Three astronauts have arrived safely at the International Space Station (ISS), temporarily bringing the crew of the station up to six. But the logistics of maintaining a continuous presence on the station are proving a challenge.
A successful launch to the ISS
On Thursday April 9, a Soyuz MS-16 launched from the Baikonur Cosmodrome in Kazakhstan arrived at the ISS, carrying three new crew members. The spacecraft docked with the station’s Poisk module following a six-hour flight, and later today the hatch will open to let the current ISS crew welcome their new arrivals.
During their stay, the new crew will conduct around 160 scientific investigations, with experiments in fields including biology, Earth science, human research, physical sciences, and technology development, according to NASA.
The new ISS crew
The new crew members are NASA’s Chris Cassidy and Roscosmos’ Anatoly Ivanishin and Ivan Vagner. These three join NASA’s Andrew Morgan and Jessica Meir and Roscosmos’ Oleg Skripochka, who are already on board the ISS since September 2019, or, in the case of Morgan, since last July.
Together, the three new crew members and the three existing crew members form the final phase of Expedition 62, the ISS designation for each crew. However, Morgan, Meir, and Skripochka will be departing the ISS in just eight days’ time, leaving Cassidy, Ivanishin, and Vagner as the new Expedition 63. Cassidy will take over from Skripochka as the commander of the mission.
The three new crewmembers will be alone for around six months. Then three more astronauts are planned to join Expedition 63 in October this year.
The logistics of ISS crew size
The original plan was to have a larger crew on-board the ISS at this time. However, the launch of a Soyuz MS-10 had to be aborted last October, which has had a cumulative effect on crew plans. At the time, Tara Ruttley, associate chief scientist for microgravity research in NASA’s Office of the Chief Scientist, said that NASA could still meet its objectives with a three-person crew. “We are still meeting record crew time hours. We haven’t needed to readjust the research planning purely associated with the decrease in crew size,” she said, as reported by Space News. “There have been no major impacts [on scientific research activities]. The crew is staying busier than ever.”
There have also been delays to NASA’s Commercial Crew Program, in which private companies SpaceX and Boeing are contracted to ferry astronauts to the ISS, such as Boeing’s troubles with its Starliner capsule.
Avoiding a decrew situation
The ISS supports a crew of up to six people, although it can be maintained by a crew of three. The station is even capable of flying itself with instructions from ground control who operate it. If a system on the station fails, there are redundancies built in to ensure it remains operational. NASA has a report detailing how “decrewing,” or evacuating all astronauts from the station, can be achieved with the station itself being maintained for as long as possible.
A great deal of planning goes into ISS crew logistics, in order to ensure a continuous human presence onboard the station. In 2011, a decrew situation was narrowly avoided after a failed Progress M-12M launch which re-entered the atmosphere shortly after launch. No astronauts were aboard the craft, but it was carrying supplies including food and fuel. Concerns about the safety of spacecraft at the time lead to a suspension of crewed spaceflights, and the ISS crew at the time were due to head back to Earth shortly.
In the end, a new crew was able to launch once the issue that caused the Progress failure was identified. But since then, contingency plans for possible decrewing of the station have been in place.
Prepared for a small crew
The challenge of working as part of a smaller crew is primarily that there are fewer crew hours available in total for all the work which needs to be done. The crew’s schedules have to be optimized to make as much time as possible for scientific experiments, as well as covering the essentials to keep the station running. There can also be a degree of psychological stress involved from being with a small number of people for a long time.
“What we’re preparing for… is a six-month duration where it’s just the three of us,” Cassidy told Space Flight Now last year. “That’s why we’re getting a lot of extra training at specialist levels for Andrei and Nikolai on all the U.S. side equipment.” Cassidy was referring to Roscosmos astronauts Andrei Babkin and Nikolai Tikhonov, who have since been replaced for medical reasons.
“We’re also ready operationally, mentally — all that — prepared to just be the three of us on the space station, which will be a change in operations really if you think about it from what we are used to today, where we have six people,” Cassidy said.
Returning home
The next step for the ISS crew, once they are settled and duties have been handed over, is for the original crew of Morgan, Meir, and Skripochka to depart the station on Friday, April 17, aboard a Soyuz MS-15 spacecraft which will land in Kazakhstan.
There will also be a change of command ceremony featuring all six crew members which will be shown live on NASA TV on Wednesday, April 15 at 1:55 p.m. PT.
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