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Manhattan Project History

Putting the "Weapon" to Military Use

509th Composite Group

The Hiroshima Mission - Timeline

Operation Centerboard...

The SEVEN B-29's of the Hiroshima Mission:

  • The "Enola Gay", piloted by Col. Tibbets carries the "Little Boy" uranium bomb.
  • "The Great Artiste", piloted by Maj. Charles Sweeney, is assigned to drop the three instruments used to measure the blast effects of the bomb.
  • "#91" (unnamed at the time - later "Necessary Evil"), flown by Capt. George Marquardt, carries the scientific observers.
  • "Top Secret", flown by Capt. Chuck Knight, acts as a standby aircraft and flew to Iwo Jima in the event of mechanical problems with the Enola Gay.
  • "Straight Flush" will act as a weather plane and fly ahead to primary target of Hiroshima.
  • "Jabbitt III" will act as a weather plane and fly ahead to the secondary target of Kokura.
  • "Full House" will act as a weather plane and fly ahead to the alternate target of Nagasaki.

The Mission's Timeline...

8/4/45; 2:00 PM - General Curtis LeMay officially confirms that the mission will take place on August 6.  After seeing numerous B-29 crashes during take-off, Navy Capt. Parsons, head of the Los Alamos Scientific Team, suggests arming the bomb in flight, inserting the uranium slugs and the explosive charge during the early stage of the mission while flying at low level.

8/4/45; 3:00 PM - Shortly after evening mess, the seven crews that would participate in the mission were gathered for a pre-flight briefing, which included discussions on routes, altitudes, radio frequencies and weather reports.  Radio call was changed from VICTOR to DIMPLES.  The first leg would be flown at 5,000 feet in order for Parsons to arm the bomb in flight.

8/5/45; 12:00 Noon - Little Boy, which is a uranium type bomb, is 12 feet long, is 28 inches in diameter, weighs 9,000 pounds, and was painted a dull gun metal gray is taken by trailer from the ordnance hut and placed in the loading pit.

8/5/45; 3:00 PM - Little Boy is loaded into the Enola Gay.  Parsons soon arrives and began practicing arming the bomb using the Double Plug system.  He emerged two hours later confidant he could arm the bomb in flight.

8/5/45; 11:00 PM; The briefing for the three crews that would actually fly the 13 hour trip to the target began.  Although the film of the Alamagordo (Trinity) test was not available, Parsons, who had seen the test, told the group about the bomb.  The word "atom" or "atomic" was never mentioned.  The Enola Gay would drop the bomb and immediately bank 155 degrees to the right.  Sweeney, in The Great Artiste, would drop the 3 instruments at the same moment and immediately bank 155 degrees to the left.  Marquardt, in the photo and observation plane, would fly slightly behind the others and thus would be out of immediate danger.

8/6/45; 12:00 Mid-Night - The final pre-flight briefing was held.

8/6/45; 1:37 AM - The 3 weather planes, Straight Flush, Full House and Jabbitt III, take off from Tinian.

8/6/45; 2:45 AM - The Enola Gay, 15,000 pounds over-weight at 65 tons, with a crew of 12, 7,000 gallons of fuel, and the 9,000 pound bomb lifts off from Tinian.

8/6/45; 2:47 AM -  The Great Artiste takes off.

8/6/45; 2:49 AM - #91 takes off.

8/6/45; 2:51 AM - Top Secret takes off.

8/6/45; 2:53 AM - Navy Capt. Parsons and Morris Jeppson descend into the bomb bay of the Enola Gay and begin the arming procedure; with Jeppson holding a shaking flashlight and Parsons inserting the components.

8/6/45; 2:55 AM - The Enola Gay crossed the northern tip of Saipan.  Communications between Parsons and Tibbets was made possible with an intercom.  Parsons began by confirming that the "green" plugs blocking the firing signal and preventing accidental detonation were in place.  Parsons then removed a rear plate, and an armor plate beneath, exposing the cannon breech and unscrewed the breech plug.  He then inserted the four pieces of cordite into the breech, then replaced the breech plug.  He then connected the firing line and reinstalled the two metal plates.  Little Boy was not armed until the cordite charges had been loaded.  Coded messages were then sent back to General Farrell, indicating Parsons' progress.

