Master of Orion II: Battle at Antares/Force Fields

The Force Fields techs appear in the bottom left box in the Research Menu.

The intro to Physics explains how the Physics and Force Fields tech trees between them force non-Creatives to make some difficult choices in order to get a decent early "beam" weapon.

0 RP: starting techs
None. You have to research all the Force Fields techs if the game starts at Pre-Warp.

250 RP: Advanced Magnetism
Ship Shield that: completely negates 1 point of damage from each weapon that attacks (it does not even weaken the shield) ; absorbs 5 times the ship's size class in damage before failing, i.e. 5 for a Frigate to 20 for a Battleship. Regenerates 30% of its maximum strength per combat turn. This shield offers negligible protection. Miniaturization: none. Ship "beam" weapon that does 6 points of damage, with no range dissipation. The unmodified Mass Driver's freedom from range dissipation makes it better than an unmodified Fusion Beam, but a fully modified Fusion Beam is better than a fully modified Mass Driver if the target has  Heavy Armor, which blocks the Mass Driver's AP effect. A fully modified PD Fusion Beam is more powerful than a fully modified PD Mass Driver, but the PD Mass Driver's freedom from range dissipation allows one ship to help defend another from a swarm of missiles or fighters. Miniaturization: Reduces size and cost. Modifications: (0) HV, PD; (1) AP; (2) AF. Ship Special System that increases the ship's Missile Evasion by +70%. ECM Jammers (all versions) are the best defense against torpedoes, as torpedoes cannot be shot down and Jammers, unlike Pulsar and Lightning Field, can defend against multiple waves of missiles and torpedoes per combat turn. Cannot be used with any other jamming device. Miniaturization: Reduces size and cost.
 * Class I Shield
 * Mass Driver
 * ECM Jammer

Best choice for non-Creatives: ECM Jammer unless you really want Fusion Rifle; in that case you choose Mass Driver as the first reasonable "beam" weapon. But then you have to choose Multi-Wave ECM Jammer if an enemy uses torpedoes, and that would rule out Class 5 Shield.

650 RP: Gravitic Fields
Achievement that improves ground units' performance by +10%. Ship Special System that increases beam defense by +50% and halves turning costs. Miniaturization: Reduces size and cost. Ship Special Weapon that spins a ship randomly and does 1-4 points of structure damage times the size class of the target ship. In the early game, when ships have poor combat mobility and wide-arc versions of "beam" weapons are too bulky, this offers a reasonable chance of being able to fire on a ship without its being able to fire back, especially at missiles. This tactical advantage does not work against Star Bases, whose "beam" weapons always have 360&deg; firing arcs. Miniaturization: Reduces size and cost. Modifications: none.
 * Anti-Grav Harness
 * Inertial Stabilizer
 * Gyro Destabilizer

Best choice for non-Creatives: Inertial Stabilizer, as it offers immediate but lasting advantages in space combat. Ground combat advantages are worthless if you lose the space battle. Gyro Destabilizers quickly become ineffective as ships become tougher and more mobile.

900 RP: Magneto Gravitics
Ship Shield that: completely negates 3 points of damage from each weapon that attacks (these do not even weaken the shield) ; absorbs 15 times the ship's size class in damage before failing, i.e. 15 for a Frigate to 60 for a Battleship. Regenerates 30% of its maximum strength per combat turn. This is the first effective shield. Miniaturization: none. Building that changes a Radiated planet to Barren for as long as the Radiation Shield is present; the change allows terraforming. Also reduces by 5 points all damage caused by attacks; since "beams" and missiles only do 50% damage to a planet, this is enough to negate Lasers and  Nuclear Missiles; and it makes  Nuclear Bombs ineffective a lot of the time although bomb damage is not reduced by the planet's atmosphere. Ship and Star Base Special System that prevents enemy ships from retreating during combat. Miniaturization: Reduces size and cost.
 * Class III Shield
 * Planetary Radiation Shield (80 PP; maintenance 1 BC)
 * Warp Dissipater

Best choice for non-Creatives: difficult, as all these techs are good at this stage in the game. In the longer term Radiation Shield offers the most lasting advantages, especially for Aquatics as on average 50% of Barren planets terraform to Tundra; but that means giving up some immediate military advantages.

Since the choice is difficult for non-Creatives, it's clear that Creatives get a significant bonus at this tech level.

