Master of Orion II: Battle at Antares/Power

The Power techs appear in the top right part of the Research menu. They are quite a mixed lot: ship speed upgrades, bombs, and various special systems for ships.

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

50 RP: Nuclear Fission
This is a "general" tech level - even Uncreatives get all the techs. Allows food and / or colonists (including Androids but not Natives) to be transported between colonies. See Freight training for details. Miniaturization: none. Ship component that moves a ship through interstellar space at 2 parsecs per turn, and in combat by 3-5 squares per combat turn in battles (bigger ships are slowest). Ship Weapon that can only be used against planets and only at zero range. Does 3 to 12 points of damage, minus whatever the planet's shield may block. Miniaturization: Decreases size and cost. Modifications: none.
 * Freighters (50 PP per 5 Freighters; maintenance 0.5 BC per 1 Freighter which is in flight)
 * Nuclear Drive
 * Nuclear Bomb

80 RP: Cold Fusion
This is a "general" tech level - even Uncreatives get all the techs. Ship that can colonize in any system within range, usually systems where you do not already have a colony. Creating a colony completely uses up the Colony Ship. You cannot design Colony Ships, and the game's hard-coded design includes Extended Fuel Tanks, which increases Colony Ships' range by 50%. When the new colony is established, it will have a population of 1. A colony that just completed making a Colony Ship does not lose a population unit. Ship whose main use is to extend your other ship's range. Creating an Outpost completely uses up the Outpost Ship. Outposts can be created on Gas Giants and Asteroid Belts as well as on planets. If you colonize a planet on which you have previously created an Outpost, the colony gets free Marine Barracks; this improves the morale of new colonies for Feudalisms and Dictatorships. Note: you cannot land an Outpost Ship on an existing colony; so if you want to use one to provide a Marine Barracks for a new colony, the Outpost Ship must land at least 1 turn earlier than the Colony Ship or Colony Base. You cannot design Outpost Ships, and the game's hard-coded design includes Extended Fuel Tanks, which increases Outpost Ships' range by 50%. Transport Ships are the only way to invade enemy colonies. Each ship carries a squad of 4 Marines. If the invasion is successful, up to 4 Marines automatically remain on the conquered colony (how many depends on your losses during ground combat). You will usually unload Marines from other Transports, up to a maximum of 1 Marine per 2 colonists (since you land Marines in groups of 4, the result is usually less than 1 Marine per 2 colonists). Placing fewer Marines on a conquered colony greatly increases the risk that the colony will rebel and rejoin the empire that founded it (not necessarily its previous owner), unless that empire has been eliminated. Troop transports whose Marines are unloaded or lost in combat are themselves scrapped but this does not give you any revenue. You cannot design Transports, and the game's hard-coded design does not include Extended Fuel Tanks; so Transports' range is limited to what is provided by your fuel cell tech (in the Chemistry subject area).
 * Colony Ship (500 PP; maintenance 1 CP or 10 BC)
 * Outpost Ship (100 PP; maintenance 1 CP or 10 BC)
 * Transport (100 PP; maintenance 1 CP or 10 BC)

Note: All of these ships will be destroyed in combat if not escorted by a warship. If the escort ship is destroyed, these ships will automatically retreat to the nearest friendly system.

250 RP: Advanced Fusion
Upgrades ships' speed to 3 parsecs per turn between systems, and 7-9 squares per combat turn in battles (bigger ships are slowest). This upgrade is free and immediate. Ship Weapon Effect that can only attack planets and only at zero range. Does 4 to 24 points of Damage, less whatever is blocked by the planet's shield. Miniaturization: Decreases size and cost. Modifications: none. Ship Special System that: increases ship combat speed by +5 combat squares per combat turn; reduces its chance of being hit by "beam" weapons (because the ship's extra mobility allows it to dodge); under the game's "ship initiative" rules, increases its chance of being allowed to fire before the enemy. Miniaturization: Decreases size and cost.
 * Fusion Drive
 * Fusion Bomb
 * Augmented Engines

Recommended choice for non-Creatives: Augmented Engines - there are better drives and bombs further up the tech tree, but there's only one Augmented Engines. For blitzkrieg war Fusion Drive is much better choice.