8/6/45; 3:18 AM - Parsons completes the procedure; Little Boy is now fully armed.  Parsons and Jeppson would continue to monitor the bomb electronically throughout the mission.  The 3 planes remained in radio contact.

8/6/45; 5:34 AM - Tibbets ascended from 4,600 feet to 5,500 feet.  20 minutes later, they reached an initial cruising altitude of 9,300 feet.

8/6/45; 5:52 AM - Enola Gay arrives over Iwo Jima and rendezvous with other planes.  Top Secret, the back up, has landed on Iwo Jima.

8/6/45; 6:07 AM - The Enola Gay, The Great Artiste, and #91, now head for Japan, a little more than 3 hours away.  They are still unsure of their target.

8/6/45; 7:30 AM - Parsons again enters the bomb bay on the Enola Gay and exchanged the "green" plugs with "red" ones, thus activating the bombs internal batteries.  He then declared that the bomb was ready.

8/6/45; 7:45 AM - The 3 planes slowly climbed to an altitude of 30,700 feet.

8/6/45; 8:30 AM - Straight Flush, the weather plane, radioed that Hiroshima had little cloud coverage (< 3/10 at all altitudes).  Sweeney and Marquardt also received this message and there was no reason to break radio silence.

8/6/45; 8:32 AM - The Enola Gay and its two companions turn toward Hiroshima.

8/6/45; 9:12:17 AM - Tibbets instructs crew members to ready their goggles.  The 3 minute bombing run began.

8/6/45; 9:13:47 AM - Tibbets turned control of the Enola Gay over to the bombardier, Thomas Ferebee for the remainder of the run.

8/6/45; 9:14:17 AM - Ferebee flicked the switch that activated a high pitched tone which would ring for one minute before the bomb was released.  This tone was heard on each of the three planes, as well as the 3 weather planes already more than 200 miles away.

8/6/45; 9:15:17 AM - The bomb was released from the Enola Gay and the 3 instruments were dropped by parachute by The Great Artiste.  After releasing the bomb, both the Enola Gay and The Great Artiste each turned into a 155 degree turn, losing 1,700 feet in altitude at the process.  All crew members put on their dark glasses and prepared for the blast.

8/6/45; 9:16:00 - Little Boy exploded at an altitude of 1,890 feet above the target.  Yield was equivalent to 12,500 tons of TNT.  At the moment of the blast, a taste of lead caused by electrolysis occurred.  This was due to the effects of radiation on the fillings in the mouths of crew members.  The first shock wave took about 1 minute to reach the planes which were now 9 miles away.  Crew member Caron could see the first shock wave coming toward the plane at 1,100 ft./sec.  Soon after, a second shock wave (echo effect) hit the planes with less intensity.  The instruments which were dropped radioed blast information back to The Great Artiste.  A coded message was sent to General Farrell on Tinian advising him of the successful detonation.  The atomic mushroom cloud remained visible for 90 minutes until the planes were more than 400 miles away.

8/6/45; 2:58 PM - The Enola Gay touches down on the runway at Tinian Island, followed a short time later by The Great Artiste and #91.  Silver stars were awarded to each man involved with the mission.  Tibbets received the Distinguished Service Cross.  Mission debriefings were immediately conducted by Hazen Payette, an intelligence officer.

8/7/45 - President Truman announces the bomb dropped on Hiroshima.  Radio Saipan began broadcasting surrender appeals while aircraft fitted with giant loudspeakers flew over Japan carrying the message of atomic destruction.  The War Office printed several million leaflets and a newspaper containing Sgt. Carron's photo of the atomic cloud rising over Hiroshima.

 

 

 

 

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