# Plausible reasons for use of combat drones instead of missiles (kamikaze drones) in space combat?

Acceptance Criteria

I am looking for an explanation that allows for a reasonable purpose for both missiles and drones, but I will accept answers that try to dissuade me from either.

Adding additional armaments is permitted within this technology base within reason. Ships should not be overly armed to stay more in line with current-era warships than with hedgehogs.

Comnbat drones should be armed with similar weapons as point defence for ships.

A drone is anything remote-controlled or any autonomous object that can maneuver freely, but has lower maximum acceleration than missiles, and its primary purpose is not to impact or detonate itself.

A missile is anything that has a drive and tries to impact or detonate close to a target and does not fall under the general drone definition.

Technological Base for Scenario

Ships have access to hyperspace technology, but will require substantial cooldown before making a second jump or will need to eject the hyperspace core without taking on its excess energy ("emergency jump"). Per-jump distance is limited by position and vector calculations of the target. A certain amount of uncertainty regarding the location and vector is to be expected.

A target point in space for the jump is calculated relative to an object, with higher accuracy the closer it is to the drive. This way, the vessel will have a close enough velocity vector to the target so that it gains the necessary orbital velocity to stay there.

Combat vessels are armed with relativistic/near relativistic weaponry, especially mass drivers. They are also armed with nuclear weapons like bomb-pumped directional plasma devices and fusion bombs (in missiles).

The main defence mechanism is the barrier plane, an energy field of fixed size, either of rectangular or circular shape and little depth. Its size and strength directly correlate to the number of projectors and the distance to those projectors. The further away, the larger the area gets, but the weaker the barrier is. The more projectors in use for a single plane, the stronger it gets.

Sandwiching of planes is limited.

The loss of projectors resulting in less than three projectors per plane results in dissipation of said plane.

Obstructing the projector beams path has the same consequences as losing a projector for practical purposes with regards to the barrier plane.

Adding a projector to a plane without calibration results in plane destabilization. A non-trivial amount of time is needed to calibrate a projector group.

Each projector group can only sustain one plane at a time.

Enabling and disabling planes does take a non-trivial amount of time.

Planes are inertially locked to the ship and will move with it. They also have no mass.

Planes can reasonably withstand a hit from a relativistic mass driver or fusion device before collapsing.

Barrier planes are completely opaque to all kinds of radiation from either side of the plane.

Ships rely on observation drones to see the enemy while hiding behind their barriers or need to temporarily shift planes to be able to see through.

Ships may be equipped with lasers and high rof low velocity mass drivers as defence against drones and missiles (point defence).

Principally, the hyperspace technology could be used to transport things without a dedicated drive on the object, this could be achieved by a catapult, with the same restrictions as the drive technology. One could teleport missiles or drones to a sufficiently close location to the target that they can maneuver reasonably with regards to the position of their targets, but not close enough to deny the target a reaction (well, it is possible, just very unlikely).

Assume that PDs, external C3-related equipment, sensors and ECM, and heat-management components are at least in some regards exposed, i.e. not under armor. (I mean, how do you armor an antenna anyways?) With this, also regard the heat problem as solved as long as there are enough functional heat-management components.

Assume, for the purpose of this question, that ships will not run out of fuel by burning and maneuvering, however the inertia problem is not solved, specifically g-forces on human personnel and hardware (yes, assume that ships have a human crew).

Question Specifics

How can I justify the use of both missiles and drones within a scenario like this, assuming the drones don't actually suicide?

Note: Why am I asking this question? It seems that there is little to no reason not to only use missiles and completely dismiss non-Intel/CounterIntel drones.

You want a drone for any situation whereby multiple less powerful shots are more useful than one big bang. That said, in a space scenario where loitering is essentially "free" the line between a suicide(-ish) drone and a missile might be very blurred. Is a loitering missile with shields or anti-anti-missile munitions (which could be used in an anti-shipborne-anti-missile-projector role) really a missile or a drone? But the real question is, why would you have people in frontline warships when you have drones?

I think you misunderstand. I defined "Missile" as any self-propelled object whose primary objective is to detonate itself, the distinction to a "drone" is purely meant as a meta distinction to have a different word, to have a clear distinction between something that is clearly a one-use weapon and something that at least has a potential to be reused.

