I have picked up ATV training with crewmate Sasha today.
One of the classes dealt with the operations related to ingressing ATV after docking. Sounds easy enough, but ingress operations actually take several hours.
For one thing, before opening any hatch you need to make sure that you have a good seal between Station and the vehicle itself. We call these type of procedures leak checks: you basically create a pressure differential between two volumes that are sealed off and check that the pressure equalization across the seal over a certain time is within the limits.
Once the leak check is passed and you open the hatch, it’s time to take a long series of air samples, part for return to ground and part to test onboard for different contaminants.
Then you need to install an air filter and let it fully clean the ATV atmosphere for many hours. Only after the filtering is complete are you allowed to enter ATV without protective mask and goggles. If you think about it, it makes sense: on Earth, small particles fall to the ground, but in space they float, so they can easily get into your eyes or your lungs. Of course, we don’t expect that on space vehicles, which are prepared in clean rooms, but better be safe than sorry!
You can see in the picture a crewmember entering ATV with protective gear. And what are those yellow things? Those are clamps that are installed on the hatch to increase the mechanic rigidity of the link between ATV and Station. After all, an ATV is a much bigger beast than a Progress or a Soyuz!
Those clamps are pretty interesting. Since you need to be able to close a hatch quickly in an emergency, they are designed so that you just need to pull on the string of one and they all come off. Just make sure you don’t have your fingers in the way when the spring loaded lever snaps to the release position!
ATV ingress. Credits: NASA
18/09/2013