Plasma Railguns.... Any Good Use?

[Spacescifi]

In a previous thread I discussed an overpowered railgun, and quickly learned that the materials would not survive the launch.... namely the projectile, and it would also need to be a ridiculously long coilgun or railgun.

 

This was due to the fact that moving mass to relativistic high speeds requires a lot of energy.

 

Plasma on the other hand is less dense than gas if I recall correctly, so shooting it via a coil or railgun up to extreme speeds (from LEO to the moon in 30 seconds) ought to require a gun that is smaller and shorter than the previous monster.

Yet the effective range due to plasma spread would be much less.

 

I presume that the only good use for coilgun plasma or railgun plasma cannon is if they can be made for point defense at short range.

 

The ability to spread would be a boon at that point since the plasma would hit more incoming missiles or projectiles.

 

So perhaps plasma weapons are far better at defense than offensw in space...  scifi is wrong again eh?

Still a power hog, but all starships with FTL are anyway. It would also have to be rapid fire.

Only better than traditional PDC in that it has longer effective range and does more damage the closer something is.

Edited March 2, 2022 by Spacescifi

[Nuke]

there may be real life precidence for this. 

https://en.wikipedia.org/wiki/MARAUDER

not only is the velocity very high (3000 km/s), it also stores a lot of energy in the form of a strong magnetic field. so not only is it very destructive (about 5 pounds of tnt) but also has a strong emp effect on its target. plasma wouldn't experience atmospheric drag like a normal projectile, at least not in the same way and may be capable of hitting targets in space from the ground.  supposedly the test was so successful that the research was classified.

its kind of a fusion research spinoff. so i figure any setting using fusion technology would also have plasma weapons. while having a fusion power plant on board will make railguns and coilguns possible, as featured in the expanse. i think they wanted weapons that are currently in development that any scifi or military nerd would recognize. gives the expanse a more grounded feel i think, and plasma weapons would have seemed a bit handwavy, despite possibly being in existence. 

i also have a theory that some of the scientists involved in this projects are battletech nerds. as ppcs are typically a staple of a maurader's loadout. 

Edited March 2, 2022 by Nuke

[Spacescifi]

18 minutes ago, Nuke said:

there may be real life precidence for this. 

https://en.wikipedia.org/wiki/MARAUDER

not only is the velocity very high (3000 km/s), it also stores a lot of energy in the form of a strong magnetic field. so not only is it very destructive (about 5 pounds of tnt) but also has a strong emp effect on its target. plasma wouldn't experience atmospheric drag like a normal projectile, at least not in the same way and may be capable of hitting targets in space from the ground.  supposedly the test was so successful that the research was classified.

its kind of a fusion research spinoff. so i figure any setting using fusion technology would also have plasma weapons. while having a fusion power plant on board will make railguns and coilguns possible, as featured in the expanse. i think they wanted weapons that are currently in development that any scifi or military nerd would recognize. gives the expanse a more grounded feel i think, and plasma weapons would have seemed a bit handwavy, despite possibly being in existence. 

i also have a theory that some of the scientists involved in this projects are battletech nerds. as ppcs are typically a staple of a maurader's loadout. 

 

Well for what it is worth it hardly seems a capitol spaceship killer.

Since I reckon that TNT damage goes down dramatically at far range.

Yet it does illustrate what could be possible.

 

I think the end result would be much like lasers.

 

You want mega effective range? Then you need a giant powerplant and radiators. At least you do not also need a large focusing lens like a laser would need.

Again.... it's best used as a forward or rearward weapon.

 

Cheap will beat expensive at the ranges the plasma railgun does heavy damage if enough missiles are launched.

 

So ultimately, in a setting with limited fuel... plasma railguns are great, since all spaceships are glass cannons anyway.... and cannot maneuver for long before running out of fuel.

 

Yet in a constant high acceleration starship setting.... plasma railguns are best used for defense, since a swarm of high thrust constant acceleration missiles could in theory overwhelm it's firing solution.

 

Yet in scifi it is quite possible to have an uber plasma railgun that just kills missiles when they get too close.

 

Who needs shields when you have a plasma railgun that is like a relativistic shotgun at close range?

Perfect point defense.

