Advanced Power Pack is a technology that can be researched at the War Center in Tech Level 4. It costs 300 Food and 200 Nova, and gives +2 attack to all Mech Factory and Troop Center units, except the Anti-Air Trooper. It's available for all civilizations except the Confederacy. Cooling Sleeves must be researched before it becomes available.
The increased attack makes the player's Mechs and Troopers more effective in battle, and the cost isn't too intimidating for a Tech Level 4 technology.
"The ultimate in blaster technology, this Tech Level 4 upgrade effectively doubles the effects of the previous Trooper and Mech weapons enhancements."