| e-Newsletter for December, 2001.
Request for Information: Anyone knowing the following individuals is asked to contact me:Bonner Wimberly, 834th, Krock crew.. Tribute to a Veteran: Rex Wilde by his son John Wilde. VIRUS ALERT: Viruses are becoming more insidious and are appearing at an alarming rate. Any one who surfs the web needs to take precautions and protect themselves with a good anti-virus software, such as Norton AntiVirus, or McAfee Antivirus. Additionally, your definitions files should be updated weekly. Jon Hall, an IT/IS expert has this advice: The KAK.HTA file IS a virus file and should be deleted from wherever you find it or your virus may return. This virus also effects your autoexec.bat file. It first saves your old file as c:\AE.KAK then changes your original autoexec.bat file. To restore the original autoexec.bat file simply delete your current one and then rename the AE.KAK file to autoexec.bat. There are a number of files that get infected with this worm. I would do a general find on everything with an .hta extension and delete them all. Specifically it will affect files in the following directories: c:\windows\kak.htm c:\windows\system\(filename).hta --- the name depends on the operating system c:\windows\start Menu\programs\startup\kak.hta c:\windows\menu demarrer\programmes\demarrage\kak.hta An additional source for timely virus alerts is www.symantec.com. This is the company that produces Norton Anti-Virus software. Even if you don't have NAV, this is a good source for the latest information. 486th Message Board: It has been suggested that a message board be added to the website so that online 486ers can have a chance to hook up and exchange information. I have used EzBoard before, and aside from all the pop-up windows, its an OK website. I wouldn't mind adding one to the website directly, but I don't know if that will cause a problem with the host, and incur additional costs. I also have to admit a certain ignorance as to how these "boards" work, and don't have time to learn or manage such a board. If you think this is a good idea, and would like to hop aboard and help manage something like this, please let me know. Book Review: I finally finished "The Wild Blue," by Stephen Ambrose, and found it an easy, and enjoyable book to read. After my time with the 486th and studying the war in the ETO (North), I found the descriptions of war-torn Italy quite a contrast. I was also able to relate to the stories about flying the B24 after my discussions with the 486ers. I finished viewing the HBO series, "A Band of Brothers," based upon the book by Stephen Ambrose. The series was excellent, and I would recommend getting the book, if you were unable to se the show, or even if you did. The Atomic Bomb (Part III) [ Part II | Association | Part IV ] The easiest solution to creating a nuclear explosion took the form of a gun-type bomb. The nuclear fuel (42 kg or 92.4 lbs) was formed into a bullet, and 3 rings. This mass is about 2.8 times the critical mass of U235. The excess was necessary for a couple reasons. First, the uranium-235 was not pure (only 80% by weight). Secondly, U235 was more fissile when bombarded by slow neutrons. Because the neutrons could not be slowed down (moderated) within the bomb, more fuel was required to ensure a sizable explosion. To get the uranium bullet inside the rings, cordite, a common explosive would be detonated to fire the bullet down the length of the gun. The target was a stainless steel "cup" attached to the muzzle, which was called a tamper. The tamper served to stop the bullet, reflect escaping neutrons back into the uranium, and to slow down the expansion of the exploding mass. The were three rings of uranium that made up the target were placed in the cup at the tip of the barrel. The bullet would fit precisely into the cores of the rings, creating a supercritical mass. The arrangement is shown in the figure below.
This bomb, referred to as "Little Boy," or sometimes "Thin Man," was 10.5 feet long, and 29 inches wide. The entire assembly weighted 9,700 lbs. Detonation of the bomb was to be done by an electronic trigger. Three emitters transmitted a radio pulse which was reflected from the ground providing a height measurement. When the reflected pulses were received they were compared against each other. If at least two showed that the bomb was at the correct altitude, the bomb was detonated. As added precautions, a barometric sensor was also included, and if that failed, the bomb was designed to detonate on impact. It was determined that an air burst would cause the most damage. If the bomb were allowed to explode on impact, most of the energy would be wasted in creating a crater. Although quite destructive in its own right, a larger destructive zone