Just got back from a briefing about the fire simulation I’ll have in the afternoon with Anton and Terry. We had this type of training once already last year, during our backup flow, as I reported in these two logbooks from last December 348: Service Module smoke and L-345: Fire evacuation training.
Since I’ve told that story already, let me dedicate a few words to an experiment I trained for in Houston couple of weeks ago and I didn’t tell you about yet. It’s called BCAT, which stands for Binary Colloidal Alloy Test.
A colloid is a special type of solution, in which tiny particles, so small that you can not see them with the naked eye, are dispersed evenly in another substance. Foam, for example, is a type of colloid: small gas particles are trapped in a liquid or a solid. If it’s liquid particles dispersed in a liquid, we talk about emulsions: milk is a common example.
Several runs of BCAT have been performed on ISS already. This particular one, BCAT-KP (Kinetic Platform), is interested in phase separation kinetics. You’ve heard about phase changes in school, I’m sure: we all learned about transition of substances between their solid, liquid or gaseous phase (ice, water and water vapor, for example). Now, phase changes in colloids are a lot more complicated. They are also very interesting both from a fundamental science point of view, as well as for immediate commercial applications (detergents, pains, inks, medicines,…). In fact, a major private company owns some of the BCAT-KP samples! Better insight into colloids could lead to new ways of producing plastic or help extending the shelf-life of some consumer products.
Let’s say we’re interested in the stability of a colloid: how long will it take for the dispersed particles, interacting with each other, to gather together, separating the two phases? What kind of structures will those particles form? These are only a few of the questions scientists are interested in. And although we’ve been studying colloids on Earth for a long time, there’s a lot we still don’t know because, guess what, gravity-induced effects are stronger than the interaction between particles, for example the electrostatic interactions. Basically, if the particles are denser that the substance they’re dispersed in, they will migrate to the bottom – that’s called sedimentation. If the opposite is true, they will migrate to the top – and that’s called creaming.
None of that happens in space!
The BCAT experiment consists of a unit that can hold 10 samples, tested one by one. When it’s time to get one started, crewmembers will use a magnet to homogenize the sample, i.e. mixing it so that the dispersed particles are evenly distributed. Then they will set up a camera, so that it will automatically take a picture at a preset interval and download it to the ground for analysis.
Each sample is observed for one week and it’s very important not to bump the unit while the experiment is running. That’s why BCAT is setup in an area of little passage, tucked between the JEM airlock and the forward wall.
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 ES) Tradducción en español aquí:
https://www.intervidia.com/category/bitacora/
(Trad FR) Traduction en français par +Anne Cpamoa ici:
https://spacetux.org/cpamoa/category/traductions/logbook-samantha/
31/07/2014