1500 RP: Electromagnetic Refraction
Ship Special System that makes ships are completely invisible on the Galaxy map except to Omniscient empires. Note that Colony Ships and Troop Transports cannot have any kind of cloaking, so this tech is only good for raids, usually aiming to bomb colonies. At this stage in the game ships are slow in combat and Radiation Shield significantly reduces bomb damage, so bombing raids are often unsuccessful; and later there are more advanced cloaking techs. Miniaturization: Reduces size and cost. Achievement that improves ground units' performance by +20%. Achievement that gives a +10% bonus for both "Spies" (espionage and sabotage against other empires) and "Agents" (your counter-intelligence operatives).
 * Stealth Field
 * Personal Shield
 * Stealth Suit

Best choice for non-Creatives: Democracies should consider Stealth Suit to reduce their weakness in counter-intelligence. For others Personal Shield may be a good investment for the time when you are ready to invade, as the alternatives offer no great immediate space combat advantage.

2000 RP: Warp Fields
Ship Special Weapon that damages all objects (friend and foe) in adjacent combat map squares. It does 2-24 points of damage times the target's size class (e.g. 2-24 against a Frigate, 8-96 against a Battleship) and is also fairly effective against missiles and fighters. Not an impressive offensive weapon: it can damage it's own side's ships, missiles and fighters; and its short range reduces its effectiveness when ships are slow in combat; later in the game enemy ships have a choice of ways to destroy ships that are armed with Pulsars before they get into range, and good "beam" or  torpedo weapons are the most effective because the Pulsar offers no protection against these. May be better than PD "beams" for players with poor computers, but Lightning Field is better. Very late in the game Subspace Teleporter may make the Pulsar a usable weapon; but it's a long time to wait, and there other ways to use the Subspace Teleporter. Building that slows all enemy ships within a range of 2 parsecs to a speed of 1 parsec per turn. Such a powerful defense for a whole system (by giving its own empire's ships plenty of time to get there) that it is often banned in multi-player games. Unlike many defenses, this gets better as the game proceeds, since your ships get faster. Its main weakness is that, if the attackers capture the colony that built the Warp Interdictor, it starts working for them, even if there are other uncaptured colonies in the system. Ship Special System that has a 50% chance of destroying groups of missiles, torpedoes or fighters attempting to hit the ship; but "fires" only once per combat turn, so can be defeated by multiple groups of missiles (see the military sections of this guide).
 * Pulsar
 * Warp Interdictor (300 PP; maintenance 3 BC)
 * Lightning Field

Best choice for non-Creatives: Warp Interdictor, if not banned; otherwise probably Lightning Field.

2750 RP: Subspace Fields
Ship Shield that: completely negates 5 points of damage from each weapon that attacks (these do not even weaken the shield) ; absorbs 25 times the ship's size class in damage before failing, i.e. 25 for a Frigate to 100 for a Battleship. Regenerates 30% of its maximum strength per combat turn. This shield is the first that offers reasonable protection against weapons in the top half of the tech tree. Miniaturization: none. Ship Special System that increases the ship's Missile Evasion by +100%. ECM Jammers (all versions) are the best defense against torpedoes, as torpedoes cannot be shot down and Jammers, unlike Pulsar and Lightning Field, can defend against multiple waves of missiles and torpedoes per combat turn. Cannot be used with any other jamming device. Miniaturization: Reduces size and cost. Ship "beam" weapon that does 18 points of damage, with no range dissipation. The normal and HV versions without other modifications are as effective against large targets as similar  Phasors, but the Phasor's set of modifications is better, in particular its PD and SP capabilities. Miniaturization: Reduces size and cost. Modifications: (0) HV but not PD; (1) AP; (2) AF.
 * Class V Shields
 * Multi-Wave ECM Jammer
 * Gauss Cannon

Best choice for non-Creatives: usually Class V Shields, as they should choose Phasors for beam weapons. They should only choose Multi-Wave ECM Jammer if they re surprised by an enemy's use of torpedoes; if they anticipated torpedoes they would have done better to choose ECM Jammer earlier, as this increases a ship's Missile Evasion by +70% and allows Class 5 Shields.

