Image Comics is an American comic book publisher. It was founded in 1992 by several high-profile illustrators as a venue for creator-owned properties, in which comics creators could publish material of their own creation without giving up the copyrights to those properties, as is the case in the work for hire-dominated American comics industry, in which the legal author is a publisher, such as Marvel Comics or DC Comics, the creator is an employee of that publisher. Image Comics was successful, remains one of the largest comic book publishers in North America, its output was dominated by superhero and fantasy series from the studios of the founding Image partners, but now includes comics in many genres by numerous independent creators. Its best-known series include The Walking Dead, Savage Dragon, The Darkness, Saga and Bone. In the early 1990s, comics creators Erik Larsen, Rob Liefeld, Jim Valentino had dinner with Malibu Comics editor-in-chief Dave Olbrich. Malibu was a small but established publishing company sympathetic to creator-ownership, Olbrich expressed interest in publishing comics created by them.
These and several other freelance illustrators doing popular work for Marvel Comics were growing frustrated with the company's work for hire policies and practices, which they felt did not sufficiently reward the talent that produced them, as the company merchandised their artwork, compensated them with modest royalties. According to Todd McFarlane, he, Jim Lee and Liefeld met with Marvel president Terry Stewart and editor Tom DeFalco in late December 1991. Larsen and Silvestri, who joined the group the night before, were not present, but the group that met with Stewart indicated that they were representing them as well. Contrary to what has been reported by other sources, McFarlane says that they made no demands of Stewart or Marvel, but informed him that they were leaving, gave their reasons why, cautioned Stewart to heed those reasons, lest the company suffer future exoduses; the creators had the same meeting with DC Comics the next day. After Whilce Portacio returned from his yearly trip to the Philippines, his Homage Studios colleague Lee asked him to join the group.
A group of eight creators announced the founding of Image Comics: illustrators Todd McFarlane, Jim Lee, Rob Liefeld, Marc Silvestri, Erik Larsen, Jim Valentino, Whilce Portacio. This development was nicknamed the "X-odus", because several of the creators involved were famous for their work on the X-Men franchise. Marvel's stock fell $3.25 / share. Image's organizing charter had two key provisions: Image would not own any creator's work. No Image partner would interfere – creatively or financially – with any other partner's work. Image itself would own no intellectual property except the company trademarks: its name and its logo, designed by writer Hank Kanalz; each Image partner founded his own studio, which published under the Image banner but was autonomous from any central editorial control. Claremont was not part of the partnership, Portacio withdrew during the formative stages to deal with his sister's illness, so Image consisted of six studios: Todd McFarlane Productions, owned by Todd McFarlane WildStorm Productions, owned by Jim Lee Highbrow Entertainment, owned by Erik Larsen Shadowline, owned by Jim Valentino Top Cow Productions, owned by Marc Silvestri Extreme Studios, owned by Rob Liefeld Their initial titles were produced under the Image imprint, but published through Malibu Comics, which provided administrative, production and marketing support for the launch of them.
The first Image comic books to arrive in stores were Liefeld's Youngblood, Larsen's The Savage Dragon, McFarlane's Spawn, Lee's WildC. A. T.s. Propelled by the artists' popularity and the eagerness of comic book collectors to get in on the "next big thing", these series sold in numbers that no publisher other than Marvel, DC, or Valiant Comics had achieved in the years since the market's decline in the 1970s. Within a few months, the Image titles' success led to Malibu having 10% of the North American comics market share exceeding that of industry giant DC Comics. By the beginning of 1993, Image's financial situation was secure enough to publish its titles independently, it left Malibu; some of the founders' studios came to resemble separate publishers, each with several ongoing series set in a shared universe. The use of freelancers to write or illustrate series that were owned by the Image partners led to criticism that some of them had reproduced the system they had rebelled against, but with them in charge instead of a corporation.
