A pumping assembly for pumping a fluid from an upstream fluid source to a downstream location, the pump comprising: - a motor comprising: - a stator; and - a rotor, configured to rotate relative the stator on a pump axis, the rotor rotatably supported by a first motor bearing and a second motor bearing, the rotor including a permanent magnet array and a rotor shaft, wherein a cavity is formed within the rotor shaft; - a drive mechanism connected to the rotor, the drive mechanism configured to receive a rotational output from the rotor and convert the rotational output into a linear input along the pump axis to cause pumping of the fluid, the drive mechanism comprising: - a drive nut connected to the rotor shaft to rotate with the rotor, the drive nut extending axially from the rotor shaft away from the motor; - a screw elongated along the pump axis and disposed coaxially with the drive nut on the pump axis, wherein the screw is configured to be linearly driven along the axis by rotation of the drive nut, the screw including a first end and a second end disposed opposite the first end; and - a plurality of rolling elements disposed radially between the drive nut and the screw and supporting the drive nut relative to the screw to maintain a radial gap between the drive nut and the screw; - a clocking member interfacing with the screw to prevent rotation of the screw about the pump axis; and - a pump comprising a piston, wherein the piston is connected to the drive mechanism to receive the linear input and is disposed coaxially with the drive mechanism and the rotor, wherein the piston is configured to reciprocate axially along the pump axis to pump fluid, wherein the first end of the screw is oriented towards the pump and the screw extends from the drive nut and into the cavity such that the second end of the screw is at least partially disposed within the cavity and extends into the motor during at least a portion of a pump cycle. - a motor comprising: - a stator; and - a rotor, configured to rotate relative the stator on a pump axis, the rotor rotatably supported by a first motor bearing and a second motor bearing, the rotor including a permanent magnet array and a rotor shaft, wherein a cavity is formed within the rotor shaft; - a stator; and - a rotor, configured to rotate relative the stator on a pump axis, the rotor rotatably supported by a first motor bearing and a second motor bearing, the rotor including a permanent magnet array and a rotor shaft, wherein a cavity is formed within the rotor shaft; - a drive mechanism connected to the rotor, the drive mechanism configured to receive a rotational output from the rotor and convert the rotational output into a linear input along the pump axis to cause pumping of the fluid, the drive mechanism comprising: - a drive nut connected to the rotor shaft to rotate with the rotor, the drive nut extending axially from the rotor shaft away from the motor; - a screw elongated along the pump axis and disposed coaxially with the drive nut on the pump axis, wherein the screw is configured to be linearly driven along the axis by rotation of the drive nut, the screw including a first end and a second end disposed opposite the first end; and - a plurality of rolling elements disposed radially between the drive nut and the screw and supporting the drive nut relative to the screw to maintain a radial gap between the drive nut and the screw; - a drive nut connected to the rotor shaft to rotate with the rotor, the drive nut extending axially from the rotor shaft away from the motor; - a screw elongated along the pump axis and disposed coaxially with the drive nut on the pump axis, wherein the screw is configured to be linearly driven along the axis by rotation of the drive nut, the screw including a first end and a second end disposed opposite the first end; and - a plurality of rolling elements disposed radially between the drive nut and the screw and supporting the drive nut relative to the screw to maintain a radial gap between the drive nut and the screw; - a clocking member interfacing with the screw to prevent rotation of the screw about the pump axis; and - a pump comprising a piston, wherein the piston is connected to the drive mechanism to receive the linear input and is disposed coaxially with the drive mechanism and the rotor, wherein the piston is configured to reciprocate axially along the pump axis to pump fluid,