12.7 Planetary Defence Centres

Updated: v2026.01.30

Planetary Defence Centres (PDCs) are ground-based military installations that provide fixed defensive firepower for colonies. Unlike ships, PDCs are immobile – they cannot manoeuvre or redeploy – but they compensate with significant advantages in size, cost efficiency, and staying power. A well-designed PDC network transforms a colony from a soft target into a fortress that demands serious firepower to crack.

PDCs occupy a unique niche in Aurora’s defensive ecosystem: they require no fuel, demand no maintenance, and can be built to enormous sizes unconstrained by engine or fuel requirements. Their primary limitation is that they cannot move to meet threats – the threat must come to them.

12.7.1 PDC Design

Updated: v2026.01.30

PDCs are designed using the same Ship Design window as conventional warships but with several key differences that reflect their ground-based nature.

Accessing PDC Design:

To create a PDC, open the Ship Design window and select the “PDC” designation (or set the design as a PDC-type hull). This removes engine-related requirements and applies ground-installation rules.

Components PDCs Do Not Need:

  • Engines: PDCs are stationary – no propulsion required
  • Fuel Tanks: No engines means no fuel consumption
  • Bridge: PDCs never receive movement orders
  • Jump Drives: Cannot transit jump points

Components PDCs Can Mount:

PDCs use the same component pool as ships, including:

  • Beam weapons (lasers, particle beams, plasma carronades, railguns, mesons, gauss cannons)
  • Missile launchers and magazines
  • Fire controls (beam and missile)
  • Active and passive sensors
  • Shield generators
  • CIWS installations
  • Electronic warfare systems (jammers and ECCM)
  • Power plants (reactors)
  • Engineering sections (for damage control)
  • Armor

Size Constraints:

Because PDCs do not allocate tonnage to engines, fuel, or jump drives, a far greater proportion of their hull can be devoted to weapons, sensors, shields, and armor. A 50,000-ton PDC might carry the firepower of a 100,000-ton warship since roughly half a warship’s tonnage typically goes to propulsion and fuel.

Tip: When designing PDCs, start by deciding their role (anti-ship, point defense, sensor platform, or combined) and then fill the hull with the appropriate systems. Without engine and fuel constraints, you have tremendous design freedom.

12.7.2 PDC Advantages

Updated: v2026.01.30

PDCs offer several critical advantages over orbital warships:

No Fuel Costs:

PDCs consume no fuel. They can remain on station indefinitely without logistical support, making them ideal for permanent defensive positions where fleet fuel logistics would be prohibitive.

No Maintenance Costs:

PDCs do not accumulate maintenance clock time. They never suffer random component failures from deployment fatigue, and they never need to rotate back to a shipyard for overhaul. This makes them extraordinarily cost-effective for long-term garrison duty.

Massive Size Potential:

Without engines, fuel tanks, bridges, or jump drives consuming hull space, PDCs can devote 80-90% of their tonnage to combat-relevant systems. A PDC of equivalent tonnage to a warship carries dramatically more firepower, armor, and shielding.

Ground Installation Durability:

PDCs are treated as ground installations for bombardment purposes. They benefit from fortification levels (see Section 13.3 Ground Combat), which reduce the effectiveness of orbital bombardment:

  • Each fortification level reduces the effective hit chance against ground installations
  • A fully fortified PDC at fortification level 6 is extremely difficult to destroy from orbit
  • Energy weapon bombardment against fortified PDCs has very low per-shot destruction probability

No Crew Transport Required:

PDC crews are drawn from the colony population. They do not require separate troop transports or crew quarters ships.

Construction Efficiency:

PDCs are built by construction factories (see Section 6.3 Construction) as prefabricated installations, using the same industrial base as other colony infrastructure. They can also be built in shipyards and transported to colonies as cargo.

Tip: PDCs are one of the best investments for homeworld defense. A few large PDCs can match the firepower of an entire fleet at a fraction of the long-term cost, since they never consume fuel or require maintenance rotations.

