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Base Defense Guide

  • Updated July 2013.

The Base Defense Guide describes suitable defenses premised on the base’s profile; how much an attacker can reasonably expect to get in pillaging the base. The goal is to provide a basic understanding of base defense that enables a player to build defenses specific to his needs. Remember, a motivated rival may take any base defense. The aim is to reduce the benefit the rival gains by taking the base.

"Fixed fortifications are a monument to the stupidity of man." --- Geo. S. Patton

While Patton’s famous saying is valid, in Astro Empires the only thing more foolhardy than fixed fortifications is no fixed fortification. Astro Empires is an economic, military, political simulation. To ignore any of these aspects is to jeopardize one’s enjoyment of the game. This guide discusses the defensive structures and offers a structure for when to have what mode of base defense.


As with the Small Fleet Doctrine, this guide is about efficiencies. You are trying to raise the efficiency of your defenses to reduce the efficiency of your rivals. If he is going to take your base, you need to ensure he does not profit in the exchange. Wise rivals only attack bases that are likely to turn a profit. The question becomes what is profit? Defenses deter those who are after momentary financial gain. Some rivals have other motives: power, shame, control and the strategic goal of suppressing an opponent in war are other reasons a rival might hit your base. To defend against these motives, a player’s only real defense is a strong mobile fleet that he closely shepherds. That mobile fleet is the purpose of the Small Fleet Doctrine.

There are essentially three things your base defenses protect. The obvious first benefactor is the base itself: its economy and productivity. The second benefactor is that base’s trade. The other benefactor is the fleet in orbit over that base.


The power of a base’s combined defenses and fleets should exceed the total economic value of the base, fleet debris and trade routes. The defenses protect the base and the fleet protects itself and the trade routes. How do you calculate the base’s economic value?

  • The value of the fleet debris is twice the percentage of the player’s Armour technology. Therefore, Armour-12 provides 24 percent of the fleet’s value of debris.
  • The trade routes are a simple addition of the value of the route viewed in your base’s Trade tab.

The economic value of the base is a little more fluid. The value is:

Base Economic Value Formula

Value = (Empire Econ / Base Econ) * Credits on Hand + Pillage Bonus

Divide the total imperial economy by that base’s economy; this is a percentage of its contribution to the economy. This provides a percentage share of the credits you have available to spend. To this, you add the pillage bonus. The table below shows the rough bonus provided derived from that base’s economy. I would argue that the bonus is what pillagers can rely on, so discount the cash-on-hand benefit by keeping those credits banked or spent.

To protect the trade routes, you need an efficient fleet (a balance of Fighters and Cruisers) overhead. To keep it simple, let us assume that the fleet’s responsibility is to defend itself and the trade routes, and the base defenses defend the base. When you get to Planetary Rings, you will learn this model flakes as the defenses are strong enough to help protect the value of the trade routes.

Base Econ Pillage Bonus Base Econ Pillage Bonus
10 54 110 6534
20 216 120 7776
30 486 130 9126
40 864 140 10584
50 1350 150 12150
60 1944 160 13824
70 2646 170 15606
80 3456 180 17496
90 4374 190 19494
100 5400 200 21600


Assume you have 7000 credits on hand, your total economy is 1000 and your base’s economy is 100. The percentage share is 10 percent (1000/100), or 700. The pillage bonus is 5400. Therefore, the rival would get 6100 in pillaging that base.

Continuing with the example above, if you have 10,000 credits in fleet over the base and your Armour technology is at level 10, then that fleet would provide 2,000 credits in salvage. Therefore, the base’s combined fleet and pillage value is 8,100.

If your base has four trade routes each valued at, say, 2000, then the piracy value is 8,000. Therefore, the economic gain to your rival is 16,100.