Image partners such as Larsen and Valentino, who did not take this approach, assumed a neutral position on it, in keeping with the requirement that none of them had any say in how the others' studios were run. Some of the Image partners used their studios to publish new works produced by independent creators, allowing them to retain ownership and editorial control over those series, an arrangement, t
William Childs Westmoreland was a United States Army general, most notably commander of United States forces during the Vietnam War from 1964 to 1968. He served as Chief of Staff of the United States Army from 1968 to 1972. Westmoreland adopted a strategy of attrition against the Viet Cong and the North Vietnamese Army, attempting to drain them of manpower and supplies, he made use of the United States' edge in artillery and air power, both in tactical confrontations and in relentless strategic bombing of North Vietnam. Many of the battles in Vietnam were technically United States victories, with the United States Army in control of the field afterward. Public support for the war diminished after the Battle of Khe Sanh and the Tet Offensive in 1968. By the time he was re-assigned as Army Chief of Staff, United States military forces in Vietnam had reached a peak of 535,000 personnel. Westmoreland's strategy was politically unsuccessful. Growing United States casualties and the draft undermined United States support for the war while large-scale casualties among non-combatants weakened South Vietnamese support.
This failed to weaken North Vietnam's will to fight, the Government of South Vietnam—a factor out of Westmoreland's control—never succeeded in establishing enough legitimacy to quell defections to the Viet Cong. William Childs Westmoreland was born in Spartanburg County, South Carolina, on March 26, 1914 to Eugenia Talley Childs and James Ripley Westmoreland, his upper middle class family was involved in textile industries. At the age of 15, William became an Eagle Scout at Troop 1 Boy Scouts, was recipient of the Distinguished Eagle Scout Award and Silver Buffalo from the Boy Scouts of America as a young adult. After spending a year at The Citadel in 1932, he was appointed to attend the United States Military Academy on the nomination of Senator James F. Byrnes, a family friend, his motive for entering West Point was "to see the world". He was a member of a distinguished West Point class that included Creighton Abrams and Benjamin O. Davis Jr. Westmoreland graduated as first captain—the highest cadet rank—and received the Pershing Sword, "presented to cadet with highest level of military proficiency".
Westmoreland served as the superintendent of the Protestant Sunday School Teachers. Following graduation from West Point in 1936, Westmoreland became an artillery officer and served in several assignments with the 18th Field Artillery at Fort Sill. In 1939, he was promoted to first lieutenant, after which he was a battery commander and battalion staff officer with the 8th Field Artillery at Schofield Barracks, Hawaii. In World War II, Westmoreland saw combat with the 34th Field Artillery Battalion, 9th Infantry Division, in Tunisia, Sicily and Germany, he reached the temporary wartime rank of colonel, on October 13, 1944, was appointed the chief of staff of the 9th Infantry Division. After the war, Westmoreland completed Airborne training at the Infantry School in 1946, he commanded the 504th Parachute Infantry Regiment, 82d Airborne Division. From 1947 to 1950, he served as chief of staff for the 82d Airborne Division, he was an instructor at the Army Command and General Staff College from 1950 to 1951.
He completed the Army War College as a student in 1951, stayed as an instructor from 1951 to 1952. Westmoreland was promoted to Brigadier General in November 1952 at the age of 38, making him one of the youngest U. S. Army generals in the post-World War II era, he commanded the 187th Airborne Regimental Combat Team in operations in Korea from 1952 to 1953. After returning to the United States, Westmoreland was deputy assistant chief of staff, G–1, for manpower control on the Army staff from 1953 to 1955. In 1954, he completed a three-month management program at Harvard Business School; as Stanley Karnow noted, "Westy was a corporation executive in uniform."After the war, Westmoreland was the United States Army's Secretary of the General Staff from 1955 to 1958. He commanded the 101st Airborne Division from 1958 to 1960, he was Superintendent of the United States Military Academy from 1960 to 1963. In 1962, Westmoreland was admitted as an honorary member of the Massachusetts Society of the Cincinnati.