3500 RP: Distortion Fields
Ship Special System that makes ships are completely invisible on the Galaxy map except to Omniscient empires, and in combat gives the ship a +80% increase in beam defense and +50% increase in missile evasion as long as it stays cloaked and does not fire (but it can stay cloaked while moving in combat). When decloaked, the ship must wait one turn without firing to recloak. Note that Colony Ships and Troop Transports cannot have any kind of cloaking, so this tech is only good for raids, usually aiming to bomb colonies. At this stage in the game ships are fairly fast in combat, bombs are more powerful and Transporters may now or soon be available, so bombing raids are a real threat, especially as the Cloaking Device also gives the ship some protection while moving into bombing range. Increased ship speed also makes it possible to use the Cloaking Device to pull off surprise attacks to eliminate Star Bases or small groups of enemy ships. Miniaturization: Reduces size and cost. Ship Special Weapon that "freezes" the target ship so that it cannot move, fire or be attacked. The "weapon" has a range of 3 combat squares and operates until its owner turns it off or the "weapon" is destroyed. This is potentially a powerful "equalizer" that could allow a relatively small ship to neutralize a very dangerous enemy ship, provided other enemy ships can be destroyed before they can destroy the Stasis Field. Miniaturization: Reduces size and cost. Modifications: none. Stasis Field is often forbidden in multiplayer games, because it allows a "cheesy" tactic: freeze the enemy ship on the first combat turn; on subsequent turns deactivate the field, fire at the enemy, and then reactivate the field, leaving it frozen once again. As a result the enemy ship spends all its own combat turns frozen and unable to act. This makes it easy to defeat the Guardian once you have researched the field. Ship Special System that: increases by 3 the damage that shields can absorb before failing; allows shields to operate inside a Nebula; prevents Transporters from being used against the ship even with shields down; prevent shield-piercing weapons from bypassing the ship's shields. Quite a package, but most of the benefits depend on having good shields.
 * Cloaking Device
 * Stasis Field
 * Hard Shields

Best choice for non-Creatives: difficult, because all are fairly useful. Hard Shields is the easiest to use and most versatile because Cloaking Device and Stasis Field require a suitable mix of ships and good tactics. Stasis Field requires good shields and armor, because any sensible opponent will try to destroy as soon as possible any ships with Stasis Fields; and the "cheesy" tactic above also requires good "beam" weapons and a good computer, as it only works with beam weapons.

4500 RP: Quantum Fields
Ship Shield that: completely negates 7 points of damage from each weapon that attacks (these do not even weaken the shield) ; absorbs 35 times the ship's size class in damage before failing, i.e. 35 for a Frigate to 140 for a Battleship. Regenerates 30% of its maximum strength per combat turn. This shield is the first that that offers reasonable protection against Plasma Cannons even when these are boosted by High Energy Focus; considering how brutal Plasma Cannons +  High Energy Focus, this level of protection may be  a life-saver. Miniaturization: none. Building that changes a Radiated planet to Barren for as long as the Flux Shield is present; the change allows  terraforming. Also reduces by 10 points all damage caused by attacks. Not such a strong defense in relation to attacking ship's capabilities as Radiation Shield was when it first became available; but ground-based defense should now have better armor, so a Flux Shield may blunt attacks by enough for them to outlast attackers, especially as "beams" and missiles only do 50% damage to a planet. Appears so late in the game that the ability to terraform may not influence the economic balance of power significantly. Ship Special System that increases the equipped ship's Missile Evasion by +130% and increases the Missile Evasion of all friendly ships in combat by +70%. Cannot be used with any other jammer, and the bonus is not cumulative with that of jammers on the other ships (they simply get whichever is better). Miniaturization: Reduces size and cost.
 * Class VII Shield
 * Planetary Flux Shield (200 PP as new build, 120 PP as upgrade of existing Radiation Shield; maintenance 3 BC)
 * Wide Area Jammer

Best choice for non-Creatives: if you already have good shields and have been able to wait this long for a Jammer, Wide Area Jammer is a good choice; install it on a ship with very good beam defense (as small as possible, with high mobility and possibly cloaking) and keep this ship out of harm's way while the heavy hitters it protects deal with enemy torpedo ships. Otherwise choose Class VII Shield, as Flux Shield makes less difference than Radiation Shield would have done earlier (if you skipped Radiation Shield earlier and then regretted it, it's probably too late for you to do much about that).

