This Skylab Gallium Arsenide Crystal Growth Experiment with M518 Furnace, designated experiment M555 , is a flight ready spare for the unit utilized onboard SKYLAB. The canister consists of the Multipurpose Electric Furnace (M518) and a M555 cartridge containing the experiment sealed within the oven. Onboard Skylab, the assembly was inserted into the M512 Materials Processing Facility (located within the Multiple Docking Adapter section of the Spacecraft) .
M555 experimental objectives included the growth of single gallium arsenide crystals in the weightless environment of space from solution in order to produce material of exceptionally high chemical and crystalline perfection, have better doping homogeneity, have more homogeneous starting melts, and achieve uniform growth. M555 was conducted during SKYLAB II (first crew).
During performance of the experiment a furnace was used to heat and cool the smaples in a controlled manner to form single crystals of the sample material. The experiment required approximately 115 hours for growing each of the single crystals. The crew was required to monitor and record temperatures of the crystal growth package every 30 minutes during the first 3 hours of the heating cycle, every 12 hours during the remaing 112 hours of the heating cycle, and every 30 minutes for the first 3 hours of the 9 hour cooldown time.