He was promoted to lieutenant general in July 1963 and was Commanding General of the XVIII Airborne Corps from 1963 to 1964. Background and overviewMaster philosopher of war Karl von Clausewitz emphasized a century and a half earlier that because war is controlled by its political object, the value of this object must determine the sacrifices to be made for it both in magnitude and in duration, he went on to say, Once the expenditure of effort exceeds the value of the political object, the object must be renounced. The attempted French re-colonization of Vietnam following World War II culminated in a decisive French defeat at the Battle of Dien Bien Phu; the Geneva Conference discussed the possibility of restoring peace in Indochina, temporarily separated Vietnam into two zones, a northern zone to be governed by the Việt Minh, a southern zone to be governed by the State of Vietnam headed by former emperor Bảo Đại. A Conference Final Declaration, issued by the British chairman of the conference, provided that a general election be held by July 1956 to create a unified Vietnamese state.
Although presented as a consensus view, this document was not accepted by the delegates of either the State of Vietnam or the United States. In addition, the Soviet Union and other communist nations recognized the North while the United States and other non-communist sta
Wernher von Braun
Wernher Magnus Maximilian Freiherr von Braun was a German-American aerospace engineer and space architect. He was the leading figure in the development of rocket technology in Germany and a pioneer of rocket technology and space science in the United States. While in his twenties and early thirties, von Braun worked in Nazi Germany's rocket development program, he helped design and develop the V-2 rocket at Peenemünde during World War II. Following the war, he was secretly moved to the United States, along with about 1,600 other German scientists and technicians, as part of Operation Paperclip, he worked for the United States Army on an intermediate-range ballistic missile program, he developed the rockets that launched the United States' first space satellite Explorer 1. His group was assimilated into NASA, where he served as director of the newly formed Marshall Space Flight Center and as the chief architect of the Saturn V super heavy-lift launch vehicle that propelled the Apollo spacecraft to the Moon.
In 1975, von Braun received the National Medal of Science. He advocated a human mission to Mars. Wernher von Braun was born on March 23, 1912, in the small town of Wirsitz, in the Posen Province, in what was the German Empire and is now Poland, he was the second of three sons. He belonged to a noble Lutheran family, from birth he held the title of Freiherr; the German nobility's legal privileges were abolished in 1919, although noble titles could still be used as part of the family name. His father, Magnus Freiherr von Braun, was conservative politician, his mother, Emmy von Quistorp, traced her ancestry through both parents to medieval European royalty and was a descendant of Philip III of France, Valdemar I of Denmark, Robert III of Scotland, Edward III of England. Wernher had an older brother, the West German diplomat Sigismund von Braun, who served as Secretary of State in the Foreign Office in the 1970s, a younger brother named Magnus von Braun, a rocket scientist and a senior executive with Chrysler.
After Wernher's confirmation, his mother gave him a telescope, he developed a passion for astronomy. The family moved to Berlin in 1915. Here in 1924, the 12-year-old Wernher, inspired by speed records established by Max Valier and Fritz von Opel in rocket-propelled cars, caused a major disruption in a crowded street by detonating a toy wagon to which he had attached fireworks, he was taken into custody by the local police. Wernher learned to play both the cello and the piano at an early age and at one time wanted to become a composer, he took lessons from the composer Paul Hindemith. The few pieces of Wernher's youthful compositions that exist are reminiscent of Hindemith's style, he could play piano pieces of Bach from memory. Beginning in 1925, Wernher attended a boarding school at Ettersburg Castle near Weimar, where he did not do well in physics and mathematics. There he acquired a copy of By Rocket into Planetary Space by rocket pioneer Hermann Oberth. In 1928, his parents moved him to the Hermann-Lietz-Internat on the East Frisian North Sea island of Spiekeroog.
