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87-436: Recently, Hyosung has become known for its technologies related to hydrogen vehicles , such as carbon fiber for the fuel tank and hydrogen charging stations. This article about a South Korean company is a stub . You can help Misplaced Pages by expanding it . This bank, insurance, or other financial services corporation article is a stub . You can help Misplaced Pages by expanding it . This chemical corporation -related article

174-593: A PHB hydrogen bicycle. In 2014, Australian scientists from the University of New South Wales presented their Hy-Cycle model. The same year, Canyon Bicycles started to work on the Eco Speed concept bicycle. In 2017, Pragma Industries of France developed a bicycle that was able to travel 100 km on a single hydrogen cylinder. In 2019, Pragma announced that the product, "Alpha Bike", has been improved to offer an electrically assisted pedalling range of 150 km, and

261-629: A class action lawsuit in California over the lack of availability of hydrogen available for fuel cell electric cars, alleging, among other things, fraudulent concealment and misrepresentation as well as violations of California’s false advertising law and breaches of implied warranty. The International Energy Agency's 2022 net-zero emissions scenario sees hydrogen meeting approximately 30% of heavy truck energy demand in 2050, mainly for long-distance heavy freight (with battery electric power accounting for around 60%). United Parcel Service began testing of

348-672: A "flying-mile" speed of 280.007 miles per hour (450.628 km/h) at the Bonneville Salt Flats in August 2008. In 2007, the Hydrogen Electric Racing Federation was formed as a racing organization for hydrogen fuel cell-powered vehicles. The organization sponsored the Hydrogen 500, a 500-mile race. Hydrogen internal combustion engine cars are different from hydrogen fuel cell cars. The hydrogen internal combustion car

435-446: A Mirai as compared with a Tesla Model 3. The molecular hydrogen needed as an onboard fuel for hydrogen vehicles can be obtained through many thermochemical methods utilizing natural gas , coal (by a process known as coal gasification), liquefied petroleum gas , biomass ( biomass gasification ), by a process called thermolysis , or as a microbial waste product called biohydrogen or Biological hydrogen production . 95% of hydrogen

522-417: A day, when you can charge a battery powered bike anywhere. [If] you were a captive fleet operator, why [not] just swap out batteries to get the range and the fast turnover?" General Motors ' military division, GM Defense , focuses on hydrogen fuel cell vehicles. Its SURUS (Silent Utility Rover Universal Superstructure) is a flexible fuel cell electric platform with autonomous capabilities. Since April 2017,

609-527: A feedstock for efuel, for vintage and muscle cars. The first road vehicle powered by a hydrogen fuel cell was the Chevrolet Electrovan, introduced by General Motors in 1966. The Toyota FCHV and Honda FCX , which began leasing on December 2, 2002, became the world's first government-certified commercial hydrogen fuel cell vehicles, and the Honda FCX Clarity , which began leasing in 2008,

696-434: A given propellant, when paired with a given engine, can accelerate its own initial mass at 1 g. The longer it can accelerate its own mass, the more delta-V it delivers to the whole system. In other words, given a particular engine and a mass of a particular propellant, specific impulse measures for how long a time that engine can exert a continuous force (thrust) until fully burning that mass of propellant. A given mass of

783-506: A group formed by Ford Motor Company , Daimler AG , and Nissan announced a collaboration on hydrogen technology development. In 2015, Toyota announced that it would offer all 5,680 patents related to hydrogen fuel cell vehicles and hydrogen fuel cell charging station technology, which it has been researching for over 20 years, to its competitors free of charge to stimulate the market for hydrogen-powered vehicles. By 2017, however, Daimler had abandoned hydrogen vehicle development, and most of

870-526: A heavier engine with a higher specific impulse may not be as effective in gaining altitude, distance, or velocity as a lighter engine with a lower specific impulse, especially if the latter engine possesses a higher thrust-to-weight ratio . This is a significant reason for most rocket designs having multiple stages. The first stage is optimised for high thrust to boost the later stages with higher specific impulse into higher altitudes where they can perform more efficiently. The most common unit for specific impulse

957-694: A hydrogen powered delivery vehicle in 2017. In 2020, Hyundai began commercial production of its Xcient fuel cell trucks and shipped ten of them to Switzerland . In 2022 in Australia, five hydrogen fuel cell class 8 trucks were placed into use to transport zinc from Sun Metals' Townsville mine to the Port of Townsville , Queensland, to be shipped around the world. Some publications project hydrogen may be used in shipping and jetplanes, while others predict that biofuels and batteries will have more commercial success. Companies such as Boeing , Lange Aviation , and

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1044-509: A hydrogen-powered tractor has been proposed. A record of 207.297 miles per hour (333.612 km/h) was set by a prototype Ford Fusion Hydrogen 999 Fuel Cell Race Car at the Bonneville Salt Flats, in August 2007, using a large compressed oxygen tank to increase power. The land-speed record for a hydrogen-powered vehicle of 286.476 miles per hour (461.038 km/h) was set by Ohio State University 's Buckeye Bullet 2 , which achieved

1131-417: A more energy-dense propellant can burn for a longer duration than some less energy-dense propellant made to exert the same force while burning in an engine. Different engine designs burning the same propellant may not be equally efficient at directing their propellant's energy into effective thrust. For all vehicles, specific impulse (impulse per unit weight-on-Earth of propellant) in seconds can be defined by

