Military strategy in a world of fixed opaque wormholes [closed]

Question

(This is based on the old wargame Starfire... but don't bother providing answers based on newer versions of said game.)

Spacecraft travel by inertialess drive -- that is, beyond mere reactionless drive, it conveys a speed rather than an acceleration. Many warships are capable of 0.1c. Smaller ships have a turning radius at that speed of about 1 light-second. There's a minimum practical size for this drive, so fighter/shuttle/etc-sized ships have to use a different drive, even faster but of much less endurance.

A long-ranged weapon has a range about 10 light-seconds. Rates of fire are comparable to naval warfare. At close range, a ship optimized for close-range combat can incapacitate a similar ship in one volley. Even at longer ranges, battles are decided within minutes.

Known space is connected by a natural(?) network of "warp points". Let's say they're roughly planet-sized, so it's impractical to build structures enclosing them. The critical thing is, you can't see through them or send radio through. Given that only ships with the inertialess drive field can survive passage, I can guess the warp points scramble up all unprotected matter and energy that goes through.

A typical star system has from 1 to less than 10 warp points. The reason I highly doubt they're natural is their positioning. They normally lead from one solar system to another, not into interstellar space. Multiple warp points in one system will very often be closer together than pure chance, usually light-minutes or even less apart. (There's one known warp point in the dreadfully inconvenient situation of having one end inside the photosphere of a red giant, but that location could've been convenient back when the star was on the main sequence... But I digress.)

Since the civilizations of this setting haven't invented an FTL drive on their own, I can assume they don't have FTL communications or sensors.

Now, what does warfare look like?

Things aren't going to look like WW2 on a strategic scale (contrary to what Starfire suggests). For example, convoys won't exist, because wartime trade routes simply won't pass through hostile territory. Within your own empire, you can move ships between systems unobserved by the enemy.

The only way to know what's in a system is to send a scout ship through the warp point and have it return. The problem is, in any system that's been inhabited for any time, all warp points are mapped. You can station ships or bases near any warp point leading to hostile territory and be ready to blast any scout that comes through.

So then the only way to expect to survive is to send a large fleet through without scouting, concentrating your forces to be greater at that point than the average defense you expect. So if the enemy has equally distributed their defenses among the possible attack routes, you can always expect to win. In a warp point assault, there's almost no room for tactics, as ships start at close range.

Or do they? Is it best to put your ships close to the warp point? It's the fastest way to kill any weaker attacker. Against any stronger attacker, it guarantees your whole defending force will be wiped out, as there's no chance to retreat.

And if you move a large fleet to attack at one location, your enemy can deduce you're weakened elsewhere, and it's the best time to launch an attack of their own. News can travel fast within your own empire. Something the game didn't show but that I can deduce will exist are communications relay ships that bob back and forth through warp points. With these and with speed-of-light communications between warp points that are often very close together, news can often be many systems away within minutes.

But if strategy then becomes based on moving big fleets around, most systems won't have effective warp point defense most of the time, and it again becomes possible to send smaller scouting forces...

In open space, you can't force an enemy to battle, so battles can only occur around fixed locations, IE, planets and warp points. And will even planets be important?

Tactics in space, with no cover and no meaningful terrain except those few fixed points, revolve around controlling the range. In a warp point assault, the defender controls the range. In a planetary assault, the attacker does. This suggests warp point defense is much more effective.

Is it ever worth mounting weapons on a planet? They can only defend that planet from attack. They can't prevent an enemy fleet from bypassing the planet to another warp point.

Do the longer-range weapon options have much use at all? In open space, the longer-range weapon essentially guarantees victory, but warp point assaults can start at close range.

Because fighters exist that can't transit warp points on their own, carriers exist. This is another case where warp point defense has the advantage: even without fighters of your own, you can (hopefully) destroy a carrier before it can launch fighters. So are carriers actually a worthwhile concept?

So, long-term, what are the prevalent attack and defense strategies in this world where you can never have meaningful information on where the enemy fleets are?

Answer 1

This sounds similar to another setup used by Larry Niven and Jerry Pournelle in their Co Dominium series (including "The Mote in God's Eye". While some of the details are different, many of the concepts are close enough to make this a useful analogy.