could be realized if the bomb were detonated above the ground. The optimal detonation altitude about the hypocenter (ground zero) was determined to be about 2,000 feet. Any higher, and the damage caused on the surface would be significantly less. Since the explosive yield of Little Boy was still only an estimate, so too was the altitude. Little Boy would detonate at about 1,900 feet AGL (above ground level) with an estimated yield of 12.5 kilotons (kt) of TNT. Implosion was the second solution for creating a critical shape from a critical mass. However, this method was also the most complex. The Gun-type was fairly straight forward, and was never tested prior to its use. The implosion type however, was very complex. Code named "Fat Man" (for its bulbous shape), a 5 kg core of Pu239 was used. Shaped into a sphere and cut in half it rested inside a natural, solid uranium sphere that acted as the tamper. At the center of the plutonium core was place a beryllium initiator, which provided an additional source of neutrons to initiate the chain reaction. Surrounding the uranium tamper was the explosive, with detonators attached at multiple locations over the surface. The configuration is shown below.
All the detonators had to fire at the same instant. However, the trick with an implosion was the spherical shock wave which emanated from the detonators. If left alone, the converging shock waves would hit the tamper non-uniformly. This would reduce the squeezing affect and minimize the yield of the bomb, if it worked at all! A method had to be devised to create a spherical shock wave that would strike the tamper evenly over its surface. The solution was elegant, and simple; in theory. Embedded in a fast burning explosive beneath each detonator, was a slower burning explosive. This created a "lensing affect" that focused the shock wave like a glass lens focuses light. As the shock wave expanded from the detonator, the slower burning explosive would effectively bend the shock wave, allowing for a uniform squeezing of the tamper. The implosion was to squeeze the tamper and plutonium to such a small volume, that the mass of plutonium was actually slightly less than critical. In this instance, the high density and the initiator would ensure a super-critical, nuclear chain reaction. The complexity, and all the variables demanded a test. On July 16th, 1945, they were ready with the prototype "Fat Man." Detonation was set for the early morning. This would allow details of the blast to be photographed with high contrasting detail. Also, an early morning blast would hope to find any prying eyes fast asleep. The test, code named "Trinity," was conducted at Alamogordo, which was well removed from Los Alamos, and neighboring towns. Weather conditions had to be such that fall out would be confined to the test area. Observation areas, and measurement areas were established to help determine the yield of the blast. Estimates ranged from just a few kilotons of TNT to over 20 kilotons of TNT. Preparations for the test went down to the wire, voids in the wedges of explosive had to be filled, and the wedges had to be fitted precisely. The weather threatened the test with rain and wind. But, conditions remained nominal enough for the test to go on. The Trinity test was estimated to have a yield of 18.6 kilotons of TNT. The Army released a press statement explaining that an ammunition dump exploded. Some "gas shells" might require the evacuation of some civilians. About the same time of the test, the first components of "Little Boy" were on their way to Tinian Island aboard the USS Indianapolis. The battle of Iwo Jima was a fierce battle, and cost both sides many casualties. The Japanese knew that losing Iwo would put the Americans on their door step. Iwo was a prime place to handle damaged bombers returning from missions from Japan, and would make a convenient airfield for fighter escorts. The commander of the 20th Air Force, Curtis LeMay, planned a mission to bomb Tokyo into oblivion as retribution for the losses at Iwo Jima. The plan called for a night raid at a low altitude, only 7,000 feet. The choice of munitions was a bomb filled with an oil gel, M-47's, and M-69's filled with jellied gasoline (Napalm). The low altitude would allow very precise bombing and render the heavy caliber anti-aircraft artillery ineffective. Pathfinder B29's were first over the target on March 10th, 1945, shortly after midnight. They were followed by an attack force of 334 B29's. The Pathfinders dropped small incendiaries to create a line of fire, then they executed a 270 degree turn and dropped another line. When the main force arrived, they were greeted with a burning "X" over the target. The following attack was horrendous, as the bombers began