The International Space Station is about to get a little packed. Tonight, three astronauts launch to the station in a Russian Soyuz rocket. Cosmonaut Sergei Volkov, Andreas Mogensen from the European Space Agency, and Aidyn Aimbetov of the Kazakh Space Agency are scheduled to take off from the Baikonur Cosmodrome in Kazakhstan at 12:37AM ET tonight. When they dock with the station two days later, a total of nine crew members will be on board the ISS. That's only one less than the total number of astronauts the orbiting lab can hold at a time.

The crowded living arrangements are only temporary, though; the astronauts will partake in a bit of musical chairs in the next few weeks. Mogensen and Aimbetov are flying to the ISS mostly to help bring station astronaut Gennady Padalka back down. Soyuz capsules need three people to operate them, so Mogensen and Aimbetov will return to Earth with Padalka on September 12th.

Volkov will remain on board the ISS, bringing together the entire crew of Expedition 45. These include astronaut Scott Kelly and Russian cosmonaut Mikhail Korniyenko, who are currently in the middle of spending one year on the ISS. But perhaps the most important aspect of the Expedition 45 crew is that they are all expertly trained in the ways of the force.