rings may be disposed against the disk between gas passageways to reduce leakage therebetween, and the pump may include regenerative pumping pockets to help prevent backflow. The housing may have a modular configuration to allow two or more pump modules to be connected and operate in series. Successive stages may be independently or commonly powered, and may counter-rotate.