Sci-fi Military Tactics and Strategy

For missiles and kinetics at hundreds of thousands of km you would need to have them being absurdly fast for them to reach the target in anything approaching a reasonable time frame.

We actually discussed this somewhere. For example a projectile going at a blistering 50 km/s to cross 50k km it would take 16 minutes. At a 100k km it would take it over 30 minutes.

If you can screen a weapon that arrives at its target in a fraction of a second you won't have any trouble screening missiles or kinetic projectiles fired from the same ranges. At those kinds of ranges kinetic projectiles and missiles are not practical because of rather long travel times. Even crossing 10k km at 50km/s is still measured in minutes.

And all of that is assumming a constant velocity no slowing or maneuvering actions for missiles.

And why would be travel time of minutes be too long ? Assuming you can wreck a spaceship with one good hit (no amount of armor will help you against a kinetic worth 250 times its mass in TNT), you need to strike as early as possible, meaning from as far away as you can. If you try to get in close you'll be exposed to enemy fire all the way.

The longer the travel time, the more options you have to survive. It's called the Evasion/Intercept Window. If it is excessively large such as 30 minutes, you are for all intents and purposes out of range. No enemy will just sit there for 30 minutes and let his own demise come. It will get shot down, dodged, blocked by ECM, basically there are a thousand all equally valid and all equally attempted options.

Dodged ? It's a missile. As long as you don't out-accelerate it, it can hit you. Shot down or otherwise disabled ? That's where the screening ships come into play, as well as the tactics to get past them.

edited 16th Jul '15 4:56:34 PM by Aetol

Missiles have a finite amount of fuel for maneuvering. Long range and/or high velocity stuff typically doesn't have a lot of delta-v for course corrections.

Plus if the missile is disabled or destroyed in space, it can no longer correct course allowing you to dodge it effortlessly with sufficient range.

Assuming you can destroy it early enough. Otherwise you won't have time to dodge the debris cloud.

Anyway, it's Tuefel Hunden IV who said it would be hundreds of thousands of kilometers. My post said hundreds or thousands of kilometers.

Let's take a missile accelerating at 10 g, fired from 1,000 km away. It will cover that distance in about 140 s, with a final velocity of 14 km/s (22 Ricks). If you intercept it 100 km from your position, its velocity will be 13.5 km/s and you will have about 7.5 s to get out of the way. Whether it's more than enough or way to short to dodge depends on the capabilities of your spaceship, obviously. If you intercept it 20 km from your position (in the case of a screening ship defending itself, for example), then your dodge time will be 1.4 s. Successfully dodging would be unlikely.

And that's where the Evasion/Intercept Window comes in. If sufficiently large, no amount of delta-v will be sufficient to make the shot.

Which is the main reason that completely sucks the wind out of the sails of folks like Atomic Rocket. If your EIW is measured in tens of minutes or more you are for all intents and purposes out of range and need to get closer. Unless you have the space magic to conjure up RKV's moving at significant or greater fractions of c the chances of an effective space engagement being more than 1000-5000 km apart is pretty slim.

And that's not even factoring in things like weapon reliability (malfunctions, etc.), the CEP dispersion and simple detection. (Your enemy could be the brightest object in space on every spectrum but if you aren't looking his way either through sensors or otherwise, he might as well be invisible.)

edited 16th Jul '15 6:01:43 PM by MajorTom

I dont agree. A missile is just a small spaceship, and theoretically could have the same capabilities or better than the target. Yes, the longer the timeframe the more time that target has to do something. But that is no guarantee that there is anything they can do. Whether or not the target can evade the munition will depend on the delta-v each have, which comes down to the thrust per weight ratio and the size of the fuel tank. You could in theory detect the missile a million kilometers away and be doomed from the get go.

As for interception, it would depend on how heavily armed the target is, how many munitions are pursuing it, and how difficult it is to destroy the munition. Firing a munition at the munition may or may not hit it, and if it hits may or may not destroy it. Lasers may not have these problems to the same degree (which is why I like them so much as point defense) but consider detection range. The "no stealth in space" arguments generally (which are correct overall) usually assume manned spaceships. Life support systems are very hot. A cruising munition which is not manuvering may not radiate enough to be detectable at the moment of launch, and may or may not be detectable until it approaches relatively closely (it depends on whether the target knows what evasive manuvers to engage in).

