Are space fighters really impossible in realistic Sci Fi?

[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.

 

[BTA]

If you are willing to be unrealistic enough to have unlimited amounts of energy to shoot lasers at all possible places the other spaceship(s) could be... Then, why not have ESP, mind assault, destroy or interfere with the smallest but most essential parts of their technology (remotely frying the transistors in the power regulator of their engine, using telekinesis or pyrokinesis, teleportation, creation of space/time warps, creation of black holes (microscopic but precisely placed would do the job), fission/fusion of their flux capacitor or dilithium crystals, astral/ethereal projection, severing their spiritual silver cord, psychic domination, projected illusions/delusions, spells, demons, entities from other dimensions,

 

[essenmein]

Because large amounts of energy are realistic, and they are large to us but absolutely normal in space, we see them happening all over the galaxy, yet we've never seen telekinesis.

A star quake on a neutron star creates an (I think) xray pulse that would take our sun several hundred thousand years to produce an equivalent amount of energy. Energy scales in space are so obscene we're going to run out of zeros pretty quickly if we keep using the tinyest of tiny unit for energy, the joule.

 

[essenmein]

Just as a reference:
"On December 27, 2004, several satellites and telescopes from around the world detected an explosion on the surface of SGR 1806-20, a neutron star 50,000 light years away. The resulting flash of energy -- which lasted only a tenth of a second -- released more energy than the Sun emits in 150,000 years."

 

[BTA]

"Because large amounts of energy are realistic..." spaceship shoots multiple xray pulses (from their miniature artificially created neutron star power source) covering most of the locations the enemy spaceship could be by the time those pulses arrive. Enemy spaceship detects incoming xray pulses because the pulses create ripples in the spacetime continuum and those ripples affect quantum entanglements, and takes evasive action. My credibility of space combat is going through catastrophic failure event.

large amounts of energy coming from a small spaceship, no. We are still trying to figure out how mantis shrimp pack so much punch. If neutron star xray pulses were an available technology, there would be an effective countermeasure and combat itself would be obsolete. Present day technology includes smart missiles, computer viruses, EMP bombs, nuclear, chemical and biological weapons. Present day technology makes beating our chest, roaring and stamping our feet.. obsolete.

 

[essenmein]

Perhaps this is an issue of definition.

To me "realistic" means it fits within our known laws of physics. Since the laws of physics to my knowledge haven't changed in millions of years or since the beginning of our universe really, nuclear power and space flight for example have always been possible within those laws, before we even existed as a species. Its just taken us this long to figure out the how. So its not inconceivable that more engineering and knowledge wouldn't give us the how for much much larger energy sources and all the possibilities that opens up. We know how to make anti matter, and we know how to make fusion, we just haven't perfected it yet, and we haven't scaled it up yet, but its not unrealistic that we could.

The only reason I raised the neutron star as an example is simply to demonstrate that absolutely ridiculous energy levels are real things that exist naturally and that us as humans think we've done some big things when in reality we haven't done any thing big at all, our planet looks big to us, but you can fit 1.3 million of them inside our sun, and our sun is a small star as far as stars go.

Will we as a species ever get to where we can release a 100k years worth of output from our sun in fractions of a second? highly unlikely, but those energy levels themselves are not fictitious, where as telekinesis ESP etc are fictitious, so IMO its a straw man argument to say well if large energy is realistic then so must be ghosts. We've seen large energy sources, we orbit one, but there is no evidence for demons.

 

[Rive]

the scales of things

Sure. If a race has 3km big fighters, then ... well, I've read stories (still Sci-Fi) where the body of an intelligent specie was big as a planet, so those fighters are still acceptable somehow.

But no figters at all? No way.

 

[essenmein]

Sure. If a race has 3km big fighters, then ... well, I've read stories (still Sci-Fi) where the body of an intelligent specie was big as a planet, so those fighters are still acceptable somehow.

But no figters at all? No way.

Well you could call any flying thing with a weapon "fighter", in which case any space battle would be basically impossible without them. Need to define the term "fighter" better!

Although when faced with planet sized intelligence, those 3km things are likely the size torpedoes you need :D

Or is that a missile? not certain there is a functional difference between torpedo and missile in space?

 

[Rive]

Need to define the term "fighter" better!

Well, maybe we can define it as the smallest manned vehicle of any fleet?

not certain there is a functional difference between torpedo and missile in space?

With reference to space games, usually a torpedo is slower and beefier, while missiles are fast and agile

 

[hmmm27]

In a space battle, most munitions wouldn't be primarily destructive ; they'd be chaffers, decoys and EM pulse, and lots and lots of disposable sensors. Everything stealthed against reflection and cooled to MBR.

 

[Lren Zvsm]

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

For about how long? Humans would not survive for long on a planet with 10x Earth's gravity, would they?

 

[Lren Zvsm]

TL;DR at bottom
It'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.

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.

 

[Lren Zvsm]

Why not scrap the laser and projectiles and rely on self-guided missiles? Could that work, or does that scheme also have fatal flaws?

 

[Lren Zvsm]

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

But for how long could a human survive 10 g's?

 

[member 656954]

While I found Jay Allan's first "Blood on the Stars" novel, 'Duel in the Dark', compelling, the space fighters aspect became annoying (and esp. in the subsequent books as the tactics were entirely repetitive). In the series, 3km++ mainline battleships are both protected and attacked by small manned fighters, some of which are configured for "plasma torpedoes", others of which are merely designed to dog fight the opposition fighters. The concept and tactics was essentially a naval battle from WWII, with little consideration for "it being in space". Issues that arose, included:

• Capital ship point defenses being lasers. Which missed. A lot! The obvious defensive weapon, some kind of kinetic grapeshot, was entirely ignored.
• Fighters with lasers as their weapon for dog fights, aimed by humans, moving at tenths percentage light speed. You'd be lucky to hit a planet in those circumstances, let alone another fighter!
  
