How Overpowered Scifi Space Combat Would Be

[Fraktal]

Going back to the topic for a bit. Say that there's a cannon that fires not antimatter, but the reaction products of the antimatter's annihilation, basically something halfway between an antimatter shaped charge and an antimatter-pumped laser. Realistically how powerful would it be?

Giant frak-off cone of death?

Big radiation flash with a little sunburn on the side?

To avoid the magazine detonation issue, the weapon is not pre-loaded with antimatter but rather, the weapon contains a compact particle accelerator that synthesizes the antimatter in situ prior to firing. This, of course, means that it takes the weapon several minutes to build up reaction mass and once it's fully charged, it must be fired or else it'll detonate with nuclear force.

Edited July 22, 2020 by Fraktal

[kerbiloid]

The only long-lasting products of the antimatter annihilation are photons, and they are flying in opposite directions, so can't be focused without hitting the shooter.

If you can produce the antimatter onboard, your ship has enough delta-V to ram into their planet and finish the war.

[kerbiloid]

Interesting fact.

Do you know that you can defeat another civilization with just one properly equipped and trained space trooper?

Spoiler

If properly take the aim and accelerate him to relativistic speed.

 

[KSK]

1 hour ago, Fraktal said:

Going back to the topic for a bit. Say that there's a cannon that fires not antimatter, but the reaction products of the antimatter's annihilation, basically something halfway between an antimatter shaped charge and an antimatter-pumped laser. Realistically how powerful would it be?

Giant frak-off cone of death?

Big radiation flash with a little sunburn on the side?

To avoid the magazine detonation issue, the weapon is not pre-loaded with antimatter but rather, the weapon contains a compact particle accelerator that synthesizes the antimatter in situ prior to firing. This, of course, means that it takes the weapon several minutes to build up reaction mass and once it's fully charged, it must be fired or else it'll detonate with nuclear force.

You’d get a burst of gamma rays and a fairly underwhelming pulse of short-lived particles. As in half lives measured in microseconds.

The gamma rays would do more harm to you than the enemy in much the same way that an exploding pistol barrel is going to hurt the shooter more than their target.

The charged particles could be used as a weapon but only a severely underwhelming one. Pure antimatter rockets (where the rocket exhaust is made of the particles produced by the matter-antimatter reaction) have been studied and basically you get ludicrous ISP (because your exhaust velocity is close to light speed) but pitiful thrust (because you don’t actually have that much exhaust). In KSP terms imagine using the Dawn ion engine as a weapon.

To be honest you’d be better off using that compact particle accelerator as your weapon and skipping the antimatter production.

Edited July 22, 2020 by KSK

[Hannu2]

21 hours ago, kerbiloid said:

So, rough estimation for a carrier-sized spaceship is ~1000+ km.

***

As there is no sense in one bomb per heavy cruiser, an AM-armed ship will destroy allied forces in tens of thousands of kilometers radius, causing a chain reaction of their explosions.

And if place ships too close, they can't assist each other and are not a fleet.

Even 10000 km or 100000 km are short distances in interplanetary space. You can also change numbers to whatever you want. It is not obvious that antimatter driven space destroyer from year 5350 is even on the same order of magnitude in size that largest current marine warcrafts. It is also impossible to say much about combat tactics of such fleet. It depends also on defenses. In my opinion it is not good fiction to assume antimatter stuff but think that such missiles are impossible to detect. If it will be possible to build such missiles, which can close to destroy range without noticed, large ships and command centers may be obsolete. There can be large number of missiles hiding in Kuiper and asteroid belt and waiting command to hit somewhere. At least fleets with small distances will be obsolete.

[kerbiloid]

2 hours ago, Hannu2 said:

It is not obvious that antimatter driven space destroyer from year 5350 is even on the same order of magnitude in size that largest current marine warcrafts.

If they still need destroyers, I'm sure they are of reaonable nowadays size, from tens to hundreds of meters.

Because otherwise they should be fortresses exchanging with long distance strikes and non-maneuverable.

 

If they are maneuverable, then they can just evade even from laser hits. Photon needs a second to pass 300 000 km, so you should just trace the enemy emitter position and predict the shot moment due to his gun preparation (recharging, pre-shot warming, etc).

2 hours ago, Hannu2 said:

In my opinion it is not good fiction to assume antimatter stuff but think that such missiles are impossible to detect.

