If you accept a cargo mission without having enough cargo-space, the mission is automaticly aborted.
The mission screen should color the missions in red that you don't have the space for, and would it be too much to ask to have the cargo-space needed listed in the mission text? I.e. "Transport 16 units of Iron to New Detroit". This would be handly, not to mention much more realistic.
Also, I'm sure it's been mentioned before, but I'd like to second the motion that the mission screen should list the actual base name, (i.e. Helen/Hector) so you can fill your cargo hold appropriatly.
BTW, thanks for making such a great game remake, it's been quite fun playing so far, even with a couple minor bugs.