The International Space Station Alpha (ISSA) conceptual design has several notable differences from previous Space Station design efforts. One key difference centers around the Intermodule Ventilation (IMV). While previous IMV designs incorporated standalone ducts at each element-to-element interface, the present approach includes several IMV ducts which are configured into the central Temperature and Humidity Control (THC) ducting networks.
A simplified analytic technique is presented, which assesses compliance of the overall IMV approach to the established requirement which limits IMV short circuiting to a maximum of 40% at a fan flow rate of 140 cfm. Test results (from the Space Station Freedom IMV Test) and theoretical performance results are input to the analytic technique. The design changes made for ISSA significantly improve the overall IMV performance; the initial design is shown to perform just at the required levels, while the improved design is shown to introduce considerable margin to overall IMV performance.