Space travel had always fascinated Wernher, from on he applied himself to physics and mathematics to pursue his interest in rocket engineering. In 1930, von Braun attended the Technische Hochschule Berlin, where he joined the Spaceflight Society and assisted Willy Ley in his liquid-fueled rocket motor tests in conjunction with Hermann Oberth. In spring 1932, he graduated from the Technische Hochschule Berlin, with a diploma in mechanical engineering, his early exposure to rocketry convinced him that the exploration of space would require far more than applications of the current engineering technology. Wanting to learn more about physics and astronomy, von Braun entered the Friedrich-Wilhelm University of Berlin for post-graduate studies and graduated with a doctorate in physics in 1934, he studied at ETH Zürich for a term from June to October 1931. Although he worked on military rockets in his years there, space travel remained his primary interest. In 1930, von Braun attended a presentation given by Auguste Piccard.
After the talk, the young student approached the famous pioneer of high-altitude balloon flight, stated to him: "You know, I plan on traveling to the Moon at some time." Piccard is said to have responded with encouraging words. Von Braun was influenced by Oberth, of whom he said: Hermann Oberth was the first, who when thinking about the possibility of spaceships grabbed a slide-rule and presented mathematically analyzed concepts and designs... I, owe to him not only the guiding-star of my life, but my first contact with the theoretical and practical aspects of rocketry and space travel. A place of honor should be reserved in the history of science and technology for his ground-breaking contributions in the field of astronautics. According to historian Norman Davies, von Braun was able to pursue a career as a rocket scientist in Germany due to a "curious oversight" in the Treaty of Versailles which did not include rocketry in its list of weapons forbidden to Germany. Von Braun had an complex relationship with the Nazi regime of the Third Reich.
He applied for official membership of the Nazi Party on November 12, 1937, was issued membership number 5,738,692. Michael J. Neufeld, a published author of aerospace history and chief of
Yuri Alekseyevich Gagarin was a Soviet pilot and cosmonaut. He became the first human to journey into outer space when his Vostok spacecraft completed one orbit of the Earth on 12 April 1961. Gagarin became an international celebrity and was awarded many medals and titles, including Hero of the Soviet Union, his nation's highest honour. Vostok 1 was his only spaceflight, but he served as the backup crew to the Soyuz 1 mission, which ended in a fatal crash. Gagarin served as the deputy training director of the Cosmonaut Training Centre outside Moscow, subsequently named after him. Gagarin died in 1968; the Fédération Aéronautique Internationale awards the Yuri A. Gagarin Gold Medal in his honour. Yuri Gagarin was born 9 March 1934 near Gzhatsk, his parents worked on a collective farm: Alexey Ivanovich Gagarin as a carpenter and bricklayer, Anna Timofeyevna Gagarina as a milkmaid. Yuri was the third of four children: older brother Valentin, older sister Zoya, younger brother Boris. Like millions of people in the Soviet Union, the Gagarin family suffered during Nazi occupation in World War II.
Klushino was occupied in November 1941 during the German advance on Moscow, an officer took over the Gagarin residence. The family was allowed to build a mud hut 3 by 3 metres inside, on the land behind their house, where they spent a year and nine months until the end of the occupation, his two older siblings were deported by the Germans to Poland for slave labour in 1943, did not return until after the war in 1945. In 1946, the family moved to Gzhatsk. In 1950, Gagarin entered into an apprenticeship at age 16 as a foundryman at the Lyubertsy Steel Plant near Moscow, enrolled at a local "young workers" school for seventh grade evening classes. After graduating in 1951 from both the seventh grade and the vocational school with honours in moldmaking and foundry work, he was selected for further training at the Saratov Industrial Technical School, where he studied tractors. While in Saratov, Gagarin volunteered for weekend training as a Soviet air cadet at a local flying club, where he learned to fly — at first in a biplane and in a Yak-18 trainer.
