The Physics of Battles in Space

by Kenneth Anderson

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.

9 Responses

  1. I ran across this space battle physics post via Futurismic and was considering linking to it here but you beat me to it!

    It’s a fascinating post, I highly recommend it to anyone interested in “high frontier” issues (and/or sci-fi).

  2. Chris, I can’t tell if we’re so cool or … so uncool.

  3. Also, see the interesting comments over at Eugene’s post.

  4. Regarding whether we are cool or uncool… we’re legal academics writing about a post on a physics blog.

    Res ipsa…

  5. Ken and Chris, I hate to say it but I’ve got you both beat in the cool or uncool discussion.  My first degree was in physics.  There’s some res ipsa for ya…

  6. Ken,

    Have you read any of the Lost Fleet series by Jack Campbell?  They have what are probably the most realistic take on futuristic space battles.

  7. John, uh oh … HLS, I like the Jack Campell, and I agree.  The comments over at VC on this are very interesting.  I was interested in the heat problem.  Even more was the comment about the problem of Mars exploration being getting off the darn planet again.  I know there’s been some discussion about solving that problem with some volunteers who might be willing to opt for a one way trip.  Not as crazy as it sounds, if you’re old and think if you can survive the trip, heck of a way to go out.  Remember the Man Who Sold the Moon?  And … tomorrow, a Retro Heinlein special post in honor of Chris!

  8. Might be time to once again re-read Heinlein’s “The Moon is a Harsh Mistress.”

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