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Archive for the ‘STEM’ Category

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SciTech Tuesday: Trinity’s 70th Anniversary

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At 5:30 am on July 16th 1945, the brightest light that had ever burnt on the Earth was ignited in the desert of New Mexico. ‘The Gadget’ had been assembled and placed the day before, and the overnight rain cleared at 4:00 am, so the first nuclear explosion to take place since the Earth had solidified was set off as a test.

The uranium bomb, Little Boy, was already heading across the Pacific for deployment. The two available plutonium bombs had a triggering mechanism that Robert Oppenheimer doubted, so it was decided that one of them would be tested. The military had plans to evacuate the nearest towns if necessary, and Enrico Fermi was wondering aloud if it would ignite the entire atmosphere, but General Leslie Groves and most of the Los Alamos team were gathered in bunkers and shelters 5 or 10 miles from the detonation site.

The steel tower holding The Gadget was vaporized, and the asphalt pad on which it stood was transformed to a green sand. A 200 ton steel container a half mile from the detonation was tossed about, landing on its side. The energy released was 4 times what had been calculated by the Los Alamos scientists. There was a general feeling of elation among the observers after the shock and heat waves had passed, and they picked themselves up from the ground. One man passed around a bottle of whiskey, while others settled bets on whether the test would be successful.

For some, including Oppenheimer, initial relief and happiness gave way to trepidation. Oppenheimer didn’t have words at first to describe his feelings, but in later years he said he thought of Prometheus, and his punishment by Zeus, and of the part of Hindu scripture where Krishna tries to impress a king by showing his godly form and saying “I am become death, destroyer of worlds.”

For Groves, this is one successful step towards a goal, but not an end on the path. When his assistant remarked to him, “Now the war is over.” Groves replied “Yes, after we drop two bombs on Japan.”

Post by Rob Wallace, STEM Education Coordinator

All images from the Department of Energy’s Office of History and Heritage Resources.

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SciTech Tuesday–When the Rubber Meets the Road

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As tensions escalated in Europe and Asia, Roosevelt knew he had to prepare the country for war. He was aware that there were critical parts of the manufacturing system that were weak, and that conflict would limit US access to resources in a way that might threaten national security. Using government institutions to support economic development was something his administration had a lot of practice with, so he turned to the Reconstruction Finance Corporation (RFC), which had been created by Congress in 1932 under the Hoover Administration.

At Roosevelt’s direction the RFC created or purchased 9 different corporations. All of these helped develop resources (like rubber or fibers or metals) or supported development of manufacturing facilities. The Rubber Reserve Company at first just controlled strategic reserves of rubber. South Asia was where most rubber plantations were located, and it was coming under the control of the Japanese. Most of the research on synthetic rubber was being conducted by German chemists, who had become expert and developing oil and coal tar into other resources. When it was created the Rubber Reservc Company had about 1 million pounds of rubber.  That seems like a lot, but the military at that time was using about 600,000 pounds a year, and if production increased, so would the need for rubber.

Under the umbrella of the Rubber Reserve Company, several private corporations, including Firestone, Goodrich, and Goodyear,  signed a patent and information sharing agreement, and a committee met to develop a plan for producing synthetic rubber.

A form of polymer called styrene-butadiene rubber was chosen for production. It was the best form for making tire treads, as it is resistant to abrasion and holds its form well. It does, however, require more adhesive than natural rubber. Other polymers were chosen for other uses (such as wiring insulation).

Although the styrene-butadiene rubber could be used on the same manufacturing equipment as natural rubber, it’s use in manufacturing required a big research investment. They used monomers of butadiene and styrene, and mixed them with soap, water, and the catalyst potassium persulfate. By late fall of 1942 the companies had begun successful production. They shared over 200 patents in their consortium. all funded by the RFC through the Rubber Reserve Corporation.

By 1945 the US was producing almost 1 million tons per year of synthetic rubber, more than half of which was produced by the companies in the Rubber Reserve Corporation’s agreement. By 1955 the government had sold all the plants, and control of production was returned to private corporations.

Post by Rob Wallace, STEM Education Coordinator

A block of synthetic rubber comes off the line, and is headed for the baler. From the Library of Congress.