 

 

 

[Nuke]

even as far as rotory cannon pdcs goes, that technology is kind of already a dinosaur. brrrrt is good and all, but ammunition is heavy, you need a lot of it, and its still only good for close in point defense. your ship might get better acceleration if you jettison your pdc ammo. that doesnt work in the expanse because the humans are ultimately what limit the acceleration, not the mass of the ship and its ammo stores. so if torch ships in your setting are not quite capable of breaking 1g, then dumping ammo and hauling tail might be a useful evasion tactic. 

there are other weapons on the drawing board. like the metalstorm gun that can hit a million rounds a minute, in theory.

obviously such a weapon would only fire a burst and would probibly take a long time to reload. traditional gatling based ciws do have the advantage of being able to fire continuously, the feed systems are the real selling point. however this weapon is not limited to firing in bursts and it can dial in its rate of fire to the operator's requirements. by the time of the expanse such weaponry should be ubiquitous. rounds are stacked in the barrel and each can be fired multiple times, but i cant imagine it being as easy as a gatling to reload and would be more subject to jamming. still in a space setting ditching the heavy ammunition will help your acceleration and high velocity plasma pdcs i think would be a good option. the "ammo" comes out of the same tank that fuels your torch drive, and you already have some kind of fusion power plant.

rail guns kind of also give you a better damage to ammo mass ratio, as much of the energy comes from the reactor. you only need big dumb slugs and no propellant or casings and each one does more damage than many times its weight in conventional ammo. plasma ciws for defence with railguns for attack might be the better way to do things. save the slug throwers for ground pounders. i think missiles are still the go to for long range combat. i think they would be more like icbms and less like the cute little torpedoes they use in the expanse, possibly with its own ciws to make it hard to intercept with other missiles.

 

[Spacescifi]

1 hour ago, Nuke said:

even as far as rotory cannon pdcs goes, that technology is kind of already a dinosaur. brrrrt is good and all, but ammunition is heavy, you need a lot of it, and its still only good for close in point defense. your ship might get better acceleration if you jettison your pdc ammo. that doesnt work in the expanse because the humans are ultimately what limit the acceleration, not the mass of the ship and its ammo stores. so if torch ships in your setting are not quite capable of breaking 1g, then dumping ammo and hauling tail might be a useful evasion tactic. 

there are other weapons on the drawing board. like the metalstorm gun that can hit a million rounds a minute, in theory.

obviously such a weapon would only fire a burst and would probibly take a long time to reload. traditional gatling based ciws do have the advantage of being able to fire continuously, the feed systems are the real selling point. however this weapon is not limited to firing in bursts and it can dial in its rate of fire to the operator's requirements. by the time of the expanse such weaponry should be ubiquitous. rounds are stacked in the barrel and each can be fired multiple times, but i cant imagine it being as easy as a gatling to reload and would be more subject to jamming. still in a space setting ditching the heavy ammunition will help your acceleration and high velocity plasma pdcs i think would be a good option. the "ammo" comes out of the same tank that fuels your torch drive, and you already have some kind of fusion power plant.

rail guns kind of also give you a better damage to ammo mass ratio, as much of the energy comes from the reactor. you only need big dumb slugs and no propellant or casings and each one does more damage than many times its weight in conventional ammo. plasma ciws for defence with railguns for attack might be the better way to do things. save the slug throwers for ground pounders. i think missiles are still the go to for long range combat. i think they would be more like icbms and less like the cute little torpedoes they use in the expanse, possibly with its own ciws to make it hard to intercept with other missiles.

 

 

Quite right.... an armored nose ICBM that releases a swarm of missiles when the nose is lased enough... or whenever fleet command tells it to.

 

Ultimately how far one can minaturize torch drive missiles will decide how much less effective PD is.

 

For example...  in the setting I have dreamed up rocket engines are history.... replaced by repulsor ray engines. Which use bell nozzles that are mirrored inside with a lens down the throat that emits 'synthetic light', an artificial form of optical radiation that is extremely repulsive to all normal mass. Reflecting off mirrors increases the maximum thrust virtually for free, so that is why spaceships using it use reflective mirrored surfaces inside their nozzles.

It's like a torch drive on steroids, since the power required is not a lot but you get a lot. it's energy use is the same as for any equivalebt bright flashlight running continuously.

Here's the real end of virtually all other weapons though.

 

Why? Pencil size repulsor missiles zooming around at 30g.

Carried by a an ICBM of sorts that launches a whose swarm of them once near enough to it's target.

 

It does not matter if your warship is unmanned and can endure high accelerations.... since whatever they are they will not match a swarm of 30g pencil size missiles launched a few thousand or less kilometers away.

