Are space fighters really impossible in realistic Sci Fi?

[Jetro]

TL;DR at bottomIt's a somewhat accepted convention that in realistic scifi space fighters should be impossible to use effectively. In general they are regarded as being easy targets that, at interstellar ranges would be unable to survive in a battlefield that employs current plausible scifi weaponry such as laser and railguns. At a glance this would seem like a reasonable assumption. Lasers travel at light speed and would only have to point at the target and at shorter distances rail projectiles move fast enough that dodging becomes impossible. But is that all there is to it? I'd take the unpopular opinion that the picture of warfare for a fighter/drone wouldn't be as bleak and clear cut as the raw science makes it seem once you start considering the realities of how those kinds of weapons might perform in real world conditions. I'd even go so far as to say that fighters/drones might actually be vital in scifi settings that are trying to accurately portray space warfare. Here's my reasoning.

The target is very small. Your gun is very big.
In Future War Stories, the author cites that a fighter craft at a range of ~239,000mi would have about 2.5 seconds to dodge an incoming laser. As such it wouldn't have enough time to evade enough shots to make it closer to a target. I think there's two problems with this suggestion. Firstly, the laser that's firing can only determine a shot based on trajectories that are 2.5 seconds old. If the fighter is always altering it's course this estimate will always be wrong and it will take 5 seconds for the firing computer to even confirm whether or not it made a hit to update it's firing solutions and try again.

Secondly, even if the fighter were traveling is a predictable straight line, would the computer be able to hit it anyways? That might seem like a simple yes, but it really isn't once you consider how far away such a small target actually is. So a laser fires at a fighter 3 yards tall 239,000mi away. Let's make it easy and say the fighter is traveling upwards at 90 degrees to the laser so the computer can use really simple trig. The fighter is also moving really slow, only 1.2m/s relative to the laser. The laser is In order for that laser to hit the target, it needs to adjust the firing mechanism on it's laser by 4X10^-7 degrees or 4 ten millionths of one degree. If the laser were 10 meters long, it would have to raise it's barrel by 4.5 x 10^-11 or 4.5 hundred trillionths of a mile, which I'm not going to covert, but it's smaller than a picometer adjustment. And that's only for adjust aim up/down.

And that's the main problem. At those ranges, the projectile isn't the limiting factor, it's the weapon firing it. At a certain point you can't make the weapon anymore precise. Even if it can adjust it's aim to ten thousandths of a degree couldn't be expected to hit a target at those ranges, even if the target was standing still relative to the gun. It doesn't matter how precise the targeting computer is at calculating since the gun will be limited by physics.

So then we have to ask, at what ranges could a large laser be expected to hit a target reliably. So let's assume it's 10 meters long, and can adjust by as little as 1/10,000 of a degree/second. At 20,000 miles which Future War Stories cited as a realistic engagement range for fighters, the gun needs to adjust by 5 millionths of one degree. Still too inaccurate.

Let's try 5,000 miles. You need to adjust by 2 hundred-thousandth of a degree.

500 miles. You're right about there at 2 ten-thousandths of a degree.

TL:DR With an incredibly ridiculously precise laser gun, firing at the easiest moving target imaginable without account for other issues, like ship vibrations, thermal expansion of the the weapon, the presence of a gravity well, and no third dimension you'd only have an effective range of ~5,000 miles. This would give fighter/drones armed with missiles a very distinct advantage as they could close distances with a larger ship from a variety of angles and fire a very large number of missiles that the targeting computer would have to deal with in addition to the fighters themselves.

And to be frank I wouldn't really expect any weapon large enough to shoot down a fighter to be reasonably expected to have more than 1/100th a degree of precision at the very most, which is just 9 miles effective range. If you can only get one-tenth a degree of precision for the weapon, you'll be able to see Luke Skywalker in his cockpit at less than a mile. At one degree of precision, an A-Wing may crash into your bridge, since your effective range is now 4700 feet.

 

[CWatters]

In Future War Stories, the author cites that a fighter craft at a range of ~239,000mi would have about 2.5 seconds to dodge an incoming laser.

How would he know it was coming?

 

[CWatters]

On my spacecraft I will have a diverging beam laser so I only have to point it in the general direction of the enemy to score a hit. Delivering enough power over such a large area won't be a problem becuse this is fiction.

 

[Drakkith]

The laser is In order for that laser to hit the target, it needs to adjust the firing mechanism on it's laser by 4X10^-7 degrees or 4 ten millionths of one degree. If the laser were 10 meters long, it would have to raise it's barrel by 4.5 x 10^-11 or 4.5 hundred trillionths of a mile, which I'm not going to covert, but it's smaller than a picometer adjustment. And that's only for adjust aim up/down.