dropping their deadly cargo on Tokyo. The first wings over the target had it easy, but by the time the last wings arrived over the target, the raging firestorm created severe updrafts that threatened the aircraft. The crews felt the heat, and were forced to go on oxygen for cooler air to breath. When all was said and done, over 15 square miles of Tokyo lay in smoldering ruins. Over 100,000 citizens were dead. Only rivers kept the city from burning entirely to the ground. The attack was such a success, that this type of attack was carried out at other Japanese cities. The pace slowed only when the supply of incendiaries was exhausted. Once "The Bomb" was tested, and the enormity of its destructive power was realized, people became squeamish about its pending use. Statesmen and scientists alike agonized over the decision. The man who is considered the driving force behind the nuclear program, Leo Szilard, turned against the military use of the bomb. Others thought that the secret should be published for all to see. Just the existence of the bomb would create a new world order of peace. But, the pragmatists pointed out the vicious attacks on Japan that were being launched continuously. They cited the statistics of casualties from past attacks, projected casualties from future attacks, and the cost in lives when the US finally invaded Japan. Some argued that Japan was already suing for peace, and a blockade would bring them to heal. Again pragmatists spoke up: Japan wasn't willing to accept the US terms of surrender, and claimed Japan would be in for a hard winter of 45 and 46. Starvation, exposure of homeless people would cause many deaths, and those that survived and had the strength to resist an invasion would have fought to the death. The decision to drop the bomb seemed clear, and the OK was finally given. However, the choice of targets was quickly dwindling as the 20th AF and 3rd Fleet reduced Japan to ashes. There was little sense to bomb a ruined city, and to fully measure the destructive power of the atomic bombs, a city which was relatively untouched was sought. Secretary of War Stimson vetoed Kyoto as a possible target because of its historical, and cultural importance to the Japanese people. The original targets were Hiroshima, Yokohama, the Kokura Arsenal and Niigata. Nagasaki would be added later. In the Summer of 1944 the 393rd Bomb Squadron was training for duty in England. There assignment was changed in the fall of '44, and they were transferred to Wendover Army Airfield, Utah. A combat veteran of the 8th AF and the ETO, LTCOL Paul Tibbet's took command of the group. They started working up in the newer B29. The B29 was the largest bomber in the US inventory, and out performed the venerable B17 and B24 in all areas; even creature comfort. However, for its new mission, it still needed some serious modifications. Modifications to the bomb bays were required to accommodate the atomic bombs and other engineering enhancements were required to enhance the aircraft's performance at high altitude with heavy loads. The tunnel connecting the flight deck from the aft compartment was partially cut away. Additional crew stations for the technical personnel flying the mission were needed. All guns but the tail gun were removed. Many engineering changes were made to improve performance. Guide rails were added to the bomb bays to ensure the bombs fell cleaning from the bays. The engines were souped up, and gave superior performance at altitudes above 30,000 feet. The crews began working up in their new B29's in late '44. There training included dropping unusual practice bombs. These bombs had shapes that were not familiar to most all combat veterans. Moreover, instead of being painted blue like other practice munitions, the bombs were painted orange (for visibility to facilitate tracking). Their shape and color earned them the sobriquet, "Pumpkins." GEN Groves also began setting up a special base of operations on Tinian Island, in the pacific, in April '45. Navy Sea Bees built the structures for the base. Because of the bombs' size, they would not fit underneath the aircraft for loading. This required the construction of pits into which the bombs would be lowered. The aircraft then parked over the pit, and the bomb loaded into their bomb bay. By June, the base was ready and the 393rd, now called the 509th Composite Group began transferring to Tinian. During the month of July the group completed installation of specialized equipment, while aircrews practice navigating to Iwo Jima, and dropping bombs which included General Purpose munitions, and more pumpkins, on islands still controlled by the Japanese. The Japanese were still resolute in their desire to repel any US invasion of Japan. Marines and soldiers who