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TEST BACT [1 fiche]

Fiche 1 2008-04-17


Subject field(s)
  • Space Physics
  • Scientific Research Methods
  • Physics of Solids

The Binary Colloidal Alloy Test-3 is an Exploration Systems' transition flight experiment in the Human System Research and Technology area. BCAT-3 provides a unique opportunity to explore fundamental physics and simultaneously develop important future technology, including computers operating on light, complex biomolecular pharmaceuticals, clean sources of geothermal power, and novel rocket engines for interplanetary travel. These studies depend entirely on the microgravity environment provided by the International Space Station (ISS); in all other locations accessible to science, gravity dominates and precludes investigation of any other effects of interest. The experiment itself [consists of] photographing samples of colloidal particles with a digital camera onboard the ISS. Colloids are tiny nanoscale spheres of plexiglass a thousand times smaller than the width of a human hair (submicron radius) that are suspended in a fluid. They are ubiquitous (e.g., milk, smoke, and paint) and therefore interesting to study directly. Colloids are also small enough that they behave much like atoms and so can be used to model all sorts of phenomena because their size, shape, and interactions can be controlled. The 10 samples in BCAT-3 are made from the same ingredients, each a recipe with different proportions, and are grouped into three experiments: critical point, binary alloy, and surface crystallization. [Text followed by an illustration of a BCAT-3 sample holder.]


BCAT-3 is comprised of three separate experiments, which are individually referred to as a binary alloy (BCAT-3-BA), surface crystallization (BCAT-3-SC) and critical point (BCAT-3-CP). The critical point investigation is continuing with additional samples on future ISS [International Space Station] expeditions and will be referred to as Binary Colloidal Alloy Test - 4. BCAT-4 will consist of two sets of samples referred to as BCAT - 3 and 4: Critical Point (BCAT-3-4-CP) and BCAT-4:Polydisperse (BCAT-4-Poly). ... The Binary Colloidal Alloy Test-3 (BCAT-3) hardware supported three investigations in which ISS crews photographed samples of colloidal particles (tiny nanoscale spheres suspended in liquid) to document liquid/gas phase changes, growth of binary crystals, and the formation of colloidal crystals confined to a surface. Colloids are small enough that in a microgravity environment without sedimentation and convection, they behave much as atoms and so can be used to model all sorts of phenomena because their size, shape, and interactions can be controlled. The BCAT-3 payload consists of ten small samples of colloid alloys in which the microscopic colloid particles are mixed together into a liquid. These ten samples are contained within a small case that is the size of a school textbook. At the start of an experiment run, all ten samples are shaken to completely remix the colloid samples, much in the same way that salad dressing must be shaken to remix oil and vinegar. After the samples are mixed, what remains is periodically photographed using a digital camera until the colloid and liquid components of those samples have separated or the polymers have formed crystals. The samples can be remixed to repeat the experiment. The ten samples in BCAT-3 were selected as part of three separate experiments examining different physical processes: critical point, binary alloys, and surface crystallization.


  • Physique spatiale
  • Méthodes de recherche scientifique
  • Physique des solides

Contexte: recherches en microgravité sur les structures colloïdales; test avec alliages binaires (c'est-à-dire composés de deux éléments) mis à l'état colloïdal.


test BACT (croissance d'alliages binaires à partir de particules colloïdales en suspension) : il faut articuler le syntagme pour rendre compte de la réalité du texte où il est question de la croissance de cristaux binaires qui se développent à partir de particules colloïdales en suspension dans un liquide.


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