So install the laser in a weapon's bay or pod that is longer than 10 meters and move the entire pod/bay. That way you have a longer lever arm to work with. Or use a lens with a variable refractive index that can alter the direction of the laser beam without physically moving. Or use a lens with a variable shape that does the same thing. Or... well, you get the idea.

Also keep in mind that a laser beam expands as it travels, so your targeting systems don't need to be nearly as accurate as you've calculated.

And to be frank I wouldn't really expect any weapon large enough to shoot down a fighter to be reasonably expected to have more than 1/100th a degree of precision at the very most, which is just 9 miles effective range.

I don't know how you calculated this kind of limit on the precision, but it's almost certainly wrong. The airborne laser system was already used to destroy targets with a diameter comparable to the size of your fighters from hundreds* of kilometers away.

*I was unable to quickly find the range-to-target during one of its tests, but the advertised range has consistently been 300+ km. The tests almost certainly would have been at ranges far greater than 9 miles though.

 

[Jetro]

So install the laser in a weapon's bay or pod that is longer than 10 meters and move the entire pod/bay. That way you have a longer lever arm to work with. Or use a lens with a variable refractive index that can alter the direction of the laser beam without physically moving. Or use a lens with a variable shape that does the same thing. Or... well, you get the idea.

Also keep in mind that a laser beam expands as it travels, so your targeting systems don't need to be nearly as accurate as you've calculated.
I don't know how you calculated this kind of limit on the precision, but it's almost certainly wrong. The airborne laser system was already used to destroy targets with a diameter comparable to the size of your fighters from hundreds* of kilometers away.

*I was unable to quickly find the range-to-target during one of its tests, but the advertised range has consistently been 300+ km. The tests almost certainly would have been at ranges far greater than 9 miles though.

It's just some basic trig. But honestly, I would need to see a source on that.

On my spacecraft I will have a diverging beam laser so I only have to point it in the general direction of the enemy to score a hit. Delivering enough power over such a large area won't be a problem becuse this is fiction.

Yeah, this is the sci fi forum.

 

[Drakkith]

It's just some basic trig. But honestly, I would need to see a source on that.

I don't have a single link, but a quick google search should turn up plenty of articles on the airborne laser.

On a related note, the U.S. military has already tested a smaller scale air-to-ground laser that was able to hit a 3x3 ft target. They don't give the actual range for this test (advertised range for the project was 20km), but it will have to be at least several miles since the operating aircraft is going to be flying several miles high. Given that current laser weaponry is still in the early prototype phases, I see no reason to think that a drastic increase in power, accuracy, and range is possible. Especially in space where the atmosphere doesn't muck things up.

Links for the above: http://www.nydailynews.com/news/wor...dvanced-tactical-laser-plane-article-1.317841
https://en.wikipedia.org/wiki/Advanced_Tactical_Laser

 

[Drakkith]

Just to clarify, I don't subscribe to the view that fighters are useless in realistic sci-fi. Space combat is so far into the future that I don't think it makes sense to rule them out. Who knows what kind of technology we'll have by then.

 

[Rive]

And to be frank I wouldn't really expect any weapon large enough to shoot down a fighter to be reasonably expected to have more than 1/100th a degree of precision at the very most, which is just 9 miles effective range. If you can only get one-tenth a degree of precision for the weapon, you'll be able to see Luke Skywalker in his cockpit at less than a mile. At one degree of precision, an A-Wing may crash into your bridge, since your effective range is now 4700 feet.

My frank opinion is that the whole laser-mania is actually very ridiculous and so far away from our actual knowledge that 'realistic' space warfare based on lasers can only be about faiths.
BTW I found the solid projectile based weaponry in the new BSG series quite well 'designed'. With fighters included.

 

[CWatters]

How would he know it was coming?

I asked because the target can't see or detect it coming. That would require faster than light communication.

 

[Bandersnatch]

I asked because the target can't see or detect it coming. That would require faster than light communication.

I believe the idea is that the crafts would approach one another already performing evasive manoeuvres. The defender 1 light-second away detects the attacking fighter in a second-old position, shoots, and the shot arrives a second later for a total of 2 seconds delay (or 2.5 in the example mentioned by the OP) during which the target can manoeuvre out of the way.

In Future War Stories, the author cites that a fighter craft at a range of ~239,000mi would have about 2.5 seconds to dodge an incoming laser. As such it wouldn't have enough time to evade enough shots to make it closer to a target. I think there's two problems with this suggestion. Firstly, the laser that's firing can only determine a shot based on trajectories that are 2.5 seconds old. If the fighter is always altering it's course this estimate will always be wrong and it will take 5 seconds for the firing computer to even confirm whether or not it made a hit to update it's firing solutions and try again.

