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Hello, I'm new to the boards and wanted to make use of the large ammount of knowledge here to help me with the yields on my weapons. I am writing a sci-fi story that takes place roughly 424 years in the future and there were some weapon yields and the ammount of energy required to fire the projectiles.

The guns my ships use are similar to halo macs. The rounds range in size from .82m-2.6m. The main used guns are caliber .82mx.88m, 1.34mx1.93m, 1.77mx2.1m, 2.6mx3.0m and 2.6mx3.7m.

The standard rounds are fired at speeds ranging from .54c-.8c, standard speeds are .54c, .59c, .666c, .74c, .77c, and .8c.

The rounds come in several materials but the primarily used ones are iridium or platium (much more plentiful nowadays) shells wrapped in either tungsten, titanium, or depleted uranium. The ratio of mass is roughly 78.4% either platium or iridium and 21.6% either tungsten, titanium or depleted uranium.

I would like to know the mass (I know I should be able to do this myself bu t alas I thought I might see if someone else could do it for me ) the ammount of energy required to move these things through space and the yield when they hit something (such as a ship). Thank you.

volume = length * (diameter/2)^2 * pi

mass = volume * density

Densities of common metals can easily be found using Wikipedia or Google.

kinetic energy at relativistic velocities is given by

KE = [mc^2/sqrt(1-v^2/c^2) ] - mc^2

where m is the mass of the object, v its velocity, and c is the speed of light (3.00E8m/s)

momentum at relativistic velocities is given by

P = mv/sqrt(1-v^2/c^2)

Grab a calculator and have fun.

What's the typical ratio of calibre to length of these railgun slugs?

.82mx.88m .93
1.34mx1.93m .694
1.77mx2.1m .84
2.6mx3.0m .5
2.6mx3.7m .617

BTW I ran some of the bore aspect ratio numbers; they seem to have no rhyme or reason as to aspect ratios across calibres.

Feil

Ah thank you very much for the equations. I will get started on them right away, unless someone beats me to it.

Einhander Sn0m4n

Caliber to length is this CaliberxLength. Ergo a .82m caliber shell is going to be .88m long.

{EDIT}

Einhander
I chose arbitrary lengths until I could determine the ammount of energy required to fire them and how the extra mass would effect the ship reactors.

Feil
What would the kinetic energy unit be, joules?

RIPP_n_WIPE wrote:Feil

Ah thank you very much for the equations. I will get started on them right away, unless someone beats me to it.

Einhander Sn0m4n

Caliber to length is this CaliberxLength. Ergo a .82m caliber shell is going to be .88m long.

{EDIT}

Einhander
I chose arbitrary lengths until I could determine the ammount of energy required to fire them and how the extra mass would effect the ship reactors.

Feil
What would the kinetic energy unit be, joules?

I thought you were referring to dimensions of a noncircular bore. Those projectile lengths seem very short to me.

Well I don't know that much about ballistics. I DO know that the majority of bullets lengths are due to propellant, not to what actually hits the target (usually only about a quarter of the bullet actually hits you if the .222 i have infront of me is standard). In a coil gun (not rail gun) there is no need for a propellant so the shells don't need to be so big, just massive and dense. I do know that more stuff hitting you is going to do more damage but I'm sure that if I made a graph of some kind their has got to be a sort of curve at which the mass, surface area, and etc aren't efficient for such a big shell.

RIPP_n_WIPE wrote: What would the kinetic energy unit be, joules?

No, cubit-talents.

---

Ripp, do yourself a favor, and just leave numbers and figures out of your narrative. Unless you start getting into distances, velocities, and accelerations, they add nothing, and get in the way of real description. Nobody cares if your Big Motherfucking Laser emits x-ray lasers in 0.5-second pulses at 1.42 gigawatts--they care what it does. What is it like on the ship when the weapon is fired? What does it do to the target when it strikes? How powerful is it relative to the other weapons onboard? As long as you make sure you stay somewhat consistent (don't melt asteroids one minute and vaporise small moons the next), it really, really doesn't matter what your facts and figures are.

