CHAPTER 10 DAY IN THE LIFE: PREPARING FOR THE UNEXPECTED 178 and one pump—either the Moderate Temperature (MT) or the Low Temperature (LT)—pushes fluid around the entire system, which is called Single MT or Single LT, respectively. This is significant because, at the time of the failure, the US Lab internal active Thermal Control System (TCS) was in Single LT mode, meaning one water pump on the LTL was performing all of the heat transport of cooling water to US Lab systems. The LTL pump remains running in the event of an LA-1 MDM failure as several key pump performance parameters are being reported to and controlled by a different MDM. However, loop pressure, flow, temperatures and, most importantly, pump accumulator quantities, are lost. The pump accumulator quantity is especially important because a sudden decrease in accumulator quantity indicates that cooling water is leaking out of the system. If the leak is not stopped, enough water will be lost to cause the cooling loop to fail and critical equipment to overheat. A sudden increase in accumulator quantity indicates that another fluid is being injected into the system. Given the way in which the internal cooling loop is plumbed, the only possible fluid that could be injected into the system is the 100% anhydrous ammonia that is used as a coolant for ISS external systems. The ammonia and water come into thermal contact to exchange heat, but are kept separate from each other at the IFHX (see Chapter 11). This grade of ammonia is fatal to humans, even in small quantities. Also, one of two redundant Internal Audio Controllers (IACs), which route all on-board voices to different destinations, failed prior to the simulation start in what is known as an initial condition of the simulation. Another initial condition was that the External TCS (ETCS) Loop B experienced a transient failure, which shut the pump down. Communications One of the most critical skills that a flight control team needs to exercise is communication. Owing to the complicated, often time-critical nature of spaceflight, a specific shorthand and cadence was developed to facilitate communication between the various controllers, the flight director, and the crew. Flight controllers in Mission Control communicate over loops, which is nothing but a dedicated phone line, so to speak, between parties. Typically, each person must listen to more than a dozen of these voice loops at the same time. Using a headset, a flight controller plugs into the system to hear the calls that are defined on a computer panel. There are literally thousands of loops from which to choose, but each person usually monitors only a small subset. Conversations can occur simultaneously on all the loops during busy times. Sometimes the flight controller needs to follow along with only a few, but at other times he or she may need to directly participate in the discussion. Learning to process all these simultaneous conversations is a key skill the flight controllers have to master. Calls between controllers begin with the name of the person being called, followed by the position that is making the call. For example, “SPARTAN, CRONUS on SYS COORD” indicates that the SPARTAN controller is calling Communications Rf Onboard Network Utilization Specialist (CRONUS) on the voice loop called SYS COORD, which stands for Systems Coordination. When CRONUS hears this, he or she will talk directly to SPARTAN. The most critical loop is the FLIGHT loop, which is owned by the flight director. In a real sense, this is the “king” of loops and everyone in every control center around the globe always has to monitor this critical loop. The only other special loop is the Space- to-Ground (S/G) loop. Only the CAPCOM talks to the astronauts on this loop. Since an astronaut’s time is so critical and communication can be limited, everyone is required to stop talking during a call from the CAPCOM to the astronauts, or vice versa. This prevents the ground from talking over and therefore missing an important item, or making it necessary for the crew members to repeat themselves. A key part of this communication training is to learn how to talk concisely. Unlike an office meeting where employees can take all the time necessary, discussions in Mission Control are usually time critical. If the discussions are not time critical, they are still kept to a minimum since everyone is monitoring multiple loops. Another way to keep communications crisp is to add a brief phrase to explain why the person is calling. This is indicated by stating “for” followed by what the call is about, thus allowing the receiver to prioritize and prepare for the discussion. Following is an example of a simple exchange during that simulation. NOTE: The transcript has been edited for readability. The