Economic Model of Reusable vs. Expendable Launch Vehicles

Abstract:

It is generally assumed by the community that reusable launch vehicles will dramatically reduce launch costs because you don’t “throw away the vehicle” every time it is used. However, this is usually taken as an element of faith, without any substantive analysis to support the conclusion. The example of the Space Shuttle, originally sold to Congress on the basis of dramatically cutting launch costs, suggests that this conclusion might not be accurate under realistic conditions of development and operations.
This paper presents an economic model of the cost per launch and cost per pound of both expendable and reusable launch vehicles. The model is presented so as to facilitate comparison between the two approaches and each cost element is discussed in terms of the impact of reusability or discard of vehicles or components. Specific numerical examples are provided. However, the model is given in a fully analytic form as well so that others can work with values of their choosing or explore alternative solutions. Finally, the model is used to determine the broad economic conditions under which reusable or expendable vehicles will be more or less expensive. This is also applied to determining under what economic conditions portions of a launch vehicle should be reused or expended.

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Wertz, J.R. 51st International Astronautical Congress, Rio de Janeiro, Brazil. Ocotber 2–6, 2000.