He earned extra money as a part-time dock labourer on the Volga River. He applied to attend the First Chkalov Air Force Pilot's School in Orenburg and was accepted as a cadet, he began his military training by flying Yak-18s. Gagarin was promoted to cadet-sergeant on 22 February 1956. Before he was permitted to fly a single-seat aircraft, he was required to show sufficient proficiency to a flight instructor. In one training incident, Gagarin was flying with an instructor, his takeoff and flight was acceptable, but while landing the instructor realized Gagarin was descending too and took over the controls. An identical incident occurred in another training flight two weeks later; this was grounds for Gagarin's dismissal from the flight school. The commander of the regiment saw Gagarin performing fitness training alone in the rain, they decided to give Gagarin another chance at landing. The instructor gave Gagarin a cushion to sit on. While the landing was still rough, it was within acceptable limits and Gagarin was permitted to solo.
He soloed in a MiG-15 in 1957. He became a lieutenant in the Soviet Air Forces on 5 November 1957 after he accumulated 166 hours and 47 minutes of flight time, he graduated the next day. After graduation, he was assigned to the Luostari airbase in Murmansk Oblast, close to the Norwegian border, where terrible weather made flying risky, his assignment there was for two years. Three months into his assignment, he became a military third class. On 6 November 1959, he received the rank of senior lieutenant. In 1960, after an extensive search and selection process, Gagarin was chosen with 19 other pilots for the Soviet space program. Gagarin was further selected for an elite training group known as the Sochi Six, from which the first cosmonauts of the Vostok programme would be chosen. Gagarin and other prospective candidates were subjected to experiments designed to test physical and psychological endurance. Gagarin experienced microgravity with the use of a drop tower, which allowed for 2–3 seconds of weightlessness.
The eventual choices for the first launch were Gagarin and Gherman Titov due to their performance during training sessions as well as their physical characteristics — space was limited in the small Vostok cockpit, both men were short. Gagarin was 1.57 metres tall. In August 1960, when Gagarin was one of 20 possible candidates, a Soviet Air Force doctor evaluated his personality as follows: Modest. Gagarin was a favoured candidate by his peers; when the 20 candidates were asked to anonymously vote for which other candidate they would like to see as the first to fly, all but t
Nick Pitarra is an American comic book artist known for his numerous collaborations with writer Jonathan Hickman, which include mini-series The Red Wing and ongoing The Manhattan Projects, both released through Image Comics. Pitarra is a member of Ten Ton Studios. Interior comic work includes: Astonishing Tales v2 #1-6: "Bobby and Sam in Mojoworld" Ten Ton Studios' Jam Comic #2: "page twenty-two" S. H. I. E. L. D.: Infinity: "Chapter One: Colossus" The Red Wing #1-4 The Manhattan Projects #1-9, 11-14, 16-18, 20, 22-25 The Sun Beyond the Stars #1-ongoing Morning Glories #27 Teenage Mutant Ninja Turtles v5 #19, 28 Teenage Mutant Ninja Turtles: Utrom Empire #1-3 And Then Emily Was Gone #2 The Life After #1-7 Rasputin #1 The Transformers vs. G. I. Joe #5 God Hates Astronauts #5 Valhalla Mad #1 Silk v1 #3 John Flood #1 Secret Wars: Red Skull #1 Secret Wars: Weirdworld #2 Judge Dredd v2 #5 Kennel Block Blues #1 Harper, David. "Artist August: Nick Pitarra". Multiversity Comics. Smithee, Alan. "Interview with Nick Pitarra".
