The System Power Analysis for Capability Evaluation (SPACE) software analyzes and predicts the minute-byminute state of the International Space Station (ISS) electrical power system (EPS) for upcoming missions as well as EPS power generation capacity as a function of ISS configuration and orbital conditions. In order to complete the Certification of Flight Readiness (CoFR) process — in which the mission is certified for flight — each ISS System must thoroughly assess every proposed mission to verify that the system will support the planned mission operations;

SPACE is the sole tool used to conduct these assessments for the power system capability. SPACE is an integrated power system model that incorporates a variety of modules tied together with integration routines and graphical output. The modules include orbit mechanics, solar array pointing/shadowing/thermal and electrical, battery performance, and power management and distribution performance. These modules are tightly integrated within a flexible architecture featuring data-file-driven configurations, source- or load-driven operation, and event scripting. SPACE also predicts the amount of power available for a given system configuration, spacecraft orientation, solar-array-pointing conditions, orbit, and the like. In the source-driven mode, the model must assure that energy balance is achieved, meaning that energy removed from the batteries must be restored (or balanced) each and every orbit. This entails an optimization scheme to ensure that energy balance is maintained without violating any other constraints. In the load-driven mode, SPACE determines whether a given distributed, time-varying electrical load profile can be supported by the power system and will determine whether the system stays in energy balance. Load-driven mode also is used to assess each space shuttle mission to ISS, in support of the CoFR process.

This work was done by Jeffrey Hojnicki, David McKissock, James Fincannon, Robert Green, Thomas Kerslake, Ann Delleur, Jeffrey Follo, Jeffrey Trudell, David J. Hoffman, Anthony Jannette, and Carlos Rodriguez for Glenn Research Center. For further information, access the Technical Support Package (TSP) free on-line at under the Software category.

Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Commercial Technology Office, Attn: Steve Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW- 17067.