12.7.3 PDC Limitations

Updated: v2026.01.30

Despite their advantages, PDCs have fundamental weaknesses that prevent them from replacing a mobile fleet:

Immobility:

PDCs cannot move. They defend only the body they are deployed on. If the enemy bypasses your defended colony and attacks elsewhere, your PDCs contribute nothing. A mobile fleet can respond to threats anywhere; PDCs cannot.

Vulnerable to Sustained Bombardment:

While fortification makes PDCs tough, they are not invulnerable. A determined attacker with sufficient missile stocks can destroy PDCs from orbit, especially if the defender lacks an orbital fleet to contest the bombardment. The attacker can stand off at extreme range and pound the PDC with impunity if no mobile forces challenge them.

Population Requirement:

PDCs require population to crew them. A small colony with minimal population may not have sufficient colonists to staff large PDC installations alongside other industrial needs. Crew requirements scale with PDC size just as they do for ships.

Cannot Pursue:

PDCs cannot chase retreating enemies, intercept raids on other systems, or project power. They are purely defensive. A player who invests too heavily in PDCs at the expense of mobile forces surrenders strategic initiative.

Range Limitations:

PDCs can only engage targets within their weapons’ maximum range. An enemy fleet sitting beyond weapon range can blockade the colony, interdict commercial shipping, and starve the colony of resources without ever entering PDC engagement envelopes. See Section 10.2.6 Blockade and Jump Point Denial for how blockades work in practice.

Warning: Never rely solely on PDCs for defense. A determined enemy can bypass, blockade, or overwhelm fixed defenses. PDCs are force multipliers for a mobile fleet, not replacements for one.

12.7.4 PDC Weapons

Updated: v2026.01.30

PDCs can mount any weapon system available to ships. The choice of armament depends on the PDC’s intended role.

Beam Weapons:

All beam weapon types are available for PDC installation:

Weapon Type PDC Role Notes
Lasers Anti-ship, PD Versatile; good range and damage
Particle Beams Anti-ship Full damage at all ranges; focused penetration
Plasma Carronades Anti-ship High damage, infrared-laser range, no damage falloff
Railguns Anti-ship, PD Multiple shots; no damage falloff
Meson Cannons Anti-ship Bypasses shields and armor
Gauss Cannons Point defense High rate of fire; anti-missile role

PDC beam weapons function identically to their ship-mounted counterparts – same damage, range, tracking speed, and fire control requirements. See Section 12.2 Beam Weapons for detailed weapon specifications.

Missile Launchers:

PDCs can mount missile launchers of any size, paired with magazines for ordnance storage. PDC missile batteries benefit from the same size freedom as other PDC systems – you can mount launchers and magazines that would consume a prohibitive proportion of a warship’s hull. PDC magazines benefit from the same square-root HTK scaling as ship magazines (see Section 12.3 Missiles).

Tip: A PDC dedicated to missile defense can carry enormous magazines with hundreds or thousands of anti-missile missiles (AMMs), providing sustained point defense that no ship could match in endurance.

Fire Controls:

PDC fire controls follow the same rules as ship-mounted fire controls:

  • Beam fire controls for energy weapons (with tracking speed and range parameters)
  • Missile fire controls for launcher guidance
  • PD-mode fire controls for point defense duty
  • STO fire controls for surface-to-orbit engagement (generated automatically for PDC-class weapons)

PDC fire controls use the same technology and range calculations as ship-mounted equivalents. No PDC-specific fire control range bonus has been verified in the game database.

12.7.5 PDC Sensors

Updated: v2026.01.30

PDCs can mount the full range of sensor systems:

  • Active sensors: Detect ships, missiles, and other contacts at long range. Resolution and sensitivity follow standard sensor rules (see Section 11.3 Active Sensors).
  • Passive sensors (Thermal/EM): Detect engine emissions and electronic signatures without revealing the PDC’s position.
  • Geological sensors: Rarely useful on PDCs but technically mountable.

