A neutrino is a fermion that interacts only via the weak subatomic force and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small that it was long thought to be zero; the mass of the neutrino is much smaller than that of the other known elementary particles. The weak force has a short range, the gravitational interaction is weak, neutrinos, as leptons, do not participate in the strong interaction. Thus, neutrinos pass through normal matter unimpeded and undetected. Weak interactions create neutrinos in one of three leptonic flavors: electron neutrinos, muon neutrinos, or tau neutrinos, in association with the corresponding charged lepton. Although neutrinos were long believed to be massless, it is now known that there are three discrete neutrino masses with different tiny values, but they do not correspond uniquely to the three flavors. A neutrino created with a specific flavor is in an associated specific quantum superposition of all three mass states.
As a result, neutrinos oscillate between different flavors in flight. For example, an electron neutrino produced in a beta decay reaction may interact in a distant detector as a muon or tau neutrino. Although only differences of squares of the three mass values are known as of 2016, cosmological observations imply that the sum of the three masses must be less than one millionth that of the electron. For each neutrino, there exists a corresponding antiparticle, called an antineutrino, which has half-integer spin and no electric charge, they are distinguished from the neutrinos by having opposite signs of lepton chirality. To conserve total lepton number, in nuclear beta decay, electron neutrinos appear together with only positrons or electron-antineutrinos, electron antineutrinos with electrons or electron neutrinos. Neutrinos are created by various radioactive decays, including in beta decay of atomic nuclei or hadrons, nuclear reactions such as those that take place in the core of a star or artificially in nuclear reactors, nuclear bombs or particle accelerators, during a supernova, in the spin-down of a neutron star, or when accelerated particle beams or cosmic rays strike atoms.
The majority of neutrinos in the vicinity of the Earth are from nuclear reactions in the Sun. In the vicinity of the Earth, about 65 billion solar neutrinos per second pass through every square centimeter perpendicular to the direction of the Sun. For study, neutrinos can be created artificially with nuclear reactors and particle accelerators. There is intense research activity involving neutrinos, with goals that include the determination of the three neutrino mass values, the measurement of the degree of CP violation in the leptonic sector. Neutrinos can be used for tomography of the interior of the earth; the neutrino was postulated first by Wolfgang Pauli in 1930 to explain how beta decay could conserve energy and angular momentum. In contrast to Niels Bohr, who proposed a statistical version of the conservation laws to explain the observed continuous energy spectra in beta decay, Pauli hypothesized an undetected particle that he called a "neutron", using the same -on ending employed for naming both the proton and the electron.
He considered that the new particle was emitted from the nucleus together with the electron or beta particle in the process of beta decay. James Chadwick discovered a much more massive neutral nuclear particle in 1932 and named it a neutron leaving two kinds of particles with the same name. Earlier Pauli had used the term "neutron" for both the neutral particle that conserved energy in beta decay, a presumed neutral particle in the nucleus; the word "neutrino" entered the scientific vocabulary through Enrico Fermi, who used it during a conference in Paris in July 1932 and at the Solvay Conference in October 1933, where Pauli employed it. The name was jokingly coined by Edoardo Amaldi during a conversation with Fermi at the Institute of Physics of via Panisperna in Rome, in order to distinguish this light neutral particle from Chadwick's heavy neutron. In Fermi's theory of beta decay, Chadwick's large neutral particle could decay to a proton and the smaller neutral particle: n0 → p+ + e− + νeFermi's paper, written in 1934, unified Pauli's neutrino with Paul Dirac's positron and Werner Heisenberg's neutron–proton model and gave a solid theoretical basis for future experimental work.
The journal Nature rejected Fermi's paper, saying that the theory was "too remote from reality". He submitted the paper to an Italian journal, which accepted it, but the general lack of interest in his theory at that early date caused him to switch to experimental physics. By 1934 there was experimental evidence against Bohr's idea that energy conservation is invalid for beta decay: At the Solvay conference of that year, measurements of the energy spectra of beta particles were reported, showing that there is a strict limit on the energy of electrons from each type of beta decay; such a limit is not expected if the conservation of energy is invalid, in which case any amount of energy would be statistically available in at least a few decays. The natural explanation of the beta decay spectrum as first measured in 1934 was that only a limited amount of en
A liquid-propellant rocket or liquid rocket is a rocket engine that uses liquid propellants. Liquids are desirable because their reasonably high density allows the volume of the propellant tanks to be low, it is possible to use lightweight centrifugal turbopumps to pump the propellant from the tanks into the combustion chamber, which means that the propellants can be kept under low pressure; this permits the use of low-mass propellant tanks. An inert gas stored in a tank at a high pressure is sometimes used instead of pumps in simpler small engines to force the propellants into the combustion chamber; these engines may have a lower mass ratio, but are more reliable, are therefore used in satellites for orbit maintenance. Liquid rockets can be monopropellant rockets using a single type of propellant, bipropellant rockets using two types of propellant, or more exotic tripropellant rockets using three types of propellant; some designs are throttleable for variable thrust operation and some may be restarted after a previous in-space shutdown.
