Scifi Space Plasma Cannons... Totally Useless?

[Spacescifi]

 

 

So we all know about the bullet speed plasma fireballs so popular with spaceships.

So provided we invented one that operated just like the scifi ones (highly unlikely but bear with me) what good would they do?

At close range I can't see them doing much better than lasers. It's a thermal based effect.

I mean wwt good use? Asteroid mining?

[DDE]

37 minutes ago, Spacescifi said:

So provided we invented one that operated just like the scifi ones (highly unlikely but bear with me) what good would they do?

The problem with this is that in sci-fi 'meta-canon' plasma weapons somehow are more damaging than lasers, i.e. either a more effective method of energy emission and transport, or a more effective method of target coupling.

[Scotius]

This

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

It might be the only way to create actually useful plasma weapons. IF someone finds a way to keep plasmoids from rapidly dissipating in the vacuum.

How useful that would be? Hard to tell

[sevenperforce]

In my head-canon, sci-fi plasma weapons actually fire some sort of tightly-bound antimatter particle cluster. They move slowly because the containment depends on their velocity, like some kind of self-sustaining particle vortex; that's the light you see from the plasma bolt. When containment fails on impact, they explode/annihilate. 

A round from a typical assault/battle rifle packs around 1.8 kJ; to duplicate that in an energy-based weapon you would need only 1e-11 grams of antimatter. For comparison, that's roughly the mass of the nucleus of a human cell. Granted, you'd probably need extra energy because an antimatter explosion is going to be less efficient than a 5.56mm NATO round, but you've got mass to burn.

It explains why larger weapons are needed for effective longer-range attacks (the containment process eats away energy as the cluster travels), why a point-blank shot is more devastating (less of the antimatter is used up in the containment vortex), and why you can "charge up" a more powerful blast or a faster-moving blast with certain weapons settings.

[WestAir]

It always bothered me that sci fi writers go straight for the rule of cool instead of being an inspiration to real world researchers. Lasers, plasma swords and shields all look shiny, but IMO more sci fi writers should go for sensible and unique countermeasures: Shooting bullets with bullets (See: Advanced Israel iron dome. I think tanks have a special shotgun that destroys incoming projectiles and don't even get me started on CIWS). Lasers being defeated by mirrors or radiators. Projectiles that defeat "cover" by changing trajectory or just exploding behind whatever someone is using as cover and littering them with shrapnel. Electronic warfare, etc etc.

Real World militaries could best a lot of sci fi factions right now. I recently saw "The edge of tomorrow" by Tom Cruise and the whole time I thought "We could absolutely annihilate these guys without even leaving the boat..."

Edited July 2, 2020 by WestAir

[sevenperforce]

8 minutes ago, WestAir said:

Real World militaries could best a lot of sci fi factions right now. I recently saw "The edge of tomorrow" by Tom Cruise and the whole time I thought "We could absolutely annihilate these guys without even leaving the boat..."

Yep, as much as I loved that movie I kept thinking "where the hell are the F35s and the M1A2s and the freaking USS George Washington? Yes, I'm US-centric but that's because I live here.

If a single frag grenade could kill an Alpha, a dozen F-35s and the USS George Washington could WASTE the Omega's entire army in a matter of minutes.

[Spacescifi]

1 hour ago, DDE said:

The problem with this is that in sci-fi 'meta-canon' plasma weapons somehow are more damaging than lasers, i.e. either a more effective method of energy emission and transport, or a more effective method of target coupling.

 

They are not IRL... just the opposite besides being impractical at best.

Assuming we had scifi plasma ball cannons in space, there is one thing they would be good for.

Hitting objects that unpowered objects that cannot dodge.

Assuming the plasma balls can hold for any sufficient amount of time you could fire of beads of plasma and do a bunch of thermal burning.

The only real advantage over lasers that plasna balls have that don't dissipate is that they don't lose much energy, so they will do more thermal damage than a laser... if they hit.

Yet even magnetic fields can deflect plasma something fierce.

So for space combat plasma cannons are one of the worst weapons you could buy, even though they are ironically more expensive to make than a laser.

Use it for showing off to your friends how awesome your ship is. Or use it for spaceship morse code... even though you could even do it with glowing bullets.