They can be detected: as any another warm body; as a hole in vacuum filled with matter; by the permanent emission of 0.511 MeV photons, etc.

2 hours ago, Hannu2 said:

At least fleets with small distances will be obsolete.

Any fleet will be obsolete. Compare the ratio of the fleet maneuvers along and across the battle field pool lake sea. They are 2d. Space battles can be only 1d, like a knight tournament of late medieval.
You build one-battle fleets of expendable crewless carriers of single-shot self-propelled emitters (gamma-lasers or particle beamers) and throw them massively into the opponent's fleet approaching to you.

Finally, somebody destroys the opponent's shipyard and the war finishes.

Edited July 22, 2020 by kerbiloid

[Fraktal]

2 hours ago, KSK said:

To be honest you’d be better off using that compact particle accelerator as your weapon and skipping the antimatter production.

They're already doing that with particle accelerators that spit out tau particles flying at high c-fractional speeds (to make the particle last long enough to actually hit the target before decaying). The idea behind those is that they deal damage via kinetic force, making them extremely accurate (high kinetic energy means they don't get pulled off-course by electromagnetic fields enough for it to matter) and highly armor-penetrating, to the point where a couple rapid-fire guns applied at broadside could turn even the most heavily armored battleship into swiss cheese.

However, the weapon's penetrating power is also its main drawback: shots tend to go in one side and come out the other side with little internal damage unless they hit something vital. Thus, simply blind-firing it at the other ship's silhouette just doesn't have the same stopping power as a spinal railgun or ship-to-ship cruise missile unless you know the other ship's internal layout and can target vital systems (since I'm explicitly not giving anyone in the setting magical detect-everything sensors; they have visual, infrared, radar and gravimetric, which is the relativistic gravity well equivalent of passive sonar).

[Guest]

2 hours ago, Hannu2 said:

Even 10000 km or 100000 km are short distances in interplanetary space. 

Do note that there's absolutely no reason for combat to take place in interplanetary space. Also, at some point you will start to run into pointing accuracy problems. Basically, even a laser won't hit if you can't aim it at the enemy. The bigger you laser, the harder it is to turn and aim, but you can't make it too small without killing its efficiency. Those factors mean that 100000km would likely be beyond any non-guided weapon's effective range, and practical combat ranges would be much shorter.

[kerbiloid]

1 hour ago, Fraktal said:

However, the weapon's penetrating power is also its main drawback: shots tend to go in one side and come out the other side with little internal damage unless they hit something vital.

Everything coming out the other side is a lost power, and there is no need to pierce. You should just break the structural integrity.

[Fraktal]

Ah, but that's the thing: the only reason why those shots even reach the target is because the particles it fires have a very short half-life, so they must be fired at a muzzle velocity where relativistic time dilation is a factor. Dial down the power and the shot won't even reach one kilometer before evaporating.

Anyway. The idea is meant to be that yes, the setting has energy weapons, but they don't replace kinetic weapons or even missiles because all of these weapon types are useful in their own use-cases. Just the other day I was also considering a ship-to-ship torpedo type that basically takes a large missile but strips out the explosive payload in favor of solid tungsten/uranium. It's lobbed off at the target with a railgun operating under reduced power compared to a normal projectile (that is, launching the torpedo with the same muzzle velocity as a normal railgun shot would tear the railgun apart), drifts under momentum until a certain pre-set distance, then fires up its engine at full blast to maximize impact velocity and provide limited terminal guidance a normal railgun shell doesn't have while simultaneously being harder to shoot down with CIWS due to being little more than a solid metal slug with an engine on one end. Again, no explosive warhead, just pure kinetic energy. Of course, if it misses the target during terminal approach, it'll be going too fast to turn back around for another pass like a normal missile could.

[Spacescifi]

Science fiction... it's not the starship science wants that matters but the starship that physics and plot deserves.

[Fraktal]

Yeah but if the tech doesn't stand up to the science for at least a cursory glance, you can be damn sure someone will nitpick about it.

[Spacescifi]

1 hour ago, Fraktal said:

Yeah but if the tech doesn't stand up to the science for at least a cursory glance, you can be damn sure someone will nitpick about it.

 

My concern is with the ignorant, not the nitpickers who know the latest in space technology.