"Alderson Points" serve similar functions to the wormholes in your setting, and their positions can be identified and located well enough to treat them like choke points in traditional naval warfare. In a modern strategic setting, this could include the Straights of Hormuz, the Malacca Straights or the gaps in the "First Island Chain". This makes the defender's job much easier, since they know there are only a few limited numbers of places that must be defended.

Depending on what you expect, your resources and the local solar system, you could choose to blockade the choke point in the old fashioned way, with a fortress based on an asteroid or even nearby planet or moon. You could choose to "mine" the approaches, so enemy ships will be at risk long before they come in range of your forces. And you could create a special fleet of monitors or other warships which sacrifice the need for speed since they are simply there to slug it out with whatever comes through the wormhole. Ideally, you would have all these different forces working in concert, but a minefield and some patrolling warships to cover the minefield is about the minimum any naval force should have on hand.

The Niven/Pournelle system is also "opaque", but their solution was to send a series of massive "bombs" through the wormhole ahead of the main body to clear any potential obstructions like mines, and to provide cover for the incoming fleet. The massive energy release of megaton to gigaton weapons would temporarily blind or overload sensors, giving the incoming fleet time to manoeuvre before the defenders can localize them. Third generation warheads utilizing the energy of the device to power weapons effects could also be useful, even a kiloton bomb can accelerate pellets to 100km/sec, and using the power of nuclear explosions to drive X-ray lasers was also considered. An automated sequence of warheads passed through the wormhole and set to automatically detonate through a timer or if they are painted by radar or lasers would make the defender think twice about being close to the wormhole exit.

So naval strategy in this setting resembles naval strategy in the modern world, where control of choke points is important, and allows you to focus your resources. Relatively small forces can "bottle up" the attacker if deployed properly. In terms of offense, given there is no realistic way to know in advance where the enemy is, and to prevent them from discovering your location and focusing their power, the best possible strategy would be to concentrate your entire fleet, and then roll a set of dice or use a random number generator to choose where to go, and where to go next.

Logistically, this is a bit difficult unless you can essentially bring along a prefab naval support base and drop it off behind you, and have further bases ready to shoot through the wormholes after your fleet. Unless there is a way to "live off the land" (and with complex machinery this is unlikely) there will come a point where you will essentially run out of steam (a culminating point). Unlike conventional warfare, since you are attacking essentially at random, you may or may not have captured important territory, seized critical resources or disrupted their economy, political or command and control system at all. You have created random disruptions and cut their wormhole network at random places, making their ability to move suspect.

As a defender, since you have no idea where and when the enemy will appear, will have to base your local defenses on having a robust and widely distributed logistics infrastructure in each solar system, and being able to swarm the enemy with lots of cheap, low value platforms. Planets, asteroids, moons and even the cometary halo all need to be seeded with shelters, stockpiles of fuel and weapons, and even enough manufacturing capability to rapidly make up losses. The enemy fleet will either be constantly harassed, try to play "whack a mole", or gradually disperse to reduce and occupy every node where opposition is coming from. The defender is essentially a fleet of corvettes or torpedo boats once you break past the forces defending the mouth of the wormhole. Long range missiles and beam weapons also help make the job of the occupier more difficult and dangerous.

So in the end, the Grand Strategy is to emphasis logistics. Building swarms of ships to defend each system, building specialized forces to cover each wormhole, and eventually building a capital fleet capable of blasting through the wormhole bottleneck and then dealing with enemy swarms.

Answer 2

To extend Thucydides' excellent answer, a lot also depends on how sparsely or densely connected (ie how close to a clique) the graph of wormhole connections is, and whether it forms any sort of natural 'regions'. Sections of the graph which are densely connected within themselves but which have few connections to the rest of the graph form natural defensive positions, and the external connections natural choke points. Everything suggested for the defence of the wormhole gateways in general would apply doubly to wormholes of particular strategic importance, as protecting a small set of 'gateways' allows you to be more relaxed about protecting a broader territory behind. Areas of the graph where there are dense and tangled interconnections are more likely to be no-man's lands with the running offensive battles described.