1 hour ago, sevenperforce said:

In my head-canon, sci-fi plasma weapons actually fire some sort of tightly-bound antimatter particle cluster. They move slowly because the containment depends on their velocity, like some kind of self-sustaining particle vortex; that's the light you see from the plasma bolt. When containment fails on impact, they explode/annihilate. 

A round from a typical assault/battle rifle packs around 1.8 kJ; to duplicate that in an energy-based weapon you would need only 1e-11 grams of antimatter. For comparison, that's roughly the mass of the nucleus of a human cell. Granted, you'd probably need extra energy because an antimatter explosion is going to be less efficient than a 5.56mm NATO round, but you've got mass to burn.

It explains why larger weapons are needed for effective longer-range attacks (the containment process eats away energy as the cluster travels), why a point-blank shot is more devastating (less of the antimatter is used up in the containment vortex), and why you can "charge up" a more powerful blast or a faster-moving blast with certain weapons settings.

 

Hmmm... farfetched. Mainly because antimatter is finicky and inside plasma is like pure chaos for antimatter.

An antimatter catalyzed nuclear pusher plate missile could be small and do the same thing AND follow it's target.

Not only that, unlike a plasmoud you can forget deflection with a magnetic field.

Antimatter catalyzed nujes change everything.

Meaning you can get nuke bombs the size of baseball.

Edited July 2, 2020 by Spacescifi

[magnemoe]

34 minutes ago, WestAir said:

It always bothered me that sci fi writers go straight for the rule of cool instead of being an inspiration to real world researchers. Lasers, plasma swords and shields all look shiny, but IMO more sci fi writers should go for sensible and unique countermeasures: Shooting bullets with bullets (See: Advanced Israel iron dome. I think tanks have a special shotgun that destroys incoming projectiles and don't even get me started on CIWS). Lasers being defeated by mirrors or radiators. Projectiles that defeat "cover" by changing trajectory or just exploding behind whatever someone is using as cover and littering them with shrapnel. Electronic warfare, etc etc.

Real World militaries could best a lot of sci fi factions right now. I recently saw "The edge of tomorrow" by Tom Cruise and the whole time I thought "We could absolutely annihilate these guys without even leaving the boat..."

One guy called it an brain worm, kind of an cannon build upon bad stories. Star trek is famous for this: one simulated battle shocked the operators the they lost, this somehow was morphed into consoles exploding who make no sense with transistors or later technology. 

And unlike lasers plasma weapons makes no sense, I guess its something survived from the golden age of sci-fi as plasma is an thing, however the closest we get to an plasma weapon is probably the Shaped charge who is not really plasma and its effective range is less than an meter against any sort of armor unless the missile is very large and would kill you anyway if just filled with explosives. 
And yes in atmosphere plasma is less dangerous than the explosion creating it, in space a little better. 
Lasers will probably be common for AAA but don't think they ever become an common infantry weapon. 

[Guest]

Plasmoid-based weapons are a great idea in atmosphere. It's basically shooting ball lighting, and could be very damaging if done right. In space... probably something with magneto-inertial containment. Basically, you want to create a '"stripped-down" thermonuclear warhead, essentially a glob of metastable plasma that would collapse and fuse when encountering something. That would be more mass-efficient than carrying full-on nuclear shells (so that's one good reason to have it), but I have no idea if that's even possible.

TBH, if you want "lasers", your best bet is actually railguns, funnily enough.  A typical weapons-grade railgun would heat the projectile to incandescence, and it would look a lot like a tracer round, which themselves look a lot like a Star Wars-style laser bolt. Space battles using high velocity railguns could very well be quite spectacular.

[WestAir]

27 minutes ago, Dragon01 said:

Plasmoid-based weapons are a great idea in atmosphere. It's basically shooting ball lighting, and could be very damaging if done right. In space... probably something with magneto-inertial containment. Basically, you want to create a '"stripped-down" thermonuclear warhead, essentially a glob of metastable plasma that would collapse and fuse when encountering something. That would be more mass-efficient than carrying full-on nuclear shells (so that's one good reason to have it), but I have no idea if that's even possible.

TBH, if you want "lasers", your best bet is actually railguns, funnily enough.  A typical weapons-grade railgun would heat the projectile to incandescence, and it would look a lot like a tracer round, which themselves look a lot like a Star Wars-style laser bolt. Space battles using high velocity railguns could very well be quite spectacular.