Thus in the foreword I will admit freely that some of my stuff (constant acceleration engines) are pure fiction powered by the needs of plot. That said, I take pains to ensure all of the plot enabler fictional tech have something that will counter them from being overpowered. I do not favor being merely arbitrary, so wherever possible, I use things that are subject to known science that could counter constant acceleration engines as a threat.

8 hours ago, kerbiloid said:

If they still need destroyers, I'm sure they are of reaonable nowadays size, from tens to hundreds of meters.

Because otherwise they should be fortresses exchanging with long distance strikes and non-maneuverable.

 

If they are maneuverable, then they can just evade even from laser hits. Photon needs a second to pass 300 000 km, so you should just trace the enemy emitter position and predict the shot moment due to his gun preparation (recharging, pre-shot warming, etc).

They can be detected: as any another warm body; as a hole in vacuum filled with matter; by the permanent emission of 0.511 MeV photons, etc.

Any fleet will be obsolete. Compare the ratio of the fleet maneuvers along and across the battle field pool lake sea. They are 2d. Space battles can be only 1d, like a knight tournament of late medieval.
You build one-battle fleets of expendable crewless carriers of single-shot self-propelled emitters (gamma-lasers or particle beamers) and throw them massively into the opponent's fleet approaching to you.

Finally, somebody destroys the opponent's shipyard and the war finishes.

 

It would require a civilazation with either war experience fighting itself, or a peaceful one that is paranoid enough to do that.

Since we are talking about putting an UNMANNED fleet in orbit ready to strike anywhere from a year to decades later or longer. In the meantime they do ABSOLUTELY nothing, waiting for a threat from space that may or may not come.

LOL. Better use some propellant that won't gas leak during the long wait for action.

Even assuming scifi aliens do exist in a universe, they may be not be keen on attacking a system with automated fleets ready to strike at explorers/instruders.

 

 

Edited July 23, 2020 by Spacescifi

[SOXBLOX]

Ship to ship probably won't even occur; war would be lobbing interplanetary torch missiles and waiting.

[Spacescifi]

1 hour ago, SOXBLOX said:

Ship to ship probably won't even occur; war would be lobbing interplanetary torch missiles and waiting.

 

Well... depends on how expendable the spacecraft are. And how the writer makes things go.

Unmanned are by their very nature expendable.

My idea of scifi combat means a homeworld fleet generates jump points a light second from any world  with 1g or higher gravity, and each jump point will only accept the ship that generated it's own jump point. Jump points stay active for 7 hours, more than long enough to reach them at constant 1g (their fleet can do that).

 

Instead of sending crew to possibly die in vessels as is common in scifi media, they send waves of unmanned vessels, which conserve their momentum and trajectory upon entering a new solar system, and the jump point closes after the vessel appears.

Tactically and strategically it means war is very much a waiting and hoping kind of affair.

Hoping that your AI controlled vessels return within a day or two via jump points with news of victory.

If they don't return at all... now people will panic and start preparing for a defend the homeworld system with everything they have... most of it unmanned spacecraft.

 

Relativistic strikes via jump points are possible, but it would take months of acceleration and you only get one chance... you miss at 99% lightspeed and it will take you months to turn around and go to the light second from 1g world or higher radius where jump points can form.

Edited July 23, 2020 by Spacescifi

[Hannu2]

13 hours ago, Dragon01 said:

Do note that there's absolutely no reason for combat to take place in interplanetary space.

I think that living on planets may be obsolete if 1t antimatter bombs are military weapons. Couple of such bombs would change planet's atmosphere unusable and spread radioactivity everywhere on surface. It is probably better to distribute people to many huge stations around solar system. Stations are much more difficult to hit and easier to defend.

 

13 hours ago, Dragon01 said:

 

Also, at some point you will start to run into pointing accuracy problems. Basically, even a laser won't hit if you can't aim it at the enemy. The bigger you laser, the harder it is to turn and aim, but you can't make it too small without killing its efficiency. Those factors mean that 100000km would likely be beyond any non-guided weapon's effective range, and practical combat ranges would be much shorter.

I think also so. Beams are not credible technomagic weapons, if we do not assume completely new natural laws. Missiles may be able to imitate asteroids, but probably very sophisticated detectors can detect and destroy them before they are in damaging range. Actually I would bet that there are completely new methods for warfare. Cyber attack to enemy stations living support system or using nanobots or some new exotic technology may be more practical way to destroy enemy units than high energy or brute force. Or maybe warfare will be just too disadvantageous to all forces. Most wars are competition for limited resources but there are practically infinite resources in space.

