| LOX/Kerosene | ||
|---|---|---|
| Max Isp | ~353 | |
| Oxidizer to Fuel Ratio | 2. Specific impulse (usually abbreviated I sp is a way to describe the efficiency of rocket and jet engines 56 | |
| Density (g/ml) | . 81-1. 02 | |
| Heat Capacity Ratio | 1. Ideal gas relations For an ideal gas the heat capacity is constant with temperature 24 | |
| Temperature of Combustion | 3,670 K | |
RP-1 (alternately, Rocket Propellant-1 or Refined Petroleum-1) is a highly refined form of kerosene outwardly similar to jet fuel, used as a rocket fuel. Petroleum ( L petroleum, from Greek πετρέλαιον, lit Kerosene, sometimes spelled kerosine in scientific and industrial usage is a Combustible Hydrocarbon liquid Jet fuel is a type of Aviation fuel designed for use in Aircraft powered by gas-turbine engines. Rocket propellant is mass that is stored usually in some form of Propellant tank prior to being used as the propulsive mass that is ejected from a rocket engine in the form Although having a lower specific impulse than liquid hydrogen and thus less thrust per unit mass, RP-1 is cheaper, can be stored at room temperature, is far less of an explosive hazard and is far more dense. Specific impulse (usually abbreviated I sp is a way to describe the efficiency of rocket and jet engines Liquid hydrogen (LH2 or LH2 is the Liquid state of the element Hydrogen. By volume, RP-1 is significantly more powerful than LH2. RP-1 also has a fraction of the toxicity and carcinogenic hazards of hydrazine, another room-temperature liquid fuel. Toxicity is the degree to which a substance is able to damage an exposed organism The term carcinogen refers to any substance Radionuclide or radiation that is an agent directly involved in the promotion of Cancer or in the fatation of its propagation Hydrazine is a Chemical compound with the formula N2H4 It has an Ammonia -like odor and is derived from the same industrial chemistry Thus, kerosene fuels are more practical for many uses.
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Usage and History
RP-1 is most commonly burned with LOX (liquid oxygen) as the oxidizer, though other oxidizers have also been used. RP-1 is a fuel in the first-stage boosters of the Delta I-III and Atlas rockets. Delta is a family of Expendable launch systems that have provided space launch capability in the United States since 1960 Atlas is a family of US space Launch vehicles The original Atlas missile was designed in the late 1950s It also powered the first stages of the Titan I, Saturn I and IB, and Saturn V. The Titan I was the United States' first true multistage ICBM. For the moon of Saturn see Mimas (moon. The Saturn I was the United States' first dedicated "space launcher" a rocket designed The Saturn V (pronounced 'Saturn Five' popularly known as the Moon Rocket was a multistage liquid-fuel expendable Rocket used by NASA 's
During and immediately after World War II, alcohols (primarily ethyl alcohol, occasionally methyl alcohol) were the single most common fuel for large liquid-fueled rockets. In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a Chemical compound A liquid rocket is a Rocket with an engine that uses Propellants in Liquid form Its high heat of vaporization kept regeneratively-cooled engines from melting, especially considering that alcohols would typically contain several percent water. The enthalpy of vaporization, (symbol \Delta{}_{v}H also known as the heat of vaporization or heat of evaporation, is the Energy required Regenerative cooling is a method of Cooling Gases in which compressed gas is cooled by allowing it to expand and and thereby taking heat from the surroundings the However, it was recognized that hydrocarbon fuels would increase engine efficiency, due to a slightly higher density, the lack of an oxygen atom in the fuel molecule, and negligible water content. In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Whatever hydrocarbon was chosen, though, would have to replicate alcohol's coolant ability.
Many early rockets had burned kerosene, but as burn times, combustion efficiencies, and combustion-chamber pressures grew, and engine masses shrank, the engine temperatures became unmanageable. Raw kerosene used as coolant would dissociate and polymerize. Dissociation is a state of acute mental Decompensation in which certain Thoughts Emotions Sensations and/or memories are In Polymer chemistry, polymerization is a process of reacting Monomer Molecules together in a Chemical reaction to form three-dimensional networks Lightweight products in the form of gas bubbles, and heavy ones in the form of engine deposits, then blocked the narrow cooling passages. The coolant starvation raised temperatures further, accelerating breakdown. This cycle would escalate rapidly until an engine wall ruptured.
