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Pentaborane(9)
Pentaborane(9) is an inorganic compound with the formula B5H9. It is one of the most common boron hydride clusters, although it is a highly reactive compound. Because of its high reactivity toward oxygen, it was once evaluated as rocket or jet fuel. Like many of the smaller boron hydrides, pentaborane is colourless, diamagnetic, and volatile. It is related to pentaborane(11) (B5H11). Structure, synthesis, properties Its structure is that of five atoms of boron arranged in a square pyramid. Each boron has a terminal hydride ligand and four hydrides span the edges of the base of the pyramid. It is classified as a nido cage. It was first prepared by Alfred Stock by pyrolysis of diborane at about 200 °C. An improved synthesis starts from salts of octahydrotriborate (B3H8−), which is converted to the bromide B3H7Br− using HBr. Pyrolysis of this bromide gives pentaborane. :5 B3H7Br− → 3 B5H9 + 5 Br− + 4 H2 In the U.S., pentaborane was produced on a commercial sc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bipropellant
The highest specific impulse chemical rockets use liquid propellants (liquid-propellant rockets). They can consist of a single chemical (a monopropellant) or a mix of two chemicals, called bipropellants. Bipropellants can further be divided into two categories; hypergolic propellants, which ignite when the fuel and oxidizer make contact, and non-hypergolic propellants which require an ignition source. About 170 different propellants made of liquid fuel have been tested, excluding minor changes to a specific propellant such as propellant additives, corrosion inhibitors, or stabilizers. In the U.S. alone at least 25 different propellant combinations have been flown. As of 2020, no completely new propellant has been used since the mid-1970s. Many factors go into choosing a propellant for a liquid-propellant rocket engine. The primary factors include ease of operation, cost, hazards/environment and performance. History Development in early 20th century Konstantin Tsiolkovsky propo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diborane
Diborane(6), generally known as diborane, is the chemical compound with the formula B2H6. It is a toxic, colorless, and pyrophoric gas with a repulsively sweet odor. Diborane is a key boron compound with a variety of applications. It has attracted wide attention for its electronic structure. Several of its derivatives are useful reagents. Structure and bonding The structure of diborane has D2h symmetry. Four hydrides are terminal, while two bridge between the boron centers. The lengths of the B–Hbridge bonds and the B–Hterminal bonds are 1.33 and 1.19 Å respectively. This difference in bond lengths reflects the difference in their strengths, the B–Hbridge bonds being relatively weaker. The weakness of the B–Hbridge compared to B–Hterminal bonds is indicated by their vibrational signatures in the infrared spectrum, being ≈2100 and 2500 cm−1 respectively. The model determined by molecular orbital theory describes the bonds between boron and the termina ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Octahydrotriborate
Octahydrotriborate is the boron hydride B3H8−. It forms a variety of salts that are colorless and air-stable. The tetrabutylammonium salt is soluble in organic solvents such as acetonitrile and methylene chloride. The anion is an intermediate is the synthesis of various higher boron hydrides, such as pentaborane(9). B3H8− can be viewed as the conjugate base of triborane B3H9. Preparation Octahydrotriborate is prepared by partial oxidation of borohydride with iodine or boron trifluoride: :3BH4− + I2 → B3H8− + 2H2 + 2I− :5BH4− + 4BF3O(C2H5)2 → 2B3H8− + 2H2 + 4O(C2H5)2 + 3BF4− Structure and reactions As shown by X-ray crystallography of various salts, B3H8− consists of a distorted triangle of three BH2 vertices. Two edges of the triangle are occupied by bridging hydrides. It is converted to the bromide B3H7Br− using HBr (illustrating its hydridic character): :B3H8− + HBr → B3H7Br− + H2 Pyrolysis of this bromide gives pentab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Debye
The debye (symbol: D) (; ) is a CGS unit (a non- SI metric unit) of electric dipole momentTwo equal and opposite charges separated by some distance constitute an electric dipole. This dipole possesses an electric dipole moment whose value is given as charge times length of separation, it is a vector whose direction is in the direction of the unit vector of the position vector of the positive charge w.r.t negative charge: :p = ''q''r. named in honour of the physicist Peter J. W. Debye. It is defined as statcoulomb-centimeters.The statcoulomb is also known as the franklin or electrostatic unit of charge. :1 statC = 1 Fr = 1 esu = 1 cm3/2⋅g1/2⋅s−1. Historically the debye was defined as the dipole moment resulting from two charges of opposite sign but an equal magnitude of 10−10 statcoulomb10−10 statcoulomb corresponds to approximately 0.2083 units of elementary charge. (generally called e.s.u. (electrostatic unit) in older scientific ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Of Combustion
The heating value (or energy value or calorific value) of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it. The ''calorific value'' is the total energy released as heat when a substance undergoes complete combustion with oxygen under standard conditions. The chemical reaction is typically a hydrocarbon or other organic molecule reacting with oxygen to form carbon dioxide and water and release heat. It may be expressed with the quantities: * energy/mole of fuel * energy/mass of fuel * energy/volume of the fuel There are two kinds of enthalpy of combustion, called high(er) and low(er) heat(ing) value, depending on how much the products are allowed to cool and whether compounds like are allowed to condense. The high heat values are conventionally measured with a bomb calorimeter. Low heat values are calculated from high heat value test data. They may also be calculated as the difference betw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Valentin Glushko