It's obvious that you don't have the scientific or mathematical background needed to write a math-heavy universe like the Honorverse, and if you try, you're more likely just to sink the quality of your prose and make a fool of yourself when your Big Motherfucking Railgun with 0.71 gigajoules of kinetic energy does the same amount of damage as your Big Motherfucking Laser because 'lol it has the same energy rite?'.

Incidentally--you think to challenge Einhander on the topic of Railguns? May the FSM have mercy on your soul.

RIPP_n_WIPE wrote:Well I don't know that much about ballistics. I DO know that the majority of bullets lengths are due to propellant,

You mean a complete round of ammunition, usually consisting of primer, brass case, propellant, and projectile (aka The Bullet). Most cases are longer than the bullets they are designed to accept

RIPP_n_WIPE wrote:not to what actually hits the target (usually only about a quarter of the bullet actually hits you if the .222 i have infront of me is standard).

Yes, the 'quarter of the bullet' is the projectile that the entire point of the gun is about. The rest of the round, consisting of a spent primer and brass case, is what gets ejected out the breech of the weapon after the propellant is burned and the projectile (THE BULLET!!!) exits the barrel.

RIPP_n_WIPE wrote:In a coil gun (not rail gun) there is no need for a propellant so the shells don't need to be so big, just massive and dense.

Same goes for railguns as well. A coilgun shot needs to be ferromagnetic, while a railgun armature simply needs low sliding friction, good conductivity, and high specific heat.

As for 'massive and dense', a long-rod kinetic penetrator made of tungsten alloy or depleted uranium would be grand.

The propellant is electrical energy converted from mechanical energy (through a generator) ultimately derived from chemical combustion, nuclear fission, fusion, or what-have-you (via an engine or reactor-coolant loop with a turbine in one of any number of configurations).

RIPP_n_WIPE wrote:I do know that more stuff hitting you is going to do more damage but I'm sure that if I made a graph of some kind their has got to be a sort of curve at which the mass, surface area, and etc aren't efficient for such a big shell.

Yes, a lot of mass striking a small area of a target (usually the same area as the projectile radius pi r squared in the case of round, width times height for your presumably rectangular bricks [well-suited for a space-only railgun, btw], or more complicated formulas for hexagons, ellipses, etc.) is highly advantageous for penetration, which brings me to another question.

What role are these weapons for? Armor defeat, orbital bombardment, cratering, soft target destruction, suppression of fighters, CIWS; what? Each one of these mission roles dictates the design and selection of your projectile and velocity, and by extension, the gun design/size and the design of the ship to carry how many of which guns.

For general military craft, you will want polyvalent capability. Special ships and weapons are ok for specific missions as long as you understand how they sacrifice capability against targets they're not optimized against. You don't want to try to attack a hardened planetary bunker with a space-only light antispaceship projectile, for example.

Feil wrote:

RIPP_n_WIPE wrote: What would the kinetic energy unit be, joules?

No, cubit-talents.

LOL!

Feil wrote:Incidentally--you think to challenge Einhander on the topic of Railguns? May the FSM have mercy on your soul.

SIGGED!

Hey I'm not trying to challenge him. It's just that my ships use coil guns not rail guns.

As for leaving numbers and figures out I need to have some sort of description of dimensions. I'm not going to have my ships have weapons that are woefully beneath or above their yield should be. I just want some weapon stats and I figure I can technobabble away the rest of it.

RIPP_n_WIPE wrote:Hey I'm not trying to challenge him. It's just that my ships use coil guns not rail guns.

As for leaving numbers and figures out I need to have some sort of description of dimensions. I'm not going to have my ships have weapons that are woefully beneath or above their yield should be. I just want some weapon stats and I figure I can technobabble away the rest of it.