This occurred even with the entire flow of kerosene used as coolant. Rocket designers turned to the fuel chemists to formulate a heat-resistant hydrocarbon. The specification was completed in the mid-50s.
Fractions and Formulation
First, sulfur compounds were severely restricted. Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 Hydrodesulfurization (HDS is a Catalytic chemical process widely used to remove Sulfur (S from Natural gas and from refined petroleum products Small amounts of sulfur are naturally present in fossil fuels. It had already been known that sulfur and sulfur compounds attack metals at high temperatures. In addition, even small amounts of sulfur will assist polymerization. Vulcanization (or Vulcanisation refers to a specific curing process of Rubber involving high heat and the addition of Sulfur or other equivalent curatives
Alkenes and aromatics were held to very low levels. In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon These unsaturated hydrocarbons tend to polymerize not only at temperature, but during long periods of storage. At the time, it was thought that kerosene-fueled missiles might remain in storage for years awaiting activation. This function was later transferred to solid-fuel rockets, though the high-temperature benefits of saturated hydrocarbons remained. A solid rocket or a solid-fuel rocket is a Rocket with a motor that uses solid propellants ( Fuel / Oxidizer) Because of the low alkenes and aromatics, RP-1 is less toxic than various jet and diesel fuels, and far less toxic than gasoline.
The more desirable isomers were selected or synthesized. This article is about the chemical concept For "isomerism" of atomic nuclei see Nuclear isomer. Linear alkanes were removed in favor of highly branched and cyclic molecules. This increased resistance to thermal breakdown, much as these isomer types improve octane rating in piston engines. The octane rating is a measure of the resistance of Gasoline and other Fuels to Detonation ( Engine knocking) in spark-ignition Jet engines and heating and lighting applications, the prior users of kerosene, had been much less concerned with thermal breakdown and isomer contents. The most desirable isomers were polycyclics, loosely resembling ladderanes.
In production, these grades were processed tightly to remove impurities and side fractions. Ashes were feared likely to block fuel lines and engine passages, as well as wear away valves and turbopump bearings which were lubricated by the fuel itself. As the name suggests a turbopump comprises basically two main components a rotodynamic Pump and a driving Turbine, both mounted on the same shaft Slightly-heavy or -light fractions affected lubrication abilities, and were likely to separate during storage and under load. The remaining hydrocarbons are at or near C12 weight. Because of the lack of light hydrocarbons, RP-1 has a high flash point, and is less of a fire hazard than gasoline/petrol or even some jet and diesel fuels. The flash point of a flammable liquid is the lowest Temperature at which it can form an ignitable mixture in air
All told, the final product is more expensive than straight-run kerosene. On paper, any petroleum can produce some RP-1 with enough processing. In practice, the fuel is sourced from a small number of oil fields with high-quality base stock. This, coupled with small demand in a niche market compared to other petroleum users, drives the price.
Soviet and Russian rocket-grade kerosenes are very similar to RP-1 and are designated T-1 and RG-1. Densities are higher, 0. 82 to 0. 85 g/ml, compared to RP-1 at 0. A gram per litre or liter ( g/L) is a measurement of Concentration used to measure the how many Grams of a certain Substance 81 g/ml. For a short period, the Soviets achieved even higher densities by super-chilling the kerosene in a rocket’s fuel tanks, but this partially defeated the purpose of using kerosene over other super-chilled fuels. In the case of the Soyuz and other R7-based rockets, the temperature penalty was minor. The Soyuz launch vehicle (Western designation A-2 is an Expendable launch system manufactured by TsSKB-Progress in Samara Russia. The R-7 Semyorka (Р-7 "Семёрка" was the world's first true Intercontinental ballistic missile and was deployed by the Soviet Union during the Facilities were already in place to manage the vehicle's cryogenic liquid oxygen and liquid nitrogen, both of which are far colder than the kerosene temperature. Liquid nitrogen (liquid density at the Triple point is 0707 g/mL is the liquid produced industrially in large quantities by Fractional distillation of The launcher's central kerosene tank is surrounded on four sides and the top by liquid oxygen tanks; the liquid nitrogen tank is nearby at the bottom. The kerosene tanks of the four boosters are relatively small and compact, and also between a liquid oxygen and a liquid nitrogen tank. Thus, once the kerosene was chilled initially, it could remain so for the brief time needed to finish launch preparations.