A lot also depends on how thoroughly the network is mapped, and whether there is any prospect of 'secret routes' to be discovered. It sounds like the connections you're describing don't move or reroute of their own accord, but if they are hidden and can only really be found accidentally (and the civilisation is still in the early/mid stages of the discovery process) then the knowledge of new routes would be valuable information that would be jealously guarded; and the discovery of a new strategically-valuable connection could be a disastrous reversal of fortune for a belligerent (and hence an exciting plot point, although easily degenerating to a deus ex machina if not carefully arrived at!).

Answer 3

Stealth/detection, concentration of force and contact points

Most of this comes from the books set in this universe, in particular In Death Ground and the second part of the same story The Shiva Option. Minimal spoilers and I am deliberately using generic terms to describe weapon types.

Broad strategy first - warp points are critical gateways, but planets are the key industrial and population centres. While it is possible to defend a planet, it is much easier to defend a warp point. If there are concerns about enemy forces slipping through an undiscovered warp point to attack a planet then the planet should have fighter bases - the planet can easily support vast numbers of fighters compared to a carrier and a squadron of fighters is much cheaper and can be more quickly replaced than a ship with equivalent firepower.

Stealth/detection - The enemy cannot shoot what they cannot see. Exploration flotillas should operate in stealth mode at all times. Sentinel ships monitoring unexplored warp points should also operate in stealth mode and be prepared to send tightbeam messages to other forces in their system if they detect any unexpected guests exiting a warp point. If available (which they are by the latter part of In Death Ground), stealth warp-capable drone flights should be used to conduct the first scan on the other side of a warp point as they are expendable and have a smaller signature. If one side can gain a marked advantage in both stealth and the ability to detect enemy ships operating in stealth mode then they have vastly improved options.

Concentration of force - Warp point battles are normally set piece affairs. The defenders know exactly where the enemy will be coming from, but will not know exactly when or in what strength. (Although the ability to send stealth warp drones through for a look may give some warning.) The key to defence, therefore, is to have a highly sustainable set of fixed defences (autonomous or remote controlled weapon platforms anchored by heavily armoured battlestations) with set plans ready to be implemented the instant any hostile force makes warp transit. Large numbers of fighters on the forts further back from the warp point gives a high firepower return for low cost, although the fighters will need to be far enough back that they have warning to launch before their base station is attacked.

On the flipside, the attackers need to go with everything they have as quickly as possible. (Note that in the books there is a risk of interpenetration and mutual destruction if ships try to transit a warp point simultaneously, although the OP does not mention this.) Ideally lead off with a mass of warp-capable robotic missile pods which make transit and immediately destroy themselves launching missiles at the defences. Follow with as many heavy ships as possible as quickly as possible and clear a lane out of the defences into open space.

However, the defender has an advantage in warp point defence because the weapons platforms and battlestations are nothing but armour and weapons (having been towed into place), compared to the attackers that must have engines to get to the battle. The defenders are also in a sphere around the warp point, meaning that the attackers will be taking fire from all directions while the defenders can concentrate their armour and shields towards the warp point. All else being equal, the attackers need a significant advantage in numbers or technology to succeed in a warp point assault. Which leads to...

Contact points - An invasion into defended territory will be a meat grinder in which the attacker will always be losing more resources than the defender in each successive warp point assault. Further, as the attacker advances their lines of supply will grow longer while the defender's supply line will get shorter. The smarter way to win is to quickly but stealthily explore and find another point of contact without revealing this to the enemy - hence the emphasis on stealth. The side that can sneakily find an undiscovered warp point leading into the heart of the enemy's industrial systems has the opportunity to open a new front with a decisive strike that will eliminate the enemy's industrial capacity. Note that in the books there are some "closed" warp points that are readily detected by survey ships on one "side" but effectively impossible to detect from the other "side" unless their location is known (by arriving from the open side or observing another ship transit from the "closed" side).

Answer 4

TL;DR

The distance and speeds you describe would create a situation in which direct fire against other naval vessels is limited to ~50 milli light-seconds (mls).

However, fog of war would only extend to 1 to 3 mls.

This would create a situation where attacker and defender both need to risk parts of their fleet getting very close to one another, so that they can call indirect fire from their peers.