It's not necessary to have an all-purpose drone, I just want some justification of why there would be a need to have drones with point-defense like armament.

The role of humans in frontline warships is to make decisions, since there is no "near-almighty" AI and no realtime FTL communication. Drones have no FTL themselves, and the accuracy of catapult gates decreases with distance. Also, for story purposes it's nicer to have humans.

• Very important: Do the drones have FTL communications? Do the ships have FTL sensors? – RBarryYoung Jul 4 '17 at 18:34
• @RBarryYoung yes and no. You can detect active hyperdrives or catapults with Ftl speeds within roughly a solar system as long as you have such a drive-system or derivative, and you could use catapult gates for maybe a couple of seconds, but other than that technology no FTL – Doomed Mind Jul 4 '17 at 18:50
• No, you also get electronic warfare and reconnaissance missiles, e.g. en.wikipedia.org/wiki/… and en.wikipedia.org/wiki/Skylark_(rocket) . A drone has wings (either fixed or rotating), so none of your space hardware are drones. – Pete Kirkham Jul 5 '17 at 11:14
• @PeteKirkham I have defined what I consider a drone in the Acceptance criteria. Per definition, HPMAMs are drones in this context if they are remote-controlled or automous operating. I don't care what the current definition of anyones military is, as the definition wouldn't have any value when the majority of battles happen in space. – Doomed Mind Jul 5 '17 at 11:27
• You want a drone for any situation whereby multiple less powerful shots are more useful than one big bang. That said, in a space scenario where loitering is essentially "free" the line between a suicide(-ish) drone and a missile might be very blurred. Is a loitering missile with shields or anti-anti-missile munitions (which could be used in an anti-shipborne-anti-missile-projector role) really a missile or a drone? But the real question is, why would you have people in frontline warships when you have drones? – Grimm The Opiner Jul 5 '17 at 14:36

You have one reason for drones: from OP /Ships rely on observation drones/ But those fall under non-Intel / CounterIntel drones.

To want drones you need them to do something a missile cannot do. The destiny of a missile is to blow up. The destiny of a drone is / not to impact or detonate themselves./

I can think of three types of offense against a ship: destroy, disable, capture. The missile can do #1 and possibly might wind up doing #2. It cannot help with #3.

Therefore your drones can help with offensive objective #3: capture the ship It might wind up disabling the ship also as part of that objective.

Consider what a huge resource and valuable prize an operating ship is. You would have to be exceedingly rich or without other options to destroy it as a first choice. Back in the days of sailing ships, defeated ships were routinely captured with flags switched over. Your drones could facilitate this - by bringing in ship-disabling tech (engine killers?) that must operate in close proximity or (for high drama!) attaching to the ship and allowing entry of boarding parties.

Consider also defensive use of drones. A flying missile is not that great defensively except in that a good offense is the best defense. A drone will not mind floating in space for a few days or months or years, waiting to see what comes, reporting in and then attacking it - maybe with missiles. Mines are good defense but drones would be great defense. One of my favorite parts of Aliens is when they watch their sentry gun drones fight off the alien incursion = https://www.youtube.com/watch?v=HQDy-5IQvuU.

• It seems the core of capture is 1) disable hyperdrive 2) zap the field projectors. At that point, the opponent is a sitting duck. And the projects are conveniently unarmored, so anything fast enough to maneuver around the field can take them out with even minimal weapons. – Erik Jul 5 '17 at 10:35
• @Erik Well, the projectors aren't unprotected, just unarmored, they may be behind protective bulges from some sides. I meant to say that the components itself aren't armored, as it would inhibit their use. But essentially, you're right, if you're close , even between the barrier and the hull, you could destroy those components with comparatively low powered weaponry. – Doomed Mind Jul 5 '17 at 11:40

## Missiles: Very good at destruction... once...

Missiles, even the smart ones just charge towards a target and goes boom. Very nice and well as long as you don't mind enemies dying and the thing you're intending to go boom be far beyond salvage. A missile does this extremely well... once...

## Drones: Quite good at quite a bit of things... multiple times...

A drone however, can be used with greater precision, eliminating vital parts of the ship to ensure safety of own vessel and then simply keep the enemy crow hostage. You're in space, every resource is very far away. As an additional danger, there is debris; Where shrapnel on earth only goes so far, in space where it's in 0g with hardly any aerial resistance it gets really tricky really quickly with any extended battle involving missiles.

