How Realistic Is It Actually?

Children of a Dead Earth was developed primarily to answer the question: What would space warfare actually be like? Various hard science fiction novels and other media have attempted to answer that question in the past, but these works have always come up short, at best relying on rampant speculation, and at worst, inventing fictitious technologies to support their conclusions.

Children of a Dead Earth solves these issues by first being a complete and utter simulation of space warfare, and second by relying only on technology that has been explicitly demonstrated to work. This is critically important: there is absolutely minimal guesswork in this game, instead everything is necessarily derived from equations, and the mathematical results of these equations.

carrier being missed.png

In case it is not obvious by now, Children of a Dead Earth was designed with no vision in mind, unlike just about every other videogame, novel, or movie attempting to do the same. This is because I never wanted to corrupt the ultimate goal of this project, which was to discover what space warfare would be like, rather than to say what space warfare would be like. To have an initial vision when building this game would have been starting with a conclusion, and then twisting reality to support that vision. By starting with no vision whatsoever, the conclusion would be generated by implementing the equations, and observing how they interact. In this way, the end result of Children of a Dead Earth was little like I had ever imagined actual space warfare would be like, and this will probably be true for you as well.

To reiterate: Children of a Dead Earth is a simulation first, and a game second. No amount of realism was compromised to make things more fun, or to make things prettier. It is science first, everything else second. Despite this, the game still remains fun, but you’ll find it plays very differently than any space warfare game you’ve ever played.

post damage6.png

Some assertions in making this game. All technologies implemented in Children of a Dead Earth have all been demonstrated to be feasible, and successful prototypes of all of them have been created in real life. For engines, this includes Nuclear Thermal Rockets, Combustion Rockets, Resistojets, and Magnetoplasmadynamic Thrusters. For weaponry, this includes Conventional Cannons, Railguns, Coilguns, Linear Induction Motor Launchers, and Arclamp Pumped Solid State Lasers. For powerplants, this includes Radioisotope Thermoelectric Generators and Thermoelectric Solid Core Fission Reactors. And of course, radiation shielding, monolithic armor plating, Whipple Shields, and heat radiators are all fully implemented in game as well.

Another assertion: stealth in space is not feasible. It’s a topic large enough for its own post, so I’ll summarize: if you actually want stealthy engines, you need to either to move so slowly that getting between planets will take centuries, or you need engines that are insanely efficient, more efficient than any technology ever imagined.engine.png

A final assertion. Spacecrafts will be crewed, but any concept of ‘fighters’ will not be a thing. The mass of having people is significant, and an issue. The spaceflight analogue to fighter jets do not need a pilot, and instead these drones can be remotely piloted by the nearest capital ship. Such a thing exists today already: UAVs. On the other hand, capital ships do need a crew, because of speed of light lag. Trying to command a spacecraft from across the solar system is not just highly prone to jamming and spoofing, but the seconds or even minutes of lag in command would prove fatal in combat. On the other hand, drones will be close enough to their carrier ship that speed of light lag is not a significant issue.

How granular is the simulation? Extremely granular. Let’s take railguns, for instance.science-railgun.pngTo determine the muzzle velocity of a railgun, an equation for the force applied on the armature was used. This equation was numerically integrated to determine the acceleration of the projectile over time steps sometimes as granular as nanoseconds across the entire rails. The equation itself requires knowledge of the inductance of the rails, as well as the resistance across the rails. Inductance is generated from another equation depending on the relations between the rail dimensions, and the resistance is calculated from the material properties and dimensions of the armature and rails. This also informs the size and mass of the railgun, which is critical for ship design later on.

But that’s just the beginning. A weapon is more than a projectile launched. It also generates heat, which can melt the rails or the armature itself. The ablation of the rails and of the armature are calculated separately from additional equations utilizing the material specific heat, conductivity, density, dimensions, and vacuum permeability. If the ablation is too significant, the railgun will not operate properly, and you will be unable to operate the railgun. Even if you do not ablate your rails, if the bulk temperature of the rails becomes too high, the materials will be unusable until they cool, and you must wait for the railgun to expel its excess heat via radiation.

