All Change for Station Crew as Ford Prepares to Take Command

The International Space Station’s Expedition 33 core crew – Commander Sunita Williams of NASA, together with Russian cosmonaut Yuri Malenchenko and Japanese astronaut Aki Hoshide – will touch down on the barren Kazakh steppe early on Monday 19 November, wrapping up a four-month tour of duty. Their Soyuz TMA-05M spacecraft is scheduled to undock from the station’s nadir-facing Rassvet mini-research module at 4:26 pm CST on Sunday (4:26 am Kazakh time on Monday) and head for a pre-dawn touchdown to the north-east of the remote town of Arkalyk about three and a half hours later. Launched on 15 July, Williams, Malenchenko and Hoshide have completed one of the most intense expeditions in ISS history, performing several spacewalks from both the US and Russian segments of the station, supporting the docking and undocking of several visiting supply craft and engaging with dozens of scientific experiments.

In keeping with tradition, Williams will officially transfer command of the ISS to fellow astronaut Kevin Ford on Saturday afternoon (early Sunday morning in Kazakhstan). This will herald the official start of Expedition 34, whose present crew of Ford and Russian cosmonauts Oleg Novitsky and Yevgeni Tarelkin – launched aboard Soyuz TMA-06M on 23 October – is due to be expanded to a full six-man staff just before Christmas, with the arrival of Soyuz TMA-07M and its Russian-US-Canadian crew.

Before launching toward the station in mid-July, Sunita Williams noted that her expedition would be a busy one and that she and her crew would be expected to hit the metaphorical ‘ground’, floating. Within days of arriving aboard the ISS, she, Hoshide and Expedition 32 crewmate Joe Acaba supported the arrival and docking of Japan’s third H-II Transfer Vehicle (HTV-3, the ‘Kounotori’ or ‘White Stork’) craft at the nadir port of the Harmony node. It marked the first occasion on which a Japanese craft had been captured and berthed at the station by a Japanese astronaut. Among the most publicly visible elements of its cargo was the Aquatic Habitat, capable of supporting three generations of Medaka fish for several months, and unpressurised hardware which Hoshide robotically transferred onto the Japanese Experiment Module’s Exposed Facility in early August.

Originally scheduled to be detached from the station on 6 September, the HTV-3 departure was delayed a few days due to the intensity of spacewalking activity. Already, in mid-August, cosmonauts Yuri Malenchenko and his Expedition 32 crewmate Gennadi Padalka had performed a six-hour excursion from the Russian Segment to relocate the Strela-2 telescoping boom from the Pirs docking compartment to the Zarya control module in readiness for the arrival of the long-delayed Nauka multi-purpose module. The two cosmonauts also installed micrometeoroid debris shields on the Zvezda service module and performed several additional get-ahead tasks.

Then, on the 30th, Sunita Williams and Aki Hoshide ventured outside the Quest airlock on the US Orbital Segment for more than eight hours in an ultimately fruitless attempt to replace the partially-functional Main Bus Switching Unit (MBSU)-1, one of four electrical distribution boxes supplying the power system of the US Segment. Although the spacewalkers successfully removed MBSU-1, they ran into difficulties as they prepared to install a replacement unit onto the station’s central S-0 truss. Metallic filings required removal and cleaning and when the time came to install the new unit onto its coldplate, a stubborn bolt refused to budge and eventually left Williams and Hoshide out of time. They secured MBSU-1 onto S-0 with a tie-down tether, but since the unit normally supplies electricity from the 1A and 1B solar array wings, the station was left in the undesirable position of a 75-percent power capability with two of its eight channels down.

Careful power planning ensured that critical experiment facilities – notably the $1.5 billion Alpha Magnetic Spectrometer (AMS)-2, delivered to the ISS last year – did not need to be shut down, but as the MBSU-4 unit took over the role of temporarily feeding most of its sibling’s electrical loads the condition was far from ideal. It was noted in the aftermath of Williams and Hoshide’s EVA that any failure of MBSU-4 would essentially knock out a sizeable portion of the power supply for the US Segment, including the Japanese Kibo and European Columbus modules. The situation worsened when a Direct Current Switching Unit also failed, taking out the 3A power channel, and bringing the total electrical capability of the station to just 62.5 percent of its normal load.