Sensor PDC Role:

A dedicated sensor PDC can serve as the detection backbone for a colony’s defenses. Without engine or fuel constraints, you can build very large sensor arrays that detect incoming threats at extreme range, giving mobile forces more time to respond.

Tip: Consider building at least one PDC as a dedicated sensor platform with the largest possible active sensor. This provides early warning for the entire colony system and supports fire control for other PDCs and orbital ships alike.

12.7.6 PDC Shields

Updated: v2026.01.30

PDCs can mount shield generators just like ships. Shields absorb incoming damage point-for-point before it reaches the PDC’s armor:

  • Shield regeneration follows standard rules (see Section 12.6 Damage and Armor)
  • Multiple shield generators stack their protection
  • Shields completely negate shock damage from any absorbed hit
  • Active shields produce an EM signature detectable by passive sensors

Shielded PDC Considerations:

  • Shields are the PDC’s first line of defense against orbital bombardment
  • Against energy weapons, shields regenerate between shots, potentially absorbing more total damage than their raw strength suggests
  • Against massed missile strikes, shields may be overwhelmed in a single salvo
  • Shield generators consume reactor power; ensure sufficient power plant capacity

Tip: Shields on PDCs are particularly valuable because fortification already protects against bombardment destruction rolls. Shields add a second layer that must be depleted before armor and internal damage occur, making shielded PDCs exceptionally durable.

12.7.7 PDC Construction and Deployment

Updated: v2026.01.30

PDCs can be produced through two methods:

Method 1: Construction Factories (Prefabricated)

Construction factories can build PDCs as prefabricated installations. The PDC is assembled on the colony surface using the same industrial output that builds mines, factories, and other installations. This is the simplest method for established colonies.

  • Uses construction factory output (Build Points per year)
  • PDC appears on the colony when complete
  • No transport required
  • Limited by construction factory capacity and mineral availability

Method 2: Shipyard Construction

PDCs can also be designed and built in shipyards, then transported to a colony as cargo aboard freighters. This method is useful for:

  • Rapidly deploying PDCs to new or distant colonies
  • Building PDCs at an industrialized homeworld and shipping them to frontier worlds
  • Taking advantage of higher shipyard throughput

Deployment:

Once a PDC is built (or transported to a colony), it is deployed to the colony surface. It immediately becomes operational, drawing crew from the local population.

Crew Requirements:

PDC crew is drawn from the colony’s population pool. Large PDCs require significant crew complements – the same formula applies as for ships. Ensure the colony has sufficient population to crew all PDCs while maintaining industrial operations.

PDC Size Approximate Crew Population Impact
5,000 tons 200-400 Negligible on most colonies
20,000 tons 800-1,600 Minor on medium colonies
50,000 tons 2,000-4,000 Noticeable on small colonies
100,000 tons 4,000-8,000+ Significant on frontier worlds

Tip: When deploying PDCs to small colonies, check that the population can support both the PDC crew and essential industry. A 50,000-ton PDC on a 100,000-person frontier colony would consume a substantial fraction of the workforce.

12.7.8 CIWS on PDCs

Updated: v2026.01.30

Close-In Weapon Systems on PDCs provide ground-based anti-missile defense for the colony. PDC-mounted CIWS engages incoming missiles during the point defense phase, protecting both the PDC itself and other ground installations.

PDC CIWS Advantages:

  • No fuel or maintenance costs for sustained anti-missile coverage
  • Can be built very large with multiple CIWS installations per PDC
  • Protects the colony against missile bombardment
  • Operates as part of the layered defense sequence (see Section 12.4 Point Defense)

PDC CIWS in the Defense Sequence:

PDC point defense fires during the planetary defense phase of missile resolution:

  1. Ship CIWS engages first (separate phase)
  2. Point Blank Defensive Fire on target ships
  3. Allied ships within PD range
  4. Planetary defenses (PDC CIWS and ground-based PD)

This means PDC CIWS is the last line of defense against incoming missiles, engaging anything that leaks through the orbital fleet’s point defense.

