This past Tuesday I did something that we don’t quite do every day: I depressurized a part of the Space Station to vacuum. Not an airlock, those actually exist for that purpose.
A vestibule: that’s the small volume that is created when two ISS modules are joined together. Just like if in your home you had not one door between rooms, but two, with a little space between them which becomes a little “room” of its own if you close both doors. On ISS we call that little volume between hatches “vestibule”. Imagine you wanted to make sure that both those hatches do not leak – the best way to do this leak check is to depressurize the vestibule between them. If air gets into the vestibule, raising the pressure, there’s a leak in the hatch seals. Here is how it goes: you connect the vestibule volume to a vacuum access point and vent all the air overboard; then you measure the residual pressure, which will be very close to zero (in my case it was about 3 mm Hg) and then you wait 24 hours and check the pressure again. Of course, there is no such thing as a perfectly tight seal, some leakage will always occur.
In the case of the vestibule, my procedure called it a good leak check if the increase in pressure in the vestibule after 24 hours was less than 5 mm Hg.
I bet you’re curious by now… what hatches did we leak check and why? Well, I’m not sure if you’ve heard already, but we’re going to do some remodeling soon on the Space Station. Time to freshen up the room distribution a bit! Our PMM module, which is currently attached to Node 1 nadir, will be relocated to Node 3 forward and the Node 1 nadir port will get a luxury upgrade that will make it capable of receiving visiting vehicles. So we did the leak check on the vestibule between PMM and Node 1, to make sure that those hatches do not leak, because they will be exposed to vacuum when we do the relocation later this year. In addition, just before the leak check Terry and I installed a feedthrough: that’s something that allows a cable connection to go through a hole in the pressure shell – you plug the cable on one side, let’s say inside, and then you plug the continuation of the cable to the other side of the feedthrough, let’s say outside. The feedthrough is inserted in a hole and has seals to make sure air doesn’t leak out.
You’ll be happy to hear that the vestibule passed the leak check, so both the hatches and the newly installed feedthrough are in good shape. Good news, ah? By the way, what you see in the picture is the long jumper hose that we used to connect the vestibule to vacuum: it had to reach all the way across the Lab to the vacuum access point. Maybe it’s just me, but connecting something to vacuum is definitely something that commands attention: there’s nothing particularly complicated in the setup to depressurize the vestibule, but I did double-check and triple-check it before opening the equalization valve that actually vented the vestibule atmosphere into space. In fact, I even had a feeling for a moment that my ears were popping, which would be a sign of the pressure in the cabin dropping; but the pressure indications were stable, so it was probably the hissing sound from the ongoing venting playing tricks on my eardrums.
Wednesday was one of those “keep-the-Station-in-shape” kind of days for me. Besides tearing down the leak check setup, I worked for example on an a periodic environmental monitoring activity that checks our potable water for coliform and other microbial growth in samples from our potable water lines after 48 hours of incubation. Luckily, I could report zero microbial colonies on the microbial capture device and no magenta color in the coloform detection packet, indicating a negative result. Always good to have confirmation that our drinking water is safe!
Futura mission website (Italian): Avamposto42
avamposto42.esa.int
(Trad IT) Traduzione in italiano a cura di +AstronautiNEWS qui:
https://www.astronautinews.it/tag/logbook
(Trad FR) Traduction en français par +Anne Cpamoa ici: https://spacetux.org/cpamoa/category/traductions/logbook-samantha
(Trad ES) Tradducción en español por Carlos Lallana Borobio aqui: https://laesteladegagarin.blogspot.com.es/search/label/SamLogBook
(Trad DE) Deutsch von https://www.logbuch-iss.de
08/02/2015