Short description

The Materials Science Laboratory consists of a Core Facility, together with associated support subsystems.

The Core Facility is a stainless steel cylinder (the Process Chamber) capable of accommodating different individual furnace inserts, within which sample processing is carried out. Processing conditions are normally either a vacuum or an inert gas (e.g., Argon).

The process chamber is divided by an Intermediate Support Plate that acts as a mechanical interface for the experiment cartridge, together with an associated experiment-dedicated electronics that may be required.

The microgravity levels during an experimental run are measured by an integrated three-axis accelerometer package. Access to exchange a furnace insert is achieved by opening the process chamber lid, and removing the sample cartridge and Intermediate Support Plate.

A furnace insert is simply an arrangement of heating elements, isolating zones and cooling zones contained in a thermal insulation assembly. On the outer envelope of this assembly is a water-cooled metal jacket forming the mechanical interface to the Core Facility.

Facility operation

A fundamental feature of the Materials Science Laboratory is the capability to exchange furnace inserts allowing the application of various processing techniques using different thermal profiles.

The current concept is to run coordinated experiment campaigns for the different furnace inserts. The crew will first insert the sample to be processed (contained within an experiment cartridge) into the furnace.

Following evacuation of the process chamber, an experiment sequence is initiated, consisting of a number of steps with pre-defined parameters (e.g., heat-up, directional melting, homogenisation, pulling/directional solidification, quenching, and cool-down). Transition from one step to another can either be time-driven or event-driven. The baseline approach is to execute the experiment sequence completely automatically (subsequent to manual insertion of the sample).

The capability also exists, to operate via 'telescience' (i.e., to adjust the process parameters and step sequences in realtime) directly from the ground or by using the crew. Following processing, the crew will remove the experiment cartridge and place it into stowage for later transportation to the ground.

The samples to be processed are contained in experiment cartridges that consist of a sample tube, crucible, sample probe and cartridge foot (i.e., the mechanical and electrical interface to the process chamber).

Different inserts for the MSL have been developed. The Low Gradient Furnace and the Solidification and Quenching Furnace are based on the Bridgman Technique with a hot and a cold zone and an adiabatic zone in between.

• Low Gradient Furnace (MSL-LGF)
• Solidification and Quenching Furnace (MSL-SQF)
• High Temperature Furnace
  A high temperature isothermal furnace insert for a maximum temperature of 1600 deg C is currently under study by DLR. The current design shall be used for diffusion experiments applying the shear cell technique with a diameter of 60 mm. The experiments can be conducted under vacuum or inert gas. The axial temperature homogeneity shall be < 1 K at 1600 deg C over 90 mm length.