Liquid propellants are used in hybrid rockets, in which a liquid oxidizer is combined with a solid fuel. The idea of liquid rocket as understood in the modern context first appears in the book The Exploration of Cosmic Space by Means of Reaction Devices, by the Russian school teacher Konstantin Tsiolkovsky; this seminal treatise on astronautics was published in May 1903, but was not distributed outside Russia until years and Russian scientists paid little attention to it. Pedro Paulet wrote a letter to a newspaper in Lima in 1927, claiming he had experimented with a liquid rocket engine while he was a student in Paris three decades earlier. Historians of early rocketry experiments, among them Max Valier, Willy Ley, John D. Clark, have given differing amounts of credence to Paulet's report. Paulet did not claim to have launched a liquid rocket; the first flight of a liquid-propellant rocket took place on March 16, 1926 at Auburn, when American professor Dr. Robert H. Goddard launched a vehicle using liquid oxygen and gasoline as propellants.
The rocket, dubbed "Nell", rose just 41 feet during a 2.5-second flight that ended in a cabbage field, but it was an important demonstration that liquid-fueled rockets were possible. Goddard proposed liquid propellants about fifteen years earlier and began to experiment with them in 1921; the German-Romanian Hermann Oberth published a book in 1922 suggesting the use of liquid propellants. In Germany and scientists became enthralled with liquid-fuel rockets and testing them in the early 1930s in a field near Berlin; this amateur rocket group, the VfR, included Wernher von Braun, who became the head of the army research station that designed the V-2 rocket weapon for the Nazis. By the late 1930s, use of rocket propulsion for manned flight began to be experimented with, as Germany's Heinkel He 176 made the first manned rocket-powered flight using a liquid-fueled rocket engine, designed by German aeronautics engineer Hellmuth Walter on June 20, 1939; the only production rocket-powered combat aircraft to see military service, the Me 163 Komet in 1944-45 used a Walter-designed liquid-fueled rocket motor, the Walter HWK 109-509, which produced up to 1,700 kgf thrust at full power.
After World War II the American government and military seriously considered liquid-propellant rockets as weapons and began to fund work on them. The Soviet Union did and thus began the Space Race. Liquid rockets have been built as monopropellant rockets using a single type of propellant, bipropellant rockets using two types of propellant, or more exotic tripropellant rockets using three types of propellant. Bipropellant liquid rockets use a liquid fuel, such as liquid hydrogen or a hydrocarbon fuel such as RP-1, a liquid oxidizer, such as liquid oxygen; the engine may be a cryogenic rocket engine, where the fuel and oxidizer, such as hydrogen and oxygen, are gases which have been liquefied at low temperatures. Liquid-propellant rockets can be throttled in realtime, have control of mixture ratio. Hybrid rockets apply a liquid oxidizer to a solid fuel. All liquid rocket engines have tankage and pipes to store and transfer propellant, an injector system, a combustion chamber, typically cylindrical, one rocket nozzles.