A block of synthetic rubber comes off the line, and is headed for the baler. From the Library of Congress.

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SciTech Tuesday–First V-1 rockets launched June 1944

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On June 13th 1944, the Germans launched the first attack of V-1 rockets on England. The rockets were really pilotless planes that depended upon compasses and gyroscopes for navigation. Detonation was achieved when the engine ran out of fuel and the vehicle crash landed. Of the rockets launched in this initial raid, five crashed near the launch site on the coastt of France, and 4 landed in England. One of the latter landed in London and killed 6 people.

The launch of these V-1 rockets was timed to match a large conventional bombing raid, but the Royal Air Force had successfully targeted the bombers on the runway the day before.

But over the next couple of weeks almost 3000 V-1s were launched against England. Many were brought down over the English Channel by fighters or anti-aircraft guns. About 800 missiles hit greater London in those early summer weeks.

In September the first V-2 rocket attacks were launched, simultaneously with V-1s. About 9000 V-2s were launched against England, killing about 2500 Londoners.

The full name of the V-1 was the Vergeltungswaffen 1. Vergeltungswaffen roughly translates as “retaliatory weapon.” They were launched after the Allied invasions on D-Day, and were also used against Belgium. The launches of V rockets continued until the launch center was over-taken by Allied forces in March 1945.

The V-1 had a fuselage of steel and wings of plywood. It was propelled by a pulsejet engine that fired 50 times per second—giving it the characteristic sound that got it the nicknames ‘doodle bug’ and ‘buzz bomb.’ The gasoline jet engine didn’t provide enough force for takeoff, so the missile was launched with a chemical explosive that got it’s speed up over 350 mph. The V-1’s mechanically complex guidance system led to its low success rate of 25%. They were, however, relatively easy and cheap to manufacture, and caused the Allies to spend a great deal of time and resources to defend against them.

The V-2 used a liquid propellent system of ethanol/water and liquid oxygen. This was a much more powerful system that allowed the missile to travel further and actually cross the boundary of space. The rocket propelled the missile up at an angle for about 65 seconds, after which it sut off and the rocket travelled under the power of gravity. The earlier V-2s used an analog computer to calculate when to shut the engine off. Later models used a radar controlled switch, so that they could be controlled from the ground.

Post by Rob Wallace, STEM Education Coordinator

A cutaway schematic of the V-1 rocket, which was really an unmanned jet aircraft.

A cutaway schematic of the V-1 rocket, which was really an unmanned jet aircraft.

A cutaway schematic of the V-2 rocket, which was propelled by liquid gas.

A cutaway schematic of the V-2 rocket, which was propelled by liquid gas.

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SciTech Tuesday: John Nash and the Legacy of WWII

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One of the hallmarks of the war effort during WWII was the use of intellectual capital. The Manhattan Project and other efforts brought together the best minds to solve big problems. With the end of the war, there was fear that the military and intelligence communities would lose all that intellectual capital.

Think-tanks like RAND (started by Douglas Aircraft Corporation) aimed to continue big science after the war. Tension with the USSR and the Soviet development of weapons so close to the war’s end fueled the fear.

John Nash was born in 1928, and so passed his teenage years in wartime West Virginia. He was a gifted student, who attended Carnegie Institute of Technology (now Carnegie Mellon University) on a merit scholarship. Nash graduated at the age of 20 with both Bachelors’ and Masters’ degrees, and headed to Princeton with this succinct recommendation from his advisor: “This man is a genius.”

Besides inventing a game that swept Princeton math’s common room, and later became Parker Brothers’ Hex, Nash wrote a dissertation called ‘Non-Cooperative Games’ in which he framed negotiation in a context that allowed prediction of benefits to parties and thus outcomes. Nash provided a way to analyze outcomes that did not require zero-sum calculations. The Nash Equilibrium, formally stated in that dissertation, won John Nash the Nobel Prize for Economics in 1994.

This advance in concept and mathematics revolutionized economics, and provided a theory for branches of evolutionary biology and other fields, where it is still influential today.

