On Tuesday, 15 September, those two carriers and North Carolina — with 10 other warships — were escorting the transports carrying the 7th Marine Regiment to Guadalcanal as reinforcements. Wasp had drawn the job of ready-duty carrier and was operating some 150 nmi (170 mi; 280 km) southeast of San Cristobal Island. Her gasoline system was in use, as planes were being refueled and rearmed for antisubmarine patrol missions; and Wasp had been at general quarters from an hour before sunrise until the time when the morning search returned to the ship at 10:00. Thereafter, the ship was in condition 2, with the air department at flight quarters. There was no contact with the Japanese during the day, with the exception of a Japanese four-engined flying boat downed by a Wasp Wildcat at 12:15.
About 14:20, the carrier turned into the wind to launch eight Wildcats and 18 Dauntlesses and to recover eight Wildcats and three Dauntlesses that had been airborne since before noon. The ship rapidly completed the recovery of the 11 planes, she then turned easily to starboard, the ship heeling slightly as the course change was made. The air department at flight quarters, as they had done in earlier operations, worked coolly at refueling and respotting the ship's planes for the afternoon mission. Suddenly, at 14:44, a lookout called out, "three torpedoes ... three points forward of the starboard beam!"
A spread of six Type 95 torpedoes were fired at Wasp at about 14:44 from the tubes of the B1 Type Japanese submarine I-19. Wasp put over her rudder hard-a-starboard, but it was too late. Three torpedoes smashed home in quick succession about 14:45. In an odd occurrence, one torpedo actually broached, left the water, and struck the ship slightly above the waterline. All hit in the vicinity of gasoline tanks and magazines. Two of the spread of torpedoes passed ahead of Wasp and were observed passing astern of Helena before O'Brien was hit by one at 14:51 while maneuvering to avoid the other. The sixth torpedo passed either astern or under Wasp, narrowly missed Lansdowne in Wasp's screen about 14:48, was seen by Mustin in North Carolina's screen about 14:50, and struck North Carolina about 14:52.
Wasp on fire shortly after being torpedoed.
In quick succession, fiery blasts ripped through the forward part of the ship. Aircraft on the flight and hangar decks were thrown about and dropped on the deck with such force that landing gears snapped. Planes triced up in the hangar overheads fell and landed upon those on the hangar deck; fires broke out almost simultaneously in the hangar and below decks. Soon, the heat of the intense gasoline fires detonated the ready ammunition at the forward anti-aircraft guns on the starboard side, and fragments showered the forward part of the ship. The number two 1.1 in (28 mm) mount was blown overboard and the corpse of the gun captain was thrown onto the bridge where it landed next to Captain Sherman.
Water mains in the forward part of the ship proved useless, since they had been broken by the force of the explosions. There was no water available to fight the fire forward; and the fires continued to set off ammunition, bombs, and gasoline. As the ship listed to starboard between 10 and 15°, oil and gasoline, released from the tanks by the torpedo hit, caught fire on the water.
Captain Sherman slowed to 10 kn (12 mph; 19 km/h), ordering the rudder put to port to try to get the wind on the starboard bow; he then went astern with right rudder until the wind was on the starboard quarter, in an attempt to keep the fire forward. At that point, some flames made the central station untenable, and communication circuits went dead. Soon, a serious gasoline fire broke out in the forward portion of the hangar, within 24 minutes of the initial attack, three additional major gasoline vapor explosions occurred. Ten minutes later, Captain Sherman consulted with his executive officer, Commander Fred C. Dickey. The two men saw no course but to abandon ship, as all fire-fighting was proving ineffectual. The survivors would have to be disembarked quickly if unnecessary loss of life was not to be incurred.
Reluctantly, after consulting with Rear Admiral Leigh Noyes, Captain Sherman ordered "abandon ship" at 15:20. All badly injured men were lowered into rafts or rubber boats. Many unwounded men had to abandon from aft because the forward fires were burning with such intensity. The departure, as Captain Sherman observed it, looked "orderly", and there was no panic. The only delays occurred when many men showed reluctance to leave until all the wounded had been taken off. The abandonment took nearly 40 minutes, and at 16:00 — satisfied that no one was left on deck, in the galleries, or in the hangar aft — Captain Sherman swung over the lifeline on the fantail and slid into the sea.
Although the submarine hazard caused the accompanying destroyers to lie well clear or to shift position, the "tin cans" carried out the rescue efforts with persistence and determination until Laffey, Lansdowne, Helena, and Salt Lake City had 1,946 men embarked. The abandoned ship drifted with her crew of remaining dead. The fires traveled aft; four more violent explosions boomed as night began to fall. Lansdowne drew the duty of destruction, and was ordered to stand by the carrier until she was sunk. Lansdowne's Mark 15 torpedoes had the same unrecognized flaws reported for the Mark 14 torpedo. The first torpedo was fired at a range of 1,000 yd (910 m) and set to run 15 ft (4.6 m) under Wasp's keel for maximum damage with the magnetic influence exploder. When no result was observed from an apparently perfect wake, a second torpedo was fired at keel depth from a range of 800 yd (730 m). Once again, an apparently perfect shot produced no results; and Lansdowne had only three more torpedoes. Lansdowne's torpedomen disabled the magnetic influence exploders and set depth at 10 ft (3.0 m). All three torpedoes detonated, but Wasp remained afloat in the orange flames of a burning pool of gasoline and oil. Lansdowne nervously zig-zagged silhouetted in the fire's glow until Wasp sank by the bow at 21:00. Coordinates: 12°24′58″S 164°8′0″E