The 2.5 seconds is already doubled from the 1.25 light-second distance. The shooter doesn't have to wait 5, or even 2.5 seconds to update firing solutions - they can do so continuously, with each shot fired at 2.5 s delayed target.
A sensible approach from the defender's perspective would be to spray the solid angle of the target area with repeated shots, each targetted at a different possible evasion path. There's only so far a craft of a given size can move to in 2.5 seconds, and the defender has a lot of time to keep trying to score a hit.
Same with kinetic weapons - rather than firing a single slug, spray the area with small projectiles.

In order to make a fighter survivable, one has to introduce some additional, arbitrary constraints. E.g. the laser can only fire every so often, and we can only have one laser, etc.

I take the second point about aiming accuracy, but one has to wonder what is the point of sending a fighter anyway? In space projectiles have unlimited range, so there's no need to have a weapons platform deliver ordnance at close quarters. Why not just send missiles right away instead?

 

[BWV]

Humans in fighters would be the silly thing, AI would be able to operate the craft and then it could take G forces that would kill a human

‘Shotgun’ blasts of small projectiles traveling at relativistic speeds would seem to be an effective weapon

Also just detonating a 100+ megaton nuke and the associated emp would also be effective

 

[Drakkith]

Also just detonating a 100+ megaton nuke and the associated emp would also be effective

Not really. A nuclear blast in empty space generates a much smaller EMP than you would think. And it is already quite possible to EMP-harden vehicles, aircraft, and facilities.

 

[Nik_2213]

Attackers would be coming in behind assorted decoys plus a cloud of chaff and buck-shot, while big target is similarly throwing chaff and buck-shot. Plus small, point-defence missiles, essentially smart rocks...

You also get a 'battle of algorithms' as target tries to anticipate attackers' evasive manoeuvres, then looses the heavy weapons...

This is not a scenario for pilot survival...

IMHO, the only reason to go near an opponent, assuming you can match their high Delta-V, is studying wreckage to gather intel...

 

[Sorcerer]

It seems finding a way to hack a system using radio waves or just using EMPs would be more effective and less risky than drones. Until that game is figured out and then everyone starts using their super advanced technology to make massive electormagnetic shields or something.

I don’t know, but it seems that if two groups have similar technology this far advanced, attacking out right is a lose-lose scenario. And since you can never be sure if you even match your opponent in technology, unless you were desperate how could the risk justify an attack?

Subterfuge seems the best class of weapon here: establish peaceful contact and then betray.

 

[Nik_2213]

I'm no gamer, but I've watched a nephew battling a swarm of 'Almost AI' opponents during a totally hectic single-player 'shoot 'em up'. IMHO, there were several algorithms in play, and scant time to spot cues for which foes would do what...

He was VERY GOOD, but those opponents could be cranked up to 'insane' numbers and/or speed for teams...

In fact, the only way to tackle such would be to have similar, scary-fast, 'Almost AI' combat bots and drones on your side.

As I see it, once your drone-carriers salvo, any wet-ware is out of the loop barring strategic oversight. Micro-management is impossible, there are simply too many ways to hack data streams and command links. Formation turns will be based on bird or bat flocking, based on near-neighbour awareness...

How could the risk justify the attack ?
Politics, Ideology, Group-Think, a 'Secret Weapon', a 'First Strike' decapitation, Maskirovka, concentration of forces etc etc etc...
{Shiver...}

 

[jbriggs444]

How would he know it was coming?

It is a similar problem faced by world war II bomber pilots navigating over enemy flak at high altitude. The targeting algorithms are aiming for your projected location. You dodge proactively.

 

[CWatters]

So I guess we are in a fictional world where we haven't yet invented faster than light travel, or we have invented it but our lasers still go at light speed.

 

[jbriggs444]

So I guess we are in a fictional world where we haven't yet invented faster than light travel, or we have invented it but our lasers still go at light speed.

Maybe there is a cube square relationship that makes it impractical to install a geometroconfabulator on a platform smaller than a fighter. Or the space time curvature present near any mass concentration worth fighting over multiplies the inaccuracies of hyper speed navigation, making accurate FTL targetting impractical. i.e. Whatever the plot requires.

 

[BWV]

Again, how could humans flying a spacecraft compete with robot craft that could withstand, say 10G acceleration that would kill a human pilot?

 

[CWatters]

I agree but just for info 10G is survivable for humans. I think it's the limit imposed on Red Bull air racers.

 

[BWV]

I agree but just for info 10G is survivable for humans. I think it's the limit imposed on Red Bull air racers.

Fair enough, but 10G is only survivable for a small amount of time, depending on the direction of acceleration

 

[Nik_2213]

In 'The Space Eater' by David Langford, the maguffin incidentally jammed all but the very simplest electronics in its vicinity.