After taking only 2 years to complete his doctorate from Princeton, Nash was recruited to work for RAND. RAND was very interested in analyzing outcomes of competitive situations–for obvious reasons. His restless mind and desire for collaboration led him to stay at RAND only briefly. He accepted a position at the Massachusetts Institute of Technology in 1951, and worked at RAND as a consultant until 1954.

Nash had always been odd–persistently whistling the same bars from Bach, and leaving equations on the boards in empty classrooms–but a year after he received tenure from MIT, it was clear he was suffering from schizophrenia. His paranoid delusions were filled with spycraft and details from his time at RAND. They were influenced also by the cryptography work he had done over the first years of his time at MIT. Alicia Nash, an MIT physics graduate who had married John Nash in 1957, admitted him to a psychiatric hospital, in 1959, and gave birth to his son a few weeks later.

Nash was seriously ill with schizophrenia until 1970, living under delusions of voices of persons involving espionage and secrecy. He began to recover when he left those visions behind. Decades later his reputation as a mathematician was rehabilitated, and his relationship with his wife was tool. They had divorced in 1963, but she had supported him in the 1970s as he worked to recover. In 2001 they remarried.

Sadly, the couple died last week, on May 23rd. They had landed at Newark on a return flight from Norway, where John Nash had received the Abel Prize. The taxi in which they were riding on the New Jersey Turnpike struck the guardrail, and they were ejected from the car. John was 86 and Alicia was 82.

Post by Rob Wallace, STEM Education Coordinator

 

The beginning of John Nash's dissertation.

The beginning of John Nash’s dissertation.

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SciTech Tuesday–2015 Robotics Challenge

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This year’s National WWII Museum Robotics Challenge, Invent for Victory, was held May 9th. Thirty-six teams from Louisiana, Mississippi, Alabama, and Florida participated in matches with LEGO® MINDSTORMS® robots. They were given 10 objectives, and their goal was to program a robot to complete those challenges. Additionally they made a music video explaining advances in STEM during WWII.

When almost 400 4th-8th graders come to your museum, bringing family, friends, and robots, it’s hard not to have a great time. For most of Saturday they filled our Museum, and with about 75 volunteers we had a brilliant time.

Prizes were awarded in 3 Categories, and there was also a Grand Champion chosen.

Best Video:

  1. Samuel Green Charter School–Green Giants of New Orleans
  2. Metairie Academy for Advanced Studies–The Avengers of Metairie
  3. Maker Krewe–The Unbreakables of New Orleans

Best Robot Design:

  1. Louisiana Children’s Discovery Center–Bayou Builders of Ponchatoula
  2. Patrick Taylor Academy SciTech Academy–The Flying Tigers of Westwego
  3. Stephens Elementary–Bruh Legos of Alexander City, Alabama

Best Robot Performance:

  1. Alexander City Middle School–Legotrons of Alexander City, Alabama
  2. Westdale Heights Academic Magnet–Techno Tick Tocks of Baton Rouge
  3. Mandeville Jr High–Purple Phyre of Mandeville
  4. Benjamin Franklin Elementary–Red Tail Squadron of New Orleans

 Grand Champions Award:

For annually showing the teamwork and perseverance it takes to be great, Lake Harbor Middle School’s Titanium Owls, of Mandeville.

Learn more about STEM at The National WWII Museum.

Post by Rob Wallace, STEM Education Coordinator

 

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SciTech Tuesday–Roosevelt’s Death and Polio

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It was April 12th, 1945, just over a month after he had reported to Congress on the Yalta Conference, and just less than a month before Truman announced Victory in Europe, that Franklin Delano Roosevelt died. That afternoon, at his vacation home in Warm Springs GA, where he had gone to rest before the Inauguration of The United Nations, he declared “I have a terrific pain in the back of my head,” before slumping forward unconscious. He died shortly after, with the death attributed to a stroke.

In 1921, when he was 39, Roosevelt was diagnosed with Poliomyelitis. This disease is caused by an infection of an enterovirus. The Poliovirus is one of the simplest viruses, containing a strand of RNA in a protein capsule. Infection is oral, and in the vast majority of cases results in no symptoms. In a very small number of cases it results in muscle paralysis, and can lead to serious motor problems and even death if it affects the diaphragm.

