Spacecraft continue to advance, and one of the latest new spacecraft to enter operation is SpaceX’s Dragon capsule. As Crew-3 prepares for launch to the station, Crew-2 needs to return home, and Crew-2’s Dragon capsule is nearing the limit for continuous-time in space. But what is that limit, and why is the spacecraft limited?
What is SpaceX Dragon?
There are two kinds of current Dragon capsules: Crew Dragon and Cargo Dragon. The Crew Dragon variant is specifically designed to carry passengers into low earth orbit (LEO) and ferry Astronauts to and from the International Space Station. Similarly, the Cargo Dragon is a more stripped-down version of Dragon that is built to transport supplies to residents of the ISS. Once at the Space Station, the Dragon capsules can stay docked for months before making the return to Earth. But for how long, exactly?
How long will Crew-2 stay at the station?
The Crew-2 Dragon capsule that is currently at the ISS has been docked for a whopping 197 days since it reached the station in April. Designated Crew Dragon Endeavor, after the space shuttle of the same name, the capsule first launched on the historic Demo-2 mission that kicked off NASA’s return to crewed flights last year. To conclude its second mission, the capsule will undock from the station this Sunday, splashing down with its four-person crew off the coast of Florida Monday morning. Astronauts Shane Kimbrough, Megan McArthur, Aki Hoshide, and Thomas Pesquet will have stayed in space for 199 days by that point. This is just 11 days below the Dragon’s minimum certification of 210 days.
Why 210 days?
The 210 day limit for Crew Dragon is mentioned in a NASA manual released in 2019 (although there are references to this standard from much earlier, like in this hearing from 2011). The NASA manual lays out various requirements for potential commercial crew capsules. Among these requirements is that a human-rated capsule must be capable of spending at least 210 days in orbit. Since this is the minimum amount of time that SpaceX designed the capsule for (it can likely stay for much longer), NASA aims for Crew-2 return before this point.
Why does Dragon have a deadline?
It might sound counterintuitive that a spacecraft like Dragon isn’t able to stay in orbit indefinitely – there’s no atmosphere! Despite this, there are actually some weathering issues that can happen in space. Namely, micrometeorites are a slight concern, along with extended sun damage. While these factors generally don’t cause much damage, prolonged exposure can lead to unexpected issues. Additionally, having a seven-month limit is more than enough time to accommodate the majority of expeditions (usually six months long) to the ISS. As time goes on, and it becomes clear how long Dragon can actually last in space, NASA may extend this certification to accommodate for longer missions.