So firing a missile from hundreds of K's away isnt necessarily completely out of the question. It may or may not make sense depending upon the specific tactical circumstances.

edited 16th Jul '15 7:40:59 PM by DeMarquis

There are lots of reasons to not use a kinetic projectile for such extreme ranges. Yes that is extreme ranges.

The 1st reason is the fact the further from the point of firing the less accurate any dumb projectile is. There are numerous factors that can affect the accuracy of any given shots point of aim even in vaccuum. Things like wear and tear, small manufacturing errors, maintenance flubs, etc. plus anything the other guy is doing to affect your ability to target them add up pretty quickly. The further out you shoot the more pronounced the effect of the assorted factors. That is also assuming you are shooting at an obliging and unmoving target.

The 2nd reason is dumb projectiles have a predictable course. They won't deviate from that trajectory. They can be tracked and their path plotted making evasion and interception easier. The longer they travel the more time there is for detection and counters.

The 3rd reason in order to even get the individual projectiles up to a speed where they are not moving at a painfully slow velocity you have to expend a lot of energy. You are very unlikely to be shooting absolutely tiny projectiles especially if you are talking about purpose built warship.

The 4th point kind of ties in to the above. You can't use too small a projectile otherwise your just wasting time and energy on something that has to possibly handle being struck by small high velocity impacts on a regular basis. You need a projectile with enough mass to overcome not only basic protection needed for a ship to travel across vast distances of space but any additional protection purpose built ships of war may be equipped with.

So in short dumbfire projectiles at those kinds of ranges will have large points of deviation, give the other guy lots of time to counter in one of a few different ways, and require a fair bit of energy to launch a projectile with enough mass and velocity to be actually useful.

Dumbfire projectiles are simply not a practical weapon at that kind of range. For the amount of energy you need to make the travel time not an issue you could make high energy weapons that do the same job faster and likely with more accuracy.

Missiles are a better choice as they at least address most of the accuracy and deviation issues but they still have to contend with travel time concerns.

Just a few techs to work with.

- Kinetic torpedo

Meant to defeat point defenses, it's a solid cone of tungsten with a powerful rocket with guidance systems hanging out on booms mounted on the sides. Very powerful but needs some distance to build up speed. Also, doesn't maneuver very well.

- Very Large Dispersed Array

Basically a Very Dangerous Array with more sensors and less explosives(Actually, I just didn't want to run into copyright issues with Usually packed in broadside bays for rapid deployment, VLDA uses hundreds of drones spread out to kilometer scale distances to obtain incredible sensor resolution. Even zero-emission objects can be found by finding obscured stars. The drones aren't very agile but they can interpose themselves between a missile and a ship.

- Microwave point defense lasers

Rather than messing with ultraviolet waves and trying to melt the missile, microwave lasers attempt to short them out. The effects of a microwave are similar to that of an EMP and are far easier to create. Dispersion is considered useful as it increases the chances of a hit at long range.

- Stealth Railgun Rounds

A conical shot coated in radar absorbing material is encased in a cooling sabot. Cooled by compressed gas and blotted out by ECM, most ships don't realize they've been fired on until they analyze the firer's trajectory and notice the recoil. By the time the difference is enough to detect it's often too late. Due to the hazards to navigation, these rounds need to be fired at over 70 Km/s to ensure that they leave solar orbit.

edited 16th Jul '15 7:45:54 PM by Belisaurius

@Tuefel: All of that is probably correct, but it's really impossible to put a number on it. Is 1000 kilometers too far? 10000? 100000? It depends on the technology being used.

edited 16th Jul '15 7:43:25 PM by DeMarquis

^ If you're talking realistic technologies, anything pushing 100 km/s is probably too far beyond real world feasibility.^Note For example the New Horizons probe presently just past Pluto is at roughly 16 km/s. (I mean yeah we have today the capability to accelerate hydrogen atoms to within .999c but that doesn't translate into the "Newton speech" style of warfare at our technology level.)