Valentin Petrovich Glushko (russian: Валенти́н Петро́вич Глушко́; uk, Валентин Петрович Глушко, Valentyn Petrovych Hlushko; born 2 September 1908 – 10 January 1989) was a Soviet engineer and the main designer of rocket engines in the Soviet space program during the heights of the Space Race between United States and the Soviet Union. Biography At the age of fourteen he became interested in aeronautics after reading novels by Jules Verne. He is known to have written a letter to Konstantin Tsiolkovsky in 1923. He studied at an Odessa trade school, where he learned to be a sheet metal worker. After graduation he apprenticed at a hydraulics fitting plant. He was first trained as a fitter, then moved to lathe operator. During his time in Odessa, Glushko performed experiments with explosives. These were recovered from unexploded artillery shells that had been left behind by the White Guards during their retreat. From 1924 to 1925 he wro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrogen Tetroxide
Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russia rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium mixture with nitrogen dioxide. Its molar mass is 92.011 g/mol. Dinitrogen tetroxide is a powerful oxidizer that is hypergolic (spontaneously reacts) upon contact with various forms of hydrazine, which has made the pair a common bipropellant for rockets. Structure and properties Dinitrogen tetroxide could be regarded as two nitro groups (-NO2) bonded together. It forms an equilibrium mixture with nitrogen dioxide. The molecule is planar with an N-N bond distance of 1.78Å and N-O distances of 1.19Å. The N-N distance corresponds to a weak bond, since it is significantly longer than the average N-N single bond length of 1.45Å. This exceptionally weak σ bond (amounting to overlapping of the ''sp''2 hybrid orbitals of the two NO2 units) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
XB-70 Valkyrie
The North American Aviation XB-70 Valkyrie was the prototype version of the planned B-70 nuclear-armed, deep-penetration supersonic strategic bomber for the United States Air Force Strategic Air Command. Designed in the late 1950s by North American Aviation (NAA), the six-engined Valkyrie was capable of cruising for thousands of miles at Mach 3+ while flying at . At these speeds, it was expected that the B-70 would be practically immune to interceptor aircraft, the only effective weapon against bomber aircraft at the time. The bomber would spend only a brief time over a particular radar station, flying out of its range before the controllers could position their fighters in a suitable location for an interception. Its high speed made the aircraft difficult to see on radar displays and its high-altitude and high-speed capabilities could not be matched by any contemporaneous Soviet interceptor or fighter aircraft. The introduction of the first Soviet surface-to-air missiles i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North American Aviation
North American Aviation (NAA) was a major American aerospace manufacturer that designed and built several notable aircraft and spacecraft. Its products included: the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the F-86 Sabre jet fighter, the X-15 rocket plane, the XB-70, the B-1 Lancer, the Apollo command and service module, the second stage of the Saturn V rocket, and the Space Shuttle orbiter. Through a series of mergers and sales, North American Aviation became part of North American Rockwell, which later became Rockwell International, and is now part of Boeing. History Early years On December 6, 1928, Clement Melville Keys founded North American as a holding company that bought and sold interests in various airlines and aviation-related companies. However, the Air Mail Act of 1934 forced the breakup of such holding companies. North American became a manufacturing company, run by James H. Kindelberger, James H. "Dutch" Kindelberger, who had bee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soviet Union
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national republics; in practice, both its government and its economy were highly centralized until its final years. It was a one-party state governed by the Communist Party of the Soviet Union, with the city of Moscow serving as its capital as well as that of its largest and most populous republic: the Russian SFSR. Other major cities included Leningrad (Russian SFSR), Kiev (Ukrainian SSR), Minsk ( Byelorussian SSR), Tashkent (Uzbek SSR), Alma-Ata (Kazakh SSR), and Novosibirsk (Russian SFSR). It was the largest country in the world, covering over and spanning eleven time zones. The country's roots lay in the October Revolution of 1917, when the Bolsheviks, under the leadership of Vladimir Lenin, overthrew the Russian Provisional Government ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Missile Gap
In the United States, during the Cold War, the missile gap was the perceived superiority of the number and power of the USSR's missiles in comparison with those of the U.S. (a lack of military parity). The gap in the ballistic missile arsenals did not exist except in exaggerated estimates, made by the Gaither Committee in 1957 and in United States Air Force (USAF) figures. Even the contradictory CIA figures for the USSR's weaponry, which showed a clear advantage for the US, were far above the actual count. Like the bomber gap of only a few years earlier, it was soon demonstrated that the gap was entirely fictional. John F. Kennedy is credited with inventing the term in 1958 as part of the ongoing election campaign in which a primary plank of his rhetoric was that the Eisenhower administration was weak on defense. It was later learned that Kennedy was apprised of the actual situation during the campaign, which has led scholars to question what Kennedy knew and when he knew it. Ther ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Race
The Space Race was a 20th-century competition between two Cold War rivals, the United States and the Soviet Union, to achieve superior spaceflight capability. It had its origins in the ballistic missile-based nuclear arms race between the two nations following World War II. The technological advantage demonstrated by spaceflight achievement was seen as necessary for national security, and became part of the symbolism and ideology of the time. The Space Race brought pioneering launches of artificial satellites, robotic space probes to the Moon, Venus, and Mars, and human spaceflight in low Earth orbit and ultimately to the Moon. Public interest in space travel originated in the 1951 publication of a Soviet youth magazine and was promptly picked up by US magazines. The competition began on July 30, 1955 when the United States announced its intent to launch artificial satellites for the International Geophysical Year. Four days later, the Soviet Union responded by declaring ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