Their cruise missiles had kamikase pilots, because there was no other practicable guidance system with the ability to navigate, dodge, weave and select alternate targets...

Brrrr...

 

[essenmein]

Interesting topic, been on and off working on a story as well, and this topic of what realistic strategies could be has been fun to think about, well realistic based on the given laws available. In "my" universe I employ three assumptions to build around, FTL travel is possible via Einstein rosen bridge, aka jumping, FTL communication is possible via entangled nodes, and artificial gravity is a thing. Other than that, same rules of physics we know and love.

First the ships are big, not big to hold large crew but big to hold the large power plants required to run the jump drives (absolutely unfathomable power needs) and the weapon systems. Everything is nuclear because that is the only thing that makes sense.

So now the issue is if you have two 3km long ships engaging each other with the mass-energy available in such large ships, and given they are all using nuclear powered weaponry (eg nuclear pumped xray pulse laser cannon), the only conclusion I have just based on the size/energy discrepancy is that if the 3km ship can go toe to toe with one of its own and possibly survive, how could a smaller vessel have any chance to even damage this thing?

There is no magic 2L pop bottles full of "stuff" that can blow up a planet (ahem new startrek), E=mc2 is a thing, and if you wanted to make a boom the size of say the Chicxulub impactor you need to convert about a 1000T of mass to energy. A medium size coast guard ship (ie in the real world) are about that weight...

So my conclusion is really that small ships are maybe useful for infiltration, spying, or ferrying the small crews around these gargantuan ships, but are of little combat use.

 

[Nik_2213]

Stand-off weaponry may have deployment 'sweet spots'. If you can co-ordinate missile salvos, perhaps briefly 'parked' by small, less detectable ships that can 'stealth' around the behemoth warships sensors and fire-control, you may overwhelm their point-defense with 'time on target' cross-fire. Even modest attrition may tilt the balance of an encounter...

Deploying counter-measures and decoys would be useful, too. Layer upon layer of 'wizard war'...

Faced with a similar situation, a core-system grimly guarded by many mega-ships, battle-stations, in-system Monitors, 'mine' fields etc etc, my Convention's planners looked at the lead time of even modular warship builds, said, 'F***k This !'
And crafted seven 'Bigger Hammers', to be hauled by huge Pleiades-Class rock-tugs...

 

[essenmein]

The stealth topic is another interesting one, at the moment I'm leaning to the side that full "stealth" is not possible (ie cloaking or what ever), I mean you can camouflage within a narrow ish band of EM radiation, but at the end of the day, ships need cooling to run the cores, and I haven't thought of a reasonable way to hide heat, esp not in the cold of space.

Although on the size topic the point I'm stuck on is a small ship simply cannot carry enough mass to convert to energy to do real damage... Its like bringing a .22 to a tank fight. I don't even think it matters how many .22's you have, you're not realistically bringing a tank down with them...

 

[Rive]

Its like bringing a .22 to a tank fight

Did you know that originally tanks were infantry support vehicles?
And even that by now they had a definite shift in their standard usage they are still rare to be used without infantry or light vehicle support?

 

[jbriggs444]

I employ three assumptions to build around, FTL travel is possible via Einstein rosen bridge, aka jumping, FTL communication is possible via entangled nodes, and artificial gravity is a thing. Other than that, same rules of physics we know and love.

What about the structural integrity to hold a kilometers-long ship together under conventional acceleration? It seems that hyper-drive capable ships must be limited to accelerations that are a small fraction of a gee.

Unless your artificial gravity generators double as tractor beams, providing for structural rigidity without needing a structure.

 

[essenmein]

What about the structural integrity to hold a kilometers-long ship together under conventional acceleration? It seems that hyper-drive capable ships must be limited to accelerations that are a small fraction of a gee.

Unless your artificial gravity generators double as tractor beams, providing for structural rigidity without needing a structure.

Yeah the AG field's (and this is I agree very hand wavey lol) primary purpose is to reduce the structural stresses on the ships during conventional (sublight) acceleration, just so happens it also helps the squishy occupants from turning into a red smear on a wall. the jump drive (FTL) does not involve large accelerations.

Thats the problem with space, the distances are so very large sub 1G accelerations basically means not going any where in any reasonable amount of time...

 

[essenmein]

Did you know that originally tanks were infantry support vehicles?
And even that by now they had a definite shift in their standard usage they are still rare to be used without infantry or light vehicle support?

To be fair though that was due to lack of imagination when tanks first appeared. Tanks are bullet magnets, I don't think any infantry wants to be near a tank for anything post ww2, esp now with the reactive armor...

 

[Rive]

I don't think any infantry wants to be near a tank for anything post ww2

As far as I know the actual routine is to go on humvees and/or APCs and assign tanks as/if necessary.

