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The Physics of Space Battles
An anonymous reader writes PBS' It's OK to be Smart made this interesting video showing us what is and isn't physically realistic or possible in the space battles we've watched on TV and the movies. From the article: "You're probably aware that most sci-fi space battles aren't realistic. The original Star Wars' Death Star scene was based on a World War II movie, for example. But have you wondered what it would really be like to duke it out in the void? PBS is more than happy to explain in its latest It's Okay To Be Smart video. As you'll see below, Newtonian physics would dictate battles that are more like Asteroids than the latest summer blockbuster. You'd need to thrust every time you wanted to change direction, and projectiles would trump lasers (which can't focus at long distances); you wouldn't hear any sound, either."
My first encounter with realistic space battle physics was with Antares Dawn: a great book by Michael McCollum... Great stuff.
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I'm not so sure missiles would dictate battle range. On Earth we have dedicated weapon platforms to shoot down anti ship missiles. USN has the AEGIS cruisers, the Russians the Kirov battle cruisers. The horizon means the really really fast ones give about 10-20 seconds notice before you have a massive hole in the side of your ship. Weapons firms claim they can shoot down missiles (I'm not so sure about the claims). To extent the interception time they use airborne radar. However if space battles are fought at 10,000,0000km then you have quite a lot of notice of the missile coming as there is no horizon to hide behind and no sea to skim. If the missiles manoeuvre, you can see it and it is telegraphing its attack and movement direction with hours if not days and weeks.
The only two "giveaways" would be the heat signature from its power source (not just propulsion, but life-support) and whatever it accidentally occults as it moves across the background of stars. The heat can be drastically reduced by towing the power source a long way behind the main craft and having it very, very dispersed so the Watts per square metre of I.R. are very small. The occultation problem can be reduced by choosing a path that stays away from the galactic plane.
So most battles would be ones of sneak attacks and defensive fire. It might be possible to devise some sort of A.I. mines, or even simply fire a cloud of sand in the general direction (assuming the relative velocites of target + sand are high enough, that could be all that's needed).
However, I have a feeling that most "wars" in the future, whether in space on on Earth, will be economic in nature and "fought" over decades rather than wham-bam shooting battles.
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If you're going to swallow the idea of FTL drives, tractor beams and shields -- among other things -- then it's not really that much of a stretch to swallow the idea of inertial control, too. Which would make such battles not resemble a game of asteroids at all.
As for sound, presuming your vehicle maintains atmospheric integrity, you'd hear anything that causes the the craft's atmosphere to be jolted into motion. Debris hitting your vehicle, the stress caused by a sealed compartment being ruptured, people screaming when they get fried, crushed or otherwise insulted as a consequence of direct or indirect battle damage or loss of, for instance, inertial damping, equipment failures and power supplies having problems. You would also hear something if a force field of any kind was imposed upon your vehicle in such a way as to deliver any kind of uncompensated-for energy in mechanically coupled framework(s) producing direct or indirect vibrations in the audio range. And furthermore , presuming a ship has sensors to detect things like the energy outputs of other vehicles as they maneuver, seems to me that converting that to audio as a handy sound cue/warning would be hardly any trick at all. Just as one example.
Likewise, perhaps *we* can't focus a laser today, but that's not an inherent limitation of lasers even by today's known physics, that's a limitation of our technology, so that objection is kind of dead on the doorstep, so to speak. Not that a visible future beam weapon is necessarily carrying its punch in the form of light anyway. Could be just a side effect, or an aiming aid. This is the future, we're talking an imaginary scenario resulting from science and technology we don't presently have and so may speculate upon (using current knowledge... pretty boring... we can barely get off the planet's surface, much less engage in space battles... that's why most SF has at least a few pure fantasy elements in it.)
And along the lines of what we accept and what we don't, if you are blase' about the idea of a magic camera floating around your space battle and instantly changing perspective from A to B to C, perhaps it's just a little bit silly to complain about, for instance, a whoosh, or what "lasers" can do. That's entirely outside of what might be realistic in terms of what the movies subjects are up to.
So yeah, it's ok to think, but don't let someone else do your thinking for you. If there are space battles as depicted in most SF(fantasy) movies, the rules as we know them right now have long since been trashed, so there doesn't really seem to be any reason to worry about it.
All of the above is why I can really enjoy Star Wars, Firefly, Trek, etc, btw. Even though I'm fairly well grounded in how we think things work at present.
I have more trouble with obvious errors that don't take into account technologies we already have. For instance, in Red Mars, some of the characters "hide" from satellite surveillance by moving over long distances in a large hollow rock (or perhaps a thing that looks like I rock, I forget), something we would spot in an instant *today* by the simple expedient of image subtraction; Take two shots under the same or similar conditions but separated by time, align them, and subtract them. Everything that's in the same place turns to black; anything that has moved will be bright. This is *trivial* surveillance technology, and has been in use since *at least* the 1970's. And the kicker is this would work even better on Mars than it does here -- thinner atmosphere. Caused me a few snickers, that one did.
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Well, it is hard to say about that. Ship to ship combat in space would probably be carried out by drones. The fragile meat bags inside would never survive the acceleration.
I sat in a radar site in Hawaii at PMRF staring at a screen during the tests I supported. A target missile was launched from a pad a few miles away (you sure as hell could hear and feel THAT!) and the intercepting ship (as in a US Navy guided missile cruiser, not a space ship) was a couple of hundred miles away. The launches I witnessed... in under a second the target was through the clouds and five seconds later was gone leaving just a trail. The interceptor makes the target look like an old lady trying to out sprint Usain Bolt (I am told it would be supersonic before it leaves the launch tube on the ship... but I never saw a ship launch but every sailor I talked to who did said it was very impressive for the brief moment they got to experience it - from inside the ship.)
Other than that there was nothing to see. The intercept itself was over the horizon, so it had to be "viewed" from an aircraft.
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