The waiting attendants hovered near the opening of the hangar, waiting for the scheduled arrival. Inside the bay there was air, breathable atmosphere; outside of it, the cold, hard vacuum of space. The hangar doors were open, a blue glow surrounding the edges; through it, the myriad stars of outer space were plainly visible.
The plasma curtain was an extension of what vacuum welders on Earth had been using for centuries—a confined window of a noble gas, usually argon, was heated to create a thin barrier through which objects could pass while confining atmosphere and vacuum on opposite sides. This caused a characteristic glow about the window’s edges; argon treated in the manner protested by exuding a bluish glow, and it was this hue that ringed the maw of the hangar.
The two-man roundabout approached, paused, then gently accelerated towards the curtain. Silently, it slipped through, and the attendants gently guided it to a locking mechanism.
“Welcome to L₄,” the head attendant greeted.