In the early part of this century Polio was greatly feared, since it strikes almost exclusively children and onset is rapid. Sometimes it was thought to be transmitted by insects, and led to the spraying of DDT, in others to the closure of swimming pools. The development of the Inactivated Polio Vaccine (IPV) by Jonas Salk in 1955 began the near eradication of the disease. There are still hotspots of infection, particularly in Afghanistan and Nigeria, but in recent years there have been only about 200 cases per year reported.

Roosevelt was diagnosed after developing a fever and losing strength in his legs over a couple of days. He had jogged and swam and hiked just before that–being an active man–and so it is unclear where he was exposed. It is rare to be infected past childhood, but Polio is the diagnosis that best fit his symptoms. He used braces to walk, a modified car that didn’t have foot controls, and a wheelchair the rest of his life. Age and the strain of events wore on him in the later years of his presidency. Observers of his speech to Congress about the Yalta Conference noted how he seemed aged and less energetic, and he sat through the address.

One of the dangers for those with partial paralysis is the development of blood clots. It may have been such a clot that led to Roosevelt’s stroke. If so, the Polio may have led to his death, but that’s not certain.

It is certain that without the developments of technology and government support of research that took place in the Depression and war years, innovations such as Salk’s vaccine would not have occurred. The systems put in place to win the war, to develop Big Science and Big Industry, continued in the post-war years.

All images from the National Archives

Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

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SciTech Tuesday–The German Tank Problem

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During  WWII the Allies wanted to find out how many weapons, and in particular tanks, the Germans were producing. The specific concern came as D-Day approached, and planners worried how the Sherman tank would perform. Encounters with the Panzer V in Italy and the Tinger 1 in Tunisia led to concerns that Western tanks would be outperformed, and were countered with the argument that norther France would be filled with lighter tanks, like the Panzer III and IV.

Military intelligence attempted to estimate the number of tanks being produced by the Germans from serial numbers on captured or destroyed tanks. This statistical approach, a new challenger to conventional methods of reconnaissance and spying, proved to be very accurate.

Scientists estimate the size of cryptic populations of animals, like mice or salamanders, by a mark and recapture method. The catch a few animals, mark and release them, and then trap some more. Based on the number of times a previously captured animal is recaptured, an estimate of the population size can be made. The less often a marked animal is recaptured, the bigger the whole population is estimated to be.

This method is not possible in the case of the tanks or other captured equipment. So how did they estimate the number produced? The math is slightly complicated, but I’ll explain the reasoning behind it.

Examination of serial numbers allows for the estimation of the largest possible number. For example, if the serial numbers follow the pattern XXX XXX XXX, then the largest possible number of tanks is 999,999,999—or just shy of 1 billion. This possible number is then compared to the actual serial numbers of captured or damaged tanks found. It is assumed that the tanks captured or damaged are randomly drawn from the population of all tanks. If that is true, then the serial numbers on them also should be randomly within the total number of tanks produced. By comparing the variation in the serial numbers of known tanks to the total possible number of tanks, with some calcuations you can estimate the total tanks actually produce. The more actual serial numbers they had to work with, the more accurate the estimate should be.

After WWII it was possible to look at production records and compare the statistically made estimates and the conventional intelligence estimates to the true production numbers. The statistical methods produced much better estimates of production. Conventional intelligence vastly overestimated production.

Over the years this mathematical approach to population size estimation has become a standard example for teaching probability. Using what has come to be called The German Tank Problem, teachers can provide an open-ended problem for students to work on. They can contrast two forms of estimation, Bayesian and Frequentist analyses, and compare models. The German Tank Problem is a standard part of contemporary AP Statistics courses in the US.

In two weeks I’ll write about a viral disease that had a major impact on the WWII generation.

Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

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SciTech Tuesday-The Jet Stream can bring more than cold air

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This past winter (which will officially end on Friday 3/20) has shown how powerful the Jet Stream can be.

