Sci-fi Weapons, Vehicles and Equipment

Well there was experiments with using semi-active homing on railgun projectiles.

Some how they were able to harden that enough, but not other tracker types.

We have a solution to making projectiles go really fast: rockets. The Chinese figured that out centuries ago.

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"

Most small arms have the muzzle velocity between 800m/s to high 900m/s. A small arms coil or rail gun can have two to three times that value without being a major hurdle.

I think that at 2700m/s a solid projectile has its weight in TNT as energy. Which IIRC is one Rick.

You don't need to get something like 30Km/s and over, just being fairly faster than regular chemical munitions is going to give a range and power advantage to the weapon.

For vehicle systems you can reach higher velocities, but there is a point where you'd start having durability, weight, heat and power issues.

Magnetic weapons, as long as you solve the issues of "it wants to explode itself", barrel wear and power supply. Would be extremely scalable compared to chemical propulsion weapons.

Inter arma enim silent leges

Every high-velocity gun has a nasty tendency to destroy the barrels. One solution is what Gerald Bull used for his super guns: guns that fired shells past the K line at rail gun speeds. It had to do with the extra-long gun and how quickly and evenly the propellant burned. The other solution that has been tested is to make the munition portion a multi-stage projectile in the form of gun-fired missiles.

Who watches the watchmen?

The .220 Swift is the fastest commercial round on the market with a muzzle velocity of about 1200 m/s normally and 1400 m/s with customized rounds. We want to go about double that speed. You may now cackle madly.

On the more practical side, the .220 Swift is hard on barrels, scraping the rifling off anything but the finest stainless steel barrels in under 300 shots. It's probably best to go smoothbore since the barrels are going to wind up like that anyway. This is actually good for APFSDS and buckshot but possibly not so good for mid-ranged combat with collateral damage concerns.

^ .22 Eargesplitten Loudenboomer is the fastest cartridge ever built. It was designed for around 1500 meters per second. It achieved no less than 1400.

The fastest chemically propelled projectiles top out at about 2300 meters per second. That’s roughly the limit of how fast you can possibly get that way in any traditional gun or artillery sense.

Chemical propellants simply aren’t energetic enough to go any faster. Even rockets can’t go much if any faster than that in normal atmosphere. Got to fly really high or even orbit to get rid of gravity and especially air resistance that prevents faster speed.

"Allah may guide their bullets, but Jesus helps those who aim down the sights."

This is also why railgun projects have died. Turns out building missiles is just much easier and they do the job just as fine.

Plus, missiles can adjust course mid flight, which does away with the issue railguns have when they shoot stuff so far away the curvature of the Earth becomes an issue.

To be clear though, i think in space applications railguns may be preferable not so much because of the firepower or anything, but rather because you don't need to store explosive ammunition. Conventional kinetics require explosives to accelerate, and a railgun simply needs power, and a space warship is going to have that power.

There may thus also be a niche for railguns in atmospheric combat with similar benefits.

But so far, the problem has been that it's more expensive, complex, high-tech for not really any benefit. The niche it fulfills simply doesn't exist.

In spacecraft it comes down to a number of factors, including "how much hand-wavium do we get to use"?

Power management is a big deal for real-life spacecraft. You need massive solar arrays, expensive nuclear-thermal generators, life-limited fuel cells, etc., and you have to deal with the heat generated by all of the things that create or use power.

Propellant is typically inert until used, so your only constraint to how many missiles you can keep on board is mass (and volume). A railgun would need an extremely dense power source that would not do anything for most of the trip, and while on it would generate an enormous of waste heat that would need to be dumped.

If we're budgeting a warship, we would be looking at tradeoffs over the mass-energy-density of each weapon system. A missile's propellant needs to be weighed (literally) against the power plant, fuel, and radiators that would allow a railgun to do a similar amount of damage.

I am assuming that the ammunition is comparable: 100 missiles have the same effective payload as, say, 1000 railgun shells, so you can do the ratios.

Edited by Fighteer on Apr 18th 2024 at 1:42:22 PM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"

True, but a missile ship is also carrying a large quantity of dead mass.

In fact, i'd argue that these constraints would heavily enforce specialization. A laser ship benefits from bigger optics, better lasers, etc. Once you've decided to add a nuclear reactor, radiators, support equipment, turrets, and a laser generator, you've decided to add quite a bit of mass for the potential of extremely long-range firepower with effectively infinite shots.

A missile ship is pretty much the opposite, in that missiles need very little support equipment but are made mostly of dead mass. It's not really useful until fired, at which point the ship does get significantly lighter.

A kinetic ship sits somewhere in the middle, in that the ammo has a decent amount of mass but so does your weapons equipment. Thermal management is probably easier because the bullet does carry away quite a bit of heat.

So the worst thing you can do, i think, is try to mix and match different weapons systems because you're paying through the nose for little extra capacity. A laser ship may carry a few missiles just in case, but i don't think you're going to see a ship both with a main lasergun and a large missile array.

I would also expect kinetics to fit a particular niche, which is that it can be convenient as a kind of final defense. But i think it could also be useful to force your opponents to dodge and to deny particular maneuvers by filling space with bullets. You don't need particularly heavy (IE large) bullets, kinetic dust doesn't have to blow up the reactor, you can be content with stripping all the vulnerable equipment off the hull like radiators or turrets.