But the point is, that while it might not be wise to bring a .22 to a tank fight, it might be useful to have something big (maybe: a tank) to support small arms.

 

[essenmein]

As far as I know the actual routine is to go on humvees and/or APCs and assign tanks as/if necessary.

But the point is, that while it might not be wise to bring a .22 to a tank fight, it might be useful to have something big (maybe: a tank) to support small arms.

Yeah depending on what your operational goal is, infantry with tank support, or is it a full armored division that's engaging?

I was looking at it from the perspective of if you've got a modern tank battle going on, that is tank vs tank, then infantry is at best track lubricant.

Are there even infantry carry-able weapons that could knock out say M1A2?

Maybe its a scale thing, if the ships are 3km+, maybe a "fighter" in that context is a 200m vessel, not a 15m fighter plane like we see in sci fi.

 

[Nik_2213]

A small ship may haul a lot of missiles, and such missiles may 'mung' their emissions etc to resemble ship-killers...

While their 'flight profile' matches, you got to 'Honour The Threat'.

It is also practicable to mask a small ship, using eg cryo-cooled hydrogen as an expendable heat-sink and/or aligning radiators away from possible threat axis.

Small ships are also handy for softer targets, 'hit and run' operations. Such attrition must divert materiel from 'Grand Fleet' operations. Like the way Ironclads found themselves vulnerable to small, nimble torpedo boats. Fast Torpedo Boat Destroyers were required to chase off such. And, yes, those Destroyers could be equipped with torpedoes, become the bane of bigger ships' stately battle-lines. So, Cruisers got the job of killing enemy Destroyers. Then Battle-Cruisers to sink those Cruisers, provide support for the big ships, learn they were too flimsy for slug-fests...

An analogy from the days of sail; IIRC, one question of an aspiring Lieutenant placed his fallen Captain's damaged ship- of- the -line on a lee shore, in a full gale. What to do ??

Modern version attacks a 'Carrier Group' with a dozen shore-launched cruise missiles.
A dozen ? No problemo...
Four salvos follow.
Fifty ? Yeah, yeah...
Eight salvos follow...
Oops...

 

[essenmein]

Yeah its always a numbers game, I can shoot down one missile! ok how about two then?

Its a guessing game of how many missiles per hr the attacker can field and how many you can shoot down.

The enemy in my story is basically employing the over whelming numbers tactic, so even though "our" weapons and ships are more advanced, there is a point where they just cannot keep up. Its quite asymmetrical in that context. The protagonists at first don't realize they are essentially fighting a guerilla war and they are the guerilla...

 

[Nik_2213]

"Are there even infantry carry-able weapons that could knock out say M1A2 ?"

IIRC, yes. Tanks are vulnerable to precision top-attack. So, instead of launching a TOW or equivalent missile on a 'line of sight', a jeep-mounted mortar or whatever could loft loitering smart-bombs over the target. Either the 'smarts' auto-identify the tank, stoop and wreck its engine, or the PBI's 'designator' lasers tag juicy prey...

 

[BWV]

What about the structural integrity to hold a kilometers-long ship together under conventional acceleration? It seems that hyper-drive capable ships must be limited to accelerations that are a small fraction of a gee.

Unless your artificial gravity generators double as tractor beams, providing for structural rigidity without needing a structure.

The Earth's tallest buildings are nearly a kilometer in height and do just fine under a constant 1G acceleration

 

[jbriggs444]

The Earth's tallest buildings are nearly a kilometer in height and do just fine under a constant 1G acceleration

Yes, that was the standard I was judging against. One gee sustained constant thrust by a earthly building of less than one kilometer. So presumably less in a spaceship of multiple kilometers. Though I am not expert on the limiting constraints that apply in the two cases.

 

[Nik_2213]

"The Earth's tallest buildings are nearly a kilometre in height and do just fine under a constant 1G acceleration"

{Cough} Straw Man ? They also have mass dampers, base isolation etc, sway in the wind and suffer badly should their foundations shift even slightly.

A more appropriate analogy may be bulk-carriers, ranging from ore ships to VLCCs. They're yay big, they don't like changing direction, they don't like sea-states that affect different parts of the ship in different ways. Even when everything was built to best practice, they may still crack where modules meet. Many design lessons continue to be bought in blood...

For a big spaceship, you may see the equivalent of the old steam-ships with their umpteen boilers, stacks and engines. Yes, it is one (1) ship, but a closer look will show a dozen near-independent power sections flying in rigid formation...

 

[essenmein]

Another thing to consider is that buildings put all their mass on the foundation, which is loosely similar to a rocket. However if you have a more distributed drive then the structural situation changes quite dramatically. You now no longer have the last part that is holding all the weight.