They could also just fire something like 5,000 rounds per minute to get the "laser" effect. It also has the added bonus of doing actual damage.

One thing from Star Trek I loved were super-nukes. Each Starship had enough yield to melt the crust off of any planet it wanted. That concept was very exciting, but the writers never really gave the trope much airtime.

Edited July 2, 2020 by WestAir

[Spacescifi]

31 minutes ago, Dragon01 said:

Plasmoid-based weapons are a great idea in atmosphere. It's basically shooting ball lighting, and could be very damaging if done right. In space... probably something with magneto-inertial containment. Basically, you want to create a '"stripped-down" thermonuclear warhead, essentially a glob of metastable plasma that would collapse and fuse when encountering something. That would be more mass-efficient than carrying full-on nuclear shells (so that's one good reason to have it), but I have no idea if that's even possible.

TBH, if you want "lasers", your best bet is actually railguns, funnily enough.  A typical weapons-grade railgun would heat the projectile to incandescence, and it would look a lot like a tracer round, which themselves look a lot like a Star Wars-style laser bolt. Space battles using high velocity railguns could very well be quite spectacular.

 

4 minutes ago, WestAir said:

They could also just fire something like 5,000 rounds per minute to get the "laser" effect. It also has the added bonus of doing actual damage.

One thing from Star Trek I loved were super-nukes. Each Starship had enough yield to melt the crust off of any planet it wanted. That concept was very exciting, but the writers never really gave the trope much airtime.

 

It also bothers me that when kinetic rounds are fired in space the firing ship is not pushed back at all.

Especially with rapid fire railguns!

I mean... the rocket equation man!

That's one way to travel lol!

[Nuke]

3 hours ago, Scotius said:

This

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

It might be the only way to create actually useful plasma weapons. IF someone finds a way to keep plasmoids from rapidly dissipating in the vacuum.

How useful that would be? Hard to tell

there was project marauder that was supposed to create a ring of self confining plasma. such a weapon would have a strong emp effect. essentially its a ppc ala battletech, even the name references a common battlemech which carries such weaponry. supposidly its results were so good that it was quickly classified by the us government. that was back in the 80s-90s so who knows how far they have come since then.

2 hours ago, WestAir said:

It always bothered me that sci fi writers go straight for the rule of cool instead of being an inspiration to real world researchers. Lasers, plasma swords and shields all look shiny, but IMO more sci fi writers should go for sensible and unique countermeasures: Shooting bullets with bullets (See: Advanced Israel iron dome. I think tanks have a special shotgun that destroys incoming projectiles and don't even get me started on CIWS). Lasers being defeated by mirrors or radiators. Projectiles that defeat "cover" by changing trajectory or just exploding behind whatever someone is using as cover and littering them with shrapnel. Electronic warfare, etc etc.

Real World militaries could best a lot of sci fi factions right now. I recently saw "The edge of tomorrow" by Tom Cruise and the whole time I thought "We could absolutely annihilate these guys without even leaving the boat..."

i think the expanse hits the nail on the head with its pdcs, railguns, and missiles.

Edited July 2, 2020 by Nuke

[Spacescifi]

4 hours ago, Nuke said:

there was project marauder that was supposed to create a ring of self confining plasma. such a weapon would have a strong emp effect. essentially its a ppc ala battletech, even the name references a common battlemech which carries such weaponry. supposidly its results were so good that it was quickly classified by the us government. that was back in the 80s-90s so who knows how far they have come since then.

 

Not too far I imagine.

I think the reason they classified it is the ongoing tensions between the only powers that launch stuff into space a lot.

They may have managed to minaturize the technology for anti-sat applications. If said plasmoid does cause X-rays on impact it could wreck anything we have up there electronically and even kill through radiation over time... since our radiation shields don't even totally block space radiation, Let alone dedicated human maliciously induced X-rays impacting a spacecraft.

But even then, we are talking about the kind of thing that can turn a cold war hot (it's not over till it's over).

Edited July 3, 2020 by Spacescifi

[kerbiloid]

Particle beams an just extreme case of railguns.
Instead of protecting the projectile from melting, it's evapourated from the very beginning.

And they are not thermal weapon, but a weapon of directional energy transfer.
It can't be thermal because of near-light speed which makes the contact duration extremely short, so the heat transfer close to zero.
(I believe, you're aware that HEAT projectiles don't pierce armor with heating, when they are purely kinetic);

According to SDI-epoch calcs, particle beams of modernly accessible parameters can be effective against warheads and sats in a thousand kilometers range.