There are other elements too, like wear and tear on components. Better have a lot of spares for those laser optics and railgun barrels. But yes, you are correct that the fundamentals of spacecraft design reward specialization.

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"

I thought the railgun projects were suspended because of the hardest battles of them all: Congressional budget battles.

They couldn’t get the budget to keep going regardless of if missiles or railguns were better. It was kind of a low hanging fruit to cut from the budget in the sequestration fights of the budget.

"Allah may guide their bullets, but Jesus helps those who aim down the sights."

If you have a cheaper weapon that works just as well... sometimes projects get cut for good reasons.

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"

It probably didn't help, but the railgun project was also not meeting it's lofty objectives. Not a total failure, but it was definitely not matching what it had to do to be a viable project.

It's primary purpose was to be a long-range shore bombardment to replace e.g. tomahawks but it wasn't hitting as accurately and producing electronics that can withstand 10000g is not trivial. It couldn't shoot as often as it would have to due to rail wear. And the main warship intended to field such a weapon - the Zumwalt- was also largely a failure.

It's not necessarily that the weapons themselves were cheaper, but the Railgun project had cost around 500 million dollars at that point. You can fire quite a few tomahawks for that, and the railgun would have to do a lot of bombardment to make up for it.

Reliable but expensive is sometimes better than uncertain and possibly also still expensive.

TBH i am not super sure how maintenance-heavy this would be. I would not expect space battles to take very long. And between battles, you'd probably get plenty of time to grind down some local materials to craft a replacement. Space warships would not have super thick armor like you see in space opera (it's too heavy) and weapons can be incredibly destructive. Also no magic spaceshields to dramatically drop in percentage at the speed of plot. It would probably be more akin to a "who hits first" type of deal.

Actualy the railgun just moved branches that is developing it from the navy to the army for much more fundamental reasons then what wither of you have said.

Warships are big, railguns poke holes...

The navy tried and tried to make the railgun have good post penetration effects but they just couldnt do it, it went in one side and out the other... which does very little to a warship that can take on thousands of tones of water and not care.

The army however picked it up not that long ago for a much more boring purpose which is probaly why no one cares any more...

Shooting airplanes.

Turns out a really fast projectile is really hard to dodge, and guns dont care too much about most countermeasures.

The range is also nice in that it let's it be competitive with most SAMs when paired with the projectile speed.

Plus anti aircraft installations are normaly spread out over multiple trucks any way, it's not that hard to make one truck into a generator.

Edited by Imca on Apr 18th 2024 at 8:40:11 PM

^ Would also make sense to move to army for another reason.

Anti tank. Make a railgun as field artillery or on a tank and you have a dialable weapon that could fling a tungsten projectile fast enough to defeat any tank or vehicle or dial it down to lob an HE round into a bunker or over a hill.

"Allah may guide their bullets, but Jesus helps those who aim down the sights."

Given how Imca described what a railgun projectile does to a warship, I'd imagine something similar happening to a tank would basically liquefy the crew on the way out. I think that actually happened in the description for a T'au railgun in Warhammer 40k.

Once you have a weapon that can achieve overpenetration on a tank, I think it's officially good enough. Well, I guess there's bunker-busting as a step up.

Edited by Fighteer on Apr 18th 2024 at 10:32:57 AM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"

The problem with anti-tank is you still need a whole flatbed to hold the generator....

This is doable with anti-air instillation, they already do so for radar... not so doable if you want it on the front lines...

Then again by the scope of this thread, give it another century on our power generation capabilities and that probably changes a bit.

Honestly, the power supply is very nearly a deal-breaker for a field-portable railgun. The great advantage of chemical propellant is that it comes pre-packaged and is (basically) inert until used. You don't need to hook your gun up to a giant battery pack to fire it; you just load the bullets and pull the trigger.

In a very real sense, an energy weapon is like lugging all of the equipment needed to make the bullets onto the battlefield. Not only is it heavy and awkward, but it creates an extra point of vulnerability.

I believe we had this exact conversation a few posts back, in fact.

Edited by Fighteer on Apr 18th 2024 at 11:58:29 AM

"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"

It's less of an issue for vehicles that can use their engines to charge the rails. Of course, this does create an issue with vehicles having to choose between moving and shooting.

Not necessarily, plenty of system generate spare power. Most engines don't run at full power and things like turbines are really good at generating power.

Inter arma enim silent leges

Also are we trying to accelerate warship caliber munitions to Mach 8+ (2720+ m/s) at all times and missions?

Theoretically you can scale down a tank gun to fire a regular sub-caliber APFSDS out of say a railgun that’s 75mm caliber. And still have the lethality of a 105-125mm weapon against armored targets like tanks.

As long as the ammunition is traveling the same speed and is the same weight as its bigger gun cousin, the performance will be similar.

Also less/no risk of cookoff in the event of damage. That has been the risk with conventional propellants since the dawn of gunpowder. Take damage, the propellant itself in your ammunition stores catches fire or explodes then starts a chain reaction with the warheads.

Quite a few ships and thousands of tanks lost to that over the past 110 years is ample proof.

"Allah may guide their bullets, but Jesus helps those who aim down the sights."

Aren't batteries explosive? I mean, railguns require a brief burst of high power, so running them off of batteries rather than a fuckhuge generator seems more efficient.