All projectiles have minor imperfections. A tiny off centering of the armature can produce significant inaccuracies in firing, and this too is calculated. The recoil of the railgun can become imbalanced, and cause significant cantilever beam deflection with the railgun barrel. Based on the tensile strength of the rail material and the Elastic Modulus, this instability is another factor that one must work around when designing railguns in Children of a Dead Earth, lest they shatter when you fire them.

And finally, don’t forget about the turrets! The more massive you make your railgun, the greater the moment of inertia of the weapon, and the harder it is to rotate with the reaction wheels inside the mantlet housing. You will find that you have to make tradeoffs with your weapon, as a railgun which takes ten minutes to aim at a target is a railgun which is not usable for combat.

That’s a taste of the depth of simulation within Children of a Dead Earth. Next up, I’ll be tackling how space warfare actually ended up, based on what has sprung forth from these equations.

 

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11 thoughts on “How Realistic Is It Actually?

  1. Just a thought. You mention how you need to limit the size of railguns so that the turret that houses it can come to bear on a target in time. Couldn’t you just place a truly massive railgun in a spinal mount running a good fraction of the length of your ship; Laugh maniacally at whatever armour your opponent attempts to use as you point your ship and let out a few rounds. You wouldn’t need to worry as much about heat or reload rate as your firing window would be limited anyway.

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    1. Absolutely! Several designs in game already use a single spinal mounted gun. These sort of weapons tend to have many pros and cons. They tend to be brutal against large enemy ships, but smaller ships and drones often can often out-dodge the gun before it can draw a bead on the target.

      One of my alpha testers actually went that route, and prefers spinal mounted guns for his ships.

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  2. what makes me wonder: what is the rationale that turrets are turned by internal reaction wheels instead of mount motors like any currently existing turret? (known to me)

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    1. Reaction wheels allow much faster turning speeds because they accelerate faster the more massive they are, and you can adjust your turn speed based on how much mass you want to spend on them.

      Most modern day turret speeds are much slower than what you need in Children of a Dead Earth. If you take a look at a modern day CIWS, even those move fairly slow for being a point defense system. In game, jerking rapidly and accurately back and forth between a hundred different targets moving in different directions is often the main use case for turrets.

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      1. im a bit sceptical about that being more efficient than simply large sets of “linear” motors around the “eyeball” socket of the turret mount.
        the gyro will likely as well “just” be connected magnetically to the turret, same way as any big motor assembly would be.
        i’ll have to look that up to be convinced.
        do you have some math for me to read up on that?

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        1. The wiki page on flywheels has much of the math needed for this: https://en.wikipedia.org/wiki/Flywheel

          A reaction wheel is a flywheel with a motor attached. Constantly spinning it makes it a momentum wheel, and two are used for each axis of rotation desired (spinning in opposite directions). By reducing the spin with the motor, conservation of angular momentum forces the turret to spin in that direction. This is advantageous because the motor need only accelerate or decelerate the already fast spinning wheel, and not be active during the entire rotation. It’s also much cheaper on the power draw, as essentially you are mostly using stored rotational energy to spin your guns, rather than directly using your main power supply.

          The downside is that due to conservation of angular momentum, the wheels must be massive, comparative to the weapon they are spinning. This is actually one of the few cases, however, that power efficiency is more important than mass efficiency. Weapons in Children of a Dead Earth are rarely mass limited, and generally are power limited (discounting enormous spinal-mounted guns).

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          1. that its more efficient in terms of power than just straight up powering it from the main power supply makes sense.
            but is it more efficient in terms of torgue?
            the flywheel couplings would be smaller in size and would have a much shorter lever than motors around the outside of the mount.
            and with the reaction wheel coupling and eventual linear motors being roughly equal in terms of power density wouldnt that result in external motors being more effective for rapid turning?
            ((in case im annoying you, i’ll stop if you ask me to :V ))

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  3. I would like to note that I made a railgun with a Degrees/sec of around .5. Its engagement range is well over 200 Kilometers for most ships so it works fine. I think that it’s the one exception though, as It is more like a particle beam than a rail gun.

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