Plasma PD would wreck them of course, but not if they spread out enough

 

One thing gaming taught me is that sometimes THERE IS NO FIRING SOLUTION.

in some circumstances you will get hit no matter what and your best defense would have been not to be there in the first place!

[kerbiloid]

10 hours ago, Nuke said:

rotory cannon

Spoiler

 

On squared wheels, too.

[KSK]

Oh this could be fun.

Space war goes disco!

I’m imagining a spherical drone packed with repulsor pencils, business ends pointing outwards, shooting repulsor rays every which way and deflecting all the battlefield ordnance around at random.

Or, more likely, warships fitted with phased arrays of repulsor ray emitters which can just bounce back any incoming ordnance.

“Swarms of pencil flashlights are no match for the power of DISCO!” - Rear Admiral J. Travolta.

Edited March 3, 2022 by KSK

[Nuke]

4 hours ago, kerbiloid said:

  Reveal hidden contents

 

On squared wheels, too.

somone probibly couldnt decide between rocket pods and gatling guns, and then had the brilliant idea. why not have both?

Edited March 3, 2022 by Nuke

[magnemoe]

15 hours ago, Nuke said:

even as far as rotory cannon pdcs goes, that technology is kind of already a dinosaur. brrrrt is good and all, but ammunition is heavy, you need a lot of it, and its still only good for close in point defense. your ship might get better acceleration if you jettison your pdc ammo. that doesnt work in the expanse because the humans are ultimately what limit the acceleration, not the mass of the ship and its ammo stores. so if torch ships in your setting are not quite capable of breaking 1g, then dumping ammo and hauling tail might be a useful evasion tactic. 

there are other weapons on the drawing board. like the metalstorm gun that can hit a million rounds a minute, in theory.

obviously such a weapon would only fire a burst and would probibly take a long time to reload. traditional gatling based ciws do have the advantage of being able to fire continuously, the feed systems are the real selling point. however this weapon is not limited to firing in bursts and it can dial in its rate of fire to the operator's requirements. by the time of the expanse such weaponry should be ubiquitous. rounds are stacked in the barrel and each can be fired multiple times, but i cant imagine it being as easy as a gatling to reload and would be more subject to jamming. still in a space setting ditching the heavy ammunition will help your acceleration and high velocity plasma pdcs i think would be a good option. the "ammo" comes out of the same tank that fuels your torch drive, and you already have some kind of fusion power plant.

rail guns kind of also give you a better damage to ammo mass ratio, as much of the energy comes from the reactor. you only need big dumb slugs and no propellant or casings and each one does more damage than many times its weight in conventional ammo. plasma ciws for defence with railguns for attack might be the better way to do things. save the slug throwers for ground pounders. i think missiles are still the go to for long range combat. i think they would be more like icbms and less like the cute little torpedoes they use in the expanse, possibly with its own ciws to make it hard to intercept with other missiles.

Metalstorm put the rounds after each other and fire them electric, think of an tube magazine who is also the chamber. Downside is that this will get long and heavy fast. As for reloading it would be like loading an long and skinny round I think and its not really designed to reload during an engagement.  Now this is not an totally new idea a few flintlocks used the same tricks for 2-4 shots and and a row of flint lock hammers down the barrel. 
Yes it was an danger of setting off the next charge so you designed for that. Not sure if it was that much better than an multi barrel pistol, a bit lighter but more cumbersome I think. 
Think metalstorm was cool but unpractical, the only projects I seen around it has been 40 mm grenades who makes some sense as they are short and wide and can have the charge integrated into the grenade and use lightweight barrels 
 

[Spacescifi]

12 hours ago, KSK said:

Oh this could be fun.

Space war goes disco!

I’m imagining a spherical drone packed with repulsor pencils, business ends pointing outwards, shooting repulsor rays every which way and deflecting all the battlefield ordnance around at random.

Or, more likely, warships fitted with phased arrays of repulsor ray emitters which can just bounce back any incoming ordnance.

“Swarms of pencil flashlights are no match for the power of DISCO!” - Rear Admiral J. Travolta.

 

That is clever, but it would only work if you are flying away from the pencil swarm and it is chasing you.

 

Why? Like normal light 'repulsor light' will spread with distance.... and it's repulsion decreases dramatically at range from it's source.

 

So much so at that at a kilometer out you would only feel a gentle breeze from the rays in some cases depending on the size of the nozzle... but if you were right up next to the nozzle... especially a rocket sized one for SSTO spaceships... you would be quite dead after being blown away literally and likely dying via lithobraking... though I reckon the initial blast might snap necks before one hit the ground anyway.