RP-1 Drawbacks
Chemically, a hydrocarbon propellant will be less efficient than hydrogen fuel. Hydrogen is the lightest atom; when combusted with oxygen, the H2O product has a low weight, and thus a high exhaust velocity. Hydrogen engines are also operated fuel-rich, so some exhaust is unreacted H2, which is even lighter. Hydrocarbons, on the other hand, produce both H2O and CO2. CO2 is over 2. 5 times heavier, slowing the exhaust. It can also absorb significant amounts of combustion energy by generating any of several oscillating modes between the oxygen atoms, in the multiple styles of a slinky. A Slinky is a Coil -shaped Toy invented by mechanical engineer Richard James in Philadelphia Pennsylvania This is energy that could have instead gone into exhaust velocity. The heavier oxygen atoms absorb much more energy than the two hydrogens of H2O. Hydrocarbon engines are also run fuel-rich, which produces some CO instead of CO2. Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. But this also results in incomplete combustion, producing some organics of high molecular weight and numerous vibration modes. All told, kerosene engines generate an Isp in the range of 270 to 335 seconds, while hydrogen engines achieve 370-465 seconds. Specific impulse (usually abbreviated I sp is a way to describe the efficiency of rocket and jet engines
Kerosene-based fuels do have handling and operations drawbacks. The temperature difference between cryogenic LOX and ambient RP-1 requires dead space or insulation between tanks, or the hydrocarbons will gel. A gel (from the lat gelu &mdashfreezing cold ice or gelatus &mdashfrozen immobile is an apparently solid jelly-like material formed from a Both designs add weight versus more-compatible propellant combinations using a common bulkhead, though skillful engineering can hold the weight penalty to a minimum.
During engine shutdown, fuel flow goes to zero rapidly, while the engine is still quite hot. Residual and trapped fuel can polymerize or even carbonize at hot spots or in hot components. Carbonization or Carbonisation is the term for the conversion of an Organic substance into Carbon or a carbon-containing residue through Pyrolysis Even without hot spots, heavy fuels can create a petroleum residue, as can be seen in gasoline, diesel, or jet fuel tanks that have been in service for years. Rocket engines have cycle lifetimes measured in minutes or even seconds, preventing truly heavy deposits. However, rockets are much more sensitive to a deposit, as described above. Thus, kerosene systems generally entail more teardowns and overhauls, creating operations and labor expenses. This is a problem for expendable engines as well as reusable ones, because engines must be ground-fired some number of times beforehand. Even cold-flow tests, in which the propellants are not ignited, can leave residues.
Recent heavy-hydrocarbon engines have modified components and new operating cycles, in attempts to better manage leftover fuel, achieve a more-gradual cooldown, or both. This still leaves the problem of non-dissociated petroleum residue. Other new engines have tried to bypass the problem entirely, by switching to light hydrocarbons such as methane or propane gas. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Propane is a three- Carbon Alkane, normally a gas but compressible to a liquid that is transportable Both are volatiles, so engine residues simply evaporate. If necessary, solvents or other purgatives can be run through the engine to finish dispersion. The short-chain carbon backbone of propane (a C3 molecule) is very difficult to break; methane, with a single carbon atom (C1), is technically not a chain at all. The breakdown products of both molecules are also gases, with fewer problems due to phase separation, and much less likelihood of polymerization and deposition. However, methane (and to a lesser extent propane) reintroduces handling inconveniences that prompted kerosenes in the first place.