7500 RP: Transwarp Fields
Type: Ship Special System that causes all attacks to have a 30% chance of missing, regardless of all other factors (the game's documentation is not clear about whether Displacement Device gives any protection against Stellar Converter). Miniaturization: Reduces size and cost. Ship Special System that allows a ship to make a jump of up to 18 squares in combat without moving using any combat movement points, i.e. it still has its full normal movement afterwards; but that means you can't perform hit-and-run attacks by doing a normal move first and then teleporting out of range of retaliation - on the other hand if an enemy is stupid enough to remain stationary within range you can fire (no turning first) and then teleport away. Subspace Teleporter can be effective against torpedo ships if you get the timing right: go in and fire on the turn in which they do not fire, teleport away when they've fired. It can also be effective against missile ships, if you can tempt them into firing all their missiles so that you can decoy the missiles to the far side of the combat map and then teleport in to do some damage. Since these tactics mostly involve firing at close range, you don't need such a good computer to make "beam" weapons effective. Subspace Teleporter might also be a way to make Pulsar (above) an effective weapon against closely grouped ships, especially as Pulsar is inherently a 360&deg; weapon so you can teleport immediately behind the enemy, where it's hard for them to hit you with most beam weapons (this tactic is even better if you get the exotic Spatial Compressor, which is a lot more powerful than Pulsar; if you beat Orion's Guardian you get a free Battleship that has this combination). Subspace Teleporter can also be used to make a superb bomber, provided it has escorts with very long-ranged weapons (possibly OV Proton Torpedoes or NR Plasma Torpedoes) - the defending ships will have nasty dilemma: if the defenders move forward to attack your long-range ships, the bomber teleports in to attack the planet; if they cluster round the planet to defend it from the bomber, they get pounded by the long-range ships. The down-side of these tactics is that the enemy get to fire their beam weapons at short range, so very good shields and armor are essential, and this might even be a rare good use for an Automatic Repair Unit. But there's a tactic that avoids this risk - if you can make a ship that has Subspace Teleporter and Stellar Converter, teleport as far away as possible from danger and then use the Stellar Converter's unlimited range and deadly accuracy. Miniaturization: Reduces size and cost. Ship Special System that increases beam defense by +100% and negates turning costs, i.e. you turn and still have your full combat movement available. Inertial Nullifier is ridiculously bulky until it's been miniaturized a few times. Miniaturization: Reduces size and cost.
 * Displacement Device
 * Subspace Teleporter
 * Inertial Nullifier

Best choice for non-Creatives: Subspace Teleporter - have fun, invent new sneaky tactics and ship designs!

15000 RP: Temporal Fields
Ship Shield that: completely negates 10 points of damage from each weapon that attacks (these do not even weaken the shield) ; absorbs 50 times the ship's size class in damage before failing, i.e. 50 for a Frigate to 200 for a Battleship. Regenerates 30% of its maximum strength per combat turn. Simply the best shield. Miniaturization: none. Building that changes a Radiated planet to Barren for as long as the Barrier Shield is present; the change allows terraforming. Also reduces by 20 points all damage caused by attacks, and completely blocks ground troop invasions and biological weapons - good of the enemy has no powerful bombs. Not such a strong defense in relation to attacking ship's capabilities as Radiation Shield was when it first became available; but ground-based defense should now have better armor, so a Barrier Shield may blunt attacks by enough for them to outlast attackers, especially as "beams" and missiles only do 50% damage to a planet. Appears so late in the game that the ability to terraform will not influence the economic balance of power significantly. Ship Special System Ship Special System that makes ships completely invisible on the Galaxy map except to Omniscient empires, and completely invisible in combat as long as it stays cloaked and does not fire (but it can stay cloaked while moving in combat). Can only provide full invisibility for 10 combat turns, then functions as a Cloaking Device. When decloaked, the ship must wait one turn without firing to recloak. Note that Colony Ships and Troop Transports cannot have any kind of cloaking, so this tech is only good for raids, usually aiming to bomb colonies. At this stage in the game ships are fairly fast in combat, bombs are more powerful and Transporters may now or soon be available, so bombing raids are a real threat, especially as the Cloaking Device also gives the ship some protection while moving into bombing range. Increased ship speed also makes it possible to use the Phasing Cloak to pull off surprise attacks to eliminate Star Bases or small groups of enemy ships. Almost guarantees that you get to shoot first, even where the enemy would usually shoot first (if your computers are inferior or if you are fighting Space Monsters or Antarans). Phasing Cloak is ridiculously bulky until it's been miniaturized a few times. Miniaturization: Reduces size and cost.
 * Class X Shield
 * Planetary Barrier Shield (500 PP as new build, 300 PP as upgrade of existing Flux Shield, 420 PP as upgrade of existing Radiation Shield; maintenance 5 BC)
 * Phasing Cloak

Best choice for non-Creatives: probably Class X Shield, as Planetary Barrier Shield will usually make little difference at this late stage and Phasing Cloak is usually too bulky to be of much use until miniaturized a few times by expensive Hyper-Advanced research.

Hyper-Advanced Fields
Some very high-tech Force Fields components are very bulky when first discovered, and will benefit a lot from a few levels of Hyper-Advanced Miniaturization.