This was done as part of a set of 3 sketches I did a few months ago. My idea for them was to tell a story about the civilization which the girl in the suit is wearing, mostly through her suit. She is the same girl, and each one is a concept of her, both the suit and the back story of where she comes from are different for the 3 different concepts. Each one is interacting with our own civilization through our meeting among the stars within our own ships, or without in the case of the first one. I've included a link to the first one at the end of this post to keep the focus on this new one. I want to go through my process of creating this.
Star Bind-Mars Mission
There is also a gif included and my reference wall for this. First I started with the loose sketch, I then turned it into a more finished piece of lineart. The reason I use lineart first is it helps me work out technical details better. After I create a flats layer to figure out my colors. At this point everything is, lineart, flats, two layers. Now I create 2 new layers, one set to screen the other multiply, the former for high lights, the latter for shadows. I take a deep purple of about 21B and 33S for the shadow, and in the yellowish hue, 100B 33S for the light. Just use HSB sliders on your color palette picker in PS and you'll get those colors. I do a base render over the flats with the lineart over it. Now, make sure you have black on your screen layer, and white on your multiply, this lets you eye dropper the values(set to current layer). After I reach a certain point, I merge everything together and cut up the elements, character form BG and the various overlapping BG elements, this gives me easier control later on when finishing up the piece. The value in doing my initial step is that I get my lighting pre mixed with the base flat colors, so I can eye dropper later once I get into straight paint. Various blending modes are used, special effects are done a number of ways, and you can see in the gif the entire process only comes together in the final stages of the render.
Link to first painting which I did back in February.