Configuration:

PDC CIWS uses the same components as ship-based CIWS:

  • Gauss cannons with integrated fire controls
  • Tracking speed matched to expected missile speeds
  • ECCM to counter missile-mounted Fire Control Jammers
  • Multiple installations for volume of fire

Tip: A dedicated anti-missile PDC with 10+ CIWS installations provides a defensive umbrella that can shred even large missile salvos. This is one of the most cost-effective ways to protect a colony against missile bombardment, since the PDC never needs fuel or maintenance.

12.7.9 Tactical Considerations

Updated: v2026.01.30

Layered Defense Doctrine:

The most effective colony defense combines PDCs with an orbital fleet in a layered approach:

  1. Long-range detection: Sensor PDCs detect incoming threats at maximum range
  2. Mobile fleet engagement: Orbital fleet intercepts attackers before they reach weapon range of the colony
  3. PDC fire support: If attackers close to engagement range, PDC weapons add their firepower to the orbital fleet’s
  4. PDC point defense: CIWS PDCs engage any missiles that leak through fleet PD
  5. Ground forces: STO weapons and garrison troops as the final defensive layer (see Section 13.3 Ground Combat)

PDC Composition for a Colony:

A balanced PDC garrison might include:

PDC Type Role Priority
Sensor PDC Early warning and fire control support High
Beam PDC Anti-ship engagement Medium
Missile PDC Long-range anti-ship strikes Medium
CIWS PDC Anti-missile defense High
Combined PDC Multi-role (weapons + sensors + PD) Flexible

When to Build PDCs vs. Ships:

Factor Favors PDCs Favors Ships
Threat is local Colony is a likely target Threats are distributed
Budget Limited fuel/maintenance budget Need power projection
Timeline Long-term garrison Rapid response needed
Population Large colony workforce Small frontier outpost
Strategy Defensive posture Offensive campaigns

Jump point defense with PDCs:

If a jump point happens to be within weapon range of a colonized body (uncommon but valuable), PDCs on that body serve as ideal jump point defenders:

  • They require no bridge, engines, or jump drive
  • They can mount massive missile batteries and beam weapons
  • They benefit from fortification against counter-bombardment
  • They are extremely cost-effective for permanent JP coverage

Key jump point defense principles: position PDCs on bodies within weapon range of the JP, use large missile batteries for alpha strikes against emerging hostiles, and pair sensor PDCs for immediate detection of transiting ships. PDCs are ideal JP defenders because they never need fuel or maintenance for permanent station. See the Jump Point Defense example for detailed JP defense strategies and Section 10.2 Jump Transit for jump point mechanics.

Countering PDCs (Attacker’s Perspective):

When facing enemy PDCs:

  • Missile bombardment is more effective than energy weapons against fortified targets (20x damage multiplier for bombardment)
  • Stand off beyond PDC weapon range if possible – blockade rather than assault
  • Suppress PDCs before committing transports to orbit (PDCs with STO capability will engage landing craft)
  • Factor in fortification levels: heavily fortified PDCs are significantly harder to damage with energy weapons per shot (exact per-level hit chance percentages unverified)
  • Allocate significant missile salvos; expect the first waves to deplete PDC shields before causing structural damage

Warning: Do not land troops on a planet with active PDCs. PDCs equipped with STO weapons will engage transports during the landing phase, potentially destroying troop ships before ground forces deploy. Always suppress PDCs with orbital bombardment first.

12.7.10 STO Mass Target Reassignment

Updated: v2026.01.30

Six buttons in the Ground Forces window enable mass reassignment of Space-To-Orbit (STO) targeting types across multiple installations simultaneously \hyperlink{ref-12.7-3}{[3]}. This feature streamlines STO management when you need to change targeting priorities across many installations at once.

