An international team of scientists have proved that a big sample of superconducting foam has a strong and stable magnetic field. Unlike usual superconductors, the foam is a light and strong material which can be produced in the form of big size samples. It can be used in space for easy and careful docking of space apparatus and collecting space garbage. The results of the research have been published in the journal Materials.

Superconductors are magnetic materials whose resistance disappears at low temperatures. They are widely used for creating strong magnetic fields and levitation effect as well as for developing sensors; they are applied in electric engines, generators and for energy transportation. Under real conditions the size of conventional superconductors is limited to 1-2 cm. A bigger sample can produce cracks or lose their properties, which makes it unsuitable for the purpose. It complicates the application of the material and considerably increases its cost.

The problem of small size has been solved by the creation of superconducting foam. It consists of hollow pores surrounded by a superconductor. In this manner it is possible to obtain superconductors of almost all sizes and the light weight and small amount of the material needed considerably decrease its cost. Such a porous structure allows the foam to be quickly cooled down, which is very important for superconductors since they reveal their properties only at low temperatures. However, before putting this invention to practice it is necessary to specify the working principles of this foam, e.g., to understand how a magnetic field can act in it.
The international scientific team from Japan and Germany, including a researcher from the Krasnoyarsk Science Center SB RAS has found out that big samples of the superconducting foam have a stable, uniform and rather strong magnetic field propagating  from all the sides of the material. It allows the foam to exhibit the same properties as in usual superconductors in spite of the big size. Owing to this, as well as to its light weight, the foam can be used in space technologies.

For synthesizing the superconducting foam  a porous polyurethane structure is created. Then, it is impregnated with the chemical elements which constitute a superconductor: yttrium, barium, copper and oxides. These elements are preliminary dissolved in polyvinyl alcohol (PVA glue). After the impregnation the foam is annealed until polyurethane is completely burned out; there remains only a compound close to a superconductor in its properties, but it is not a superconductor yet. Thus, a superconducting crystal is placed into the center of the foam and the whole structure is again heated.  It can be made at home in a usual oven. Besides, such a foam can be used in space, especially, in satellites.  For space apparatus, the light weight of the materials is of importance and the obtained foam is extraordinarily light. 90 % of the foam is represented by pores, with only 10% being represented by the conductor itself, thus it is 10 times lighter than a usual superconducting material.», – explains  Denis Gokhfeld ,the co-author of the study, Candidate of Physical and Mathematical Sciences, senior research associate of the Kirensky Institute of Physics SB RAS.

One of the interesting applications of the superconducting foam is in the equipment for docking spaceships and satellites. By controlling the magnetic field in the superconductor it is possible to control approach, docking and push off. Due to the field formed it can also be applied as a magnet for collecting space garbage. In addition, the foam can be used as an element of electric engines or a source of magnetic communication in electric power lines.