When you have a plasma nozzle whose thrust is enough high to push a giant ship, you can make more powerful particle beams.

To estimate, we can take the Compton length of a particle = h/mc. (2.5*10^-12 m for e^-, 1.3*10^-15 m for p)
Divergence angle, rad ~wavelength / initial_beam_diameter
Spot diameter ~ distance * wavelength / initial_beam_diameter

So, the heavier is the particle - the better.
But to accelerate it, it should be ionized.
But ionized particles repulse and make the beam dissipate.
So, the particles should be ionized inside the gun and get neutral outside of it.
So, you can't use just ionised protons, you have to add an electron to a hydrogen atom, accelerate it and partially ionize it to remove the excessive elctrons, so it's not a beam of protons, it's a jet of neutral hydrogen .
This means, you hardly can use someting more complex than hydrogen isotopes. Because they have just one electrons, while heavier elements will produce a mess of partially ionized atoms.

This means that all you can use is hydrogen or deuterium beam.

As unlikely you can store a lot of it for a long time in liquid form, it should be stored as hydrogen-rich and easily splittable molecule, like hydrazine or ammonia.

***

The antimatter catalyzed nuclear pusher plate is also useful in this context.

If unscrew it and hit with a nuke, it will smash into the enemy ship, and you will need no plasma guns.

  

5 hours ago, Spacescifi said:

It also bothers me that when kinetic rounds are fired in space the firing ship is not pushed back at all.

Probably because piercing of their wall requires much less energy than to push the ship, so the recoil is weak relative to the ship mass.
Why bombers don't stop on turrets shooting?

  

6 hours ago, magnemoe said:

And unlike lasers plasma weapons makes no sense

It interacts with matter better than gamma rays.

***

P.S.
By dividing the jet length on the OP picture by light speed, we can calculate the plasma shot duration.

Edited July 3, 2020 by kerbiloid

[magnemoe]

8 hours ago, Dragon01 said:

Plasmoid-based weapons are a great idea in atmosphere. It's basically shooting ball lighting, and could be very damaging if done right. In space... probably something with magneto-inertial containment. Basically, you want to create a '"stripped-down" thermonuclear warhead, essentially a glob of metastable plasma that would collapse and fuse when encountering something. That would be more mass-efficient than carrying full-on nuclear shells (so that's one good reason to have it), but I have no idea if that's even possible.

TBH, if you want "lasers", your best bet is actually railguns, funnily enough.  A typical weapons-grade railgun would heat the projectile to incandescence, and it would look a lot like a tracer round, which themselves look a lot like a Star Wars-style laser bolt. Space battles using high velocity railguns could very well be quite spectacular.

In the atmosphere you would have to pass trough lots of air, as you want an projectile to have significant speed I don't see it last long. Much the same way particle beams don't work well in atmosphere. 
Lasers has an problem here too however laser should work well enough as close in weapons. 

Railguns, yes but not sure how easy its to make an rapid firing railgun but if you figured out the wear on the rails then yes that would look cool. 

[KSK]

11 hours ago, WestAir said:

It always bothered me that sci fi writers go straight for the rule of cool instead of being an inspiration to real world researchers. Lasers, plasma swords and shields all look shiny, but IMO more sci fi writers should go for sensible and unique countermeasures: Shooting bullets with bullets (See: Advanced Israel iron dome. I think tanks have a special shotgun that destroys incoming projectiles and don't even get me started on CIWS). Lasers being defeated by mirrors or radiators. Projectiles that defeat "cover" by changing trajectory or just exploding behind whatever someone is using as cover and littering them with shrapnel. Electronic warfare, etc etc.

Real World militaries could best a lot of sci fi factions right now. I recently saw "The edge of tomorrow" by Tom Cruise and the whole time I thought "We could absolutely annihilate these guys without even leaving the boat..."