So, missiles for destruction, drones for precision. They can be used in combination with one another for greater tactical purposes and threats.

To build slightly on Hyfnae's answer: "professionals talk logistics". If you can recover and refuel the drones after the fight, you can have another one; once the missiles are fired, they're gone. (This would work better if you were using energy weapons rather than ammunition-consuming ones, but the chance of a drone using all its ammunition and reaction mass seem fairly small.) This is even more true of observation drones: those need to carry worthwhile sensors, which are going to be big and expensive.

You can teleport missiles into place for a close strike, so that rules out the obvious missile-carrying drone.

• Lasers are permitted for combat drones, as they are considered PD by larger ships. I'm not quite convinced by the reusability, as the drones themselves will be targeted by the defending vessels point defense – Doomed Mind Jul 4 '17 at 18:22
• Drones will become priority targets. If you don't destroy them, they will return to attack again. Ship crews can become emotional about them. Drone operators will become attached to a drone that survives many missions. Crews under attack will hate them with the rage of a thousand suns, and they will start recognizing them by sight. Specially if drones are successful on killing their friends or on making their life difficult. Drone designers will get sad when their "babies" fail to perform well. Plenty of opportunities for character development. – Enric Naval Jul 5 '17 at 6:29

Consider a current military (and sometimes police) strategy: Covering fire.

When you engage in covering fire you do not expect to hit your target. Rather, your objective is to make the target avoid your fire, thus preventing him from firing on a friendly.

Lets apply this to your battles. You have drones whose job it is to pelt the ship with kinetic fire. There is no expectation that you will actually hit the ship, the objective is to keep the shields oriented to block it. Send several drones against the ship and it's got a big headache blocking and squirming away from your fire.

When the ship is struggling against this attack you send in the missiles. The ship can't squirm away from them (they can match it's movements, there's no lag like there is with the kinetic fire from the drones that is ballistic) and they can figure out how to attack from any unshielded direction.

Your "drones" can create a VDA.

The only reasons to not load a warhead into your drones would be cost*, or civilian applications.

*cost or maneuverability (which is a again cost of a drive), or size (which is again cost of the parent vessel)

• That is, more or less, the reason I ask this question. – Doomed Mind Jul 5 '17 at 9:44

Because drones beat missiles

One way this can work is if drones were reasonably effective at intercepting missiles. While ships can mount PD themselves, individual ships can become overwhelmed by large numbers of missiles, especially since only those PD guns in a certain specific arc can fire on missiles approaching from that direction. Drones meanwhile can easily re-orient themselves to protect ships from missile attacks from any direction, can position themselves in the direction of possible missile fire to offer ships the longest time to react, and if you have enough, can even crowd around enemy ships shooting down their missiles the moment they are launched.

Drones would be more cost-effective in this role than missiles, because each drone can potentially take out many missiles, and being more versatile they can knock out even the opponents' own drones. And PD weaponry would likely be better at sweeping space of small targets than direct collision. One other thing is that there is no problem with multiple drones targetting the same missile with PD, whereas an anti-missile missile would have to spend vital miliseconds communicating with its peers to make sure the entire formation is not dragged out of position by a single decoy.

In this situation it would be reasonable to use a mix of drones and missiles. Once your drones eliminate those of the enemy (and maybe can help damage enemy ship-PD), then anti-ship missiles can be launched to do the real damage. You don't kamikaze your drones because as long as your drones are present you've locked down their missile weaponry.

I'll try to keep this short (it won't work)

Warfare in space should be a bit more dynamic than just shooting at the enemy with stuff. Remember for example the often quoted Sun Tzu:

All warfare is based on deception.

You know whats scary? 10 Fusion rockets coming for you.
But it is scarier if the missiles are equipped with a (short-lived) plane projector - because you have no way of knowing whats under it. The missile has to steer with data from a spy drone of course, but that shouldn't be a problem.

Now lets up it a bit: Send 10 big missiles and 50 cheap and fast drones equipped with projectors. The enemy has no way to know which thing he CAN'T see is the biggest threat.

