The Japan Aerospace Exploration Agency said it was surprised at the number of people who submitted applications to take part in a two-week trial to test stress levels in a closed environment that will simulate conditions on the International Space Station.
JAXA showed the test facility in Tsukuba, Ibaraki Prefecture, to media on Wednesday.
Officials with the agency said that about 4,400 people — from students to businessmen — applied for the eight spots reserved for "men-only" from Dec. 24, when it started taking applications, until Tuesday's deadline.
"We didn't expect this huge reaction," one official said. "People's interest in outer space might be growing. We want to carry out a successful test."
JAXA will narrow down the list until it reaches eight by looking at such things as the applicants' motivations for wanting to take part in the study and their physical health.
The eight participants will receive ¥380,000 (about $3,200) each for spending two weeks in the enclosed facility where they will have no contact with the outside world beginning Feb. 5.
The facility, based on the International Space Station, will have cameras and other equipment throughout that will monitor everything from their facial expressions to their speech patterns.