Space freighters for the 21st century

Abstract

The useful life cycle of space launchers derived from the military long range missiles, developed during the fifties in East and West, will come to an end with the turn of the century. They have served the space faring nations of this planet well in the past and are a good basis to start from to develop space freighters for the 21st century. The market potential expected in a changing geopolitical environment and mission requirements give a fairly good frame of reference in which future launch vehicle developments can be discussed. The near future will have to live with existing space transportation systems such as Space Shuttle, Proton, Titan 4 and Energia when larger payloads look for transportation. The unmanned Shuttle C concept is marginal in performance and offers minor improvements in economy only. Thus it is not the space launcher we are looking for, at best a stop gap solution. In the present geopolitical situation it might become acceptable to use the Energia for large civilian payloads by all space faring nations. This would be an economical solution for medium-sized space freighters and serve the market for the next 20 years. The concept of an “Advanced Launch Vehicle” as favoured by the U.S. Air Force for their conceived requirements is not a popular project anymore, since even the latest concepts in connection with the space defense initiative (SDI) are no longer based on such a space launcher. Considering the fact that a Moon project and more so a Mars expedition appears likely for the first half of the 21st century it is easy to see that present launch vehicles are not suitable for such a program. The answer would be a heavy “Space Freighter” in the Post-Saturn class as already analysed in the sixties for those missions. Since these early studies the rule “What you can do on Earth you should do there”! is now more apparent than ever. This will reduce the number and complexities of expensive operations in space! Or in other words: The larger the launch vehicle, the cheaper and faster the space program! A representative space freighter which can transport 300 metric tons to low Earth orbit or about 100 metric tons to the geostationary and lunar orbits is presented with respect to performance, size, operations, schedule and cost to indicate that the technology is not the limiting factor. Most of it is available now. The problem is the market and the determination to provide for the future in time—with the decline in military expenditures during the next decade it appears probable that a major new launch vehicle development is feasible from the financial viewpoint and desirable from the political viewpoint if seen in the international context.