fought in the campaign of the Solomons, returned home with stories of Japanese ferocity in battle and "fight to the death" attitude. Japanese civilians were being prepared for invasion both physically and emotionally. It was apparent that any attack on Japan was going to be bloody. However, there were factions within Japan that were trying to convince the government to surrender. The Japanese Ambassador in Russia was trying to get the Russians to help negotiate that surrender. But, since the Japanese refused the unconditional terms demanded by the Americans, negotians didn't get underway. Meanwhile, the Russians hesitated declaring war against Japan in hopes of using that as leverage for control of Eastern Europe. The Japanese reluctance to submit, and the Russian reluctance to join the war in the Pacific sealed Japan's fate. The first attack was set for early August. Two bombs would be prepared for immediate use, and a third one was promised shortly after the first two were delivered. The plane chosen for the first mission, #082, was not named, nor did it have any nose art. It was normally flown by LT Robert Lewis. However, for the first strike, Lewis would occupy the right seat, while his CO, COL Tibbets, flew in the left seat. At the same time, Tibbets christened the ship, "Enola Gay," in honor of his mother. Lewis was incensed, and did not demure when it came time to confront Tibbets. However, having had his say, he accepted the change. The crew was briefed on the mission on August 5th, and at take off was scheduled for 0245 hours on the 6th, the crews were readied. The crews were little informed as to the exact nature of the bombs they carried. But, they did have their suspicions. Only after the flight was well underway did Tibbets enlighten his crew. The start of the mission was atypical to say the least. In the early dawn hours, the Enola Gay was bathed in a flood of light. Photographers, and motion cameras were busy documenting everything. The crew posed for photos, then mounted their aircraft. In his pilots seat Tibbets began his pref-flight, which began with a request to kill the lights. Japanese observers still on the island must have been bewildered by the spectacle. Three weather planes were already airborne, stand-byes, the Enola Gay's two escorts stood bye at Iwo Jima. The 20th Air Force had been preparing the Japanese for this attack in previous weeks. Solo B29 flights were sortied to fly over Japan at various times. Those aircraft dropped no bombs, and the Japanese would not harass them, focusing their attention on the main strike groups burning their cities to the ground. So, when Enola Gay and her troupe arrived at Hiroshima, they would arrive with little trouble. Enola Gay, call sign "Dimples 82," started her engines at 0227 hours, finished her pre-flight then requested clearance to taxi. Their take off would be to the east on Runway "A." At the opposite end of the runway a jeep stood with its headlights on to allow the pilot and copilot to properly orient themselves on the runway. Once ready the jeep departed, and the Gay made her final checks. She weight 65 tons, which included 3.5 tons of fuel, 9,700 lbs of bomb, and 12 crewmen. This put her 7.5 tons over the standard weight for a combat mission. The Gay would need every foot of runway to get airborne. This required extreme skill on the part of the pilot and copilot to keep the aircraft on the runway and get airborne before running out of runway. Normally, the engines, all rotating in the same direction, generate torque that will force the aircraft to wander off the side of the runway. This is true of any aircraft, except the P38 which had counter-rotating props. B29 pilots would use the wheel brakes to counter that torque, but this caused a 10 knot loss of speed. As air begins to move sufficiently over the control surfaces, the rudder can then be used to counter the torque. Tibbets trained his crews in another method, which involved differential thrusting. The left engines were throttled up in advance of the right engines. Once the ship was at 80 knots the rudder became useful, and all engines could be set to 100% thrust. Tibbets also kept his nose down as long as possible to gain enough speed and, thereby, generate enough speed to give them every opportunity to get safely airborne. Tibbets got Dimples 82 airborne and turned North. At 0255 they flew over Saipan at an altitude of 4,700 feet heading toward Iwo Jima for rendezvous. They kept the aircraft at the low altitude to maximize the use of their fuel. They had plenty of time to reach their bombing altitude, and there was no point in burning fuel to lift fuel. This also gave he weaponeers the comfort of working in a relatively warm bomb bay without oxygen. The two weaponeers