And the next step. Those small drones? If the attack makes your planes flicker enough (or if matter can pass through it somehow) those are now sitting on your ship - too close for your point defense. And some of them have some kind of welding beam. Usually useless for combat since its range is a metre or so, but cuts through armor and is very energy efficient. They weld gun barrels shut, destroy your plane projectors, disable heat sinks, cut antennas...
maybe the missiles were less dangerous after all.

But wait! There is more! Remember I said "some" of them had welding beams. Some others carry tools to connect to your the ships intranet, others might carry a small container with neurotoxins. As soon as the welders found some cables and laid them bare (lets say under an antenna) the ship is suddenly victim of a hacker attack. NOT funny if that hacker could for example deactivate lifesupport or amplify gravity by a factor of 10.
And while the ships techies try to deal with that the third kind of drone tries to infiltrate the air circulation system and poison everybody on board.

Missiles explode and are gone. Sometimes thats the only thing you want.
Drones can be so much scarier. Because I got propably a dozen more nasty ideas what drones might do in space.

• "I'll answer under the assumption that missiles are neither "smart" nor remotely controlled, because if so they are basically just drones that blow themselves up." ...but OP literally called missiles "kamikaze drones"... your assumption contradicts the question title ^^U – xDaizu Jul 5 '17 at 8:47
• @xDaizu well, I guess the question was so long I forgot the title when i was at the end of it. Doesn't invalidate the rest of the answer, but I guess since I already earned a downvote nobodys gonna read it anyway so I'm not gonna bother to edit. – Haquim Jul 5 '17 at 9:53
• Oh, don't be like that! There's value in your answer. If you think that the sentence does not affect the answer, just remove it. A quick edit here and there may turn your answer around and bring home some upvotes! :) – xDaizu Jul 5 '17 at 10:01
• @xDaizu I guess you're right. It doesn't take a lot of time after all.. – Haquim Jul 5 '17 at 10:03
• @Haquim while I do not intent to equip neither drones nor missiles with barriers, this is a vaild answer in the context I defined. What I think is interesting is to indeed use barrier planes as a counter-intel tactic – Doomed Mind Jul 5 '17 at 15:06

I'm going to suggest something slightly different.

The reason to use drones is to create weapons which are not limited by the presence of human beings, so are capable of greater acceleration, or can dispense with the mass of shielding and life support systems, or can mount single purpose weapons with far greater power than a manned ship of comparable size. In this conception of space warfare, the manned spacecraft is a command and control centre which can be a light second behind a cloud of unmanned spacecraft which carry a multitude of sensors and weapons.

So drones could be the analogues of the USN "arsenal ship" or USAF "arsenal plane" concepts of vessels as firing platforms for other ships or airplanes (or indeed anything. A recent USMC test had an F-35B detect a drone, then cue, fire and guide a missile from a nearby warship to destroy it).

Using a cloud of drones also allows you to conduct manoeuvres which could sandwich the enemy between two or more groups of enemy ships, or allow you to split your forces and make a run for the enemy portal with a portion of your force, or otherwise confuse the enemy as to your actual intention.

The use of distinctive manned command and control ships could be considered a good thing (both sides observe a convention of not firing on manned vessels or infrastructure, limiting the collateral damage in Space Warfare), or not (both sides make frenzied attacks seeking out the manned command and control ships in order to defeat the rest of the constellation of warships).

Missiles and drones might have a lot of functional overlap, they're often both intended to destroy targets, but their approach to that can differ substantially. For example, missiles often employ high speed, some with deliberately erratic flight paths, and explosives to damage their targets. Drones can sneak in more slowly, they can tuck into blind spots, and because they're not jetting out propellant constantly they're harder to spot.

One simple way of splitting these is that missiles are used for overt destruction and drones are used for covert sabotage. Some might latch on and siphon power, cripple systems, or would chew through the hull using chemicals or high-temperature plasma beams. They can target with surgical precision. They could also carve open a hole to introduce even smaller drones into the interior of the ship.

The division between drones and missiles in your scenario is basically comparable to the division between drones (or manned aircraft) and missiles launched from a carrier in the real world, so I think that's a useful analogy to work from. So in a world where various forms of missiles have existed for decades, and manned aircraft especially have clear downsides, why do we still have planes?