[kerbiloid]

So, you can just send a homing missile with a single-shot beamer onboard, to get close and make headshot.

[Terwin]

7 hours ago, Spacescifi said:

Relativistic strikes via jump points are possible, but it would take months of acceleration and you only get one chance... you miss at 99% lightspeed and it will take you months to turn around and go to the light second from 1g world or higher radius where jump points can form.

umm, if you are at 99% of light speed, then it takes all of 1.01 seconds to travel 1 light second away from your target, so you might just get to make a second try before the observation station has a chance to send out the alert...

 

Also, if you have access to a sizeable black hole(such as a galactic core), it might only take a few hours(and some very precise timing) to accelerate a vessel to relativistic speeds.  For this, larger is better as it not only gives higher acceleration further out, but also lets you get much closer(thus higher acceleration) before tidal forces rip you apart(possibly even inside the event horizon if you find one big enough).

 

Note: a 200 ton nickle/iron asteroid with a steel wrapper to keep it from breaking up and a remote controlled/pre-programmed jump engine is going to be far cheaper than any method of manufacturing a ton of antimatter, and when it hits something big enough(like a planet or moon), the energy released will be orders of magnitude larger.  As an added bonus, blowing up the asteroid just turns it into relativistic shrapnel and thus it will be even more devastating.

[kerbiloid]

By having a black hole, you can get close to its horizon, and wait a little while your enemies are getting extinct.

Then return with glory, dig out their petrified remains, and put them in museum.

[Bej Kerman]

On 7/11/2020 at 3:30 PM, Spacescifi said:

How powerful is one ton of antimatter?

According to one calculation that is 43000 megatons, with a incinerate to burn damage of a 500 kilometer radius!

Antimatter on its own interacts with itself like matter does, so is that mixing 500kg of antimatter and matter, or dropping one bit of matter into a mass of antimatter?

[kerbiloid]

1 hour ago, Bej Kerman said:

Antimatter on its own interacts with itself like matter does, so is that mixing 500kg of antimatter and matter, or dropping one bit of matter into a mass of antimatter?

1t+1t

[Bej Kerman]

Just now, kerbiloid said:

1 hour ago, Bej Kerman said:

Antimatter on its own interacts with itself like matter does, so is that mixing 500kg of antimatter and matter, or dropping one bit of matter into a mass of antimatter?

1t+1t

Right

[Spacescifi]

2 hours ago, Terwin said:

umm, if you are at 99% of light speed, then it takes all of 1.01 seconds to travel 1 light second away from your target, so you might just get to make a second try before the observation station has a chance to send out the alert...

 

 

What? How?

Inerta won't let a vessel reverse course at 99% lightspeed, these are constant acceleration 1g engines.

2 hours ago, kerbiloid said:

By having a black hole, you can get close to its horizon, and wait a little while your enemies are getting extinct.

Then return with glory, dig out their petrified remains, and put them in museum.

 

Lazy... but efficient.

[magnemoe]

22 hours ago, Dragon01 said:

Do note that there's absolutely no reason for combat to take place in interplanetary space. Also, at some point you will start to run into pointing accuracy problems. Basically, even a laser won't hit if you can't aim it at the enemy. The bigger you laser, the harder it is to turn and aim, but you can't make it too small without killing its efficiency. Those factors mean that 100000km would likely be beyond any non-guided weapon's effective range, and practical combat ranges would be much shorter.

Agree on lasers, yes you could do tricks here like launching an missile with an mirror but for long range they start to get impractical. 
On the other hand lobbing missiles as an incoming fleet makes sense, more so as they probably get degraded sensors having to look trough their own rocket plume. On the other hand the enemy can just lighten their ships dropping off stuff 

An missile in futuristic space combat has little to do with existing missiles. You have an first stage who bring the missile up to speed, however if you stop trusting you will continue so you only need an intercept trajectory. 
Now the problem is that an ship is likely to have an better engine than an missile. 

[DDE]

1 hour ago, magnemoe said:

Now the problem is that an ship is likely to have an better engine than an missile. 

Define "better". Higher acceleration? Unlikely. Higher dV reserves? Perhaps, but are they high enough to both dodge missiles and carry out the original mission and get home? How high is that margin?