had to make final installations of various items. #082 flew mostly on autopilot for the first leg of the trip, but some changes of course were required to stay clear of towering cumulus clouds. At 0552 hours they begin a climb to 9,300 feet to rendezvous with their escorts; one for observation, and the other for photography. After assembly, the three aircraft turned NWN and headed for Japan. At 0730 hours, the bomb was armed, and Tibbets began the 45 minute climb to bombing altitude. The weather plane over Hiroshima reported 2/10 clouds at low altitudes, and a middle layer of 2/10. The primary target received clearance, and the mission proceeded as planned. At 0840 the Enola Gay was level at 31,000 feet. The interior of the aircraft was pressurized and heated, so the crew did not have to don the necessary equipment so familiar to B17 and B24 crews. (Typically, B29s would be depressurized once the entered enemy air space to avoid the dangers of explosive decompression.) At 0850 the navigator reported landfall over Shikoku, and the crew readied themselves for the bomb run. The escorts fell back to a "safe" distance. Tibbets made one final reminder to his crew to wear their special goggles. The bombardier had visual on the city twelve miles out, and took over lateral control of the aircraft from Tibbets and Lewis. They were now officially on the bomb run, at a ground speed of 285 knots (328 mph). The aiming point (AP), was a "T" shaped bridge over a fork in the Otu River. Two minutes from the target the radio operator sent a warning signal to the other aircraft in the area. At t-minutes 15 seconds a steady tone was emitted. The crews donned their goggles, the observers and photographers prepared themselves, and all waited. The crew knew immediately that the bomb was away. Instantaneously 4.5 tons lighter the Enola Gay jumped upward. The bombardier unclutched the Norden bombsight, and Tibbets had control once again. Immediately he executed a dive to gain speed and entered into a turn. Arming wires started the clocks on Little Boy. After falling 7,000 feet her radio altimeters began transmitting. 43 seconds after bombs away, at an altitude of 1,900 feet, the computers aboard Little Boy gave the signal and set the bomb off; the local time was 08:16:02. The hypocenter was 550 feet SE of the AP, and the estimated yield was 12.5 kilotons of TNT. The world would never be the same. The tail gunner saw the approach of the first shock wave, but didn't understand what he saw and it hit the Enola Gay hard. The crew's immediate reaction was to call out "FLAK!" Enola Gay bumped and protested at the severe over-pressure. When the reflected shock wave approached the tail gunner gave warning to his crewmates. The initial fire ball filled the Enola Gay with a bright light, but were safe from most of the emitted radiation. Distance would minimize their exposure to gamma rays. Tibbets turned his ship around, and the crew got their first glimpse of their days work as they saw the enormous cloud of smoke and debris billowing skyward. The spectacle awed the crew into silence, but once they recovered from their shock the ship came alive with chatter. The impressions of this moment were indelibly impressed into the minds of those who witnessed the blast. The crew turned toward Tinian to conclude their mission. The prewar population of Hiroshima was about 400,000 people. On Aug 6, 1945, the population was reduced to under 290,000 civilians and 43,000 soldiers. At 07:09 local time, air raid sirens blared at the approach of the first weather plane. The all clear came at 07:31 as the aircraft left the area. When the Enola Gay and her escorts approached they were largely ignored. For more information about the affects on the ground visit wagingpeace.org. Three days later, Fat Man was dropped by Boch's Car on the port city of Nagasaki. The Japanese Emperor declared a cease-fire and agreed to surrender unconditionally against the protest of his war ministers. The Emperor took great empathy for the suffering of his people and saw little hope of avoiding more attacks. The US was notified through the Swiss embassy on the 10th of August. It would be another 4 days before official documents accepting terms would be drafted and delivered to the US. On September 2nd, 1945, aboard the USS MISSOURI (BB-63), in Tokyo Bay, representatives of the Japanese government and the US signed the peace accord officially ending the war. The Russians, having learned of the successful tests of the bomb, and the bombing of Hiroshima immediately declared war on Japan. The US trump card was played, and the Russians lost, and were not part of the negotiations in the Pacific. Rex Wilde Biography Next Month: Atomic bomb projects of the Japanese, Germans and Russians. |
