Astrotropes: Space Battles part 1

Space battles really are one of the coolest things in sci fi aren’t they? They’re the fast paced sections full of flashy lasers, awesome sound effects, explosions, cool space ships… They also make the scale of things seem that much more epic. After all, you’re in space, fighting against starships which may be kilometres in size, in fleets containing thousands of vessels. The TV Tropes Rule of Cool states that “The limit of the willing suspension of disbelief for a given element is directly proportional to the element’s awesomeness.” And given how awesome the battle scenes in movies are, I usually just throw disbelief completely out of the window. But that said, what might an actual space battle be like?

I’m going to say right from the start, that the Space Battle is a huge trope. There’s a lot to cover, and I’m not going to cover it all in a single blog post. For now, I’m just going to cover the basics.

So, for a start, there would be no visible laser beams and no sounds of any kind. In fact, thinking about it scientifically, a space battle would be much more like the Hunt for Red October than anything you’d see in Star Wars. In space, it would be all about range – by which I don’t mean the range of your weapons, I mean the range of your eyes. Or more accurately, your sensors. You’d be taking careful aim at your opponent long before you could actually see them. With any luck, you’d be doing so long before they even knew you were there.

So let’s suppose, hypothetically speaking, that you had two space ships going toe to toe in a real life space battle scenario. And purely for the hell of it, let’s say that those two space ships are the Starship Enterprise (the original) and the Millennium Falcon. Let’s look at the numbers… Though I know someone out there will end up correcting me on this, the original Enterprise has a saucer with a diameter of 127.8 m, and the dimensions of the Millennium Falcon are a rather more modest 34.37 m in length by 26.21 m breadth.  For a start, this means that the Enterprise is a hugely bigger target, making it a lot easier to hit. But you’d need to be close enough to see it first.

So let’s assume that our starships have scanners with an angular resolution of 0.1″ (that’s 0.1 arcseconds) which, by modern standards, is a pretty good resolution for a decent sized telescope. In order to fire at a target, you’d need to be able to resolve it – that is, you’d need to be able to see it as more than just a distant point of light. Once you can resolve its actual shape, you can begin to take aim. Before that, the margin of error would be too high and it wouldn’t be worth the waste of energy aiming at a target which you would probably miss. Throwing in the numbers and sparing you the trigonometry… Seen from the Enterprise, you’d start to be able to resolve the Falcon’s shape when it was 1227.5 km away. Unfortunately, the Enterprise is at a serious disadvantage because with it’s much larger size, the Falcon would be able to resolve it when it was 4564.2 km away! By the time the Enterprise was close enough to attack the Falcon, chances are the Falcon would have taken several shots at the Enterprise, perhaps inflicting some serious damage on it. Interestingly, this has the effect of leveling the playing field rather effectively. A larger ship with more armour and more firepower would take a lot longer to be able to target a smaller vessel. In fact, it could be possible for a smaller ship to cripple a larger ship before they could even be resolved. Of course, on the other hand, a larger ship would be able to have larger telescopes and so have a correspondingly more powerful resolution (or in non-technical terms, it could be able to see you from further away).

Then, of course, there’s the matter of making sure that you were firing at the right space ship, or indeed making sure you were firing on a ship at all, and not just an asteroid. Trying not to reveal your location would be vital.

Chances are, the crew of a battleship would need to be pretty good astronomers, and their ships would need to be equipped with several telescopes, covering different wavelengths. Then the crew would need to look at images and data from those wavelengths and rapidly figure out whether or not it was their target. Ships could also attempt to disguise themselves by reducing their ship’s reflectiveness (again, a bright white Enterprise would be extremely easy to spot), but they’d likely be very bright in the infrared – no air cooling in space means excess heat created by the ship’s engines and machinery would need to be radiated away into space. So any object which was peculiarly bright in the infrared could be another ship. Looking at the spectrum of an object can tell astronomers the difference between different kinds of asteroid. In the midst of a space battle, it would probably let a ships crew determine whether or not it was a ship they were looking at, and possibly say a little about what kind of ship it was. And thankfully for our protagonists, photometric and spectroscopic analyses like this could be quite safely done while still out of range.

But how would you know the range? Distance is notoriously hard to measure in space. Radar would still be quite effective in determining your distance to any nearby objects… But it would also give away your position.

Keep reading for Space Battles part two, where I’ll talk about lasers, torpedos and other space weaponry!

trope is a recurring theme in any narrative which conveys information to the audience. These are snippets of information which have somehow ended up in our collective subconscious as ways in which storytellers have gotten their points across. Overused tropes end up as clichés.