It bears repeating. Technology and good story need not have any relation. Red Imperators The Humanist Inheritence is a great example of a fic with not so many hard details spoken, but still a technically accurate fic.

The problem with involving any sort of numbers is that it forces you to be self consistent to them, and carries the chance of hijacking the story into being about the technology, not about the characters.

And frankly, as a fucking hardware lover, who really enjoys going nitty gritty into details, it's fucking boring.

RIPP_n_WIPE wrote:Hey I'm not trying to challenge him. It's just that my ships use coil guns not rail guns.

As for leaving numbers and figures out I need to have some sort of description of dimensions. I'm not going to have my ships have weapons that are woefully beneath or above their yield should be. I just want some weapon stats and I figure I can technobabble away the rest of it.

A speed of .54c or greater is 160,000,000+ m/s. For example, neglecting relativistic effects, the launcher would need to deliver more than 13000 TJ per kilogram of projectile mass, to a projectile massing thousands of kilograms (according to any of the dimensions and material densities). If the launcher is under 1 km in length, accelerating an object to that velocity corresponds to 1.3+ trillion g's acceleration and a timeframe of around 0.000012 seconds or less. Such corresponds to literally trillions of terawatts of required power. Lesser projectile velocity would be more realistic, if the projectiles are to be more than microscopic size.

For a futuristic space warship weapon seeking high velocity, coilguns are better than railguns in the sense that physical rail erosion limits the velocity of the latter (commonly to < 6 km/s, though that would vary somewhat depending upon design & technology). But even coilguns are limited by obtainable acceleration and power. For future technology, millions of g's acceleration for some coilgun projectiles might be plausible, possibly, depending upon assumptions. But trillions of g's for the large projectiles is orders of magnitude beyond anything likely to be obtainable for such, not with real-world materials as suggested by the mention of titanium, etc.

Within hard sci-fi, the only way to accelerate a large object to a substantial fraction of lightspeed is with far lesser acceleration over great distance, such as real-world studies on hypothetical interstellar probes where they would accelerate over billions or trillions of kilometers distance, much different from the length of a launcher on a warship.

A future warship might have even a few terawatts of power, especially if in a brief pulse. However, if a ship had trillions of terawatts even for 0.012 milliseconds without being an astronomically huge ship, such exceeds anything plausible within known science, considering materials limits, waste heat, etc.

Even aside from the preceding concerns, there would tend to be unintended consequences for the setting if the civilization could casually use trillions of terawatts like that in a weapon on a single ship, given the kind of technological capabilities it implies. For general perspective, all power plants on earth today combined generate about 2 terawatts of electricity. A gigantic civilization that disassembled planets, that could build quadrillions of ships, etc. might be capable of using trillions of terawatts, though still not tending to be able to do so like that within a single object, but such probably isn't the intended setting.

Within a regular setting, if high yield is the goal, megaton-yield or gigaton-yield thermonuclear warheads on projectiles of much lower velocity than 160,000+ km/s are plausible, and hundreds of km/s is fast enough for many purposes.

You may want to mainly "show instead of tell" in the story, describing the effects of the weapons like the explosions they create on the target, without needing to state their velocity in specific figures.

Thank you for everones assistance. I appreciate all comments, suggestions, and equations etc. I will use this to the best of my ability in my tale and most likely will have to technobabble most of it away.

RIPP_n_WIPE wrote:Thank you for everones assistance. I appreciate all comments, suggestions, and equations etc. I will use this to the best of my ability in my tale and most likely will have to technobabble most of it away.

Oh, come now. Go read some of Mr. Wong's articles on Star Wars and such. If you want to get more into what constitutes "hard" sci-fi, the Atomic Rocket is an excellent resource.

As long as you understand what kind of force will do what, essentially, and why, and you stay consistent with the technotoys' limits, you'll be okay. You may want to read the stickied thread about joining the Writer's Guild, though.