Liquid systems enable higher specific impulse than solids and hybrid rocket engines and can provide high tankage efficiency. Unlike gases, a typical liquid propellant has a density similar to water 0.7–1.4g/cm³, while requiring only modest pressure to prevent vapourisation. This combination of density and low pressure permits lightweight tankage. For injection into the combustion chamber, the propellant pressure at the injectors needs to be greater than the chamber pressure. Suitable pumps use centrifugal turbopumps due to their high power and light weight, although reciprocating pumps have been employed in the past. Turbopumps are extremely lightweight and can give excellent performance. Indeed, overall rocket engine thrust to weight ratios including a turbopump have been as high as 155:1 with the SpaceX Merlin 1D ro
Eugen Sänger was an Austrian aerospace engineer best known for his contributions to lifting body and ramjet technology. Sänger was born in the former mining town of Preßnitz, near Chomutov in Bohemia, at that time part of the Austro-Hungarian Empire, he studied civil engineering at the Technical Universities of Vienna. As a student, he came in contact with Hermann Oberth's book Die Rakete zu den Planetenräumen, which inspired him to change from studying civil engineering to aeronautics, he joined Germany's amateur rocket movement, the Verein für Raumschiffahrt, centered on Oberth. In 1932 Sänger became a member of the SS and was a member of the NSDAP. Sänger made rocket-powered flight the subject of his thesis, but it was rejected by the university as too fanciful, he was allowed to graduate when he submitted a far more mundane paper on the statics of wing trusses. Sänger would publish his rejected thesis under the title Raketenflugtechnik in 1933. In 1935 and 1936, he published articles on rocket-powered flight for the Austrian journal Flug.
These attracted the attention of the Reichsluftfahrtministerium which saw Sänger's ideas as a potential way to accomplish the goal of building a bomber that could strike the United States from Germany. The RLM gave him a research institute near Braunschweig and built a liquid oxygen plant and a test stand for a 100 tonne thrust engine. At the time, Sänger's hiring was opposed by Wernher von Braun, who felt that his own work was being duplicated and may have seen the Austrian and his work as a threat to his own dominance of the field. Sänger agreed to lead a rocket development team in the Lüneburger Heide region in 1936, he conceived a rocket-powered sled that would launch a bomber with its own rocket engines that would climb to the fringe of space and skip along the upper atmosphere – not entering orbit, but able to cover vast distances in a series of sub-orbital hops. This remarkable design was called the Silbervogel and would have relied on its fuselage creating lift to carry it along its sub-orbital path.
Sänger was assisted in this design by mathematician Irene Bredt, whom he married in 1951. Sänger designed the rocket motors that the space-plane would use, which would need to generate 1 meganewton of thrust. In this design, he was one of the first to suggest using the rocket's fuel as a way of cooling the engine, by circulating it around the rocket nozzle before burning it in the engine. By 1942, the Reich Air Ministry canceled this project along with other more ambitious and theoretical designs in favour of concentrating on proven technologies. Sänger was sent to work for the Deutsche Forschungsanstalt für Segelflug. There he did important work on ramjet technology, working on projects such as the Skoda-Kauba Sk P.14 interceptor, until the end of World War II. After the war ended, Sänger worked for the French government and in 1949 founded the Fédération Astronautique. Whilst in France, he was the subject of a botched attempt by Soviet agents to win him over. Joseph Stalin had become intrigued by reports of the Silbervogel design and sent his son and scientist Grigori Tokaty to convince him to come to the Soviet Union, but they failed to do so.
It has been reported that Stalin instructed the NKVD to kidnap him. In 1951, he became the first President of the International Astronautical Federation. By 1954, Sänger had returned to Germany and three years was directing a jet propulsion research institute in Stuttgart. Between 1961 and 1963 he acted as a consultant for Junkers in designing a ramjet-powered space-plane that never left the drawing board. Sänger's other theoretical innovations during this period were proposing means of using photons for interplanetary and interstellar spacecraft propulsion prefiguring the concept of laser propulsion and the solar sail. In 1960, he assisted the United Arab Republic in developing the Al-Zafir, he died in Berlin. Sänger's grave is located in the cemetery "Alter Friedhof" in Stuttgart-Vaihingen, his work on the Silbervogel would prove important to the X-15, X-20 Dyna-Soar, Space Shuttle programs. Honorary member of numerous societies for Space Research in Germany, Great Britain, the United States of America, Sweden, Argentina, Italy.
