Based on the nature of the combatants being machines, atmospheres are a moot point from planet picking. However, what if the effectiveness of orbital bombs (kinetic or otherwise; asteroids/bombs) is affected by the density of the atmosphere. Meaning, if you are on a moon with no appreciable atmosphere, then there is nothing to slow down/reduce a kinetic asteroid bomb. However, if you're on a planet with a heavy dense atmosphere, you gain some protection from the smaller bombs that could be lobbed your way. Thoughts?
Interesting I suppose. I would say a interplanetary cannon could be a tiered weapon. The first tier is effective at bombarding moons and asteroids, planetoids lacking any atmosphere. The higher the tier, the better the "atmospheric penetration", something like that. Maybe shells from the tier one cannon burn up in planets with atmospheres, so you need better shells/better cannon.
I wrote about this before: This could be an effective (if not always present) counter to having "the higher ground" on asteroids or atmosphere-less planetoids and moons. Heavier atmospheres means that it costs more to leave the planet (tied to heavier gravity as well!), but it also means that non-specialized projectiles and weapons will be unable to be as effective. Really thick atmospheres would also result in denser fog, possibly a higher chance for bad weather, etc.