Planes and drones are generally, at least in principle, reusable. So if they cost more per airframe, that may be OK. In turn that means they can carry hardware that you wouldn't want to put on a missile or suicidal drone; an expensive but powerful sensor suite, for example, which may allow for more precise targeting or the ability to defeat some sort of countermeasures. They may be better-hardened against certain types of defenses.

Planes typically carry multiple types of weapons and ordnance, giving them flexibility to use different weapons for different purposes. Maybe kinetic or energy weapons are especially effective against certain targets or parts of a hostile ship. They can also attack multiple targets, which a missile generally cannot do. Target selection may be more effective than it would be with a missile; it might reasonably be done on-the-fly (autonomously or under direction from the mothership) and therefore with more information. To achieve the same effect with missiles might require firing off a salvo and hoping they work things out (if autonomous/"fire and forget") or hoping that you can direct them effectively once they reach the target (if able to accept commands), so you may end up wasting missiles (using them unsuccessfully or firing more than you actually needed). Then you have to do battle damage assessment, decide whether to fire more, fire them, wait for them to reach the target, etc., all of which takes time.

Related to the above is the ability to loiter. A fighter aircraft can fly in patrol of an area for quite some time (and a space drone could presumably just quietly sit in place near-indefinitely), then engage a target when an opportunity presents itself. But that sort of thing is not really compatible with what people generally mean when they say "missile". Imagine not a ship rapidly jumping across space, but one orbiting a planet for a while to collect data or resources, or conduct repairs. Or imagine a space station surrounded by a fleet of sleeping drones that can jump to its defense when needed.

Drones also open up the option of attacking from multiple points around a target, which would be a desirable way to get around the barrier planes as you've described them, as well as many other defenses. For any kind of missile that obeys physics, there will be some inherent tradeoff of maneuverability for speed; so just launching them "away" from the target and having them turn back toward it may be undesirable.

It may also be harder to defend against weapons fired from drones that fly in close, as opposed to weapons fired from the mothership, due to reduced travel time. Depending on the nature of the available defenses, surrounding the target with drones and then having them all fire simultaneously may be effective in saturating its defense systems, allowing you to do some damage.

Moving beyond the analogy somewhat, there may also be size differences between missiles and (some?) drones. Maybe I have a swarm of small, lightly-armed drones that my opponent can't easily distinguish from space debris. They may need to be slow (lack of power plus preserving the illusion of being debris) and they probably can't do a lot of damage individually, but they may be able to move undetected to their target. This becomes even more useful if my opponent has one really important ship surrounded by escorts. Those escorts will block or destroy a lot of missiles fired from the mothership... but maybe the swarm of drones gets through. And even if not, maybe that means my opponent wastes time and resources firing at actual debris for fear of this tactic.

• Welcome to WorldBuilding.SE Sam! If you have a moment please take the tour and visit the help center to learn more about the site. Have fun! – Secespitus Jul 5 '17 at 8:09
• @Sam I haven't considered offensive drones as target painters/directors, nice. Due to the way barriers work this might actually very useful. I would think though that missiles could loiter, nothing is stopping them from it, they are basically just drones with a single warhead instead of a warfare array. – Doomed Mind Jul 5 '17 at 9:19

Look at David Weber's Honor Harrington series. It's heavily concerned with space combat, mostly using missiles. But most of the missiles in the series are drones by your definition -- they don't close to point-blank distance and explode, they close to stand-off distance and emit a bomb-pumped laser beam at the target. That's because close-in point defence systems are good enough to destroy missiles that close to point-blank range, but not good enough to destroy drones closing to a few million miles away.

• Interesting. Hamilton used a concept for drones he called wasp, which were mostly high-yield autonomous fusion and anti-matter missiles, which were both used as an attack vector and defense against the same by detonating and saturating a volume with hard radiation, either to burn out systems on the enemy vessel or on the enemies wasps. However, I think both would still qualify as a non-drone, as I assume that using the bomb-pumped laser will destroy the carrier vehicle, hence it's "detonating itself", violating my definition of drone. – Doomed Mind Jul 5 '17 at 13:04
• They are missiles in that they destroy themselves, and are one-use items, however. We can quibble about what 'stand off range' means in a universe where 500Gs of acceleration is normal... – Tony Ennis Jul 5 '17 at 15:25

Tl/Dr: War is too important to rely only on drones or missiles. No matter what you do, in any environment, you'll find a desire for both. This will come naturally out of the total nature of warfare.