In no particular order:

• Science fiction is a broad church. Sometimes the technology in a given story is either present day technology or a plausible, not too far-future extrapolation from it. Sometimes the technology is obviously fictional but remains consistent to an internal logic and set of constraints. Sometimes the technology is just pure rule of cool. In all cases, it may be a significant plot point, it may just be window dressing for the story, or it may be something in between.
•  Science fiction is not necessarily space fiction, still less space war fiction.
• The job of the science-fiction writer is to tell a good story. If they end up being an inspiration to real-world researchers in the process, then that's a bonus. Besides, I would argue that a significant part of that inspiration arises from researchers reading about an obviously (at the time) rule-of-cool fictional technology which then spurs them to try and figure out how to turn fiction into reality. 
• Sometimes the inspiration from science fiction is more abstract. I recently listened to a very good podcast (the Washington Post's Moonrise) which, amongst other things, explored the role of science fiction on the Apollo Program. In a nutshell, the popularity of science fiction helped to shape public perception of what was or could be possible, turning a Moon landing from an outright impossibility (and therefore waste of time) into something that would be incredibly hard but also possible. Remember that Kennedy's 'before this decade is out' speech happened in the very earliest days of manned spaceflight. Gagarin had only just flown, Shepard had just made his suborbital hop. To aim at a Moon landing from there required a huge leap of faith and science fiction helped to shape the backdrop against which that leap was made.
• Science fiction writers don't necessarily have any military experience, are not necessarily versed in military theory or, indeed, are not necessarily scientists. Of course the obvious counter to that statement is the old advice of 'write what you know'. If you're writing about future warfare then it would probably help if you do know something military tactics and/or strategy. Likewise if a particular aspect of real-world science or technology is crucial to your story, it's probably a good idea if you know enough about it (or can research enough about it) to sound plausible.
•  Defeating lasers with mirrors is an old trope that doesn't bear up too well in real life. Even high quality mirrors are not 100% reflective, so they will absorb some of the incoming laser energy. If the laser is powerful enough to damage the target, that small percentage of absorbed energy will be enough to damage the protective mirror to the point where it's much less reflective and therefore much less effective as a laser countermeasure.

Returning to the original question:

A plasma projectile may or may not be as effective as a laser in terms of raw damage output but there are other considerations that may come into play.

• Weapon cost. High powered lasers are expensive,  require a lot of precision equipment and, depending on the lasing medium being used, are not necessarily very efficient. For a space weapon grade laser that might mean a relatively fragile weapon with significant heat dissipation requirements. Plasma weaponry may or may not suffer from those disadvantages.
• It's very setting dependent but I could well imagine, or be persuaded in the context of a sci-fi story, that there are tactical advantages to using plasma weaponry over lasers:
  • Damage mode. A plasma projectile, assuming that the 'plasma' is actually plasma and not just a name for some other concept, is basically a blob of charged particles. How they interact with spacecraft armour may be very different to how a laser beam interacts with that armour. Consider the somewhat analogous case of radiation shielding - the materials that you want in your shield are heavily dependent on the type of radiation you're trying to block.
  • A plasma projectile (compared to a laser) might be just the thing for quickly wrecking large areas of relatively fragile spacecraft components such as radiators. It's the difference between cutting a hole in a window with a glass cutter and just lobbing a brick through the window. 
  • Secondary weapon effects, aka the classic Star Wars ion cannon. Realistic threat? Who knows. But the very presence of plasma weaponry might force spacecraft designers to add additional shielding or make other performance limiting design changes to their spacecraft, making those spacecraft less combat-effective than would otherwise be possible.

Incidentally, I always imagined plasma weapons as a rather more high tech version of these:

https://www.stevespanglerscience.com/lab/experiments/dry-ice-smoke-ring-launcher/

 

Edited July 3, 2020 by KSK

[DDE]

14 hours ago, sevenperforce said:

In my head-canon, sci-fi plasma weapons actually fire some sort of tightly-bound antimatter particle cluster.

Mine is monomolecular hydrogen. Metallicity optional.

Which brings me nicely to another point I want to make: in much of sci-fi, plasma is a power source (e.g. 'plasma reactor'). So the difference between a laser and a plasma weapon is supposed to be the one between guns and flamethrowers.

Of course, this runs completely contrary to what plasma actually is.

[Codraroll]

14 hours ago, sevenperforce said:

Yep, as much as I loved that movie I kept thinking "where the hell are the F35s and the M1A2s and the freaking USS George Washington? Yes, I'm US-centric but that's because I live here.

If a single frag grenade could kill an Alpha, a dozen F-35s and the USS George Washington could WASTE the Omega's entire army in a matter of minutes.

