FOAM-Stability studies the behavior of wet foams in microgravity conditions.Principal Investigator(s)
European Space Agency (ESA)Sponsoring Organization
Information PendingISS Expedition Duration:
March 2009 - March 2010
19/20,21/22Previous ISS Missions
Information PendingEarth Applications
Information PendingOperational Protocols
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).
Langevin D, Vandewalle N, Caps H, Delon G, Saint-Jalmes A, Rio E, Saulnier L, Adler M, Biance AL, Pitois O, Addad SCohen, Hohler R, Weaire D, Hutzler S. Foam Stability in Microgravity. Journal of Physics: Conference Series. 2011; 327: 1-8. DOI: 10.1088/1742-6596/327/1/012024.