Annually, I create a few illustrations for the Omaha, NE apparel brand, Curbside Clothing. The following illustration is (very loosely) based on a short story by Ted Chiang in his book Exhalation.
The initial concept sketch was pretty rough. I typically start thinking things through in more detail once I get the 3-D modeling stage. The astronauts' suits were loosely based on the Mercury astronauts' design. The good thing about working in 3D, is that once an object is created, it can be repeated. 3D models were created in Blender.
And then it's a matter of creating the line work, color fills, and then refining the colors.
The final illustration... Shirt is available at Curbside Clothing.