Space Servicing, Mobility, and Logistics (SML) Technology for the United States Space Force (USSF) Update

The first paper in this series was presented at the 2024 SciTech Forum special session on Space Maneuver and Logistics. This paper presents the need to achieve architecture-level interoperability. Many space vehicles used for in-space logistics may be comprised of hundreds of satellite nodes within dozens of constellations and should interoperate to be efficient and effective. It will be described how the emerging Space Mobility & Logistics (SML) function could capitalize on & augment interoperability for all in-space nodes & constellations. SML services are enabled by built-in interoperability features embedded in both client & servicing space vehicles. Additional interoperability features are needed to embed resilience & effectiveness into all nodes of the architecture. The Department of Defense (DoD) is limited in its ability to accomplish orbit-to-orbit transfer of meaningful payloads to higher-energy orbits of interest in a responsive manner (e.g., Low-Earth Orbit (LEO) to Mid-Earth Orbit (MEO), LEO to Geosynchronous Earth Orbit (GEO)). Rideshares are limited in where they deliver payloads requiring the space vehicle to provide its own propulsion to reach its final desired destination. This can require months and may result in having little residual delta-V left to conduct missions. The United States Space Force (USSF) is developing a Tactically Responsive Space Program of Record (PoR). Technical breakthroughs could include: 1) development of upper stages and orbital transfer vehicles powered by high-performance liquid rocket engines capable of the high delta-Vs needed for insertion in high-energy orbits, along with deep throttling, multiple restarts, and highly-transient engine operations; 2) Orbit Transfer Vehicle (OTV) and upper stage propulsion options featuring high exhaust velocity and non-toxic propellant combinations that are more readily employable and easily handled than traditional highly-toxic storable propellants; and 3) enablement of mission planning and concept of operations for responsive space missions to high-energy orbits. Next, the paper will present an Air Force Research Laboratory (AFRL) on-orbit refueling option using Modular Propulsion (ModProp) units to enable the USSF to perform sustained maneuver operations, Tactically Responsive Space (TacRS), and SML across the space domain. Finally, this paper will present a hub-and-spoke (node-and-leg) framework. It will describe how the terrestrial supply chain could be replicated in space by utilizing logistics infrastructure to establish an in-space supply-aggregation-and-distribution network utilizing a hub-and-spoke framework, considers the technologies needed to establish, and maintain this logistics system.