Why Space Elevators? Unmatched Logistics & Delivery Efficiency

by Peter Swan, Ph.D

The conundrum of rockets is that the delivery of mass to its destination is an insignificant percentage of the mass on the launch pad.? The most glaring example is the delivery of a half a percent of the launch pad mass to the surface of the moon for Apollo 11.? It is up to 2% for delivery to Geosynchronous Orbit and woefully small for delivery to Mars' orbit, much less to Mars' surface.? The question is why would you employ a methodology for delivery that only delivers less than one percent to your desired location (let’s say the future Gateway around the Moon).? Modern-Day Space Elevators solve this conundrum by delivering 70% of the mass at liftoff to GEO and beyond (the other 30% is the tether climber which is reused repeatedly) by leveraging electricity.

This estimate is developed to illustrate efficiencies of both. The future is bright for commercial advanced propulsion capabilities.? Rockets will be less expensive than today, more reusable, with greater capacity in loads. However, they cannot escape the rocket equation and those limitations on lift efficiencies [2% to GEO, 0.5% to lunar surface, etc.].? Rockets do have tremendous advantages. They are operational today and can start huge programs immediately; and more importantly, they move people through radiation belts rapidly for trips to the Moon and Mars.? ??This conundrum of rockets cannot be beaten, even when we get to very advanced thrusters in the nuclear propulsion arena. Another factor that hurts performance is the reusability of rockets, as that improvement has a tremendous ability to help on cost, reliability and on-schedule launches;? however, reusability does not improve the conundrum of the rocket equation. It? actually hurts delivery statistics because it adds weight on the pad to accomplish re-entry, return to Earth, and reusability.? ?

As a comparison, Space Elevators deliver about 70% of the mass on the pad to GEO and beyond with the other 30% being completely reusable tether climbers.? Their delivery statistic of 70%, a ratio compared to rockets of 140 to one, ensures the customer will quicky raise the desired mass towards their destination.