A carriage for use in a rocket launch system for cooperating with an electromotive cableway traction drives conveyed beneath a two axis pivot anchored to the earth, elevated into a co-axial transfer tube leading to three primary tether cables whose weight is offset by balloons. The carriage has traction drives which grip cables from which they derive power and rotate to drive the carriage from the low altitude to the high altitude. The traction drives rotate in the opposite direction as the carriage descends the cable following the launch of a rocket under gravitational force. The kinetic energy of the traction drive is converted to electrical energy which is fed back to the cables during descent of the carriage.