Meaning if say 300 seconds (5 minutes) is the relative cutoff in effective range at 100 km/s that maximum range is going to be around 30,000 km. A tenth the distance between Earth and the Moon. Hardly the AU-spanning light-seconds defined style of warfare that Atomic Rocket folks cream themselves over.

Because beyond that 300 seconds mark, probably of a hit goes through the floor. But close the distance and probability of a hit from all weapons increases.

Like I said, you cant really put a number on it. Why five minutes? Why not five hours or five days? The longer the timeframe the lower the odds of a hit go down, but by how much? We really dont know. For fictional purposes it isnt too hard to create a tech level where 100000 kilometers could be justified.

It's a huge scale. For example a weapon with 1 MOA shot disperion in reality qualifies as a Sniper Rifle. One MOA is 2.9 cm of one-way dispersion from the point of aim at 100 meters.

At 1000 km, 1 MOA translates to a maximum one-way deviation of 29,000 cm or 290 m. Meaning the CEP or Circular Error Probable of a 1 MOA shot at 1000 km translates into a diameter of 580 m. For comparison a Nimitz class supercarrier in the US Navy is 332 meters in length. The CEP of a 1 MOA shot at 1000 km is bigger than a fucking aircraft carrier.

And that's unguided munitions. The slightest error or miscalculation with missiles means the difference between a hit and being a clean miss by a long shot. Meaning if that missile is off on its final approach when it runs out of delta-v by just as little as a centimeter that can translate into a clean miss if the range is measured beyond a few kilometers.

De Marquis: You start needing to use some absolutely ridiculous velocities to make those really vast distances at most a minor concern in terms of travel time alone. It is pretty easy to point out the more time you give the other guy the more time they have to do something. If they have 30 minutes to move chances are pretty good that ship won't be where it last was in 30 minutes by an appreciable degree. To counter that a missile would have to constantly adjust its course periodically to at least keep it close to being on target.

If you are talking about detecting, tracking and launching attacks that will even pass within the neighborhood of a ship at those ranges there is a good chance the other guy can see you too and a very strong possibility they will know you shot a missile at them. Like you said you just shot a space ship at them.

Missiles have another factor to consider. How you accelerate them to max velocity. Do you do it as soon as you can with only fuel for correctional maneuvers or do you save some for course correction later on and acceleration to keep target maunvering affecting accuracy to a minimum? Both have their own benefits and draw backs. The first one the missile gets to the target faster but if it just has enough fuel to do the small adjustments instead of possible larger course correction and final acceleration it isn't going to be as accurate as the other option. The other method it takes it longer to get out to the target but it has fuel to spare for course correction and final acceleration. It is more accurate and that last minute sprint adds another factor to make interception possibly more difficult.

When you start thinking of those ranges and travel times you have to consider the other guy is moving as well. Here is a very simple example. You are shooting at a target clocking in around 16km/s in it's direction of travel. You are firing at really long range even at 50km/s which is nothing to sneeze at by any means it takes your projectile 30 minutes to reach out that far. The target is not maneuvering just flying a straight line. That gives us 16km/s * 1800 seconds = 28,800 km traveled in 30 minutes. In the time from launch to target your target has moved 28K/km just over a 1/4th of total 100k/km range. That isn't even accounting for any number of variable vectors in relation to the point of firing. That can easily result in a very large deviation from original point of aim for pretty much anything short of energy weapons due to travel time alone.

Now some vectors make that shot take less time others makes it take longer it all depends on angles and vectors in relation to everything. If they are fleeing almost directly away it is likely best to just save the ammo for expendables and take pot shots with lasers or other energy weapons if you have them.

As a missiler, let me add my $0.02:

• A lot of "hit to kill" missiles use a booster to get up to speed and then have some on board maneuver control system to move around.
  • That said, there is a point where even the most robust system would miss. That's why a system will predict the intercept point and the best solution.

• Short range systems have a combo: the main rocket and maneuver control system. They are short range so they try to either hit the target or get between the target and the protected assets.

