The Airtight Hangar Door is a Large Ship-only block that telescopes from its standard size of 1x1x1 to 3x1x1. Unlike the previously available blast doors (built using various iterations of Blast Door blocks and Pistons), this block does not form a separate grid and, once closed, creates an enclosed space that can be pressurized via Air Vents.
The block's functionality and user interface are largely identical to the Door. However, instead of sealing a gap through it, the block extends outwards. If it meets another block of the same grid, they form a sealed connection. Hangar Doors can be put in a row to create seamless doors of unlimited length.
The first and obvious application is construction of doors that can let through objects other than a walking engineer. The basic arrangement allows maximum size of 5 m along one of the axes. Two doors put opposite of each other yield 10 m. For larger craft, elaborate solutions have been produced, using a large door assembly, a part of which is attached via Merge Blocks and can be removed.
Additional suggested applications are as sliding doors to cover weapons, thrusters, windows, turrets, et cetera.