With a third of their power gone, efforts moved into high gear to manifest an unscheduled EVA on 5 September to resolve the issue. In a spectacular six-and-a-half-hour excursion, Williams and Hoshide removed the partially-installed MBSU-1, cleaned and lubricated its bolts and their receptacles on the S-0 truss. On this second occasion, the bolts proved less awkward and the installation was completed successfully – to ringing applause from Mission Control – as Williams broke the world record for EVA time for a female spacewalker, eclipsing Peggy Whitson’s previous record of almost 40 hours. By the end of Expedition 33, and the completion of another outing, Williams has presently logged more than 50 hours of spacewalking across seven career EVAs.

The third excursion by Williams and Hoshide on 1 November was ordered in response to an ammonia coolant leak from the 2B power channel on the P-6 solar array, as described in this recent AmericaSpace article. In this case, an already extant leak accelerated almost fourfold since June 2012, threatening to render the channel inoperable by the end of December and prompting mission managers to stage an EVA to rectify it. During their six and a half hours outside, the astronauts isolated the 2B coolant loop to enable engineers to better diagnose the exact location of the leak and deployed a Trailing Thermal Control Radiator to provide ongoing cooling.

Dovetailed into the weeks surrounding these critical EVAs were several departures and arrivals at the ISS. Japan’s HTV-3, originally scheduled to depart on 6 September, was actually unberthed a few days later on the 12th and sent on a destructive dive into the atmosphere. Europe’s third Automated Transfer Vehicle (ATV-3, named in honour of the Italian physicist Edoardo Amaldi) was also undocked on 28 September, after six months attached to the outpost, and similarly deorbited a few days later. Next up was the first dedicated mission of SpaceX’s Dragon cargo craft – which thundered into space in an eventful ascent on 7 October – under its $1.6 billion Commercial Resupply Services (CRS) contract with NASA.

A problem with one of the nine engines on the Falcon 9 rocket’s first stage appears to have caused a fuel dome rupture and although SpaceX declared that the event vindicated its ‘engine-out’ capability, it is becoming increasingly likely that the CRS-2 mission will be delayed from December until at least March of next year. Nonetheless, Dragon performed as intended and delivered upwards of 1,000 pounds of usable items to the crew and returned around 1,670 pounds back to Earth when it splashed down in the Pacific Ocean, off southern California, on 28 October.

The detachment of the Dragon from the nadir port of the Harmony node was completed by one of Expedition 33’s new arrivals, NASA astronaut Kevin Ford, who is destined to assume command of the station as Williams and her crew prepare to leave. Ford and his Russian crewmates, Oleg Novitsky and Yevgeni Tarelkin, will thus begin Expedition 34, but must wait until 19 December to receive news of the launch of Roman Romanenko, Chris Hadfield and Tom Marshburn aboard Soyuz TMA-07M from Baikonur. With the arrival of the new crew on the 21st – just four days before Christmas – the ISS will return to its full staff of six men. Yet the plans for the early part of the New Year remain unclear. It appears unlikely that the CRS-2 Dragon will fly much before Ford, Novitsky and Tarelkin return home in mid-March and there has been speculation in recent days that Orbital Sciences’ Cygnus craft may not fly its first demo mission until around April. Certainly, Orbital has yet to stage the first flight of its Antares booster, which is currently undergoing tests at the Mid-Atlantic Regional Spaceport (MARS) on Wallops Island, Virginia.

Next year, 2013, promises to be a historic one, with Chris Hadfield slated to become the first Canadian to command the station when he takes over the baton from Ford in March. Two weeks later, the next crew will fly into orbit aboard Soyuz TMA-08M, possibly docking at the ISS within six hours of launch. This follows the successful demonstration of a new ‘fast-rendezvous’ profile, first tested by Russia’s Progress M-16M on 1 August, and is expected to be introduced for manned flights as a means of reducing the negative physical impact on the crew during what is acknowledged to be a particularly stressful stages at the start of a mission. The Soyuz TMA-08M crew includes cosmonaut Pavel Vinogradov, who will turn 60 years of age whilst aboard the station, easily securing himself a new record as the oldest Russian yet to enter space. Other occupants of the ISS will include Italy’s Luca Parmitano, Mike Hopkins – the first member of NASA’s 2009 astronaut class to fly – and Koichi Wakata, who will become the first Japanese commander of the station.