Spatial torpedoes were the original projectile weapons of Enterprise NX-01, later supplemented by more powerful photonic torpedoes.
When Enterprise launched in 2151, its armament included spatial torpedoes, guided projectiles that were a step up from earlier Earth weapons but modest by the standards of many alien powers. They lacked the power and speed of the matter-antimatter weapons that followed.
The ship was soon refitted with photonic torpedoes, which offered far greater destructive force and became especially important during the dangerous mission into the Delphic Expanse. Spatial torpedoes nonetheless mark the beginning of Starfleet's line of torpedo weapons.