Analysis of on-orbit refueling opportunity using flexible architecture assessment framework

Abstract

A space system is unique in that it is a complex system without routine repair, maintenance, and upgrade since the access to operating space systems requires plenty of resources. Therefore, the cost to develop, produce, and operate space systems is very high. High cost and difficulty in maintenance requires longer lifetime and more reliability. As a result, they induce the increase of cost. To overcome these difficulties, many researches have been done or are being developed to enable the on-orbit maintenance and upgrade. Technical difficulties must be removed, and moreover, the cost-effectiveness of on-orbit servicing must be proven in the early stage of development. Refueling is one of on-orbit servicing, and this thesis analyzes on-orbit refueling opportunities using flexible architecture assessment framework. This framework provides important information on whether on-orbit refueling needs to be investigated with enough resources in the early stage of development. First, the dual-mode disaster monitoring constellation supported by on-orbit refueling depots are proposed. The switches between two modes are done by orbit transfers, and the fuel required for orbit transfers is supplied by on-orbit refueling depots. In addition, trade-off studies regarding operation of the constellation and on-orbit refueling depots are performed. Through this analysis, the limits of traditional approach to assess on-orbit refueling service are revealed and in order to overcome these limits, flexible architecture assessment framework is introduced. This thesis evaluates the value of flexibility that the on-orbit refueling may provide, using the real options theory. The flexibility of systems can change forms or functions to respond to uncertainties. As a result, it is able to reduce risks and catch opportunities. Flexible architecture assessment framework consists of four steps to help system architects define the elements of the framework. System architects can evaluate the va...