Finally, deduce how much salvage he may get in recovering his own fleet. Assuming his fleet was evenly matched with yours (10,000) and had the same Armour tech, then he would recover 2,000. This makes the total economic value at 18,100. Your defenses must create more economic loss than 18,100 to make that base non-profitable. Based on the rule of thumb above, your base defenses need to handle 9,000 credits of this value, with the overhead fleet able to handle the other 9,000 credits (or more).

Let us assume your fleet defenses are a split mix of Cruisers and Fighters (5,000 or 25 Cruisers and 5,000 or 1,000 Fighters). Assuming power technology (Laser and Plasma) at 10, then the combined firepower of this fleet is 39,000; but you have to be mindful of the weakness of Fighters against shielded units, which reduces the overall efficacy of the fleet. Faced with Dreadnoughts, the Fighters and Cruisers are effectively worthless. What can we do to even the odds?

First, the solution is not always more fleet. More fleet equals more debris. So, the fleet becomes its own problem. Therefore the base defenses should be self-sustaining.


This section discusses the four categories of Base Defenses. For the purpose of this article, Commanders are not considered.

Command Centers (CC)


Command Centers value lies in raising occupation.

Because Command Centers raise the base-owner’s overhead fleet’s power, their value lies in the offensive. This means they provide limited value on the defensive, because a wise attacker will bring the fleet necessary to take out the fleet’s armour, thus limiting his fleet’s exposure to the higher power.

The only context, therefore, where Command Centers can be used in the offensive is in raising or harassing occupations. Specifically, Fighters can deliver more punch to harvesting Recyclers. Therefore, you should always have some Command Centers available in the event you need to raise or harass an occupation fleet.

Each Command Center boosts your overall defensive power by five percent. Veterans will build ten to fifteen CCs on a base to improve the power of the defensive fleet up to 75 percent. Building ten is reasonable for a free player. A Heavy Cruiser with 10 CCs and medium plasma research (10-15 levels) will dish out 125 points of damage. Command Centers protect the overhead fleet, which protects trade routes.

In the example above, the Cruisers delivered only 36 points, six after passing through the shield. With 10 Command Centers, they would deliver 54 points, or 24 points. That is four times more effective damage. Fifteen Centers would allow 33 points to penetrate the shields. So, instead of needing 128 Cruisers (25,600cr) to defeat a rival Dreadnought, you need 35 (7,000) or 32 (6,400) respectively. This improvement makes the Cruisers viable against Dreadnaughts (but not against Titans). So do not underestimate the value of Command Centers.

A wise attacker reduces his damage profile (how much he will lose) by sending the minimum quantity of fleet necessary to destroy the defense fleet. It does not matter if your fleet can deliver 50 percent more damage if the attacker does not give you the extra fleet to kill. He needs the firepower to kill your defense fleet regardless of your Command Centers.


Best of Three Rule of Thumb:

With Turrets, build three of your best, disband the rest.

This guide groups Turrets together. They do not benefit from Command Centers. When you look at the destructive value of Turrets, you discover they are weak. In the beginning of your empire (before Level 20) Unshielded Turrets, Ion Turrets and Photon Turrets are of some utility. The rule of thumb is three of your best turrets and always scrap the weaker turrets. You need the space for other structures. Weaker turrets can undermine the value of the higher turrets. You will notice, however, that Turrets have limits.

For example, the Photon Turret delivers 480 points per structure, or 1,440 at the Three-Turret Rule. That is suitable for bases with a value of 2,900. Based on the table above, this is a base with an Econ of 70 or less; assuming the fleet can protect the trade routes.

Disruptor Turrets provide 4,032, which handles a base economy of 86. Many Veteran players recommend that bases not exceed that economy until you attain Planetary Rings. Keeping the economy under 100 is what I would recommend.

Unshielded Turrets are useful only when the player is threatened primarily by Destroyers, Corvettes and Fighters. We build them in the early days of the Empire, then quickly upgraded to Photon and Disruptor. Ion Turrets have value in their shield penetrability; able to place 510 power against shielded units.