 

[BWV]

"The Earth's tallest buildings are nearly a kilometre in height and do just fine under a constant 1G acceleration"

{Cough} Straw Man ? They also have mass dampers, base isolation etc, sway in the wind and suffer badly should their foundations shift even slightly.

A more appropriate analogy may be bulk-carriers, ranging from ore ships to VLCCs. They're yay big, they don't like changing direction, they don't like sea-states that affect different parts of the ship in different ways. Even when everything was built to best practice, they may still crack where modules meet. Many design lessons continue to be bought in blood...

For a big spaceship, you may see the equivalent of the old steam-ships with their umpteen boilers, stacks and engines. Yes, it is one (1) ship, but a closer look will show a dozen near-independent power sections flying in rigid formation...

Right - unlike a tall building, a spacecraft under 1G acceleration faces no other forces so it can be much longer. Bulk carriers are a terrible comparison because they face all the forces of the ocean at different angles than the direction of motion. A spacecraft only needs 1G acceleration in one direction because presumably to decelerate it would just stop the drive, rotate 180 degrees, then re-ignite it. BTW he Japanese have viable, if uneconomic plans, for a four kilometer skyscraper. These arent my original ideas - read Alistair Reynolds - IMO the best living SF writer (who has a PhD in Astrophysics and worked professionally in the field before he quit to write full time).

 

[jbriggs444]

On the other hand, a typical tall building will be built for office space. You can manage height because you only have to support people, desks, chairs, file cabinets, soda machines and microwave ovens. In the case at hand, we are told that the spacecraft size is based on the need for great heaping gobs of unimaginable power. One would expect them to be pretty dense.

Hmmm, offhand, I'm not sure how feasible it is to generate great heaping gobs of unimaginable power using only radiative cooling and a radiating surface that only scales as the square of the linear dimension. Maybe these ships are pretty light after all. Or maybe they get cooling by cyclically heaving thermally hot beads away and then pulling them back with artificial gravity tractor beams.

You kill such ships by blowing away their cooling clouds.

 

[essenmein]

On the other hand, a typical tall building will be built for office space. You can manage height because you only have to support people, desks, chairs, file cabinets, soda machines and microwave ovens. In the case at hand, we are told that the spacecraft size is based on the need for great heaping gobs of unimaginable power. One would expect them to be pretty dense.

Hmmm, offhand, I'm not sure how feasible it is to generate great heaping gobs of unimaginable power using only radiative cooling and a radiating surface that only scales as the square of the linear dimension. Maybe these ships are pretty light after all. Or maybe they get cooling by cyclically heaving thermally hot beads away and then pulling them back with artificial gravity tractor beams.

You kill such ships by blowing away their cooling clouds.

Actually you'd be surprised how much heat you can dissipate with a black body radiator into space (~0K). Its a delta t^4 relationship. The orange white glowing things on these ships are not drive exhaust or "rockets", but cooling plates. Keep in mind the area for cooling increases proportionally with ship size.

For perspective, to keep 10m2 at ~1300C in space requires about 3MW.

 

[Rive]

Yeah depending on what your operational goal is, infantry with tank support, or is it a full armored division that's engaging?

Well, one thing is sure: while fighting for superiority is done with the big ones, everything else is for the cheapest available option. Even in space, there will be something what will be considered cheap and (relatively) expendable => fighter.
Yeah, you are right: it might be a bit bigger than usual. But maybe not - maybe that 200m 'figher' will have some smaller drones...

 

[essenmein]

Well, one thing is sure: while fighting for superiority is done with the big ones, everything else is for the cheapest available option. Even in space, there will be something what will be considered cheap and (relatively) expendable => fighter.
Yeah, you are right: it might be a bit bigger than usual. But maybe not - maybe that 200m 'figher' will have some smaller drones...

Cost does weigh in, in my case though its mass/energy cost not $$$, at the end of the day a $ really is an energy value (potential work? lol).

The thing I wanted to work through is that it doesn't matter how cheap if it logically/strategically doesn't work. I didn't want to have these little pew pew fighters blowing up these 3km ships which are meant to be hard to kill by something its own size, because why then would you build the big ships?

Watched a lot of docos on tank development (interesting stuff humans do in times of need) You either have tanks that can kill the other tank, or, the shells bounce off, in which case you went to essentially zero chance of a kill before you get killed (note pre sabot rounds..). In any reasonable scenario if 3km ship can take a hit or two from another 3km ship, then even a kamikaze 15m fighter is like a bug splat on a windscreen.

Note also, these ships do not have the bridge any where near any outside surface, all deep within the hull.

 

[Rive]

it logically/strategically doesn't work.

vs.

