Sid Meier's Alpha Centauri/Chassis

The chassis is the most important part of the unit. It will determine where it can go (land/sea/air), how fast it goes, and what weapons or equipment it may use.

'Copter

 * Prerequisite: Mind/Machine Interface
 * Speed: 10
 * Terrain: air

The 'copter is like the needlejet, except that it can survive running out of fuel in a space without a city or airbase. Instead of being destroyed outright, it simply crash-lands, taking some damage. The 'copter can also attack as many times per turn as it has fuel remaining; however, attacking with the last unit of fuel will result in the unit crash-landing. Care must be taken when assigning go-to commands to a 'copter, as they will always end their turn upon entering a friendly base square, regardless of how many moves they have left. They are unique among non-land units in that they can blitz, or attack multiple times per turn.

Cruiser

 * Prerequisite: Doctrine: Initiative
 * Speed: 6 (8 with Maritime Control)
 * Terrain: Water

The cruiser is the ultimate transport unit. When fully upgraded, it can carry up to 16 units! In addition, it has the most movement points of any sea unit. Ideal for large maps, and long range transportation.

For warships, it may be better to buy the cheaper foil, unless of course, the distance from your base to the target is a far away.

Consider using for maritime probe team strikes, simply due to the large amounts of movement points. Do not engage in probe team warfare unless you can afford to lose the probe team. Just get to the target, do whatever sabotage you need to do, and do it quickly.

Foil

 * Prerequisite: Doctrine: Flexibility
 * Speed: 4 (6 with Maritime Control)
 * Terrain: Water

The early waterborne unit isn't as fast as a cruiser, but it's cheaper.

Gravship

 * Prerequisite: Graviton Theory
 * Speed: 8
 * Terrain: air

Late-game chassis that is strictly superior to the needlejet, equal in speed but with no fuel limitations. Very valuable chassis when equipped with high-power weapons and armor. However, unlike the 'Copter, it can only attack once per turn.

Hovertank

 * Prerequisite: Nanominiaturization
 * Speed: 3
 * Terrain: land

This is a middle-to-late-game unit that moves faster than the rover. One strategy that could be effective is building the ascent to transcendence at whatever city has the highest industry, then building these with a supply module attached to them at every other city you own and rushing them toward that city.

Infantry

 * Prerequisite: None
 * Speed: 1
 * Terrain: land

The default chassis for units. Some units (Crawlers, Formers, Colony Pods) do not display an actual infantryman in the unit graphic, instead using a custom chassis graphic sitting on enlarged treads. Infantry have a bonus to attacking cities.

Missile

 * Prerequisite: Orbital Spaceflight
 * Speed: 20 (depends on fuel)
 * Terrain: air

Middle-game chassis designed for kamikaze-style attacks. Cannot be equipped with weapons (except for special missile-only weapons) or armor and very few abilities. Can be very powerful if one uses it wisely.

Needlejet

 * Prerequisite: Doctrine: Air Power
 * Speed: 20 (depends on fuel)
 * Terrain: air

Though it can move an impressive distance, the needlejet will crash and burn if it ends two consecutive turns outside of a city or airbase. The needlejet can attack once per turn (doing so forfeits all movment points and ends its turn), on either or both of its first or second turns, but a needlejet that attacks on its second turn will die. Upgrading any Unit in SMAC/AX uses one turn. So do not ever upgrade your airborne Needlejets, since they will lose their turn for returning to their bases. Thus you will not only lose the needlejet but the upgrade cost as well.

Speeder

 * Prerequisite: Doctrine: Mobility
 * Speed: 2
 * Terrain: land

This creates a rover, which, in addition to its increased speed, also applies other properties, such as the loss of the infantry unit's bonus to city invasions, countered by a bonus if it attacks while in open terrain. It also has the ability to disengage (retreat) if attacked. Also, it counts as a mobile unit for the purposes of special armor bonuses.