Here’s an awesome photo to start your day: The International Space Station currently has five spacecraft docked to it — the most that can be currently attached. If any of the world’s space agencies, or private companies like SpaceX were to send up another spacecraft today, they’d need to circle until another parking space becomes available (which is tomorrow, incidentally).
The spacecraft docked to the ISS are as follows: Soyuz TMA-12M, Soyuz TMA-13M, Cygnus 2, Progress 56, and ATV-5. The two Soyuz spacecraft are for ferrying Expedition 39/40 and 40/41 to and from Earth. The remaining three capsules are unmanned resupply vehicles. In case you’re wondering, no, I don’t know how NASA captured the photo at the top of the story — presumably there’s a camera on the far edge of the ISS’s solar array? Or it’s a render.
Cygnus 2 is the second commercial resupply mission by Orbital Sciences, which so far, in addition to SpaceX, is the only other space company to have picked up a lucrative NASA commercial resupply contract. Unlike the SpaceX Dragon capsule, Cygnus cannot return to Earth, instead burning up in the atmosphere. In other words, after delivering up to 2,000 kilos (4,400 lbs) to the ISS, the Cygnus is essentially a glorified waste disposal machine. (The astronauts aboard the ISS load it up with waste, and then kick it off into Earth’s atmosphere.)
ATV-5 is notable as the European Space Agency’s last resupply mission to the ISS. The ATV, or Automated Transfer Vehicle, is a beastly spacecraft with a payload of up to 7,700 kilos (17,000 lbs) — about twice that of any other resupply spacecraft. It too lacks the ability to return to Earth, instead burning up in the atmosphere.
There are actually two remaining docking points on the International Space Station — PMA-2 and PMA-3 — but since the retirement of the Space Shuttle, there haven’t been any vehicles that can use them. PMA-2, which stands for Pressurized Mating Adapter, will probably be used by whoever wins the race to develop the next manned spacecraft — most likely Boeing’s CST-100 or SpaceX’s Dragon V2. PMA-3 is scheduled to be used next year by the Bigelow Expandable Activity Module — a temporary module that will test whether inflatable/expandable spacecraft are viable or not. PMA-1, in case you’re wondering, is permanently in use: It’s where the US (Unity) and Russian (Zarya) halves of the space station join.
The Cygnus capsule is scheduled to be jettisoned tomorrow, Friday. Some of Expedition 40 will then leave on the Soyuz TMA-12M capsule on September 11, and then SpaceX’s CRS-4 Dragon capsule will arrive a few days later on September 18.