The Jet Stream (by which we usually mean the North Polar Jet Stream) is a relatively narrow, high velocity band of wind. Over time it tends to meander. The air north of it is cold, since it originates in the the Arctic. When in winter we have a big dip in the Jet Stream it can bring very cold air south with the dip. When the Jet Stream makes just the right (or wrong, as your perspective may determine) configuration, it can bring very cold air into contact with very moist air. This leads to heavy snowfall in a region. Since the Jet Stream moves and wobbles a bit more slowly than common storms and weather fronts, it can lead to longer patterns of weather—like the heavy winter snow totals that Boston received this winter.

Since the Jet Stream is pretty predictable throughout a season, it could in theory be used to carry floating objects with no propulsion of their own. It is at its peak from November through March.

Seventy years ago, in the winter of 1944-45, the Japanese military used the Jet Stream to do just that. They had been doing research on the Jet Stream, found that at about 9 km of altitude the wind could carry a large balloon across the Pacific (about 8,000 km) in three days.  That winter they engaged a plan to deliver explosives to North America.

They called these Fu-Go, or ‘windship weapons.’ They were 10 meter hydrogen-filled balloons carrying either a 15 kg antipersonnel bomb or a set of incendiary bombs. They had a relatively sophisticated system for maintaining their altitude.

In sunshine, the helium in the balloon would warm and expand and rise higher. At night the helium would cool and the balloon would descend. The Japanese military engineers designed a control system that used an altimeter that caused the balloon to drop some of its ballast when it descended below 9 km. When the balloon rose too high, to about 12 km, it was at risk of bursting. At this altitude the control system opened a valve to vent some of the hydrogen in the balloon.

The system carried enough ballast and hydrogen to take it through 3 days and nights of travel in the Jet Stream. At that time the bombs were released and the balloon destroyed.

These balloons could carry about 450 kg of payload. The first balloons were rubberized silk, but later versions were made of mulberry paper, that leaked less hydrogen. (Silkworms eat mulberry leaves and make cocoons that are turned into silk—so in either case the balloons depended on mulberry).

The bombs were largely ineffective. During the war, US Military Intelligence estimated that about 350 of these balloons reached the US. Arrivals of balloons were kept very quiet in the press so that the Japanese would have no information about their arrival or effectiveness. The campaign of Fu-Go ended in March of 1945.

In May of 1945 a Sunday School teacher and her 5 students were on an outing in rural Oregon investigated an unusual object they found in the woods. The bomb detonated, killing them all.

Earlier in the war, from 1942 to 1944, Great Britain released 99,000 balloons meant to cause damage to the Axis. About 40% of these carried no bomb, but a very long strand of piano wire. Equipped with automatic timers and fuses, these would inflate and then descend over Germany, unspooling their wire. This was meant to short electrical lines. Shortly after their release (1,000 at a time) their were forest fires near Berlin and in Eastern Germany. One balloon knocked out power in Leipzig.

Barrage balloons were used extensively by all sides in both WWI and WWII. They were blimp-shaped balloons meant to interfere with aircraft. They had long tethers and sometimes nets spanned between them. There were only useful against low-flying craft, but there were 1,400 hundred defending England in 1940, and 3,000 in 1944. Some of them were designed to release explosive charges when the cable was contacted. These explosive-rigged barrage balloons were believed to have stopped at least 200 V1 rockets heading towards the cities of England.

During our busy Spring season, SciTech Tuesday posts will come every other week. 

Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

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SciTech Tuesday: Operation Meetinghouse and Napalm

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Just after midnight on March 9th 1945, residents of Tokyo heard the rumble of over 300 B-29s approaching. In a short time the bombers dropped their payloads of E-46 cluster bombs. This was Operation Meetinghouse, 70 years ago.

Earlier raids, including the Doolittle Raid, had not been very effective, so the March bombing of Tokyo was planned differently. Instead of high altitude strikes with conventional bombs, this raid used the B-29s at low altitude (5,000-9,000 ft) and at night, to take advantage of weaknesses in air defense, and to better target the cluster bombs.

Each of the cluster bombs held 38 M-69 bomblets, which the cluster bomb released at about 2,000 ft. These M-69s were pipes, filled with explosives, cloth, and a jelled gasoline called Napalm. The M-69s ignited a few seconds after landing, and sprayed globs of ignited fuel. These devices had been used earlier in Dresden.

