xxiii pump cannot simply be pulled out because the cooling fluid will go everywhere. Therefore, valves that can be closed off to isolate the pump from the fluid must be installed. These extra valves add cost and weight, and require software to control them. Since valves can fail, they too must be replaceable. ORUs exist on the inside or outside of the ISS. External ORUs are usually stored on External Stowage Platforms (ESPs) or Expedite the Processing of Experiments to the Space Station (EXPRESS) Logistical Carriers that are mounted on the truss of the ISS. FLIGHT DIRECTOR AUTHORITY A. THE MISSION CONTROL CENTER HOUSTON (MCC-H) FLIGHT DIRECTOR OR THE MISSION CONTROL CENTER MOSCOW (MCC-M) FLIGHT DIRECTOR WILL BE IN CHARGE OF EXECUTION OF REAL-TIME STATION OPERATIONS AT ALL TIMES AS THE LEAD FLIGHT DIRECTOR. REFERENCE FLIGHT RULE {B1-10}, LEAD ROLE HANDOVER. The ISS crew and flight control teams must have a clear understanding at all times of who is directing the real-time station operations. B. THE MISSION CONTROL CENTER-HOUSTON (MCC-H) FLIGHT DIRECTOR HAS INTEGRATION RESPONSIBILITY OF THE ON- ORBIT OPS SUMMARY (OOS), THE OOS UPDATES, SHORT TERM PLANS (STP’S), ONBOARD STP’S (OSTP’S) (IF DIFFERENT FROM THE STP’S), AND THE EXECUTE PACKAGES, SUMMARY PLANS, WEEKLY PLANS, AND DAILY PLANS (IF DIFFERENT FROM THE WEEKLY PLANS), AND OVERSIGHT OF REAL TIME OPERATIONS CONSISTENT WITH RULE {B1-9}, MCC RESPONSIBILITY MCC-H and MCC-M will be involved at all stages of ISS assembly and operation. The lead MCC Flight Director will always work to forge a consensus among all partner control teams both when working real time and in planning issues. Figure 7. A sample of a flight rule, in this case showing the authority of the flight director between the Mission Control Centers in Houston and Moscow. The Team Behind The Curtain Flight control has been a key part of spaceflight since the first rockets left the Earth’s gravity. In fact, the roots of flight control go back to aircraft tests that were conducted before the space age, such as the breaking of the sound barrier by Chuck Yeager in 1948, or the ultra- high altitude balloon flights of the 1950s (Ryan, 2003). Christopher Columbus Kraft Jr. adapted existing flight control processes for operating NASA’s crewed spacecraft in the beginning days of Project Mercury in the early 1960s (Kraft 2001). Additional historical details may be found in Herd, Dempsey, and van Leeuwen (2013). The FCT is a rather large group of console operators, support personnel, and systems engineers. A clear hierarchy starts at the flight director’s console. While on console, “Flight” leads all the real-time operations. In reality, there are layers above Flight including the ISS Mission Management Team (IMMT), which is controlled by the Program Office. Technically, the ISS Program Office owns the space station and its operation is delegated to the FCT in the Flight Operations Division. The head of the ISS Program manages the mission requirements and objectives as well as the vehicle constraints. The head of the ISS Program Office, or his or her delegate, chairs the IMMT. Before a mission or activity, the FCT will write flight rules and a mission plan based on these objectives and constraints. Flight rules are pre- planned decisions and agreements that have been approved by the program. They are used to guide the FCT when time is of the essence. An example is shown in Figure 7. The mission plan is not only a timeline, it is a schedule of constraints (e.g., activity B is dependent upon the successful completion of activity A). When things go well, the team follows the rules, procedures, and timeline. Where possible, likely failures are anticipated and some level of products dealing with those cases are also created. If something goes wrong, or off-nominal, the flight director will determine whether the preapproved