Limitations to Direct-Fire Engagement Due to Near-Light Ship Speeds

You have a unique situation where both attacker and defender are able to maneuver and proactively evade fire at a good percentage of the detection velocity.

If the evasion is truly random, it's impossible to know where the enemy is without sending a sheet of photons to query, bouncing off the enemy hull and returning back to you. The return time for those photons is roughly the distance between you both, in light seconds.

Your knowledge of the enemy position and velocity will always be at least that old (1 second per light-second range). In that time, the enemy vessel pilot (or autopilot) has applied one or more a truly random changes in it's acceleration vector.

The deterministic part of what your targeting computer can rely on for a fire solution is like the center part of a Venn diagram showing all of the possible new positions the enemy ship could take.

The equation for this shape is the greater of $s = v t$ or $s = {1 \over 2} a t^2$

For your large ships, you've stated that they have a turning radius of 1 light-second at 0.1c. Using centripedal acceleration $a = {v^2 \over r}$ , plugging in $0.1c$ for $v$ and $c$ for $r$, we get ${0.01c^2 \over c} = a$ or $a = 0.01c$

Now knowing that, how long does it take before the position and velocity data returned by a ping is useless for a direct-fire solution?

$t = max \{ {{\sqrt{{2 s} \over {a}}}, {s \over v }} \}$; where $s$ is the hull profile radius.

Choosing s = 1 meter :

$t = max \{ {{\sqrt{2 \over 0.01c}}, {1 \over 0.1c }} \}$; $\rightarrow$ $max \{ {{\sqrt{1 \over 0.005c}}, {1 \over 0.1c }} \}$ $\rightarrow$ $max \{ 0.002, 3 \times 10^{-8} \}$

This creates a practical limit on direct fire. Direct fire engagement is limited to 2 milli light-seconds per meter of width on the enemy's hull profile.

But, actually, it's even lower than that. The direct fire weapon must reach travel to the target at $c$, cutting the solution time in half: 0.5 millilightsecond per meter of enemy hull profile.

For scale, Earth's diamater (and your wormholes, by extension) is 40 millilightseconds (mls). Unfortunately, range scales as a square root. Ships 100 meters thick would have an engagement range of (8 mls) roughly ${1 \over 5}^{th}$ the diameter of the wormhole or planet they are fighting for.

What about performance envelopes?

A firing computer could fire without a direct fire solution, just putting shots into the envelope of where the enemy might be in the hopes of hitting something.

Such flack fire creates a long-range hazard to any friendly units further downrange. But, if the enemy navy is the only thing directly above, might be appropriate.

Also, very intelligent algorithms may be able to identify a pattern in an enemy navy's evasion, essentially out-smarting the enemy autopilot and providing more distant direct fire solutions. And you could engage with self-guided weapons at even greater distances.

Stationary Targets

Any target whose velocity is predictable (defense satellites in orbit) could be engaged at the maximum range of your weapons.

Indirect Fire

If a spotter establishes range and motion for a target, how long is that information good for?

The data remains good until stale, regardless of who possesses it. So, the enemy position can be communicated to colleagues. Provided the total range from target $\rightarrow$ to spotter $\rightarrow$ to firer $\rightarrow$ back to target is less than the stale time.

Limitations to Fog of War (Active Scan) Because of Scale

Space, even a few light-seconds of space, is very big. If you are actively tracking a target than can move 0.1c, you'll need a search area at least 0.1c $\times$ the engagement distance. The area of that search cone is $\pi (0.1cr)^2$ or$2 \times 10^{15} m^2$. The signal return in omni-directional, which creates $1 \times 10^{18} m^2$ dilution of your signal.

And this doesn't include modern detection evasion technologies like Vantablack, that would absorb 99.965% of the incoming radar or lidar beam. Or noise generators. Or the noise of a moving receiver.

It isn't until engagement ranges get below 1 milli-lightsecond that a 1 megawatt active scanner for a ship-size target starts to return intensities above thermal noise (if I'm doing this math correctly). You could add transmitter power, but at 1 megawatt, your almost radiating enough energy to be considered an omnidirectional attack.

Passive Detection

The enemy (and you) are both radiating some sort of gravitational waves to create these inertialess drives, probably. Gravitational waves also travel at the speed of light. Detectors exist to pick up these waves.

