The Physics of Battles in Space

I do realize that Copenhagen is still underway, so this is a little like whispering in church (I’ll put it mostly under the fold) … however, it’s a Friday afternoon, and this Gizmodo article on the physics of combat in space was highly distracting (h/t Eugene Volokh).

The most interesting bit to me, actually, in Joseph Shoer’s article was the observation that in a war between planets, such as Mars and Earth, the trajectories of approach are not unlimited.  That is, launch windows and orbital relations between the planets matters hugely.  There are logical places for defense, in other words, even if they shift over time with solar orbits, beyond the planetary defensive orbit itself.  This means room for strategy in space combat, in other words, and not merely tactics in skirmishing among ships:

[S]uppose we get out there, go terraform Mars, and the Martian colonists actually revolt. Or suppose we encounter hostile aliens. How would space combat actually go?

First, let me point out something that Ender’s Game got right and something it got wrong. What it got right is the essentially three-dimensional nature of space combat, and how that would be fundamentally different from land, sea, and air combat. In principle, yes, your enemy could come at you from any direction at all. In practice, though, the Buggers are going to do no such thing. At least, not until someone invents an FTL drive, and we can actually pop our battle fleets into existence anywhere near our enemies. The marauding space fleets are going to be governed by orbit dynamics – not just of their own ships in orbit around planets and suns, but those planets’ orbits. For the same reason that we have Space Shuttle launch delays, we’ll be able to tell exactly what trajectories our enemies could take between planets: the launch window. At any given point in time, there are only so many routes from here to Mars that will leave our imperialist forces enough fuel and energy to put down the colonists’ revolt. So, it would actually make sense to build space defense platforms in certain orbits, to point high-power radar-reflection surveillance satellites at certain empty reaches of space, or even to mine parts of the void. It also means that strategy is not as hopeless when we finally get to the Bugger homeworld: the enemy ships will be concentrated into certain orbits, leaving some avenues of attack guarded and some open. (Of course, once our ships maneuver towards those unguarded orbits, they will be easily observed – and potentially countered.)

I’m shallow and easily distracted, true, although I hope not quite as shallow as this main character of this book.  Back to climate change and Copenhagen.