A centrifugal brake mechanism for a controlled descent device, the centrifugal brake mechanism being configured to be attached to a harness wearable by a descending user, and comprising: a support structure configured for attachment to the harness; a circular wheel located inside said support structure and configured and operable to rotate about an axis of rotation thereof, said circular wheel comprising a circular central cavity and an inner wall encircling the cavity; an axle mounted inside said central cavity, the axle extending along and rotatable about said axis of rotation inside said central cavity, and two or more parallel shaft rods attached to the axle and extending substantially perpendicular to the axis of rotation inside the cavity; a gear system configured and operable to transfer rotations of said wheel into counter-rotations of said axle; one or more brake elements mounted on said two or more parallel shaft rods, each brake element having two or more pass-through bores for slidably moving along said two or more parallel shaft rods inside said central cavity, and two or more springs mounted over at least one of said shaft rods between the brake element and the axle, said one or more brake elements being configured and operable to radially slide over the parallel shaft rods towards the inner wall of the wheel encircling said cavity in response to the counter-rotations of said axle; and a friction enhancement mechanism for increasing friction forces responsive to increase in angular velocity of the wheel, said friction enhancement mechanism being configured for providing additional engagement between the circular wheel and the brake element and comprising one or more circular rails and corresponding one or more curved grooves engageable with said one or more rails, to thereby progressively increase friction between said brake elements and the inner wall of the wheel responsive to increase in angular velocity of the wheel. a support structure configured for attachment to the harness; a circular wheel located inside said support structure and configured and operable to rotate about an axis of rotation thereof, said circular wheel comprising a circular central cavity and an inner wall encircling the cavity; an axle mounted inside said central cavity, the axle extending along and rotatable about said axis of rotation inside said central cavity, and two or more parallel shaft rods attached to the axle and extending substantially perpendicular to the axis of rotation inside the cavity; a gear system configured and operable to transfer rotations of said wheel into counter-rotations of said axle; one or more brake elements mounted on said two or more parallel shaft rods, each brake element having two or more pass-through bores for slidably moving along said two or more parallel shaft rods inside said central cavity, and two or more springs mounted over at least one of said shaft rods between the brake element and the axle, said one or more brake elements being configured and operable to radially slide over the parallel shaft rods towards the inner wall of the wheel encircling said cavity in response to the counter-rotations of said axle; and a friction enhancement mechanism for increasing friction forces responsive to increase in angular velocity of the wheel, said friction enhancement mechanism being configured for providing additional engagement between the circular wheel and the brake element and comprising one or more circular rails and corresponding one or more curved grooves engageable with said one or more rails, to thereby progressively increase friction between said brake elements and the inner wall of the wheel responsive to increase in angular velocity of the wheel.