Copy Buttons (Apply Current Selection):

Button Scope Effect
Copy Pop Same population Applies the current STO’s target type to all STOs on the same colony
Copy System Same system Applies the current STO’s target type to all STOs in the same star system
Copy All Empire-wide Applies the current STO’s target type to all STOs across your entire empire

Type Buttons (Apply Selected Type):

Button Scope Effect
Type Pop Same population Applies the selected target type from the dropdown to all STOs on the same colony
Type Sys Same system Applies the selected target type from the dropdown to all STOs in the same star system
Type All Empire-wide Applies the selected target type from the dropdown to all STOs across your entire empire

Use Cases:

  • Invasion Alert: When an enemy fleet enters a system, quickly switch all STOs in that system to prioritize troop transports using “Type Sys”
  • Empire-Wide Policy: Set all STOs to a default targeting priority (e.g., largest ship first) using “Type All”
  • Colony-Specific Defense: Configure STOs on a single high-value colony to target specific ship classes without affecting other colonies

Tip: The “Copy” buttons are useful when you’ve fine-tuned targeting on one STO and want to replicate those settings. The “Type” buttons are faster when you know exactly what targeting type you want and need to apply it broadly.

12.7.11 PDC Design Examples

Updated: v2026.01.28

Example 1: Anti-Missile PDC (10,000 tons)

Role: Colony anti-missile umbrella

  • 8x Triple Gauss Cannon Turrets (CIWS)
  • 4x CIWS Fire Controls (maximum tracking speed)
  • 2x Active Sensors (resolution 1, for missile detection)
  • Reactor (sufficient for sensors)
  • 4 layers armor
  • Engineering section

This PDC fires 24+ bursts per combat tick against incoming missiles, providing robust anti-missile coverage for minimal tonnage.

Example 2: Beam Defence PDC (30,000 tons)

Role: Anti-ship engagement

  • 6x 30cm Ultraviolet Lasers
  • 2x 20cm Lasers (backup/secondary targets)
  • 4x Beam Fire Controls (anti-ship tracking speed)
  • 2x Active Sensors (high resolution, long range)
  • Shield generators (2-3 layers of shielding)
  • 8 layers armor
  • Engineering section
  • 2x CIWS installations (self-defense)

This PDC delivers concentrated beam firepower against approaching warships while maintaining self-defense against missiles.

Example 3: Missile Battery PDC (50,000 tons)

Role: Long-range anti-ship strikes

  • 20x Size-12 Missile Launchers
  • Large magazines (80% of remaining hull space)
  • 4x Missile Fire Controls (maximum range)
  • 2x Active Sensors (targeting resolution matched to expected threats)
  • Shield generators
  • 6 layers armor
  • 4x CIWS installations (self-defense)
  • Engineering section

This PDC provides sustained missile bombardment capability with magazine depth that no ship could match.

Tip: When designing PDC networks, ensure sensor coverage is adequate. A colony with beam PDCs but no sensor PDC may not detect threats until they are within visual range. Build sensor PDCs first, then add firepower.

References

\hypertarget{ref-12.7-1}{[1]}. Aurora C# game database (AuroraDB.db v2.7.1) – DIM_PlanetaryInstallation: Construction Factory TargetSize = 20 (verified); PDC destruction from orbit follows standard bombardment mechanics (Weapon Damage / Target Size). See also Section 12.6.4 Planetary Bombardment for the missile 20x multiplier.

\hypertarget{ref-12.7-2}{[2]}. Aurora Wiki (C-PDC, C-Ship-Design) and official forum sources – PDC design removes engine, fuel tank, bridge, and jump drive requirements. PDC fire controls use STO fire control designation. PDC crews drawn from colony population. No maintenance clock accumulation for ground installations.

\hypertarget{ref-12.7-3}{[3]}. Aurora Forums — https://aurora2.pentarch.org/index.php?topic=13884.msg176533 — Steve Walmsley, December 31, 2025. Six new buttons for mass STO target type reassignment: Copy Pop, Copy System, Copy All, Type Pop, Type Sys, Type All.

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Aurora 4X Manual & Guide - Unofficial community documentation for Aurora C# (game by Steve Walmsley)

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