The engine performance for your navies hasn't been specified, but let's say it requires 1 kg of mass-energy per second to move one vessel at top speed. Three tons of fuel (as much as a 747) would provide about one hour's worth of service between re-fuelings.

That same energy signature would be 10 petawatts of power, and a spaceship size emitter should be detectable up to a light-second away.

A navy at rest this way is almost indetectible. Decoys generating ship noise could be employed to cover movement, giving the enemy only a general idea of the fleet's new position (if they are detected at all).

Facing

If the enemy navy can turn inertialessly, they will in all long-range engagements have the opportunity to present their most heavily armoured + slimmest profile side to incoming fire.

This will increase the importance of enfilade positioning. Enfilade partially surrounds the enemy, forcing the exposure of vulnerable side to one of your fire groups.

Defilade Positions

For tanks, a defilade position is one taken hiding your vehicle behind an shot-proof obstacle (such as a hill or mountain ridge).

In space, it's possible to take hills with you, by strapping engines on rocks. It seems like it would be a basic tactic of any navy to "dig in" by building a 2D (wall) or 3D (sphere) screen around your force, to avoid exposure to fire.

A larger rock takes a tremendous amount of energy to evaporate, and recent studies have indicated they are more durable to physical shocks than previously thought, meaning they won't turn to dust with a simple missile strike.

A ship behind such a shield could pop-out of cover merely long enough to fire a shot at a target that's been communicated by an indirect-fire spotter. After firing, the ship returns to cover.

Planetary Engagement

A defending or attacking navy can use the planet's horizon as cover for landing vessels sent to the surface, provided ground defense has been neutralized and the enemy's navy is kept over the horizon.

Other large, almost indestructible objects (wormholes) could similarly be used for cover.

Because orbital and ground defense assets have predictable locations, these targets can be engaged at the full effective range of your navy's weapons (10 light seconds).

Unless the planet is tidally locked, ground targets will rotate into view within one local day. Much of a defender's supply lines and reason for fighting is exposed if a defender attempts to "dig in".

Clearing

When a navy wishes to engage a defended wormhole, there are a few options for clearing :

Nuke clearing. Send a remote craft emitting a cloud of fusion, fission, or antimatter warheads. The warheads will be hard to distinguish from the debris of the swiftly-destroyed carrier vehicle (the carrier can self-detonate if not engaged). The screen will kill or stun any defenses in immediate proximity.

Shield screen. Next, send fleets of small remote craft that can put up umbrella utility fogs, shielding the vessels behind them.

Fire ships. Finally, multiple fire ships should enter behind the shield screen to engage all targets, starting with the closest.

Fleet. Behind the fire ships would come the primary fleet. It's composition depends on your technology :

• If small craft are effective against super-hard targets, this is a carrier.
• If small craft are ineffective, this a battleship. The battleship should begin engaging it's peers in the enemy fleet.
• One or more stealth ships (submarines) should attempt to sneak through with the fleet. These are vessels equipped with the best-available anti-detection technology, running as quietly as possible, and firing guided weapons that probably drift sometime before becoming active, so as not to betray the firing ship's position.
• One or more point-defense ships for detecting and engaging small craft on behalf of the fleet.
• One or more beyond line-of-sight ships specializing in detecting and engaging orbital and ground threats.
• One or more anti-stealth ships, that can detect and eliminate defenders attempting to engage the fleet from the dark, and
• Additional fire ships and multi-purpose ships.

The fleet will attempt to secure everything within it's engagement range. Small craft and guided weapons will be employed to increase security past effective line-of-sight.

Digging In

If the invading fleet is planning to stay, the next thing to do is to bring a large rock as a forward base. Possibly surrounded with other large rocks as a defensive screen.

This is a place for small-craft to launch and return. It's also a sheltered port from beyond line-of-sight fire where ships in the fleet can repair, refuel, and resupply.

One or more small craft will need to secure the path where fuel, parts, and personnel will be brought out to re-supply the fleet.

Disengagement

The fleet can disengage by moving into interplanetary space. Space is big. Even a few light-minutes of distance from any object of significance is far enough away to hide a fleet, as small as it is against the big sky.