Cold box (Glossary) for ISS // On 4 July 2006, the spaceship Discovery transported the MELFI (Minus Eighty Degree Laboratory Freezer for ISS) system to the ISS (International Space Station). The Engineering Division was part of the team of companies that spent eight years collaborating on the freezer system’s development and construction. MELFI provides the ISS with storage facilities for biological samples and other degradable matter over a longer period. One of the challenges in developing MELFI involved storing samples at temperatures as low as –80 degrees Celsius. The other main challenge was to fit the system into the cupboard-like ISS payload rack.

The MELFI technology consists of a cold box to generate the cooling power, four cylindrical, double-walled cooling containers (dewars) each with 75 litre capacity, a vacuum-insulated piping system for cold-distribution and the electronics for system control. A cooling machine is used to generate a cold stream of gaseous nitrogen (Brayton cycle) in the cold box, transported to the four dewars via the 2,000 metre insulated pipe system. The temperature of each dewar can be regulated independently using control valves and they are able to house a large number of samples. MELFI has been designed for an operational lifespan of at least ten years.