The low vapor pressure of kerosenes gives safety for ground crews. Vapor pressure (also known as equilibrium vapor pressure or saturation vapor pressure) is the Pressure of a Vapor in equilibrium However, in flight the kerosene tank will need a separate system of pressurization, to replace fuel volume as it drains. Generally, this is a separate tank of liquid or high-pressure inert gas, such as nitrogen or helium. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical This creates extra cost and weight. Cryogenic or volatile propellants generally do not need a separate pressurant; instead, some propellant is expanded (often with engine heat) into low-density gas, and routed back to its tank. Cryogenics is often used incorrectly to refer to Cryonics, cryopreserving humans or animals A few highly-volatile propellant designs do not even need the gas loop; some of the liquid automatically vaporizes to fill its own container. Some rockets use gas from a gas generator to pressurize the fuel tank; usually, this is exhaust from a turbopump. A gas generator usually refers to a Propellant mixture often similar to a Solid rocket propellant that burns to produce large volumes of Gas. As the name suggests a turbopump comprises basically two main components a rotodynamic Pump and a driving Turbine, both mounted on the same shaft Although this saves the weight of a separate gas system, the loop now has to handle a hot, reactive gas instead of a cool, inert one.
Regardless of chemical constraints, RP-1 has supply constraints, due to the very small size of the launch-vehicle industry versus other consumers of petroleum. While the material price of such a highly-refined hydrocarbon is still less than many other rocket propellants, the number of RP-1 suppliers is limited. A few engines have attempted to use more standard, wide-distribution petroleum products such as jet fuel or even diesel. By using alternate or supplemental engine cooling methods, some can tolerate the non-optimal formulations.
RP-1-Like Fuels
Goddard's initial rockets used gasoline. Robert Hutchings Goddard, PhD ( October 5, 1882 &ndash August 10 1945 U
Clark mentions in "Ignition!" that while the RP-1 specification was being developed, Rocketdyne was experimenting with diethyl cyclohexane. John Drury Clark PhD ( August 15, 1907 -July 1988 was a noted American Rocket fuel developer Chemist, and Science fiction Pratt & Whitney Rocketdyne is a United States company that designs and produces Rocket engines that use liquid propellants. However, it offered few advantages over RP-1, and was dropped. In addition, the military (NASA did not yet exist) preferred RP-1 because it was processed alongside jet fuels in the same refineries.
Soviet formulations are discussed above. In addition, the Soviets briefly used a fuel, transliterated as "sintin" or "syntin. Transliteration is the practice of Transcribing a Word or text written in one Writing system into another writing system or system of rules for such practice " This was a higher-energy formulation, used in upper stages. Though full details have not been made public, it was chilled somewhat below room temperature.
After the RP-1 standard, RP-2 was developed. The primary difference is an even lower sulfur content. However, as most users accept RP-1, there was little incentive to produce and stock a second, even rarer and more expensive formulation.
It is possible that some groups experimented with turpentine fuels. Turpentine (also called spirit of turpentine oil of turpentine wood turpentine gum turpentine is a fluid obtained by the Distillation of Resin obtained from trees The isoprene monomer would form a fairly robust molecule, and blends of its dimer and trimer would be at kerosene weight. Isoprene is a common synonym for the chemical compound 2-methylbuta-13-diene It is also possible that the words "turpentine" and "turps" are merely colloquial terms for kerosene, and such references do not actually refer to the tree extract.
The OTRAG group launched test vehicles using more-common blends. OTRAG ( German: Orbital Transport und Raketen AG, or Orbital Transport and Rockets Inc In at least one instance, a rocket was propelled by diesel fuel. Diesel or Diesel fuel (ˈdiːzəl in general is any Fuel used in Diesel engines The most common is a specific fractional distillate of petroleum However, no OTRAG rocket came even close to orbit. The later, loosely-similar Scorpius rocket used Jet A, again without ever reaching orbit. Jet fuel is a type of Aviation fuel designed for use in Aircraft powered by gas-turbine engines.
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