Small ships are also handy for softer targets, 'hit and run' operations. Such attrition must divert materiel from 'Grand Fleet' operations. Like the way Ironclads found themselves vulnerable to small, nimble torpedo boats. Fast Torpedo Boat Destroyers were required to chase off such. And, yes, those Destroyers could be equipped with torpedoes, become the bane of bigger ships' stately battle-lines. So, Cruisers got the job of killing enemy Destroyers. Then Battle-Cruisers to sink those Cruisers, provide support for the big ships, learn they were too flimsy for slug-fests...

Those 3km gigants are supposed to be the big ones, but they will still need a support fleet of smaller ships. And those smaller ships will be good candidates for operations where those 3km gigants are not necessary, but that means they will also need some even smaller ships for support... And so on.

I just can't see a scenario where something really small is NOT needed at the end of the line.

 

[essenmein]

vs.Those 3km gigants are supposed to be the big ones, but they will still need a support fleet of smaller ships. And those smaller ships will be good candidates for operations where those 3km gigants are not necessary, but that means they will also need some even smaller ships for support... And so on.

I just can't see a scenario where something really small is NOT needed at the end of the line.

That would be true against another human like enemy, however that is not the case with the main protagonist. The type of enemy has to be considered. These aliens in the story are very alien that operate at a different scale, temperature, energy source (ie food), in the story they don't even make an attempt to communicate, they don't care, to them we are equivalent to what insects are to us. Our first encounter is "oh look there is a weird hot alien ship, oh what's tha..." (boom exploration ship gone). There is no boarding party, there is no capturing ships, there is no small ship. There is only survive or die against extremely hostile extremely large alien things. And if we happen to survive, they just keep pouring in ships because they now know where we are (in that instance at least).

The size of our ships is simple A10 thunderbolt math, here is the gun or guns we need to kill these things, now wrap an engine and air frame around it. Go.

In that context to me at least, fighters don't make sense.

I don't want to go to far into it, but the big ships we have are not human origin, we find alien tech from one side of an ancient war and accidentally inherit the responsibility that comes learning about that and knowing the mere existence of this alien force. For the time being the only thing keeping us from total annihilation/extinction is that they simply don't know where Earth is.

Then later in the story when us humans meet other carbon based creatures not too dissimilar from us, is when we realize that ummm, all our weapons are so large we can't even fire them near your planets atmosphere for fear of the collateral damage... One xray laser blast is created with mega tons of anti matter explosion yield as the pump source. Every time one gun barrel fires its like tzar bombas going off.

To me that's actually a annoyance I have with a lot of scifi, the energy scales of the weapons. Say you have a rail gun, but if you want to give your projectile say 10kt yeild equivalent in kinetic energy, they you need to put that 10kt in there on launch. I think that would make rail guns much larger than people think...

 

[essenmein]

Thinking about it, even without special aliens, I don't think fighter craft make sense in even in a near - medium future human context.

Absolutely for support, escort, and other ancillary tasks, but I doubt maned small craft would be much good against a equal foe on a front line space war.

Reasons:
1) weapon capacity is too small and a pilot limits evasive manouvers due to g force limits, drones would be more sensible.
2) since its unlikely something like a full startrek cloak is realistic across all EM they would be detectable.
3) small craft = small armour means CIWS type systems would render them useless, this is essentially already the case today hence all the grumbling about the F35 having lower dog fight capability due to long range weapons. No reason to think that would change in favour of the fighter in the future, if any thing it would only go more against it.
4) We can already shoot down a high speed projectiles, hence I think even missiles would have limited use, unless they are more used as recoiless high speed mass round.

Now this hinges on the following:
Actual battle ships and larger craft are in play, basically I don't think carrier style fleets make as much sense in space as they do on the ocean since once away from planets its essentially a direct fire exchange, carriers work because they can send their planes over the horizon and themselves remain out of direct fire range (ie minimal armour requirements). They would not have that luxury in space.

Since in space its direct fire combat the entire time, any small craft would just get chewed up by a wall of high speed projectiles, no dodging around geographic features. Leaving the large ships lobbing larger hunks of mass at each other.

I also don't think lasers make much sense, unless the photons themselves are high energy (eg xray/gamma), a chunky xray pulse is just a neat way of transferring the energy of a nuclear blast to a targeted point. Nukes in space are just a blink of xray/gamma, its not until that light hits some mass that bad things happen.

But I think mass drivers is the most realist space weapon, after pondering it for a while, there is no way I can think of to effectively stop v high speed mass (like 2-3% speed of light) unless you invoke the magic of shields.

 

[Rive]

not the case with the main protagonist.

No one can beat a story plot, that's sure.

But story plots better to have some touch of realities regarding resource-effectiveness.
OK, it is entirely possible even to shave with a splitting axe. There are even competitions for this, as far as I know.
But can you imagine somebody who would try to do everything with that same splitting axe?