Elected Honorary Fellow of the British Interplanetary Society in 1949 Hermann Oberth Medal for services to aerospace research Austrian Cross of Honour for Science and Art, 1st class Commander of the Ordre du Merite pour la Recherche et l'Invention, Paris Gagarin Gold Medal Assoziazione Internazionale Uomo nello Spazio, Rome Gold Medal at the Milan Fair Sängergasse named after him in Vienna Simmering Keldysh bomber Laser propulsion Silbervogel Spacecraft propulsion Sänger, Eugen. Zur Mechanik der Photonen-Strahlantriebe. München,: R. Oldenbourg. P. 92. Sänger, Eugen. Zur Stahlungsphysik der Photonen-Strahlantriebe und Waffenstrahlen. München: R. Oldenbourg. P. 173. Sänger, Eugen. Rocket Flight Engineering.: NASA Tech. Trans. F-223. Sänger, Eugen. "A Rocket Drive For Long Range Bombers". Astronautix.com. Retrieved 2008-01-17. Saenger, Hartmut E and Szames, Alexandre D, From the Silverbird to Interstellar Voyages, IAC-03-IAA.2.4.a.07. Sänger, Eugen. Space Flight: Countdown for the Future. New York: McGraw-Hill.
Duffy, James P.. TARGET: AMERICA: Hitler's Plan to Attack the United S
A nuclear reactor known as an atomic pile, is a device used to initiate and control a self-sustained nuclear chain reaction. Nuclear reactors are used at nuclear power plants for electricity generation and in propulsion of ships. Heat from nuclear fission is passed to a working fluid; these either turn electrical generators' shafts. Nuclear generated steam in principle can be used for industrial process heat or for district heating; some reactors are used to produce isotopes for medical and industrial use, or for production of weapons-grade plutonium. Some are run only for research; as of early 2019, the IAEA reports there are 454 nuclear power reactors and 226 nuclear research reactors in operation around the world. Just as conventional power-stations generate electricity by harnessing the thermal energy released from burning fossil fuels, nuclear reactors convert the energy released by controlled nuclear fission into thermal energy for further conversion to mechanical or electrical forms; when a large fissile atomic nucleus such as uranium-235 or plutonium-239 absorbs a neutron, it may undergo nuclear fission.
The heavy nucleus splits into two or more lighter nuclei, releasing kinetic energy, gamma radiation, free neutrons. A portion of these neutrons may be absorbed by other fissile atoms and trigger further fission events, which release more neutrons, so on; this is known as a nuclear chain reaction. To control such a nuclear chain reaction, neutron poisons and neutron moderators can change the portion of neutrons that will go on to cause more fission. Nuclear reactors have automatic and manual systems to shut the fission reaction down if monitoring detects unsafe conditions. Used moderators include regular water, solid graphite and heavy water; some experimental types of reactor have used beryllium, hydrocarbons have been suggested as another possibility. The reactor core generates heat in a number of ways: The kinetic energy of fission products is converted to thermal energy when these nuclei collide with nearby atoms; the reactor absorbs some of the gamma rays produced during fission and converts their energy into heat.
Heat is produced by the radioactive decay of fission products and materials that have been activated by neutron absorption. This decay heat-source will remain for some time after the reactor is shut down. A kilogram of uranium-235 converted via nuclear processes releases three million times more energy than a kilogram of coal burned conventionally. A nuclear reactor coolant — water but sometimes a gas or a liquid metal or molten salt — is circulated past the reactor core to absorb the heat that it generates; the heat is carried away from the reactor and is used to generate steam. Most reactor systems employ a cooling system, physically separated from the water that will be boiled to produce pressurized steam for the turbines, like the pressurized water reactor. However, in some reactors the water for the steam turbines is boiled directly by the reactor core; the rate of fission reactions within a reactor core can be adjusted by controlling the quantity of neutrons that are able to induce further fission events.
Nuclear reactors employ several methods of neutron control to adjust the reactor's power output. Some of these methods arising from the physics of radioactive decay and are accounted for during the reactor's operation, while others are mechanisms engineered into the reactor design for a distinct purpose; the fastest method for adjusting levels of fission-inducing neutrons in a reactor is via movement of the control rods. Control rods therefore tend to absorb neutrons; when a control rod is inserted deeper into the reactor, it absorbs more neutrons than the material it displaces—often the moderator. This action results in fewer neutrons available to cause fission and reduces the reactor's power output. Conversely, extracting the control rod will result in an increase in the rate of fission events and an increase in power; the physics of radioactive decay affects neutron populations in a reactor. One such process is delayed neutron emission by a number of neutron-rich fission isotopes; these delayed neutrons account for about 0.65% of the total neutrons produced in fission, with the remainder released upon fission.