## Cost is everything

As per your definitions, the real difference between a missile and a drone is that a missile only has to fly once. It them does something spectacular and goes to whatever deity missiles worship. So how meaningful is that difference in reality? It turns out the primary differentiator is cost.

Let's flip it around. You have a fancy drone with all sorts of advanced sensors and communications and stuff. It can use those sensors to make intelligent battle decisions at the moment they are needed. This means it can find opportunities to put itself in a position to do serious damage. Let's use current terms. A modern Predator drone costs \$4 million. A fancy F-22 stealth fighter costs \$150 million. If I got the opportunity to make a Predator go boom and take out a F-22, I'm going to take that opportunity. It's a 37.5:1 win ratio, financially.

The real reason we don't see these sorts of things is because missiles specialize in flying once. They're cheaper, for one thing. Anti-aircraft missiles are typically much cheaper than a Predator. They also tend to go faster and be more maneuverable. Why? Because they don't have to return.

Which leads us to the interesting natural pattern. You'll constantly see drones getting faster and cheaper, lending themselves to more suicidal missions. You'll constantly see missiles getting smarter. The two naturally try to converge. The only reason we draw a line between drones and missiles is we haven't hit the convergence point yet!

## Heterogeneous Opportunities

Now the reality is, we don't really use one or the other. Consider the air-to-air missile. It can't get to the target on its own. It needs a host plane to fly it hundreds of miles before getting into position to be launched. Likewise, the aircraft really can't survive on its own. It needs the lethal energy of the missiles to kill the enemy before the enemy shoots down the aircraft. The two are synergistic, not antagonistic. Consider the reality that drones like the Predator have already been armed with Hellfire missiles.

So this is where it gets interesting. If you send a "drone" up into combat with a missile strapped to it, and it comes back sans-missile, did the "drone" come back in one piece? Or did only part of the drone come back? The phrasing is strange, but the reality of war is that we are always leaving valuable stuff behind -- jet fuel, missiles fired. When you go to war, you are expending resources to overcome someone.

## Pulling it together

So what it really looks like you're doing is trying to maximize how much value comes back in one piece. We like our spacecraft to come back in one piece, after all. That's why we're launching all these drones, missiles, and drones with missiles strapped to them.

What you really want is a heterogeneous environment where all sorts of weapons are recoverable, and all sorts of ships are sacrificable, and everything in between. What you describe isn't unusual for warfare. In fact, it is the reality of warfare. Every single competitor in every single war that has ever been fought since the beginning of time has sought to minimize their sacrificed assets. Every single competitor in every single war that has ever been fought since the beginning of time was ready to sacrifice any and all assets needed to accomplish their goals in warfare. These are fundamental realities of warfare. Thus you will always find that every army in your space battle minimizes sacrificial assets by deploying combat drones with which to better place their sacrificial assets for maximum impact. It will never not be the case.

The real question will be what is the balance. Space is an unforgiving medium. The delta-V requirements need to strike out and then come back are brutal. This currently favors missile style thinking. If you want more drones, consider making your hyperspace technology friendly for re-capturing drones. Perhaps there is some concept of a "hyperspace leash" which you can use to retrieve drones launched in combat. Alternatively, make combat more about sensory input. If breaking shields calls for nuanced skill rather than brute force, having enough sensors in the sky to target the missiles to their final resting place would be essential.

On the other hand, consider that we currently rely 99% on drones in space today. The vast majority of hardware that we've flung into space has been satellites, which are really just big drones. Only a tiny bit of what we send up has been sacrificial (mostly weapons tests). Right now, I'd argue the drones are winning. If you want more missiles, create a more hostile environment which makes it harder to preserve the value of a drone. Whether you intended to blow the drone up or not, a drone that gets shot down doesn't come back... just as a drone that blew itself up doesn't come back. Conveniently enough, this is easy... just add more missiles. Nothing makes space more hostile than a bunch of devices who have no self preservation instincts and a mean temper!

The reason drones would exist? Cost and flexibility.

I could see what a handwavium-fast engine could propel a warhead to great speeds very quickly, with said engine destroying itself in the process. That's a missile.

