The present invention provides a supersonic compressor comprising a supersonic compressor rotor (100) comprising a dockable rotor disk allowing restriction or opening of portions of a fluid flow channel of the rotor in order to enhance performance of the rotor during different operational stages, for example rotor start-up or steady state. The supersonic compressor rotor (100) comprises a first rotor disk (101), a second rotor disk (102) and a third rotor disk (103) which share a common axis of rotation. The first and second rotor disks (101, 102) are rotatably coupled, and the third rotor disk (103) is disposed between them. The third rotor disk (103) is independently rotatable relative to said first and second disks (101, 102), and comprises a raised surface structure (110) for restricting or opening a portion of the flow channel defined by the rotor disks (101, 102, 103) and at least two vanes (150). The flow channel comprises a supersonic compression ramp (120) and encompasses the raised surface structure (110).