 

Second example: Disco ball loses likely.

If a pencil swarm is coming head on then their sheer momentum may be too high even for a ship to repel them with multiple repulsor nozzles used to ward them off.

Remember that spaceships due to sheer mass have lower accelerations (often 3g for manned and 10g for unmanned vessels that have been made as light as possible with only essentials they need).

A repulsor beam would be ideal of course.... but so far I have more or less canceled such a concept... since I have no idea how it would look since repulsor rays can be emitted from a lens but after that if another lens is between it and the chamber it came from it would only repel (*blast*) it into shrapnel.

So I figure using them in nozzles is about the best the aliens who made themcan do...  unless you are also clever enough to figure a way to make a repulsor beam even though it cannot actually go through any lens to be focused after emission.... it would just repel.

 

In theory a race with precise artificial gravity manipulation and control could create a repulsor beam if they got their 'hands' on the technology.... but not all aliens in the setting I am dreaming up use repulsor ray propulsion, just the main one in the story. Artificial gravitational lensing I presume could be used to make a repulsor beam.... but the main aliens in the story do not have that. 1g acceleration is good enough.

 

Quite clever idea though... the disco repulsor ball drone, and defense repulsor turrets! I had not thought of all that and will adopt it. Thank you!

 

Basically, the larger your nozzle the further the distance the repulsor rays will go without weakening as fast.

So in theory.... yes, moon bases could have a few giant nozzle turrets to blast any number of 'pencil swarms' that came it's way.

 

Although the caveat is that if the pencil swarm is moving at a significant portion of lightspeed I am not sure what would happen.

 

I reckon the pencil swarm would either be crushed by the oncoming long range repulsor rays or just plow through them and obliterate the mega nozzle turrets and the moon base.

 

At least now I know all spaceships using repulsor ray drives have very good reason for using one big nozzle instead of multiple smaller ones.

And for a bonus the main engine nozzle should be capable of thrust vectoring (tilting the nozzle under thrust).

That would keep the pencil swarms at bay if not slow them down altogether if chasing a repulsor ray spaceship.

Edited March 4, 2022 by Spacescifi

[KSK]

You're welcome - glad the ideas helped a bit!

As for repulsor beams, the physics of these repulsor rays are already quite odd (can be reflected, can only pass through a single lens, unsure whether they obey inverse-square law), so how they behave is pretty much up to you.  

I mentioned phased arrays because they're one way of producing a beam from an array of emitters.  They're comparatively simple for radar systems (for generous definitions of 'comparatively'  ), less so for optical systems, although optical beam steering is a thing. Plus, you've already mentioned that repulsor rays can be reflected, which potentially brings them into the realm of adaptive optics  and/or active optics.  Or heck, just use a parabolic mirror to reshape a divergent source into a planar source. So, presuming that repulsor rays are waves,  there's a variety of technologies you could invoke to justify steerable repulsor beams, if you wanted to.

As for the pencil swarm vs defense turret question, I have a mental image of a keyring torch (or phone 'torch' app) vs a searchlight. If the keyring torch is enough to accelerate the pencil at 30g, then the gods alone know what accelerations could be produced by a searchlight.  I suspect the pencil swarm would be crushed to dust and the dust would be rapidly dispelled, but without knowing more details it's hard to say for sure.

One thing to consider though is that the repulsor defense turrets have presumably been designed with the capabilities of pencil swarms and similar munitions in mind, so they ought to be capable of repelling them at the kinds of speeds that one could reasonably expect on a battlefield. And, even if the defense turret couldn't stop a head on attack from a pencil swarm, it might be able to deflect them enough to miss their target. Or, with the forces involved, a glancing strike from a defense beam on a given 'pencil' might be enough to catastrophically damage it.

Edited March 4, 2022 by KSK

[Spacescifi]

3 hours ago, KSK said:

You're welcome - glad the ideas helped a bit!

As for repulsor beams, the physics of these repulsor rays are already quite odd (can be reflected, can only pass through a single lens, unsure whether they obey inverse-square law), so how they behave is pretty much up to you.  

I mentioned phased arrays because they're one way of producing a beam from an array of emitters.  They're comparatively simple for radar systems (for generous definitions of 'comparatively'  ), less so for optical systems, although optical beam steering is a thing. Plus, you've already mentioned that repulsor rays can be reflected, which potentially brings them into the realm of adaptive optics  and/or active optics.  Or heck, just use a parabolic mirror to reshape a divergent source into a planar source. So, presuming that repulsor rays are waves,  there's a variety of technologies you could invoke to justify steerable repulsor beams, if you wanted to.