The same missile, in a stealthy launch tube, floating in space, is a mine. The launcher detects a ship with a certain signature, roughly points the missile, programs it with targeting information, and launches it.

That's a lot of blunt-force trauma. And they are cheap. Having a similar weapons system would be a loser.

Thus the drone is more flexible. Sometimes pelting the enemy with a lot of missiles is not the best answer.

The drone has a real engine on it. It accelerates maybe not as fast as a missile, but it can maneuver, stop, start again, and return to base. It is stealthy. It could carry a hyper-light transmitter and serve as a communication mechanism between manned and unmanned ships in a battle and a command ship that's safely in the rear. Without FTL communications, even in-system decisions could be hours behind reality.

A drone could carry the best of weapons so when you absolutely must destroy a target, the drone could perform what's probably akin to an assassination. For example, another optional component for a drone is an anti-matter generator. You don't want that too close :-D When the need arises, the drone produces antimatter, puts the warhead into a missile, and shoots. This missile is probably very stealthy to increase the chance it makes it to the target.

The missile has a nice computer in it. The drone has a real AI, possibly with a biological (aka \$) component.

Of course, only best offensive and defensive ECM gear are installed.

Another optional component could be a re-supply ship. The drone navigates a sensor network and blockading warships, disables satellites where it can, and drops supplies for marines. Then it escapes, causing (possibly non-lethal) havoc in the process, using ECM, decoys, etc.

The engines, communication systems, extra components, and weaponry are too large for a missile and too expensive, making it impractical to attach these to a disposable weapon.

Where the missile's shape is probably very familiar, the drone would be more like a small space ship.

If you're writing, a drone could be an antagonist or protagonist because of its AI.

Some games (like the outstanding Letters from Whitechapel) use a hidden movement system. So a game designer could work off the theme to create a cat-and-mouse sort of game where players hunt the stealth drone, or perform an incursion.

Adding a projector to a plane without calibration results in plane destabilization. A non-trivial amount of time is needed to calibrate a projector group.

Missiles carry a single projector, which they will aim at the barrier plane in their way to destabilize it, and an explosive warhead. Possibly armored so it can penetrate the now-instabilized barrier plane.

Now, the enemy ship would absolutely LOVE to shoot down your missile before it gets to do that - to prevent this, you send out a swarm of drones pelting the ship with constant fire. The ship can now either keep the barrier planes up and be unable to locate incoming missiles, or drop the barrier planes and risk having its sensors (and heat management, and projectors...) shot to scrap by the drones. If they keep the barrier plane up, it will protect the ship until the missile destabilizes and penetrates it... also a bad ending.

So obviously, the target ship needs drones too - those drones can fly around outside the opaque barrier planes and shoot at missiles (and enemy drones) to reduce the incoming (barrier-requiring) drone fire and prevent missiles from reaching the ship itself.

Thus we have entered an arms race, where every side tries to bring out more and more better and better drones to shoot down enemy missiles (to protect the ship) and drones (to protect their own drones and allow the ship to drop barrier planes and fire the main guns and/or PD guns). Meanwhile the missiles are still out there, either flying a holding pattern until the drone war is won or racing to the enemy ship trying to get at least one or two of the hundreds of missiles through the defensive drone (and PD, if enough barrier planes can be lowered) fire.

A hit from a missile would likely decide the battle, because that'd utterly destroy the projectors and PD in the affected area, so the goal is to prevent a missile hit. Main focus of any battle would thus be the drone skirmishes.

/edit in response to OP comment on another answer:

Also, you cannot reasonably cover the whole ship, as the barriers will contain your expelled waste radiation and reduce the ships ability to function. Some radiation will be reflected from the barrier back onto the ship.

Even more reason to try to MAKE the enemy have to keep up ALL their shields. Constant drone fire from all angles means either you cook yourself, or you let some drone shots through and allow them to damage your projectors (and radiators, and sensors...) - so offensive drones are even better, and defensive ones even more important

As per your description of your shields, the use of combat drones would be preferable to missiles assuming the drone were fitted with energy weapons.

The shields serve to protect the capital ship but are also a hindrance. They block all forms of radiation which includes visible light, radio waves, microwaves etc which means the ship is blind when protected.

The ship cannot rely observation drones without leaving a hole which the drones can target. Drones would have to be AI controlled and in all likelihood all communication would be jammed. If observation drones were used, they'd be the first target.

