Three motors (9, 13, 17) are operated independently to extend telescopically first, second, and third coaxial stages (30, 38, 52). Each motor (9, 13, 17) has an axial extension (28, 36, 48) on its rotor (12, 16, 20) that threadedly engages the respective stage (30, 38, 52). Extension (28) is fixed to rotor (12). Extensions (36, 48) are spline connected to rotors (16, 20). First stage (30) is attached to extension (36) by a bearing (62). Second stage (38) is attached to extension (48) by a bearing (64). When first stage (30) extends or retracts, it carries with it second and third stages (38, 52) and extensions (36, 48). When second stage (38) extends or retracts, it carries with it third stage (52) and extension (48). Stages (30, 38, 52) are fixed against rotation relative to a housing (4).