As for the pencil swarm vs defense turret question, I have a mental image of a keyring torch (or phone 'torch' app) vs a searchlight. If the keyring torch is enough to accelerate the pencil at 30g, then the gods alone know what accelerations could be produced by a searchlight.  I suspect the pencil swarm would be crushed to dust and the dust would be rapidly dispelled, but without knowing more details it's hard to say for sure.

One thing to consider though is that the repulsor defense turrets have presumably been designed with the capabilities of pencil swarms and similar munitions in mind, so they ought to be capable of repelling them at the kinds of speeds that one could reasonably expect on a battlefield. And, even if the defense turret couldn't stop a head on attack from a pencil swarm, it might be able to deflect them enough to miss their target. Or, with the forces involved, a glancing strike from a defense beam on a given 'pencil' might be enough to catastrophically damage it.

 

inverse square law applies... it is behaves like light in virtually all respects, although it's repulsion does drop off dramatically.

 

Three ways to increase max thrust/range of repusor rays.

1. Add more electric power to produce more repulsor rays (brighter). This has energy production and waste heat limits

2. Reflectors increase thrust artficially, the bigger the surface the more the max thrust is increased. SSTO large vessels typically use both methods 1 and 2.

3. Reduce mass.... obviously hardly much of an option for large heavy vessels.... and even the ones that are cannot compete with 'dart swarms' (ny name for the pencil swarms).

Edited March 4, 2022 by Spacescifi

[KSK]

Cool.

In that case, my basic, low tech defensive system would be a repulsor beam searchlight. As powerful a repulsor ray source as can be managed, placed at the focus of a parabolic mirror, the whole thing mounted on some kind of swivel mount for pointing.

That should produce an approximately parallel repulsor beam, at least over a few kilometres which was the kind of effective repulsion range you were talking about.

The Wikipedia article has some nice images which make the point quite well.

 

[Spacescifi]

11 hours ago, KSK said:

Cool.

In that case, my basic, low tech defensive system would be a repulsor beam searchlight. As powerful a repulsor ray source as can be managed, placed at the focus of a parabolic mirror, the whole thing mounted on some kind of swivel mount for pointing.

That should produce an approximately parallel repulsor beam, at least over a few kilometres which was the kind of effective repulsion range you were talking about.

The Wikipedia article has some nice images which make the point quite well.

 

 

Thanks... the irony is that during creation it can be so easy to overlook possible uses of a scifi technology because of it's limitations.

For example, although increasing the reflective nozzle surface is a thrust multiplier, it too has limits.

Why? If you're not emitting enough repulsor rays to adequately 'push off' the nozzle then it would be just more dead weight to push.... lowering overall thrust.

So what I am saying is that the bigger the nozzle the more repulsor rays are required to get the max thrust such a nozzle can can actually yield... otherwise it would be underpowered not utilizing it's max potential.

Actual repulsor missiles would also exist, and due to a larger power plant than the tiny darts they can zoom along at 30g continually and go 60g for for a temporary period before releasing radiator fins to cool down.

 

So perhapd the greatest irony of repulsor ray technology is that bigger is always better for speed so long it's unmanned.

 

The main limit on acceleration is sheer waste heat from generating the repulsor rays for high thrust for heavy spaceships... NOT the mass of them. The larger the ship the more resources it has to deal with waste heat efficiently.

So what I am getting at is there is no reason why unmanned drone ships could not go faster than both missiles and darts.... 50g large unmanned spaceships! 80g max but only for short periods before radiating the heat away.

With unmanned large spaceships that move faster than missiles and darts it would fundamentally change the traditional view of space combat.

Missiles and darts could take out slower targets, but the speedy 50g unmanned large vessels would probably be only efficiently killed by massive laser stations in orbit or from a moon base.

Or if the drone flew close enough to get 'smashed' by a several giant converging repulsor 'search lights' emitting from a moon base.

 

EDIT: Scratch that.... if you want to kill spaceships at range most efficiently you need an antimatter particle beam fired at near lightspeed.

No doubt such would be a power hog, but core world defense stations could afford them.

 

So the irony is that repulsor ray drives actually makes defense as valid an option in space combat as offense... since unlike IRL incoming objects can be deflected or even crushed by repulsor rays.

Edited March 5, 2022 by Spacescifi