The outer layer of the pants assembly is made from a micrometeorite (MM) proof material to protect astronauts from particles in space. Meteorites range from 30 micrometers to 1 meter, of which MMs are smaller than 1 millimeter, or submillimeter in size. Without proper protection such particles can travel at an immense relative speed and puncture multiple layers of the PSEMU¹ and its components causing many troubles.
The outer layer is highly reflectant to a wide spectrum of radiation, protecting both the astronauts and the components of the PSEMU from otherwise extremely harmful doses. This reflective capability also adds to an increased stabilisation of the inside temperature of the PSEMU.
In favour of the mobility of the astronauts, the material is designed to be highly flexible while remaining relatively light weight.
The maneuverability of the astronaut is key for a successful completion of any mission. Pressurised sub-assemblies (0.2 to 1.2 ATM²) have therefore been tested under various outside pressures (0 to 5 ATM).
Impact tests have been performed on the outer layer. Resistance to a wide variety of particle shapes, sizes and speeds is required. The outer layer material was tested in resting and strained suspensions to simulate impact during movement.
Radiation tests have resulted in slight adjustments to the areas of the PSEMU that insufficiently reflected radiation away from the suit because of creases and other geometrical radiation traps.
The outer layer remains its reflective capabilities in the tested temperatures (3.15K to 453K).
¹PSEMU: Planetary Surface Exploration Mobility Unit
²ATM: Standard Atmosphere. Earth’s atmospheric pressure at sea level is approximately 1 atm.