FOAM-Stability (FOAM-S)

Foam stability is an important property of liquids. Most liquids do not stabilise into foam structures because liquid films are drained by gravity until they break.

Amphiphilic (surfactant) molecules are commonly used to prevent this rupture of the liquid films. Those molecules stabilize the films by forming layers of electrostatic charges at the molecular level along the liquid/air interfaces.

Amphiphilic (surfactant) molecules are commonly used to prevent this rupture of the liquid films. Those molecules stabilize the films by forming layers of electrostatic charges at the molecular level along the liquid/air interfaces.

While the difference between foaming and not-foaming solutions is clear, the case of slightly-foaming product is more complicated. For the latter, it is observed that although agitation does not produce stable bubbles and liquid films on Earth, some liquid solutions can nevertheless produce foams in microgravity.

This surprising result has been confirmed during parabolic flight experiments performed in autumn 2007. Among others, pure water may exhibit this degree of foamability. The presence of tiny solid particles in the liquid could also enhance this physical phenomenon and stabilise the water foam.

The FOAM-Stability experiment will address the following questions:

  • How does microgravity affect/enhance the foamability of liquid solutions?
  • How long can those foams be stable?
  • What is the role of solid particles?
  • Is it possible to create very wet foams in microgravity?

Current status The measurements will be carried out in 5 arrays of 12 tubes (about 1 cm in diameter). The foam is formed by hand-shaking by the astronaut and then mounted on a laptop screen (on the Station) for illumination. A camera on the Station will record the foam evolution over a period of one hour.

Last update: 13 May 2009

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