So much of our sci-fi, particularly in movies, revolves around good people getting up and close with the bad people. The parties that engage in a battle can't be farther apart than those that engage in conversation. What good is a battle if the good guy can't throw a quip at the bad guy during the action? As such, the ideal weapon in cinematic fights are swords or even fists. See the prequel trilogy of Star Wars, for instance, where sword fighters engage large armies of blaster-wielding robots and win handily.

This might suit the storytelling medium a lot better, but it does give an unrealistic view on how battles are actually fought, and - to flip it around a little - it means we won't see realistic battles portrayed  on screen very often. Has there even been a non-historical movie showing the effects of artillery in a battle? To believe the movies or even most video games, field battles are fought by running up to the enemy and shooting a rifle at them at a range no greater than the distance you can spit.

I think my "favourite" example here is Starship Troopers, where a modern army of riflemen engage with huge, monstrous bugs - by getting within two meters of them and spraying them with hundreds of rounds of ammo while trying to avoid the bugs' dangerous claws. Meanwhile, a short clip halfway through the movie shows a few low-flying aircraft clearing an entire valley packed with bugs by dropping some cluster munitions - and then it's back to face-to-face infantry battles again. They clearly have effective weapons and effective tactics, but choose not to use either, because the screenwriters want it to be "personal". The same movie shows the bugs' claws easily piercing the armour worn by the human soldiers, which makes me wonder why they even bother to be encumbered with it in the first place.

To tie this back to the question posed by the OP: Not only are plasma cannons useless, they may be totally irrelevant depending on the medium. What he fails to grasp through his endless torrent of question threads like this is that the needs of the story tends to come before the realities of hard science, that's why it's fiction. Every sci-fi story has to include a bit of magic, where the author assumes "this works, somehow". If everything described would work within the current understanding of physics, engineering, and economics, we could have built it already. If you want plasma cannons, use them. If you want plasma cannons that work, have them work your way. 

Or in other words: make assumptions and use them to tell your story. No need to spray new threads all over this subforum every other day because you've hit another snag in your writing process.

[kerbiloid]

SW plasma swords are sick. You can't touch this take their blade to use it as a sharpened wooden stick _{деревянный кол} to stab _{пырнуть} the opponent, unlike the b-ard knight sword.
(The word filter would block even the names of medieval weapons, what a shame...)

The old German WWI Mauser's plasmatic blaster of Han Solo in New Hope is better, but requires a wooden holster to be authentic, and its barrel is strangely thin for a plasma thrower.

The Starship Pedants are not about guns&insects, they are about teens with guns in stylish uniform and their hierarchical problems. I still can't get, what kind of troops they are.

[Spacescifi]

3 hours ago, Codraroll said:

So much of our sci-fi, particularly in movies, revolves around good people getting up and close with the bad people. The parties that engage in a battle can't be farther apart than those that engage in conversation. What good is a battle if the good guy can't throw a quip at the bad guy during the action? As such, the ideal weapon in cinematic fights are swords or even fists. See the prequel trilogy of Star Wars, for instance, where sword fighters engage large armies of blaster-wielding robots and win handily.

This might suit the storytelling medium a lot better, but it does give an unrealistic view on how battles are actually fought, and - to flip it around a little - it means we won't see realistic battles portrayed  on screen very often. Has there even been a non-historical movie showing the effects of artillery in a battle? To believe the movies or even most video games, field battles are fought by running up to the enemy and shooting a rifle at them at a range no greater than the distance you can spit.

I think my "favourite" example here is Starship Troopers, where a modern army of riflemen engage with huge, monstrous bugs - by getting within two meters of them and spraying them with hundreds of rounds of ammo while trying to avoid the bugs' dangerous claws. Meanwhile, a short clip halfway through the movie shows a few low-flying aircraft clearing an entire valley packed with bugs by dropping some cluster munitions - and then it's back to face-to-face infantry battles again. They clearly have effective weapons and effective tactics, but choose not to use either, because the screenwriters want it to be "personal". The same movie shows the bugs' claws easily piercing the armour worn by the human soldiers, which makes me wonder why they even bother to be encumbered with it in the first place.