Price of Admission Warning:

Shields raise the "price of admission" for an attacker, but not the "price of conquest." Build shields to support planetary rings—only.

Planetary Shields, and the lesser cousin the Deflection Shields, provide a measure of protection for your turrets and Planetary Rings. Shields regenerate the defenses (turrets and rings) when an attack does not destroy them. We base the amount of regeneration on a percentage of the remaining defensive strength. Fortunately, the battle report has two values that help with this calculation: “Start Defenses” and “End Defenses.” To calculate regeneration, multiply the original defensive level by the End Defenses percentage (e.g. Defense * .65 for a net Defenses of 65 percent). We calculate net Defenses based on the sum of armour present at the end of the battle, divided by the sum of the full-strength armor.

Planetary Rings

Planetary Rings are the first true deterrent to capital ships. A bank of Prings delivers 15,360 points of Photonic trouble to any attacker.

Following the Best of Three Rule of Thumb, you should seek to have three levels of Planetary Rings, which delivers 15,360 points. Against a Death Star, it would inflict 14,790 power. Three sets would deliver 44,370 power, able to take down a Death Star, three Levis, ten Titans, or 85 Cruisers. The point is that a Planetary Ring is sufficient to defend a combined base value of over 40,000 credits.

“Pringles” is a term for a pair of Prings and Pshields. When you finish a set of Pringles, then you can start downsizing your defensive fleet. Or, more accurately, you can get those lazy bums into the attack. With Pringles-2, you can usually drop your defenses down to about 4000 FT and 2 BB.


I have information on the optimal defensive fleet configurations below, which supersedes the above reference to fighters and BBs.

Trade Pring Effect

When efficiently defending a base, the first pring is actually dedicated to supporting the base defense fleet. Merovech calls this the Trade Pring Effect. When the base has long-distance trades and Dreads defending them, the value of the base, trades and derbs exceeds a single pring’s ability to defend them. Therefore, you need to discount the first pring in your base defenses.

Practical Example


Merovech attained prings in the following timeframes:

  • First pring in Epsilon + 69 in a E7 cluster galaxy.
  • First pring in Fenix + 51 in a F1 cluster galaxy.
  • First pring in Gamma + 49 in a G1 cluster galaxy.
  • First pring in Helion + 46 in a H0 cluster galaxy.
  • First pring in Ixion + 45 days in a I0 cluster galaxy.

How does Merovech reach prings quickly? When in scenarios where there are players more than ten levels above him, he rigidly adheres to the principle of staying under Level 30. This limits This limits the “overhead” threat of higher level players, but leaves him somewhat vulnerable.

Merovech has managed to build prings without researching Disruptor (even in a zero-cluster galaxy) or having Disruptor turrets by keeping with the defense standards below.

To remain below Level-30 your combined economy (times 100), fleet and technology must be less than 810,000.

Formula for Staying Below Level-30:

810,000> (econ * 100) + Fleet + Technology

With all technology required for Planetary Rings, Merovech usually has less than 340,000 technology. He keeps his fleet to under 150,000. Under this formula, he needs to keep his economy under 3,200. He could double his fleet to 300,000 and keep his economy under 2,100 and stayed below Level-30. However, this leaves him vulnerable to Levels above 37, which geometrically increased his vulnerability. So, at Level-27, Merovech started building five of the ten necessary Planetary Rings to defend his bases.

When at the beginning of a server, staying under Level 30 does not matter. However, Merovech typically stays under Level 30 out of habit. He keeps as few as 500 Fighters overhead, the rest of his fleet is mobile. With 10 bases, 500 Fighters total only 25,000 total fleet. As Merovech adds one base per month, he typically has 12 bases by the time he builds prings.

Each base met or slightly exceeds the minimum construction goals of the Advanced Base Guide, with a 19:15:8:2 MR:RF:NF:AF production structures ratio. The bases also had Command Centers-10, and in many cases Spaceports-15. When building prings on an Asteroid, these structures complete the work in under six days; depending on your Cybernetics. It normally takes Merovech 10 days to build prings on a Moon. Merovech never settles on a Planet.


