The SPARE Model (Spares Prioritization and Availability to Resource Evaluation) Users Guide
Abstract
At the request of the National Aeronautics and Space Administration (NASA), the Logistics Management Institute developed a methodology that estimates the optimal orbital replaceable unit (ORU) spares inventory for the Space Station Freedom. That methodology selects spares for the inventory to maximize station availability - the probability that no ORU had more demands during a resupply cycle than it had spares to satisfy those demands. It uses a marginal analysis approach. Spares are ranked in order of decreasing benefit per cost (essentially the improvement provided to station availability per dollar), and added, in that order, to the inventory until a target resource expenditure or station availability is reached. To demonstrate that methodology, we developed the prototype Spares Prioritization and Availability to Resource Evaluation (SPARE) model. This users guide describes how we implemented the methodology and how a user can operate the prototype model on a personal computer. The SPARE model prototype is restricted to estimating the optimal mix of life-critical ORU spares stored on board the station. Unlike other models that present a single point solution, the SPARE model presents the maximum availability for an entire range of resource expenditures, a station resource- versus-availability curve. Thus, if the model user wishes to determine what is the best mix of spares for a specific budget, the model will determine not only the mix and the station availability associated with that mix but also how the availability and mix will change if the budget changes. Keywords: Inventory management, Space station, Optimization, Availability.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1990
- Accession Number
- ADA221887
Entities
People
- Craig C. Sherbrooke
- Robert C. Kline
- T. J. O'malley
Organizations
- LMI