Orbital Refueling System Ors

With the ever-shrinking military budget constraints facing military and civilian contractors, the ability to extend the operational life of any system for minimal cost compared to a replacement is desirable. This fact has never been more true than in today's space industry. This thesis addresses the possibility of extending satellite life through the use of on-orbit refueling. Through compilation and analysis of satellite operational life span data, it is shown that maneuvering fuel depletion has a significant impact on satellite operations in geosynchronous orbit. If these satellites could be refueled economically this would prove not only cost effective but also improve satellite tactical employment for space support to the warfighter. Through the manipulation of satellite data, launch/design cost, on-orbit refueling vehicle design/construction costs and on-orbit operational requirements, it can be shown that on-orbit refueling can be done cost effectively. Single versus multiple satellite refueling operations were evaluated to determine the concept's viability.

Existing on-orbit refueling systems have steadily increased the mass of propellant they can refuel from Orbital Express' 22 kilograms in 2007 to Tianzhou 2's delivery of 2000 kilograms in 2021, yet refueling rates like the industry-leading Robotic and Refueling Mission's .155 kilograms per second demonstrated in 2012 shows that some technology areas could still hold back legitimate refueling operations. Refueling system designers should consider a few insights from this research to help define architectures that close existing gaps in refueling system performance.

Next, the results of a parametric study analyzing the effects of staging, mass ratio, and specific impulse on optimal refueling orbit placement and mass savings are shown and discussed. Specifically, this parametric study confirms that orbital refueling can offer significant launch vehicle mass savings, potentially providing equivalent missions for 1.4-7.3 times less total mass than the traditional single rocket architecture for two-stage rockets and enabling utilization of single-stage to orbit (SSTO) launch vehicles for more demanding missions. Additionally, upcoming missions, such as NASA's Artemis 1 mission and a SpaceX Starship Mars mission are assessed with refueling in mind, and potential mass savings are tabulated for applicable optimal refueling architectures. Finally, the idea of sustainable, on-orbit cryogenic refueling infrastructures is discussed as a whole, with long-term effects on the human exploration of the solar system theorized and presented. The second topic of research in this thesis concerns itself with developing technologies and methods needed to achieve on-orbit refueling.