The fission products which produce delayed neutrons have half lives for their decay by neutron emission that range from milliseconds to as long as several minutes, so considerable time is required to determine when a reactor reaches the critical point. Keeping the reactor in the zone of chain-reactivity where delayed neutrons are necessary to achieve a critical mass state allows mechanical devices or human operators to control a chain reaction in "real time"; this last stage, where delayed neutrons are no longer required to maintain criticality, is known as the prompt critical point. There is a scale for describing criticality in numerical form, in which bare criticality is known as zero dollars and the prompt critical point is one dollar, other points in the process interpolated in cents. In some reactors, the coolant acts as a neutron moderator. A moderator increases the power of the reactor by causin
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1 e, a spin of 1/2, has the same mass as an electron; when a positron collides with an electron, annihilation occurs. If this collision occurs at low energies, it results in the production of two or more gamma ray photons. Positrons can be created by positron emission radioactive decay, or by pair production from a sufficiently energetic photon, interacting with an atom in a material. In 1928, Paul Dirac published a paper proposing that electrons can have both a positive and negative charge; this paper introduced the Dirac equation, a unification of quantum mechanics, special relativity, the then-new concept of electron spin to explain the Zeeman effect. The paper did not explicitly predict a new particle but did allow for electrons having either positive or negative energy as solutions. Hermann Weyl published a paper discussing the mathematical implications of the negative energy solution.
The positive-energy solution explained experimental results, but Dirac was puzzled by the valid negative-energy solution that the mathematical model allowed. Quantum mechanics did not allow the negative energy solution to be ignored, as classical mechanics did in such equations. However, no such transition had yet been observed experimentally. Dirac wrote a follow-up paper in December 1929 that attempted to explain the unavoidable negative-energy solution for the relativistic electron, he argued that "... an electron with negative energy moves in an external field as though it carries a positive charge." He further asserted that all of space could be regarded as a "sea" of negative energy states that were filled, so as to prevent electrons jumping between positive energy states and negative energy states. The paper explored the possibility of the proton being an island in this sea, that it might be a negative-energy electron. Dirac acknowledged that the proton having a much greater mass than the electron was a problem, but expressed "hope" that a future theory would resolve the issue.
Robert Oppenheimer argued against the proton being the negative-energy electron solution to Dirac's equation. He asserted that if it were, the hydrogen atom would self-destruct. Persuaded by Oppenheimer's argument, Dirac published a paper in 1931 that predicted the existence of an as-yet-unobserved particle that he called an "anti-electron" that would have the same mass and the opposite charge as an electron and that would mutually annihilate upon contact with an electron. Feynman, earlier Stueckelberg, proposed an interpretation of the positron as an electron moving backward in time, reinterpreting the negative-energy solutions of the Dirac equation. Electrons moving backward in time would have a positive electric charge. Wheeler invoked this concept to explain the identical properties shared by all electrons, suggesting that "they are all the same electron" with a complex, self-intersecting worldline. Yoichiro Nambu applied it to all production and annihilation of particle-antiparticle pairs, stating that "the eventual creation and annihilation of pairs that may occur now and is no creation or annihilation, but only a change of direction of moving particles, from the past to the future, or from the future to the past."
The backwards in time point of view is nowadays accepted as equivalent to other pictures, but it does not have anything to do with the macroscopic terms "cause" and "effect", which do not appear in a microscopic physical description. Dmitri Skobeltsyn first observed the positron in 1929. While using a Wilson cloud chamber to try to detect gamma radiation in cosmic rays, Skobeltsyn detected particles that acted like electrons but curved in the opposite direction in an applied magnetic field. In 1929 Chung-Yao Chao, a graduate student at Caltech, noticed some anomalous results that indicated particles behaving like electrons, but with a positive charge, though the results were inconclusive and the phenomenon was not pursued. Carl David Anderson discovered the positron on 2 August 1932, for which he won the Nobel Prize for Physics in 1936. Anderson did not coin the term positron, but allowed it at the suggestion of the Physical Review journal editor to whom he submitted his discovery paper in late 1932.
The positron was the first evidence of antimatter and was discovered when Anderson allowed cosmic rays to pass through a cloud chamber and a lead plate. A magnet surrounded this apparatus, causing particles to bend in different directions based on their electric charge; the ion trail left by each positron appeared on the photographic plate with a curvature matching the mass-to-charge ratio of an electron, but in a direction that showed its charge was positive. Anderson wrote in retrospect that the positron could have been discovered earlier based on Chung-Yao Chao's work, if only it had been followed up on. Frédéric and Irène Joliot-Curie in Paris had evidence of positrons in old photographs when Anderson's results came out, but they had dismissed them as protons; the positron had been contemporaneously discovered by Patrick Blackett and Giuseppe Occhialini at the Cavendish Laboratory in 1932. Blackett and Occhialini had delayed publication to obtain more solid evidence, so Anderson was able to publish the discovery first.