Images: Screencaptures from Star Trek © Paramount and Star Wars © Lucasfilm – used here in accordance with fair use policies.

About Invader Xan

Molecular astrophysicist, usually found writing frenziedly, staring at the sky, or drinking mojitos.
This entry was posted in astrotropes, Sci Fi, space and tagged . Bookmark the permalink.

12 Responses to Astrotropes: Space Battles part 1

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  4. Baribal says:

    Let me just doublecheck the math so you can triple-check it. I love Python. But I also don’t even know IDL.

    from math import pi, tan
    def distance(size, angle_of_resolution = 0.1, min_pixel = 1):
    “””Gives the distance beyond which an object can’t be resolved anymore, assuming perfect CCDs.”””
    one_arc = (size/2.) / tan(angle_of_resolution/2.)
    return one_arc / float(min_pixel)

    res_arc = 0.1/3600.
    target_size = 127.8 # Enterprise
    #In [6]: distance(target_size, res_arc)
    #Out[6]: 4600799.999704166

    Okay, that’s 4600.8km, close to your 4564.2km. However, there’s one factor missing: What are the emissions? We can either assume that there are no emissions boosting the signal, which means that we’d need several such pixels to identify a ship as such. Assuming a 40×40 sample image, that’d work out to a mere 115km detection distance. Or we can assume a lot of emissions, i.e. engines or firing rockets, then detection, though not exact locaization, can be achieved by finding the artifact left in the image. Did you try a Bayesian analysis? Apropos artifact, if background noise is strong, detection/identification on the relevant spectrum may happen a lot later. For instance while I don’t know the microwave emissions (or even blackbody radiation) of a firing rocket, I assume that it’d fade into the CMB. Those engines on Galactica which look like they vent a lot of plasma into space may be another matter altogether. IR may reveal a ships position when firing thrusters (and maybe just thrust/distance ratio), but maybe not its direction. That’d be Scotland Yard in space…
    Sooo, I guess I’ll have to read up on the EM-spectrum and grill you on what background noise there is. Apropos, how much radio emissions does the sun put out relative to TV transmissions over the decades? Is Earths signal shell even actually detectable?

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  6. Paul Edmon says:

    Great analysis. I’ve done this sort of Fermi problem before as well out of pure curiosity. Targeting is a major factor. Heck even reverse targeting based off of an active radar ping would be a pain as you would need to reverse calculate the convergence of the radar front which assumes you have enough of a baseline to see the curvature.

    • Paul Edmon says:

      I suppose an additional solution to this problem though would be to have small scout ships or drones feeding data to the main ship. Then you could make a larger baseline and make up for the poor angular resolution of your solitary telescope. That would help with astrometry but not so much with id.

      • invaderxan says:

        Oh, that raises an interesting point which I hadn’t thought of. A small flotilla (if flotilla is even an appropriate word to use for space ships) could effectively network their telescopes together to act as a makeshift interferometer and, given the scales involved, dramatically increase their resolution. If they were to communicate using highly directional signals, lasers for instance, the fact that they were doing this could remain undetectable to their opponents…

        • Paul Edmon says:

          I’ve seen a few scifi and scifi animes that have done just that. A thing that occurred to me the other day regarding point cast communications is that over a large distance it would be hard to hit the receiver on the other end effectively, especially if they are in motion. This is especially true for interstellar communications. I once read an arXiv paper about that with regards to SETI. If you really don’t want your communications intercepted then it may be tough to get a tight enough beam and still be able to hit the target. But I guess it depends on how paranoid you are.

    • invaderxan says:

      It’s quite fun to toy with, it has to be said. :)

      And I hadn’t really thought of it like that actually, but it’s a good point. With only a short baseline, you’d get the general direction, but getting an exact location would be difficult. Still, it would significantly increase the chances of the craft using the radar being spotted…

  7. Ash says:

    I suspect that tracking is a lot easier in space – asteroids follow simple, predictable trajectories. Anything that doesn’t is a bad guy. You can;t hide because you are always against a backgrop of stars. Real space war would be – as you say – very, very, boring.

    • invaderxan says:

      Predictable, yes, but most of them are technically uncharted (there are far too many to keep track of all of the smaller ones constantly) and they have all sorts of trajectories. You’d likely still need to make sure you knew what you were looking at. And I wouldn’t say boring, necessarily. It just wouldn’t be fast paced. It’s likely it would be tense and quite nerve wracking…

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