Wednesday's Heroes. Tabrys, Jason. "Nick Pitarra Talks Conspiring with Hickman On "Manhattan Projects"". Comic Book Resources. Hudson, Jeremy. "Comic Interview: THE MANHATTAN PROJECTS' Nick Pitarra". Screen Invasion. Magnett, Chase. "Interview: Nick Pitarra: the Project of'Manhattan Projects'". Comics Bulletin. Nick Pitarra at the Grand Comics Database Nick Pitarra at the Comic Book DB
Haroutune Krikor "Harry" Daghlian Jr. was a physicist with the Manhattan Project which designed and produced the atomic bombs that were used in World War II. He accidentally irradiated himself on August 21, 1945, during a critical mass experiment at the remote Omega Site of the Los Alamos Laboratory in New Mexico, resulting in his death 25 days later. Daghlian was irradiated as a result of a criticality accident that occurred when he accidentally dropped a tungsten carbide brick onto a 6.2 kg plutonium–gallium alloy bomb core. This core, subsequently nicknamed the "demon core", was involved in the death of another physicist, Louis Slotin. Haroutune Krikor Daghlian Jr. of Armenian-American descent, was born in Waterbury, Connecticut, on May 4, 1921, one of three children of Margaret Rose and Haroutune Krikor Daghlian. He had a sister, a brother, Edward. Soon after his birth the family moved across state to the coastal town of Connecticut, he was educated at Harbor Elementary School, where he played violin in the school orchestra, at Bulkeley High School.
In 1938, at the age of 17, he entered the Massachusetts Institute of Technology, intending to study mathematics, but became interested in physics particle physics emerging as an exciting new field. This interest led him to transfer to the West Lafayette, campus of Purdue University, where he graduated with a bachelor of Science degree in 1942, he commenced work on his doctorate, assisting Marshall Holloway with the cyclotrons. In 1944, while still a graduate student, he joined Otto Frisch's Critical Assembly Group at the Los Alamos Laboratory of the Manhattan Project. During an experiment on August 21, 1945, Daghlian was attempting to build a neutron reflector manually by stacking a set of 4.4-kilogram tungsten carbide bricks in an incremental fashion around a plutonium core. The purpose of the neutron reflector was to reduce the mass required for the plutonium core to attain criticality, he was moving the final brick over the assembly, but neutron counters alerted Daghlian to the fact that the addition of that brick would render the system supercritical.
As he withdrew his hand, he inadvertently dropped the brick onto the center of the assembly. Since the assembly was nearly in the critical state, the accidental addition of that brick caused the reaction to go into the prompt critical region of neutronic behavior; this resulted in a criticality accident. Daghlian reacted after dropping the brick and attempted to knock the brick off the assembly without success, he was forced to disassemble part of the tungsten-carbide pile in order to halt the reaction. Daghlian was estimated to have received a dose of 510 rem of neutron radiation, from a yield of 1016 fissions. Despite intensive medical care, he developed symptoms of severe radiation poisoning and his mother and sister were flown out to care for him, he fell into a coma, died 25 days after the accident. He was the first known fatality caused by a criticality accident, his body was returned to New London. As a result of the incident, safety regulations for the project were revised. A special committee was established to review any similar experiments and recommend appropriate safety procedures.
This change of procedures included needing a minimum of two people involved in such an experiment, using at least two instruments monitoring neutron intensities with audible alerts, preparing a plan for operating methods and any contingencies that might occur during similar experiments. Additionally and designs for remote-controlled test devices were initiated leading to the creation of the Godiva device; these changes did not prevent another criticality accident from happening at Los Alamos the following year. Louis Slotin, a colleague of Daghlian's, was killed in 1946 while performing criticality tests on the same plutonium core. After these two incidents it became known as the "demon core", all similar criticality experiments were halted until remote-controlled assembly devices were more developed and available. Daghlian was memorialized on May 20, 2000, by the city of New London, with the erection of a memorial stone and flagpole in Calkins Park, unveiled by his brother and sister, it read: "though not in uniform, he died in service to his country."