Positrons are produced in β+ decays of occurring radioactive isotopes and in interactions of gamma quanta with matter. Antineutrinos a
The electron is a subatomic particle, symbol e− or β−, whose electric charge is negative one elementary charge. Electrons belong to the first generation of the lepton particle family, are thought to be elementary particles because they have no known components or substructure; the electron has a mass, 1/1836 that of the proton. Quantum mechanical properties of the electron include an intrinsic angular momentum of a half-integer value, expressed in units of the reduced Planck constant, ħ; as it is a fermion, no two electrons can occupy the same quantum state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of both particles and waves: they can collide with other particles and can be diffracted like light; the wave properties of electrons are easier to observe with experiments than those of other particles like neutrons and protons because electrons have a lower mass and hence a longer de Broglie wavelength for a given energy. Electrons play an essential role in numerous physical phenomena, such as electricity, magnetism and thermal conductivity, they participate in gravitational and weak interactions.
Since an electron has charge, it has a surrounding electric field, if that electron is moving relative to an observer, it will generate a magnetic field. Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law. Electrons absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields. Special telescopes can detect electron plasma in outer space. Electrons are involved in many applications such as electronics, cathode ray tubes, electron microscopes, radiation therapy, gaseous ionization detectors and particle accelerators. Interactions involving electrons with other subatomic particles are of interest in fields such as chemistry and nuclear physics; the Coulomb force interaction between the positive protons within atomic nuclei and the negative electrons without, allows the composition of the two known as atoms.
Ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the main cause of chemical bonding. In 1838, British natural philosopher Richard Laming first hypothesized the concept of an indivisible quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge'electron' in 1891, J. J. Thomson and his team of British physicists identified it as a particle in 1897. Electrons can participate in nuclear reactions, such as nucleosynthesis in stars, where they are known as beta particles. Electrons can be created through beta decay of radioactive isotopes and in high-energy collisions, for instance when cosmic rays enter the atmosphere; the antiparticle of the electron is called the positron. When an electron collides with a positron, both particles can be annihilated, producing gamma ray photons.
The ancient Greeks noticed. Along with lightning, this phenomenon is one of humanity's earliest recorded experiences with electricity. In his 1600 treatise De Magnete, the English scientist William Gilbert coined the New Latin term electrica, to refer to those substances with property similar to that of amber which attract small objects after being rubbed. Both electric and electricity are derived from the Latin ēlectrum, which came from the Greek word for amber, ἤλεκτρον. In the early 1700s, Francis Hauksbee and French chemist Charles François du Fay independently discovered what they believed were two kinds of frictional electricity—one generated from rubbing glass, the other from rubbing resin. From this, du Fay theorized that electricity consists of two electrical fluids and resinous, that are separated by friction, that neutralize each other when combined. American scientist Ebenezer Kinnersley also independently reached the same conclusion. A decade Benjamin Franklin proposed that electricity was not from different types of electrical fluid, but a single electrical fluid showing an excess or deficit.
He gave them the modern charge nomenclature of negative respectively. Franklin thought of the charge carrier as being positive, but he did not identify which situation was a surplus of the charge carrier, which situation was a deficit. Between 1838 and 1851, British natural philosopher Richard Laming developed the idea that an atom is composed of a core of matter surrounded by subatomic particles that had unit electric charges. Beginning in 1846, German physicist William Weber theorized that electricity was composed of positively and negatively charged fluids, their interaction was governed by the inverse square law. After studying the phenomenon of electrolysis in 1874, Irish physicist George Johnstone Stoney suggested that there existed a "single definite quantity of electricity", the charge of a monovalent ion, he was able to estimate the value of this elementary charge e by means of Faraday's laws of electrolysis. However, Stoney could not be removed. In 1881, German physicist Hermann von Helmholtz argued that both positive and negative charges were divided into elementary parts, each of which "behaves like atoms of electricity".