• The fighters were fantastically maneuverable, jinking madly, with no real consideration for momentum or even how to apply sufficient thrust in three dimensions to redirect their trajectory.
• Fuel! This totally bugged me. These little craft were zipping about for hours on end, at multi-gee accelerations - every novel had 10G and often 12G bursts - and were jigging this way and that, but only ever seemed to run out of fuel after the main crisis had passed. Besides which, what powered them anyway?
  
• Human brain superior to AI. This also bugged me...and does most novels where "humanity has something special" that overcomes terrible odds. Anyway, it didn't make sense because a fighter, piloted by a fast-thinking disposable brain, would have huge advantages in the type of 3D engagement you'd find in the depths of space.
• The plasma torpedo. Each fighter could only carry a couple (or 4, can't recall exactly, but it wasn't many) and attaching them was slow work (huh? Who designed that?!?) and made the fighter sluggish (again, who designed them). Then the fighter (bomber, really) had to get within a set distance to fire because the torpedo turned from some physical form into plasma but once it did that, it's trajectory was fixed. It seemed a silly constraint when the kinetic energy of a reasonably heavy torpedo would have done a huge amount of damage all by itself.

Finally, in Allan's universe, we have artificial gravity. So... Set your capital ship up so that it travels in a massively repulsive gravitational gradient. Then those pesky fighters and their plasma torpedoes can't hit you, even if they can catch you. (Bobby Adair's "Freedoms Fire" series has something along these lines, it's a terrific set of books!)

So, if you decide to write fighters into your novel, consider that you'll need a lot of constraints for them to make any sense at all.

 

[Vagn]

0

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.

I'm not sure the numbers here hold out. 4.5x10^-11x 1 mile is ~72 nm, which is well within the typical stroke of a piezoelectric actuator, and could even be achieved by microstepping a stepper motor. Such fine adjustments can already be performed under high radiation, UHV environments at synchrotrons.
Piezoelectric actuators can easily have sub-nm resolution, which at a distance of 10 m would correspond to a nominal angular resolution of <10^-8 degrees. Synchrotron beamline components frequently have angular resolutions of the order of 10s of nrad (~10^-6 degrees) over distances of ~100 mm, so an angular change of 1x10^-7 degrees over 10 m is not that unreasonable.

 

[GTOM]

They can have their place in Hard Sf.
In orbital combat, their range is enough, and with short range missiles, they pretty much able to take out bigger targets.
Or they might have antimatter fuel.

 

[GTOM]

0
I'm not sure the numbers here hold out. 4.5x10^-11x 1 mile is ~72 nm, which is well within the typical stroke of a piezoelectric actuator, and could even be achieved by microstepping a stepper motor. Such fine adjustments can already be performed under high radiation, UHV environments at synchrotrons.
Piezoelectric actuators can easily have sub-nm resolution, which at a distance of 10 m would correspond to a nominal angular resolution of <10^-8 degrees. Synchrotron beamline components frequently have angular resolutions of the order of 10s of nrad (~10^-6 degrees) over distances of ~100 mm, so an angular change of 1x10^-7 degrees over 10 m is not that unreasonable.

Due to heat stress on laser focusing equipment, i doubt they will be extremely accurate.

 

[BWV]

Why did fighter planes and carriers become the dominant naval weapons? Carriers provide longer range than gunned ships - but the Earth's atmosphere and curvature put limits on gun ranges not applicable to space. Also, one can imagine missiles fully replacing fighter planes and smaller, more nimble ships replacing carriers. In either case, this stems from the reality that offensive weapon capabilities trump any defensive technologies available for large vessels. Carrier-based fighters and small missile firing ships accomplish the same function - dispersing targets. So if there is some killer defensive tech - say super-powerful force fields, then large ships might just slug it out with one another like WW1 battleships. But in the absence of that, then it makes sense to disperse the ships. Maybe interstellar travel requires a huge ship, then fighters would absolutely make sense to extend force beyond the range at which the mothership would be at risk. But manned fighters would make no sense - why waste space and energy for life support and limit maneuverability to what a human could survive?

 

[GTOM]

Why did fighter planes and carriers become the dominant naval weapons? Carriers provide longer range than gunned ships - but the Earth's atmosphere and curvature put limits on gun ranges not applicable to space. Also, one can imagine missiles fully replacing fighter planes and smaller, more nimble ships replacing carriers. In either case, this stems from the reality that offensive weapon capabilities trump any defensive technologies available for large vessels. Carrier-based fighters and small missile firing ships accomplish the same function - dispersing targets. So if there is some killer defensive tech - say super-powerful force fields, then large ships might just slug it out with one another like WW1 battleships. But in the absence of that, then it makes sense to disperse the ships. Maybe interstellar travel requires a huge ship, then fighters would absolutely make sense to extend force beyond the range at which the mothership would be at risk. But manned fighters would make no sense - why waste space and energy for life support and limit maneuverability to what a human could survive?

Because in some situations, human level intelligence, decision making is needed. It is possible that no reliable wide band ftl comm, or enemy can take out, jam sats that transmits signals beyond horizont.
With some transhumanism, a human pilot could withstand bigger G forces.

 

[BWV]

Because in some situations, human level intelligence, decision making is needed. It is possible that no reliable wide band ftl comm, or enemy can take out, jam sats that transmits signals beyond horizont.
With some transhumanism, a human pilot could withstand bigger G forces.

then have one human whom can make those decisions escort the fighters in a hard-to-detect escort ship