An impulse-based turn system is a game mechanic where a game turn is broken up into a series of discrete, repeating segments, or impulses. It can be considered a fairly complex mechanic, but has been used in three games that have enjoyed long-term success, the wargames Star Fleet Battles and Car Wars, and the Hero System role-playing game (also known as Champions or Fantasy Hero).
It is most often seen in games that feature high-paced combat where units can move much further in one turn than common effective weapons ranges. (In Star Fleet Battles, a ship may move as far as 31 hexes in a single turn, and can usually move 20. 'Effective' weapon's range is generally 4-8 hexes at best.)