Stoney coined the term
A hybrid-propellant rocket is a rocket with a rocket motor that uses rocket propellants in two different phases: one solid and the other either gas or liquid. The hybrid rocket concept can be traced back at least 75 years. Hybrid rockets avoid some of the disadvantages of solid rockets like the dangers of propellant handling, while avoiding some disadvantages of liquid rockets like their mechanical complexity; because it is difficult for the fuel and oxidizer to be mixed intimately, hybrid rockets tend to fail more benignly than liquids or solids. Like liquid rocket engines, hybrid rocket motors can be shut down and the thrust is throttleable; the theoretical specific impulse performance of hybrids is higher than solid motors and lower than liquid engines. I s p as high. Hybrid systems are more complex than solid ones, but they avoid significant hazards of manufacturing and handling solid rocket motors by storing the oxidizer and the fuel separately; the first work on hybrid rockets was performed in the late 1930s at IG Farben in Germany and concurrently at the California Rocket Society in the United States.
Leonid Andrussow, working in Germany, first theorized hybrid propellant rockets. O. Lutz, W. Noeggerath, Andrussow tested a 10 kilonewtons hybrid rocket motor using coal and gaseous N2O as the propellants. Oberth worked on a hybrid rocket motor using LOX as the oxidizer and graphite as the fuel; the high heat of sublimation of carbon prevented these rocket motors from operating efficiently, as it resulted in a negligible burning rate. In the 1940s, the California Pacific Rocket Society used LOX in combination with several different fuel types, including wood and rubber; the most successful of these tests was with the rubber fuel, still the dominant fuel in use today. In June 1951, a LOX/rubber rocket was flown to an altitude of 9 kilometres. Two major efforts occurred in the 1950s. One of these efforts was by K. Berman at General Electric; the duo used 90 % polyethylene in a rod and tube grain design. They drew several significant conclusions from their work; the fuel grain had uniform burning. Grain cracks did not affect combustion.
No hard starts were observed. The fuel surface acted as a flame holder; the oxidizer could be throttled with one valve, a high oxidizer to fuel ratio helped simplify combustion. The negative observations were low burning rates and that the thermal instability of peroxide was problematic for safety reasons. Another effort that occurred in the 1950s was development of a reverse hybrid. In a standard hybrid rocket motor, the solid material is the fuel. In a reverse hybrid rocket motor, the oxidizer is solid. William Avery of the Applied Physics Laboratory used jet fuel and ammonium nitrate, selected for their low cost, his O/F ratio was 0.035, 200 times smaller than the ratio used by Moore and Berman. In 1953 Pacific Rocket Society was developing the XDF-23, a 4 inches x 72 inches hybrid rocket, designed by Jim Nuding, using LOX and rubber polymer called "Thiokol", they had tried other fuels in prior iterations including cotton, paraffin wax and wood. The XDF name. In the 1960s, European organizations began work on hybrid rockets.
ONERA, based in France, Volvo Flygmotor, based in Sweden, developed sounding rockets using hybrid rocket motor technology. The ONERA group focused on a hypergolic rocket motor, using an amine fuel; the company flew eight rockets: once in April 1964, three times in June 1965, four times in 1967. The maximum altitude the flights achieved was over 100 kilometres; the Volvo Flygmotor group used a hypergolic propellant combination. They used nitric acid for their oxidizer, but used Tagaform as their fuel, their flight was in 1969. Meanwhile, in the United States, United Technologies Center and Beech Aircraft were working on a supersonic target drone, known as Sandpiper, it used polymethyl methacrylate - Mg for the fuel. The drone flew six times in 1968, for more than 300 seconds and to an altitude greater than 160 kilometres; the second iteration of the rocket, known as the HAST, had IRFNA-PB/PMM for its propellants and was throttleable over a 10/1 range. HAST could carry a heavier payload than the Sandpiper.
Another iteration, which used the same propellant combination as the HAST, was developed by Chemical Systems Division and Teledyne Aircraft. Development for this program ended in the mid-1980s. Chemical Systems Division worked on a propellant combination of lithium and FLOx; this was an efficient hypergolic rocket, throtteable. The vacuum specific impulse was 380 seconds at 93% combustion efficiency. AMROC developed the largest hybrid rockets created in the late 1980s and early 1990s; the first version of their engine, fired at the Air Force Phillips Laboratory, produced 312,000 newtons of thrust for 70 seconds with a propellant combination of LOX and hydroxyl-terminated polybutadiene. The second version of the motor, known as the H-250F, produced more than 1,000,000 newtons o