ISS: Expedition 24

Launch from the Baikonur Cosmodrome (Yurchikhin, Walker and Wheelock with Soyuz TMA-19). Skvortsov, Korniyenko and Caldwell-Dyson were onboard since 04.04.2010 (arrival with Soyuz TMA-18).

On June 28, 2010 Yurchikhin, Walker and Wheelock boarded the Soyuz TMA-19 vehicle that docked to Zvezda on June 18, 2010. They flew the Soyuz vehicle a short distance to Rassvet. The change of location made the Zvezda port free for the docking of a new Progress resupply vehicle on July 2, 2010. That port is the preferred location for the Progress, so it can help reboost the station and adjust its altitude.

EVA by Yurchikhin and Korniyenko on July 27, 2010 (6h 42m) to prepare the recently delivered Russian Rassvet Module for future automated dockings by Russian spacecraft. The spacewalk also included routing and mating Command and Data Handling cables on the Zvezda and Zarya modules. A video camera was removed and replaced from the aft end of Zvezda which will be used to provide television views of the final approach and docking of future European Automated Transfer Vehicles carrying cargo to the complex. This was the 25th Russian spacewalk and the 147th spacewalk overall in support of station assembly and maintenance.
During the spacewalk, two objects were detected floating away from the station. One was tentatively identified as a cable clamp, left outside the station from a previous Russian spacewalk. That object and another, not conclusively identified, both departed well below the vicinity of the complex and pose no threat to the orbiting laboratory.

On July 31, 2010 the ammonia pump module that is part of coolant loop A, mounted on the right side of the station's main power truss, failed. A problem somewhere in the system caused a circuit breaker to trip, setting off multiple alarms and waking the crew. With half the station's cooling gone, flight controllers were forced to shut down two of the station's four U.S. control moment gyroscopes, used to help maintain the lab's orientation in space, one communications channel, several solar power current converters and a variety of computer control boxes known as multiplexer-demultiplexers.
Tracy Caldwell-Dyson and Douglas Wheelock assisted with the powerdowns and hooked up jumper cables between the Russian Zarya module and the U.S. segment of the station to prevent additional cooling problems.
The space station remained in a safe configuration throughout, officials said, with critical life support systems, computers and communications gear operating with coolant loop B. The six-member crew, they said, was never in any danger.
Several hours later flight controllers attempted to restart the stalled pump, resetting the circuit breaker that opened late Saturday. Once again, the crew was awakened by alarms.
Later in the morning, engineers restarted one of the two powered-down control moment gyroscopes and while the main bus switching units that direct power to various subsystems ran hotter than normal, engineers said the lab was stable.
The space station features two independent coolant loops that use ammonia circulating through huge radiators to dissipate the heat generated by the station's electronic systems. Each loop is fed by a large tank of ammonia that includes an internal bellows pressurized by nitrogen. That pressurization system allows the loops to handle the periodic expansion and contraction of the ammonia coolant due to temperature changes in orbit.
Spare coolant system components, including two pump modules, are mounted on external stowage platforms, one on the left side of the station and the other on the right, just ahead of the Quest airlock module. Meanwhile the managers decided to fix the problem in two difficult spacewalk repair jobs.

EVA by Wheelock and Caldwell-Dyson on August 07, 2010 (8h 03m). They removed hose clamps and then started disconnecting umbilicals from the broken space station coolant pump. However, difficulty unplugging one of the ammonia lines consumed a couple of hours and a leak seen from that connector once it finally cooperated prevented the astronauts from progressing any further in their work.
Original plans had called for the pump's removal and installation of the new pump today, with a second spacewalk on August 11, 2010 to finish hooking up the replacement and stowing the old one.

Second EVA by Wheelock and Caldwell-Dyson on August 11, 2010 (7h 26m) to repair the failed pump. They removed the old pump and stowed it on a payload attachment bracket on the Mobile Base System on the station's truss while preparing the replacement pump for its removal from a stowage platform adjacent to the Quest airlock and its installation on the truss during a third spacewalk.

Third EVA by Wheelock and Caldwell-Dyson on August 16, 2010 (7h 20m) to repair the failed pump. The astronauts performed the installation of a spare ammonia pump module on the S1 Truss.