воскресенье, 8 декабря 2019 г.

Life of a foam













ISS - International Space Station logo.

Dec. 6, 2019

Foam bubbles

A fine coffee froth does not last forever. The bubbles that make the milk light and creamy are eventually torn apart by the pull of gravity. But there is a place where foams have a more stable life – in the weightless environment of the International Space Station, bubbles don’t burst so quickly and foams remain wet for longer.

Beyond the pleasures of sipping a cappuccino with its signature froth, the presence of foams in our daily lives extends to food, detergents, cosmetics and medicines. However, creating the perfect bubble for the right foam is tricky.

Three experiments will investigate properties of foam

On Earth, the mixture of gas and liquid that makes up a foam quickly starts to change. Gravity pulls the liquid between the bubbles downwards, and the small bubbles shrink while the larger ones tend to grow at the expense of others. Due to the drainage, coarsening and rupture of the bubbles, foam starts to collapse back to a liquid state.

A foam’s existence in space is marked by more equilibrium because drainage is suppressed. Bubble sizes are evenly spread and that makes it easier for scientists to study it in more detail.

Lessons on foams in space

In 2009, ESA astronaut Frank De Winne ran the Foam Stability experiment on the International Space Station. Frank shook several liquid solutions contained in 60 closed cells and recorded what happened next. The samples ranged from pure water to protein-based fluids, like the ones used for chocolate foams, and antifoaming agents.

De Winne with the Foam Stability experiment

After just ten seconds, fluids stabilised more quickly and produced more foam than on Earth. Scientists discovered that it was possible to create super stable foams in zero gravity.

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