To tie this back to the question posed by the OP: Not only are plasma cannons useless, they may be totally irrelevant depending on the medium. What he fails to grasp through his endless torrent of question threads like this is that the needs of the story tends to come before the realities of hard science, that's why it's fiction. Every sci-fi story has to include a bit of magic, where the author assumes "this works, somehow". If everything described would work within the current understanding of physics, engineering, and economics, we could have built it already. If you want plasma cannons, use them. If you want plasma cannons that work, have them work your way. 

Or in other words: make assumptions and use them to tell your story. No need to spray new threads all over this subforum every other day because you've hit another snag in your writing process.

How fictional stuff works is of no importance at all... other than it's effect on character's who reader's are supposed to love/hate.

I came to this thread thinking scifi plasma weapons were totally useless, and they just about are.

Yet the realistic version, which is fired so fast you won't see it. While doing spread damage, would be an excellent choice if you want to disable unshielded satellites without blowing them up.

One shot or two is alll it takes, rather than the prolonged beaming a laser would take to hit the right spotson the target's surface.

In other words, it would work well against 2020 human satellites, but not scifi spaccraft that are expecting this sort of thing.

[KSK]

2 hours ago, Codraroll said:

To tie this back to the question posed by the OP: Not only are plasma cannons useless, they may be totally irrelevant depending on the medium. What he fails to grasp through his endless torrent of question threads like this is that the needs of the story tends to come before the realities of hard science, that's why it's fiction. Every sci-fi story has to include a bit of magic, where the author assumes "this works, somehow". If everything described would work within the current understanding of physics, engineering, and economics, we could have built it already. If you want plasma cannons, use them. If you want plasma cannons that work, have them work your way. 

Or in other words: make assumptions and use them to tell your story. No need to spray new threads all over this subforum every other day because you've hit another snag in your writing process.

I'm wondering - perhaps we, or rather @Spacescifi could approach this from another angle. A lot of his(?) questions are difficult to answer because we don't get a lot of context and so we don't get a clear idea of what he wants his fictional spaceships to do and therefore what limitations need to be overcome when thinking about the kind of technologies that would be required, or whether his suggested technologies would be effective.

If we could start with an outline of that context and the sci-fi setting he's developing then maybe folks could help figure out some suitable technologies that would work within that setting? We wouldn't need anything super detailed but an idea of:

• How populated the setting is and so how much space-based infrastructure would be reasonable to use;
• Where most of the action is likely to take place - for example does it mostly take place on a handful of planets or are the main characters doing a lot of hopping between star systems;
• How long a space journey would ideally take;
• What the spacecraft need to do - explore, move cargo, fight, all of the above;
• Whether the setting includes FTL communication;

would be helpful.

Rather than yet another thread on the merits (or otherwise) of a particular spaceship drive or other piece of technology, why not give us the big picture, so we can help figure out how that big picture might work. Given the background of the folks on this forum, I suspect we could go quite far down the rabbit hole of spacecraft design if asked to.

 

 

[KSK]

39 minutes ago, Spacescifi said:

How fictional stuff works is of no importance at all... other than it's effect on character's who reader's are supposed to love/hate.

I came to this thread thinking scifi plasma weapons were totally useless, and they just about are.

Yet the realistic version, which is fired so fast you won't see it. While doing spread damage, would be an excellent choice if you want to disable unshielded satellites without blowing them up.

One shot or two is alll it takes, rather than the prolonged beaming a laser would take to hit the right spotson the target's surface.

In other words, it would work well against 2020 human satellites, but not scifi spaccraft that are expecting this sort of thing.

Again, it totally depends on your setting. Taking an example from the top of my head, as you already pointed out, a magnetic shield could effectively protect a sci-fi spacecraft against plasma weaponry. However that assumes that the spacecraft can generate a strong enough magnetic field to sufficiently deflect an incoming plasma bolt. Complete protection would also require the shielding to be active over the entire ship and to be continually active. Neither of those needs to hold true when you consider that magnetic shielding would also require power and that the spacecraft might simply not be capable of generating enough energy to power the shields as well as the engines, weapons, life support and other ship systems simultaneously.

So you could choose to go for a Star Wars type solution where the magnetics shields are angled or set to defend against incoming fire from the most likely directions.

"Set deflectors on double front! Rear turrets - watch for enemy fighters!"

At which point battles become quite tactical. Being able to attack from multiple directions becomes especially  important. Predicting the enemy's attack patterns to set your shields accordingly, becomes a real consideration. Lots of good story telling scope there.