The only real way to tell what is going on is to drop the defenses. Now this might only take a fraction of a second to do before restoring the defenses which would leave insufficient time for a missile to connect.

Drones would surround the ship and when it drops the shield for a quick peek, they would target the shield generators, point defense system, engines or any other weak points.

Now drones would be faster at firing than the ship because the drones can already be aiming before the shield comes down but the ship would have to find and target the drones each time because the drones move.

Missiles would have no role until the drones break the defenses.

• I don't see ships having barriers up constantly covering every part of the ship. The biggest threat, and the main reason of why equipping barrier planes was so useful, are relativistic mass drivers throwing chunks of metal at velocities shattering anything armor-wise you could ever reasonably fit to a spaceship. I'd guess you would focus on the most likely attack vectors and have constant connection to your eyes and ears / observation drones via laser coms (try to jam that) and to launch drones and missiles from your open sides. – Doomed Mind Jul 5 '17 at 9:29
• Also, you cannot reasonably cover the whole ship, as the barriers will contain your expelled waste radiation and reduce the ships ability to function. Some radiation will be reflected from the barrier back onto the ship. – Doomed Mind Jul 5 '17 at 9:31
• I don't see how drones could reasonably target external components on the ship if it is covered in barrier planes, the drones would need to be there before the target even raises its shields, otherwise, as the shields are opaque, they wouldn't know where to shoot other than just spraying it. – Doomed Mind Jul 5 '17 at 9:33
• The shield moves in relationship to the ship therefore the position of the shield and be used to calculate the position of the ship As for where to fire, you either need to see the ship once or know it's layout beforehand. Once you know the layout, you can calculate the correct angle. – Thorne Jul 5 '17 at 23:54
• But the ship can change the relative locations. – Mathmagician Jul 6 '17 at 6:25

There are many reasons to have both Drones and Missiles. This assumes that the drones cannot cause large structural damage. Thus, drones are multi shot weapons and missiles are ship killers.

1. Anti-missile. As Fhnuzoag said, drones are good for anti-missile applications as well as anti drone applications. From the way your shields work, point defense cannot fire through them. That means that point defense is probably on pylons and will get scraped off after the first "hit" (near misses will do for scraping). Drones allow you to use anti missile point defense at a distance. This thins the missile swarm so point defense does not get overwhelmed.

2. Anti anti-missile drones. Since you want your missiles to get to the target, lace the swarm with anti-drone drones.

3. Hull cleaners. If any drones from a missile swarm make it to the target, they try to get behind the shields and take out shield generators and other useful targets.

4. Anti-personnel. Why send a manned vehicle when you need to strafe a soft target that doesn't rate a missile.

I like some notions I've seen in the thread, specifically: drones shooting from various directions to exercise the enemy's shields; and drones protecting the missiles. Let's add in a couple more notions...

Attention

In addition to making the enemy keep shields up to protect against attacks from more than one direction, having drones flitting around being naughty does one more important thing -- it soaks up attention that the enemy could be paying to knocking down your missiles, or doing mischief to you. Any given drone could be the "secret weapon drone" with the new shipkiller weapon. Therefore all drones present a threat which has to be neutralized or at least evaluated and triaged. There's only so much attention to go around... you might be able to saturate the enemy's brainspace until he becomes distracted and vulnerable to otherwise-blockable threats.

Missile Removal

I'm assuming that missiles accelerate almost constantly on their way toward your ship. So the earlier you detect them, the easier they'll be to target. Your drones should be hanging around as close to the enemy ship as they dare, taking down enemy missiles as soon as they're launched while they're still going slow.

Strategy Evaluation

Your drones, being pre-programmed, have to encode certain assumptions about how the enemy reacts, what his point defense capabilities are, and what are good ways for you to hurt him. Your ideas about this will evolve over time, as he ... teaches you about his style. Your drones can have different versions of your Enemy Assumption package, so you can see which ones do best. They can report back via elint drones.

Targeting

Might be that drones have more computing power and better penaids than missiles. The enemy ship might be pretty good at deceiving missiles. So you can tell Drone B3395 to zip around behind the enemy vessel, and tell your missiles to target the drone. This tactic will probably be discovered either by mistake or out of desperation...