TWO YEARS OF OPERATIONS IN ISS FOR THE MELFI FREEZER AND THE WAY FORWARD

摘要

The first flight unit of the Minus Eighty degrees freezer MELFI has completed in July 2008 its two first years on board of the ISS. This was the initial requirement for on orbit operational life, assuming a return to earth for refurbishment before the next flight. Now, with the Shuttle flights reduction and the Shuttle planned retirement in 2010, MELFI will stay on orbit after the 2 first years and possibly more than 7 years.A second MELFI flight unit is waiting on ground for a possible launch during 2009. With two units on orbit the necessary refrigeration capabilities in ISS will be secured for years even during contingencies. A third unit is also available on ground either for an additional capability on orbit, or for supporting the spares traffic.The paper will present the outcomes of the two years on orbit comparing the performance with the predictions and assessing the behaviour of the components identified as critical for the mission: the Brayton machine with its bearings, the dewar valves, the thermal sensors, the electrical units and the thermal control.This evaluation will serve as feed-back both on the initial design choices and on the modifications anticipated for the extended lifetime with the objective to ensure and improve operations for the following years in orbit.