 

[BTA]

I think there is a basic flaw in this line of thinking, the original question is wrong. Use of conventional planet based warfare and technology would not be used off planet. Our concepts of combat originate in "face to face", "within visual range" and "line of sight" situations. The way we think about attack and defense is not applicable to space combat. We are a ways from being able to imagine space combat in realistic terms, even between ourselves.

And, there are too many variables about what the situation could be. Lasers or other energy beam weapons could easily be counteracted, especially when a spaceship has to be hardy enough to be in space. What field effect shields would a spaceship have? A spaceship would have to be immune or highly resistant to micro-meteorites effectively moving at faster than light speeds, example: the meteorite is moving toward the spaceship at 3/4 the speed of light and the spaceship is moving toward the meteorite at 3/4 the speed of light for an effective 1.5 times the speed of light speed of impact.

It takes energy to project an energy beam, shooting multiple beams to cover all possible places the target could be would be a huge, ineffective and inefficient, waste. Shooting bullets or other projectiles would be much more of a waste - you had to make the projectiles and haul them around on the spaceship: you had to use more fuel and other resources to carry around projectiles. Where does your spaceship get more fuel, etc when it runs low?

And, whatever form of attack you use, that reveals your location, your intent and the extent of your offensive capabilities. Your enemy now knows where you are, that you are hostile and what you can do.

Destroy or disarm the point of origin of the spaceship. Make peace with the enemy. Hack their programs. Be seen as either too powerful or not rich enough to be worth conquering. Or, be seen as too useful or not useful enough to disrupt.

 

[essenmein]

No one can beat a story plot, that's sure.

But story plots better to have some touch of realities regarding resource-effectiveness.
OK, it is entirely possible even to shave with a splitting axe. There are even competitions for this, as far as I know.
But can you imagine somebody who would try to do everything with that same splitting axe?

Heh, that's the thing about storys, you're in control :)

Resource effectiveness is something that's important though, and after just looking at the scales of things that happen in space, and more precisely the scales of energy that occur, its my feeling that human scale, ie what we think is big, and what we think is a "WMD" I think needs a re think when talking galactic terms. Then the question is if you can manipulate much larger energy or power quantities, what could then be "realistic".

The chicxulub impactor, is a great example to compare what we call a "WMD" and what is actually a WMD. Based on those scales our biggest nuke is barely a firecracker. And that was a relatively small rock, ~15km in dia.

 

[essenmein]

I think there is a basic flaw in this line of thinking, the original question is wrong. Use of conventional planet based warfare and technology would not be used off planet. Our concepts of combat originate in "face to face", "within visual range" and "line of sight" situations. The way we think about attack and defense is not applicable to space combat. We are a ways from being able to imagine space combat in realistic terms, even between ourselves.

And, there are too many variables about what the situation could be. Lasers or other energy beam weapons could easily be counteracted, especially when a spaceship has to be hardy enough to be in space. What field effect shields would a spaceship have? A spaceship would have to be immune or highly resistant to micro-meteorites effectively moving at faster than light speeds, example: the meteorite is moving toward the spaceship at 3/4 the speed of light and the spaceship is moving toward the meteorite at 3/4 the speed of light for an effective 1.5 times the speed of light speed of impact.

It takes energy to project an energy beam, shooting multiple beams to cover all possible places the target could be would be a huge, ineffective and inefficient, waste. Shooting bullets or other projectiles would be much more of a waste - you had to make the projectiles and haul them around on the spaceship: you had to use more fuel and other resources to carry around projectiles. Where does your spaceship get more fuel, etc when it runs low?

And, whatever form of attack you use, that reveals your location, your intent and the extent of your offensive capabilities. Your enemy now knows where you are, that you are hostile and what you can do.

Destroy or disarm the point of origin of the spaceship. Make peace with the enemy. Hack their programs. Be seen as either too powerful or not rich enough to be worth conquering. Or, be seen as too useful or not useful enough to disrupt.

First since the OP was talking about realistic scifi, relativity is real and your 1.5x light speed effective impact is not correct. However the micro meteor thing is a real problem and basically some sort of composite armour is all I can think of to stop them.

I also don't see a mechanism that we know about at the moment that would allow this "shield" thing to work, but please, if I'm wrong here let me know lol.

Then re combat since distances are extremely large in space, and hitting things from those large distances involves needing to essentially look into the future to see where you need to shoot since even light can take significant amounts of time. That makes me think that if two foes are aiming to shoot at each other and actually do anything other than create more micro meteors that will find a planet in a few 100k years or some random blinks of light for a future civilisation to wonder about, they will have to get close to each other to be effective.