Foam Optics And Mechanics - Stability (Foam-Stability) - 01.09.14
Science Objectives for Everyone FOAM-Stability studies the behavior of wet foams in microgravity conditions.
Science Results for Everyone Information Pending
Sponsoring Space Agency
European Space Agency (ESA)
ISS Expedition Duration:
March 2009 - March 2010
Previous ISS Missions
- FOAM-Stability studies aqueous and non-aqueous foams in microgravity environment. The behavior of foams in microgravity and on earth are very different, because the process of drainage is absent in microgravity conditions.
- Other fundamental questions addressed are:
- How long can those foams be stable?
- What is the role of solid particles in the liquid in water foam stabilization?
- Is it possible to create very "wet" foams in microgravity?
The main process which controls the stability of a foam on Earth is the gravity drainage which eventually causes film thinning of the bubbles toward a critical thickness at which they become unstable and burst. This process is not a factor in microgravity and foams containing large amounts of liquid can be studied for longer time. Foam experiments in space allow researchers to explore a new sort of very "wet" foams with liquid fractions around 30%. The high liquid fraction enables bubbles to keep their spherical shape. On Earth, such materials are unstable and most of the time not called foams but bubbly liquid. In space, drainage is suppressed such that liquid films remains thick, but bubble coalescence events are nevertheless seen. However, after some time, bubble motions become rare events such that the foam is more stable even when shaken. In most cases, the foamability (the volume fraction occupied by the foam only) is almost two times larger on the ISS than on Earth. A striking and unexpected result is that a non-foaming solution on Earth exhibits a significant foam column in space.
From the FOAM-S experiment, it is discovered that super stable aqueous foams can be created in microgravity conditions. On Earth, coarsening and film ruptures are always present for a solution even with foaming agents. In zero gravity, the foam still evolves but the amount of foam does not appear to change significantly. Surprisingly, antifoaming agents have a reduced effect in microgravity, and the resulting foam appears to be stable. This behavior was completely unexpected since anti-foaming agents are meant to avoid foam creation and stabilization. These observations raise new fundamental questions that should be investigated in future works (Vandewalle et al. 2011).
Vandewalle N, Caps H, Delon G, Saint-Jalmes A, Rio E, Saulnier L, Adler M, Biance AL, Pitois O, Addad SC, Hohler R, Weaire D, Hutzler S, Langevin D. Foam Stability in Microgravity. Journal of Physics: Conference Series. 2011; 327: 1-8.
Ground Based Results Publications
Banhart J, Garcia-Moreno F, Hutzler S, Langevin D, Liggieri L, Miller R, Saint-Jalmes A, Weaire D. Foams and emulsions in space. Europhysics News. 2008 July 26; 39(4): 26-28. DOI: 10.1051/epn:2008402.
Carpy R, Picker G, Amann B, Ranebo H, Vincent-Bonnieu S, Minster O, Winter J, Dettmann J, Castiglione L, Höhler R, Langevin D. Foam generation and sample composition optimization for the FOAM-C experiment of the ISS. Journal of Physics: Conference Series. 2011 December 6; 327: 012025. DOI: 10.1088/1742-6596/327/1/012025.
NASA Image: ISS020E042309 - Expedition 20 flight engineer, Frank De Winne is pictured near an ESA Foam Stability experiment floating freely in the Columbus laboratory of the International Space Station.
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