900 RP: Ion Fission
Upgrades ships' speed to 4 parsecs per turn between systems, and 9-11 squares per combat turn in battles (bigger ships are slowest). This upgrade is free and immediate. Ship / Star Base Weapon that bypasses armour and structure, attacking the target's systems, and does 2 to 10 points of damage minus whatever is blocked by the target's shields. This may sound puny, but 2 shots that penetrate the shields are usually enough to makes a ship's drive explode; and the Ion Pulse Cannon can also completely disable Star Bases, although you will need other weapons to destroy the Star Base, win the battle, and have your wicked way with the enemy colony. The Ion Pulse Cannon does have some limitations: it requires a lot of space and its range is short (useless in Ground Batteries); Class 3 Shields (Force Fields subject area) completely block damage from Ion Pulse Cannon; and it is totally ineffective against Space Monsters and Antarans, and ineffective against planet-based defenses. Miniaturization: Decreases size and cost. Modifications: (0) HV; (1) CO; (2) AF. Ship Special System that triples the shield recharge rate. Miniaturization: Decreases size and cost.
 * Ion Drive
 * Ion Pulse Cannon
 * Shield Capacitor

Recommended choice for non-Creatives: depends on your strategy, but Ion Drive is usually best if you chose Augmented Engines rather than Fusion Drive at the previous level of Power tech - unless you intend to research Antimatter Drive very soon; but Antimatter Torpedoes are often an excellent choice at the next level of the Power tech tree. Shield Capacitor is good if you have or intend soon to have Class 3 or better Shields. Ion Pulse Cannon is good in the short term if your opponents cannot research Class 3 Shields because they chose some other tech at that level (you can check this in the Races Screen), but Ion Drive and Shield Capacitor give more lasting benefits in the right conditions.

2000 RP: Anti-Matter Fission
Upgrades ships' speed to 5 parsecs per turn between systems, and 10-12 squares per combat turn in battles (bigger ships are slowest). This upgrade is free and immediate. Ship Weapon that does 25 damage, only fires every other combat turn but, unlike missiles, has unlimited ammunition and can't be shot down by PD weapons. The only defense against torpedoes is ECM Jammers, but non-Creatives seldom research these and Jammers take ship space that many players would prefer to use for other components. Miniaturization: Decreases size and cost. Modifications: (0) none; (1) ECCM, FST; (2) OV, ENV. Ship Weapon that can only attack planets and only at zero range (unless you have Transporters, higher up the Power tech tree). Does 5 to 40 points of Damage, less whatever is blocked by the planet's shield. Miniaturization: Decreases size and cost. Modifications: none.
 * Anti-Matter Drive
 * Anti-Matter Torpedoes
 * Anti-Matter Bomb

Recommended choice for non-Creatives: Anti-Matter Torpedoes, especially if you do not have good targeting computers for beam weapons. You don't need Anti-Matter Drive if you chose Augmented Engines and Ion Drive at previous levels of Power tech. You seldom really need Anti-matter Bombs, because Anti-Matter Torps also do reasonable damage against planet-based defenses.

2750 RP: Matter-Energy Conversion
Ship Special System that:"beams" Marines into enemy ships and Star Bases, and enables you to bomb planets from up to 12 spaces away. Miniaturization: Decreases size and cost. Building that converts 2 production into 1 food when needed. The conversion ratio means that Food Replicators are only usable on highly industrial planets, where using them can actually increase net production if output per worker is very high, but their maintenance cost is absurdly high(which is likely a mistake that was never fixed, since no other building comes close, even buildings that are several times more expensive and a lot more useful).
 * Transporters
 * Food Replicators (200 PP; maintenance 10 BC!)

Recommended choice for non-Creatives: Transporters. Food Replicators have a ridiculous maintenance cost making it the worst building in the game and rather a detriment than a bonus.

