Six astronauts are currently sealed in a 430-sq-ft simulated spacecraft in Moscow, where they will remain for 17 days. The crew—three men and three women—will not leave Earth but are laying the groundwork for future moon voyages. One of the things being tested on this static mission is the right ratio of men to women on any given trip.
The test is the first in a new collaboration between Russian and American space agencies, part of a project known as Sirius (short for Scientific International Research In a Unique terrestrial Station). Sirius-17, named for its length, began on Nov. 7. The team will spend their two-plus weeks together at Moscow’s Institute for Biomedical Problems in a contraption equivalent in size to a tiny house.
The six subjects of the experiment, who have already trained to live in isolation and in the absence of gravity, will themselves be conducting 40 different scientific experiments during this time. “By [the] mid-2020s we will probably be ready for the actual flight,” Oleg Orlov, who heads the Sirius-17 endeavor, told AFP. Orlov also said that one of the goals of the experiment is finding out what gender ratio is optimal for a long-term space mission. As the project’s psychologist, Vadim Gushchin, told AFP, “this is the first time in Russian or Soviet history when a space crew has included more than one woman.”
Lisa Spence, a flight analogs program manager for NASA, said in the US space agency’s statement about the mission that it is “designed to test the capabilities of the Russian facility.” (NASA also conducts analog missions at sites in the US, Canada, Germany, and Antarctica.) She made no mention of testing the gender ratio specifically, saying only, “We want to exercise the facility capabilities, mission planning and integration procedures to identify challenges or issues now as opposed to during a longer duration mission.”
Still, if NASA’s latest class of astronauts is any indication, gender parity beyond Earth is a consideration for the space agency. Of the 12 new astronauts accepted in 2017 to prepare for space travel with NASA, five were women and seven were men, putting the agency just shy of a 50-50 split.
Read next: How a stray dog became the world’s first cosmonaut, 60 years ago