Supply chain strategies for responsive space missions

One proposed approach to responsive space missions involves the building of spacecraft payloads and spacecraft busses to inventory, to be mated and launched based on immediate warfighter needs. This paper explores optimal inventory strategies for payloads and busses based on anticipated demand, demand uncertainty, unit costs and cost of non-availability. Demand for responsive missions is highly uncertain. Other than periodic demonstration and training flights, the need could be for zero per month to five or ten or more per month, and may be zero for many consecutive months or even years if international tensions are low. This uncertainty drives a tension between minimizing cost and guaranteeing performance. Consequently, determination of the optimal level of investment in inventory or, more generally, in supply chain responsiveness is both important and non-trivial. The co-authors have developed a Microsoft Excel based tool to determine optimal inventory levels for a scenario involving two payload/mission types (A and B), and three bus options: an A-optimized bus, a B-optimized bus, and a hybrid bus which can support both types of missions. For various levels of demand, demand uncertainty, unit costs and non-availability costs, the tool calculates the optimal number of each type of bus. For reasonable values of the input parameters, there have been some surprising and somewhat non-intuitive results -results suggesting that a broader supply chain analytics and modeling capability could prove to be a valuable decision support tool. The paper presents the tool structure and analytical approach, along with input parameter sets and associated findings. It will explore the implications for cost reduction and responsiveness of vendor managed inventory and various levels of work-in-process inventory. In addition, it will provide a broader discussion of responsive space supply chains and the potential for models and analytical tools to enable decision processes and to provid- - e visibility into current and future performance and cost.