3500 RP: High Energy Distribution
Ship Special System that increase "beam" weapons' damage by +50%. This can extend the useful life of lower-tech "beam" weapons by enabling them to penetrate shields that would otherwise negate them; this is excellent because lower-tech weapons with useful modifications generally provide more firepower per unit of ship space than your latest weapons. Miniaturization: Decreases size and cost. Ship Special System that decreases by 25% the damage your ships take, and store this energy for an attack you can use released in the next turn. Miniaturization: Decreases size and cost. Achievement that increases available space on all ships by +25%. Usually halve space in ship is used for defensive equipment, so it's allow you to increase weapon's quantity by about 50%. And not only beams. Miniaturization: Not applicable.
 * High Energy Focus
 * Energy Absorber
 * Megafluxers

Best choice for non-Creatives: depends on your strategy. If opponent use top shields, High Energy Focus provides the greatest increase in firepower. Otherwise take Megafluxers.

This tech level is not always reached in competitive games, but it's a huge payday for Creatives: High Energy Focus + Megafluxers almost doubles a Battleship's firepower, assuming that a lot of the ship's space was already used by Special Systems such as Structural Analyzer (in the Computers tech tree).

4500 RP: Hyper-Dimensional Fission
Ship Weapon that does 40 damage, only fires every other combat turn but, unlike missiles, has unlimited ammunition and can't be shot down by PD weapons; and, unlike most torps, Proton Torpedoes fly FTL (faster-than-light) and hit in the same combat turn. The only defense against torpedoes is ECM Jammers, but non-Creatives seldom research these and Jammers take ship space that many players would prefer to use for other components. Miniaturization: Reduces size and cost. Modifications: (0) none; (1) ECCM; (2) OV, ENV. Upgrades ships' speed to 6 parsecs per turn between systems, and 12-14 squares per combat turn in battles (bigger ships are slowest). This upgrade is free and immediate. Ship Special System that enables "beam" weapons to fire twice in a combat turn; but the ship then has to wait 1 combat turn without firing.
 * Proton Torpedo
 * Hyper Drive
 * Hyper-X Capacitors

Best choice for non-Creatives: depends on the situation. Hyper-X Capacitors is very good if you mainly use "beam" weapons. Otherwise Proton Torpedo is excellent and out-ranges any "beam" weapon (except Stellar Converter, which the manual classifies as a Special Weapon, although it benefits from some Special Systems that assist "beam" weapons). Hyper Drive is the least likely choice since Ion Drive crosses most gaps between systems in 1 turn and Ion Drive + Augmented engines gives you excellent combat speed, while real speed freaks will choose Interphased Drive at the next Power tech level; but Hyper Drive may be useful if there are large gaps between systems.

10000 RP: Interphased Fission
Type: Achievement Upgrades ships' speed to 7 parsecs per turn between systems, and 14-16 squares per combat turn in battles (bigger ships are slowest). This upgrade is free and immediate. Ship Weapon that does 120 damage minus 5 for every square it travels (but the NR mod prevents this reduction), only fires every other combat turn but, unlike missiles, has unlimited ammunition and can't be shot down by PD weapons. This travel at a "normal" speed and seldom hits in the same combat turn. The only defense against torpedoes is ECM Jammers, but non-Creatives seldom research these and Jammers take ship space that many players would prefer to use for other components. Miniaturization: Reduces size and cost. Modifications: (0) none; (1) ECCM, NR; (2) OV, ENV. Ship Weapon that can only attack planets and only at zero range unless your ship has Transporters. Does 10 to 60 points of Damage, less whatever is blocked by the planet's shield. Miniaturization: Reduces size and cost. Modifications: none.
 * Interphased Drive
 * Plasma Torpedo
 * Neutronium Bomb

Best choice for non-Creatives: depends on the situation and your strategy, and this level is not often reached as most competitive games don't last long enough and this is one of the most expensive top levels. If you are not going for "beam" weapons, Plasma Torpedo is excellent. Otherwise Interphased Drive is generally better than Neutronium Bomb: in standard MOO II you don't need bombs, and Interphased Drive's amazing combat mobility helps big ships and some high-tech "beam" weapons that do brutal damage but have twice normal dissipation (Plasma Cannon, Mauler Device; see Physics tech tree).

Hyper-advanced Power
The Power tech tree contains several high-tech weapons and systems that would benefit from further miniaturization, especially if you use torpedoes. But if you use mainly "beam" weapons Hyper-advanced Physics is more beneficial. And Hyper-advanced research in Force Fields is almost always desirable too.