And it may well be that plasma weapons are completely ineffective against fast moving craft because your setting is using movie style, relatively slow moving, plasma projectiles. That's fine. Use something else for picking off the fighters and make your plasma cannons the big capital ship killers. Or forget about plasma cannons. Take a leaf out of the Homeworld playbook and have plasma bombs or missiles equipped with plasma warheads, both of which can be deployed from fighters if need be. The warhead could be an antimatter containment unit which is set to deliberately fail when some predetermined condition is met. At which point the antimatter annihilates and turns the rest of the warhead into a cloud of plasma.

 

TL: DR. Plasma weapons are only useless if you, as the writer,  choose to make them useless.

Edited July 3, 2020 by KSK

[kerbiloid]

And lastly, the plasmaballs can be mini-suns, surrounded by mini-planets inhabited by life evolved from scratch _{(the scratch on the kitchen table)} to sapient beings who are looking at the inevitably approaching target while you are throwing their worlds one-by-one, and sadly complain about your cruelty.

Edited July 3, 2020 by kerbiloid

[magnemoe]

4 hours ago, Codraroll said:

So much of our sci-fi, particularly in movies, revolves around good people getting up and close with the bad people. The parties that engage in a battle can't be farther apart than those that engage in conversation. What good is a battle if the good guy can't throw a quip at the bad guy during the action? As such, the ideal weapon in cinematic fights are swords or even fists. See the prequel trilogy of Star Wars, for instance, where sword fighters engage large armies of blaster-wielding robots and win handily.

This might suit the storytelling medium a lot better, but it does give an unrealistic view on how battles are actually fought, and - to flip it around a little - it means we won't see realistic battles portrayed  on screen very often. Has there even been a non-historical movie showing the effects of artillery in a battle? To believe the movies or even most video games, field battles are fought by running up to the enemy and shooting a rifle at them at a range no greater than the distance you can spit.

I think my "favourite" example here is Starship Troopers, where a modern army of riflemen engage with huge, monstrous bugs - by getting within two meters of them and spraying them with hundreds of rounds of ammo while trying to avoid the bugs' dangerous claws. Meanwhile, a short clip halfway through the movie shows a few low-flying aircraft clearing an entire valley packed with bugs by dropping some cluster munitions - and then it's back to face-to-face infantry battles again. They clearly have effective weapons and effective tactics, but choose not to use either, because the screenwriters want it to be "personal". The same movie shows the bugs' claws easily piercing the armour worn by the human soldiers, which makes me wonder why they even bother to be encumbered with it in the first place.

To tie this back to the question posed by the OP: Not only are plasma cannons useless, they may be totally irrelevant depending on the medium. What he fails to grasp through his endless torrent of question threads like this is that the needs of the story tends to come before the realities of hard science, that's why it's fiction. Every sci-fi story has to include a bit of magic, where the author assumes "this works, somehow". If everything described would work within the current understanding of physics, engineering, and economics, we could have built it already. If you want plasma cannons, use them. If you want plasma cannons that work, have them work your way. 

Or in other words: make assumptions and use them to tell your story. No need to spray new threads all over this subforum every other day because you've hit another snag in your writing process.

Yes battle ranges for everything outside infantry are far to long to make for good action movies. This is not an new thing, battle of Jutland back during WW1, was mostly fought at ranges of more than 10 km among the capital ships, I say it mostly was closer to 20, destroyers went in within torpedo range to drop them but then moved back to protect against enemy destroyers. 

Now air combat during WW2 was an exception as it was fast and close including staffing and dive bombing. Star wars is inspired by this. More fun then you saw star wars before starting watching var documentaries
And suddenly lots of tactic makes sense like fighter buzzing around, the do staffing runs on the ship to suppress anti air guns, the smaller guns like 20 and most 40 mm was was not in turrets but had an gun shield at best so shooting at an battleship with an machine gun made sense. 
And having the guns fire at the close up weaving planes let other planes with torpedoes and bombs an easier time. 

Today ranges has increased more, yes you will still get some very close encounters but this tend to include infantry and being the exception 

[kerbiloid]

Nowadays war movie.

You are sitting in a chair in small underground room. Then you enter the code, turn the key(s), then for a half an hour do a crossword. Then a half a minute of earthquake, you shake off the dust and keep sitting for a couple of weeks more.