For the March 9th raid on Tokyo, the initial wave of about 225 bombers targeted a part of the city that held working class residents who worked in manufacturing. These neighborhoods included the port and docks. The pattern of targets was made to take the shape of an X. This way the second wave of bombers could use the flames as a target. The bombing was meant to overwhelm firefighting abilities and cause a great conflagration.

From that perspective, it was a success. an area of almost 16 square miles was completely destroyed in a huge fire that burned at 1,000oF. Most of the structures in the targeted area were older, traditional buildings made of wood, and so they were vulnerable to fire. Most estimates put deaths at 100,000, injuries at 1 million, and homeless at 1 million. The industrial output of Tokyo was cut in half.

These estimates of casualties are likely very low. The population density of that part of Tokyo was at least 100,000 per square mile. This means that over 1.5 million people lived in the completely burned area, where the bombs and fire came and passed very quickly. Even at the low estimates, Operation Meetinghouse killed more people than any other single raid in WWII, including Dresden, and the nuclear detonations at Hiroshima and Nagasaki.

Napalm was developed in 1942 by chemists at Harvard University. Early incendiaries used plant latex, which was in short supply during the war. It included phosphorus, so that it would burn for a long time and be resistant to extinguishers. Napalm is made by mixing a dry brown powder with gasoline, at which point it gets sticky and extremely flammable. It was first tested on the Harvard University football field.

Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

This is a map made by occupying US Military of bombed portions of Tokyo in 1947.

This is a map made by occupying US Military of bombed portions of Tokyo in 1947.

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SciTech Tuesday: Plans for The Gadget

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In early 1945 the Manhattan Project had made great progress, but its promise to provide bombs by August of the same year was very optimistic.

In simplest terms, an atomic bomb works by creating an uncontrolled nuclear reaction in radioactive materials like 238Ur or 239Pu. The project, at great effort and expense, was producing sufficient quantities of these isotopes, but the problem of how to build a bomb that created a critical mass of them at detonation and not before had yet to be solved.

A gun mechanism, in which a small amount of material was shot into a larger amount of the same material, was originally planned for use. It ended up being the trigger for the 238Ur bomb that was used on Hiroshima. 239Pu was easier to produce in large quantities for a bomb than 238Ur, but it would take more to bring it to critical mass. Seth Neddermeyer showed the teams at Los Alamos that as it began to undergo fission, a mass of 239Pu would expand and become less dense, thus not achieving critical mass. He suggested a different trigger mechanism—implosion. The idea was that several smaller masses of 239Pu arranged around a hollow core would be pushed together quickly by explosions surrounding them. Working out the right dynamics to find a configuration and triggering mechanism took almost a year of experimentation. John von Neumann, who contributed mathematical work to optimize the size and placement of charges, and Edward Teller, who figured out how to change the density of the plutonium metal to achieve critical mass, were prominent members of the implosion team.

Another challenge of the plutonium bomb was that the plutonium samples they had contained a lot of 240Pu. This isotope spontaneously undergoes fission at a high rate, and might prevent a large chain reaction. This also meant that implosion would be necessary.

The complexity of the implosion mechanism required the scientists and engineers working on that part of the project to conduct many experiments. Most of these (called the RaLa tests) used 140Lanthanum because it was less dangerous and expensive. Eventually they also tested what we would call today a ‘dirty bomb.’ Using waste products from reactors, they detonated a test bomb to see the results.

All this work testing the bomb mechanics culminated in the Trinity Test in July 1945. This bomb was code-named The Gadget. At first Groves and Oppenheimer were concerned it might not work, so they built a very expensive metal containment chamber in which they planned to detonate the bomb. This would allow them to recover the 239Pu which had cost so much time and money to isolate. However, by the time they actually conducted the test they were confident it would work, having been through over 240 RaLa tests.

After the Trinity Test, the path was clear to delivery of the bombs on schedule.

This is the last week to apply for Real World Science, a weeklong residential seminar to learn how to teach STEM with history.

Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

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