Online Journal of Space Communication

Article Title

The Spaceplane Equation


Revenue earning space missions for deployment of space solar power satellites are economically competitive only when launch costs are in the region of $100-200 / kg in orbit. Nearly one half the capital cost of a solar power station is attributed to space transportation. To meet the objective of safe, affordable space transportation, an abundance of reusable space vehicle design concepts and programs emerged world-over, from 1985 to the present day. All these have been either abandoned or sub-optimally supported. Their designs emerged by the application of the ideal rocket equation derived in 1903 by Konstantin Tsiolkovsky. It had served as the scientific foundation for the design of multi-stage space rockets and ballistic missiles throughout the 20th century. The rocket equation emerged from a simple systems concept: the expendable space rocket that carries all the oxygen needed from earth for propulsion into space with low fuel efficiency rocket engines.

New fully reusable space vehicle concepts use the earth's atmosphere to enhance fuel efficiency and reduce/avoid carrying oxygen on board from earth to orbit. Their shape and aerodynamics call for adopting aircraft design practices. The classical rocket equation is unable to provide a satisfying and adequate theoretical framework to guide design of more complex systems concepts. A modification of the Tsiolkovsky rocket equation is developed here that introduces a "mass ratio multiplier factor," which enables a better understanding of spaceplanes. The Spaceplane Equation shows how mass ratios obtainable only by 2-and 3-stage rockets can be realized in a single stage. Novel spaceplane design and technology domains emerge from parametric mapping using the Spaceplane Equation that could synergize more effective design and development of space transportation systems for space solar power missions.



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