Been thinking about the Astrolasians a bit more.
in particular - why would they come to Earth to raid for coal? There's no oxygen to burn it with.
Answer:
The primary form of settlement is crater domes. Since safety, insulation and radiation filtering are important things, and they're working with iron and glass (think crystal palace) the dome is multi skinned. Between the outside and inner skin, a large gap exists which is primarily filled with CO2. This helps trap heat and transfers some pressure loading to the outside skin (keeping it stretched tight like a bubble) while relieving some of the tension forces in the inner skin. If the outer skin is punctured, it acts like an insurance option, sacrificing the C02 rather then breathable atmosphere while repairs are made. This gap is also a resivoir for the green houses, allowing plants to grow at their full potential in the constant daylight.
How is this CO2 made?
simple. Where iron ore (or similar) has been collected, it is crushed, mixed with coal and fed along a long, tubular ceramic mixer. This mixer is heated to extreme tempretures by an array of solar powered Fresnel Lenses, with the resulting iron slag and CO2 bubbling out the other end.
http://en.wikipedia.org/wiki/Fresnel_lensThe Astrolasians use similar weaponry to the British Empire, but have found the land frigates quite impractical to adapt to pressured air batteries, and so use lighter constructions typified by large wheels on the end of legs.