Media related to Haroutune Krikor Daghlian, Jr. at Wikimedia Commons Harry Daghlian at Find a Grave
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or from a combination of fission and fusion reactions. Both bomb types release large quantities of energy from small amounts of matter; the first test of a fission bomb released an amount of energy equal to 20,000 tons of TNT. The first thermonuclear bomb test released energy equal to 10 million tons of TNT. A thermonuclear weapon weighing little more than 2,400 pounds can release energy equal to more than 1.2 million tons of TNT. A nuclear device no larger than traditional bombs can devastate an entire city by blast and radiation. Since they are weapons of mass destruction, the proliferation of nuclear weapons is a focus of international relations policy. Nuclear weapons have been used twice in war, both times by the United States against Japan near the end of World War II. On August 6, 1945, the U. S. Army Air Forces detonated a uranium gun-type fission bomb nicknamed "Little Boy" over the Japanese city of Hiroshima.
S. Army Air Forces detonated a plutonium implosion-type fission bomb nicknamed "Fat Man" over the Japanese city of Nagasaki; these bombings caused injuries that resulted in the deaths of 200,000 civilians and military personnel. The ethics of these bombings and their role in Japan's surrender are subjects of debate. Since the atomic bombings of Hiroshima and Nagasaki, nuclear weapons have been detonated over two thousand times for testing and demonstration. Only a few nations are suspected of seeking them; the only countries known to have detonated nuclear weapons—and acknowledge possessing them—are the United States, the Soviet Union, the United Kingdom, China, India and North Korea. Israel is believed to possess nuclear weapons, though, in a policy of deliberate ambiguity, it does not acknowledge having them. Germany, Turkey and the Netherlands are nuclear weapons sharing states. South Africa is the only country to have independently developed and renounced and dismantled its nuclear weapons.
The Treaty on the Non-Proliferation of Nuclear Weapons aims to reduce the spread of nuclear weapons, but its effectiveness has been questioned, political tensions remained high in the 1970s and 1980s. Modernisation of weapons continues to this day. There are two basic types of nuclear weapons: those that derive the majority of their energy from nuclear fission reactions alone, those that use fission reactions to begin nuclear fusion reactions that produce a large amount of the total energy output. All existing nuclear weapons derive some of their explosive energy from nuclear fission reactions. Weapons whose explosive output is from fission reactions are referred to as atomic bombs or atom bombs; this has long been noted as something of a misnomer, as their energy comes from the nucleus of the atom, just as it does with fusion weapons. In fission weapons, a mass of fissile material is forced into supercriticality—allowing an exponential growth of nuclear chain reactions—either by shooting one piece of sub-critical material into another or by compression of a sub-critical sphere or cylinder of fissile material using chemically-fueled explosive lenses.
The latter approach, the "implosion" method, is more sophisticated than the former. A major challenge in all nuclear weapon designs is to ensure that a significant fraction of the fuel is consumed before the weapon destroys itself; the amount of energy released by fission bombs can range from the equivalent of just under a ton to upwards of 500,000 tons of TNT. All fission reactions generate the remains of the split atomic nuclei. Many fission products are either radioactive or moderately radioactive, as such, they are a serious form of radioactive contamination. Fission products are the principal radioactive component of nuclear fallout. Another source of radioactivity is the burst of free neutrons produced by the weapon; when they collide with other nuclei in surrounding material, the neutrons transmute those nuclei into other isotopes, altering their stability and making them radioactive. The most used fissile materials for nuclear weapons applications have been uranium-235 and plutonium-239.
Less used has been uranium-233. Neptunium-237 and some isotopes of americium may be usable for nuclear explosives as well, but it is not clear that this has been implemented, their plausible use in nuclear weapons is a matter of dispute; the other basic type of nuclear weapon produces a large proportion of its energy in nuclear fusion reactions. Such fusion weapons are referred to as thermonuclear weapons or more colloquially as hydrogen bombs, as they rely on fusion reactions between isotopes of hydrogen. All such weapons derive a significant portion of their energy from fission reactions used to "trigger" fusion reactions, fusion reactions can themselves trigger additional fission reactions. Only six countries—United States, United Kingdom, China and India—have conducted thermonuclear weapon tests. North Korea claims to have tested a fusion weapon as of January 2016. Thermonuclear weapons a