The reason lasers and railguns are being looked at: more shots and a faster reaction time. But missiles won't go away just yet.

Directed-energy weapon article on The Other Wiki.

edited 16th Jul '15 11:55:03 PM by TairaMai

All this talk of missiles running out of fuel because the ship manoeuvres is laughable really. And ship capable of going even interplanetary with a significant payload and crew will be pretty big (I can't see anything less than the shuttle making a journey, and probably significantly more), and thus pretty massy. As such it will be hard to manoeuvre, and as such, sounds rather like trying to dodge torpedoes with a ship. Sure it was done, but it wasn't something you'd want to be the house on, so realistically, active defences are going to be more likely to ward off an attack than an attempt to manoeuvre. Also, it's difficult to tell at long ranges what a ship is actually doing, so one theoretical tactic might be so send a load of unmanned missile buses in to disgorge missiles at an effective range while the manned fleet sits back and tries to swat anything aimed its way.

Actually it's the most pressing concern. A Saturn V rocket which is Moon-launch capable once up in orbit only had about 90 seconds of fuel to burn. A missile the size of an AIM-9 Sidewinder will have less than 15 seconds of delta-v in all forms. And that delta-v is everything. Launch, acceleration, maneuvers, terminal flight path, ultimate impact.

The advantage of missiles is that they can drift so the actual duration of the dV isn't an issue. Rather, it's possible for a ship to put on so much acceleration that a missile simply doesn't have the fuel to make intercept. However, this would take a very severe maneuver, akin to a 180 turn for a sailing ship. Keep in mind that while a missile may have dramatically less fuel than a ship it can pour on more acceleration.

It makes more sense to just shoot down a missile with lasers or counter missiles.

I dont have the time or the energy to fully engage the comments here. Maybe later. I'll just point out that New Horizons intercepted Pluto with amazing accuracy despite a distance of 3 billion miles and a 9 year time frame. Apparently space probes are more accurate than sniper rifles. As long as the target is following a predictable trajectory it isnt hard to plot an intercept.

@Matt II/Bel: A missile is nothing more than a small unmanned spaceship. There is no reason to assume that either the target or the munition has more delta-v. That said, I think Tuefel and Tom are exaggerating the difficulties.

edited 17th Jul '15 6:09:30 AM by DeMarquis

That last bit is somewhat important. Pluto wasn't trying to dodge.

Who said the target was? There are many scenarios to consider here. The Target ship may not detect the launch of the missile, in which case they have no reason to dodge. In a large-scale space battle, the target's tracking systems may be overwhelmed. If they detect the launch, they may not be able to plot the correct trajectory of the missile (esp if there is a planetary body nearby) and thus wont know which evasive manuvers are the correct ones. If they know what the trajectory of the missile is, they may not have the Delta-V to evade. This could be true regardless of the distance or time to arrival. They would then have to fall back on their point defense system. The missile might be traveling too fast, or there may be too many warheads, or in some other way the defense system can be overwhelmed. I'm seeing too many possibilities here to dismiss long range firing.

Pluto wasn't exactly doing anything more then swinging in an consistent orbit. It can't exactly stop, turn, or change velocity. That and Voyager wasn't exactly aimed to smash a space ship but fly by a planet at a distance.

Missiles drifting is a well and good but it comes with a big catch. That is unpowered and non-guided flight. You need to expend power to maneuver and keep pointed on target. Again at those extreme ranges just letting it drift is a less then ideal solution. A missile drifting is no different then a dumb fire projectile and everything that entails. To keep on target with a moving target and everything that might entail the missile will have to keep expending fuel through out its flight.

Well, what's bad for the goose is bad for the gander. Yes, a target can manuver, but it expends Delta-V doing that. So what do you do- dodge as soon as you detect the missile launch and have little left over when the missile gets near? Or what until the missile is getting close, but then have a lot of manuvering capability left?

If we assume that the missile can accelerate faster than a ship then you want to start dodging very early, forcing the missile to make massive course corrections and burn through it's fuel. Otherwise, course corrections would be rather minor and you're still within their engagement envelope.