The Navy said it hoped to find and correct the cause of a Trident 2 missile explosion in time to fire the next missile in April and complete a series of submarine tests by year’s end. The Navy’s goal is to have the long-range missile operational by December. That goal could be jeopardized if the problem is not found quickly, but a Navy statement said it would be premature to suggest the missile would not be ready for deployment then. The first submarine launch of the Navy’s newest and most powerful weapon ended in fiery failure shortly after one of the 44-foot missiles vaulted out of a tube in the deck of the submerged Tennessee and shot to the surface. The first stage ignited and the projectile immediately spun like a burning pinwheel and exploded four seconds after launch about 100 feet above the Atlantic Ocean.