This section offers a suggested set of personal standards the player should strive to. The fundamental goal is to ensure you have enough defenses to deter a profit-seeker, and enough fleet to protect the trade routes.

Command Centers

The table below offers standards for Command Centers based on economy; though Merovech argues more than 10 is a waste of space after prings. The goal is to boost your defensive fleet’s power to reduce your rival’s ability to take your trade routes. At base essentially increases its economy by 20 percent per trade route, so the requirement follows. The Metal Refinery column is for those who like to balance their structure builds. The cost of that level of Refinery is approximate to the level of Command Center.

Econ Count Metal Refineries
< 50 5 12
< 100 10 17
Free Players 10 17
< 150 15 22
> 150 20

Turrets and Prings

The table below illustrates the relative value of structures and the economy they may be able to protect, based on the power delivered and the pillage bonus of the base. When considering these defenses, you must remain aware of the efficiency of larger units (e.g. Battleships) against defenses and adjust accordingly.

Keep Only the Highest Turret

Build the highest turret you have researched to the quantity necessary to satisfy your economic defense needs, but at least 2. Disband all lesser turrets.

Defense Power (@10) Econ Power (@15) Econ
Barracks 77 < 12 115 < 15
Laser Turrets 150 < 16 225 < 20
Missile Turrets 220 < 20 330 < 25
Plasma Turrets 400 < 27 600 < 33
Ion Turrets 465 < 30 690 < 35
Photon Turrets 965 < 42 1440 < 50
Disruptor Turrets-5 1,344     < 50
Disruptor Turrets-10 2,688     < 70
Disruptor Turrets-15 4,032     < 86
Prings-5 15,360     < 168
Prings-10 30,720     < 238
Prings-15 46,090     < 290
Prings-20 61,440     < 337
  • Power@10 means two turret structures of that type (e.g. Laser Turret-10)
  • Power@15 means three turret structures of that type (e.g. Ion Turret-10)
  • Prings & D-Turrets are listed separately due to the power differential.

Weak Turret Syndrome:

Do not group turrets. Weaker turrets provide substantially less protection as the base economy increases.


The rule for shields is easy. When you have researched enough for Deflection shields, build one level. When you have researched Planetary Shields, you build two. Disband the Deflection Shields when the first Planetary Shield is built. The net result is Pring-15, Pshield-10.


Defense fleets protect the trade routes. Before you have prings, constrain yourself to self-trades or short-distance ( <1000 paces) trades. This reduces profits made by the attacker. Once you have prings, you can start moving toward long-distance trades (LD trades). You should also push for Dread tech to protect your LD trades. As Dreads use the same technology as prings, make sure you pay attention to Warp tech.

How much fleet? Merovech’s calculations is one Dread for every 7,400 paces of trades. That’s about seven power per pace. While a Dread is inefficient against Cruisers, Heavy Cruisers and Battleships, the base prings will kill any of those units not killed by the Dreads—leveling the playing field.

Dread Pring Coverage Rule:

When relying on base prings to cover Dreads, do not use that pring in calculating the base defense coverage! It either supports the base or the trades. Otherwise, an attacker can hit the base, the trades and collect the derbs for a modest profit.


To have adequate defenses, the player needs to ensure they have a balance of fleet, command centers and base defenses. The fleet protects itself and the trade routes and benefits from the Command Centers. The base defenses should be able to offset the pillage bonus, plus a ratio of the cash-in-hand. With this model followed, a base is an inefficient target, but is still vulnerable to a motivated rival. This guide seeks to inform the player in an approach to analyzing base defenses, but expects the player to adjust to his specific needs. This guide further seeks to show the player that Astro Empires is a bean-counting endeavor, and that taking time to look at the underlying structure helps find efficient ways to play the game.