1218-421: A much larger specific impulse than a rocket; for example a turbofan jet engine may have a specific impulse of 6,000 seconds or more at sea level whereas a rocket would be between 200 and 400 seconds. An air-breathing engine is thus much more propellant efficient than a rocket engine, because the air serves as reaction mass and oxidizer for combustion which does not have to be carried as propellant, and

1305-456: A range-extender for smaller, short-distance, low-speed electric vessels, such as ferries. Hydrogen in ammonia is being considered as a long-distance fuel. Fuel-cell buses were trialed in Ursus Lublin in 2017. Solaris Bus & Coach introduced its Urbino 12 hydrogen electric buses in 2019. Several dozen were ordered. The first city in the U.S. to have a fleet of hydrogen powered buses

1392-499: A rocket (including its propellant) per unit time is equal to the thrust. The higher the specific impulse, the less propellant is needed to produce a given thrust for a given time and the more efficient the propellant is. This should not be confused with the physics concept of energy efficiency , which can decrease as specific impulse increases, since propulsion systems that give high specific impulse require high energy to do so. Thrust and specific impulse should not be confused. Thrust

1479-400: A rocket can be defined in terms of thrust per unit mass flow of propellant. This is an equally valid (and in some ways somewhat simpler) way of defining the effectiveness of a rocket propellant. For a rocket, the specific impulse defined in this way is simply the effective exhaust velocity relative to the rocket, v e . "In actual rocket nozzles, the exhaust velocity is not really uniform over

1566-443: A significant part of transportation needs. In a few countries, renewable sources are being used more widely to produce energy and hydrogen. For example, Iceland is using geothermal power to produce hydrogen, and Denmark is using wind . Compressed hydrogen in hydrogen tanks at 350 bar (5,000 psi) and 700 bar (10,000 psi) is used for hydrogen tank systems in vehicles, based on type IV carbon-composite technology. Hydrogen has

1653-433: A static 3 litre 300 bar refillable hydrogen cylinder. The HydroCargo bike has a range of up to 100 km on 80 grams of hydrogen. Lloyd Alter of TreeHugger responded to the announcement, asking "why … go through the trouble of using electricity to make hydrogen, only to turn it back into electricity to charge a battery to run the e-bike [or] pick a fuel that needs an expensive filling station that can only handle 35 bikes

1740-409: A very low volumetric energy density at ambient conditions, compared with gasoline and other vehicle fuels. It must be stored in a vehicle either as a super-cooled liquid or as highly compressed gas, which require additional energy to accomplish. In 2018, researchers at CSIRO in Australia powered a Toyota Mirai and Hyundai Nexo with hydrogen separated from ammonia using a membrane technology. Ammonia

1827-417: Is a stub . You can help Misplaced Pages by expanding it . This article related to a manufacturing company is a stub . You can help Misplaced Pages by expanding it . Hydrogen vehicle A hydrogen vehicle is a vehicle that uses hydrogen to move . Hydrogen vehicles include some road vehicles , rail vehicles , space rockets , forklifts , ships and aircraft . Motive power is generated by converting

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1914-628: Is a hydrogen fueled, internal combustion engine -powered industrial forklift truck used for lifting and transporting materials. The first production HICE forklift truck based on the Linde X39 Diesel was presented at an exposition in Hannover on May 27, 2008. It used a 2.0 litre, 43 kW (58 hp) diesel internal combustion engine converted to use hydrogen as a fuel with the use of a compressor and direct injection . In 2013 there were over 4,000 fuel cell forklifts used in material handling in

2001-490: Is a notional velocity called the effective exhaust velocity . This is higher than the actual exhaust velocity because the mass of the combustion air is not being accounted for. Actual and effective exhaust velocity are the same in rocket engines operating in a vacuum. The amount of propellant can be measured either in units of mass or weight. If mass is used, specific impulse is an impulse per unit of mass, which dimensional analysis shows to have units of speed, specifically

2088-445: Is a slightly modified version of the traditional gasoline internal combustion engine car. These hydrogen engines burn fuel in the same manner that gasoline engines do; the main difference is the exhaust product. Gasoline combustion results in emissions of mostly carbon dioxide and water, plus trace amounts of carbon monoxide , NO x , particulates and unburned hydrocarbons, while the main exhaust product of hydrogen combustion

2175-490: Is also ionized, which would interfere with radio communication with the rocket. Nuclear thermal rocket engines differ from conventional rocket engines in that energy is supplied to the propellants by an external nuclear heat source instead of the heat of combustion . The nuclear rocket typically operates by passing liquid hydrogen gas through an operating nuclear reactor. Testing in the 1960s yielded specific impulses of about 850 seconds (8,340 m/s), about twice that of

2262-450: Is also valid for air-breathing jet engines, but is rarely used in practice. (Note that different symbols are sometimes used; for example, c is also sometimes seen for exhaust velocity. While the symbol I sp {\displaystyle I_{\text{sp}}} might logically be used for specific impulse in units of (N·s )/(m·kg); to avoid confusion, it is desirable to reserve this for specific impulse measured in seconds.) It

2349-405: Is easier to transport safely in tankers than pure hydrogen. Effective exhaust velocity Specific impulse (usually abbreviated I sp ) is a measure of how efficiently a reaction mass engine, such as a rocket using propellant or a jet engine using fuel, generates thrust . A propulsion system with a higher specific impulse uses the mass of the propellant more efficiently. In

2436-434: Is impractical. Lithium and fluorine are both extremely corrosive, lithium ignites on contact with air, fluorine ignites on contact with most fuels, and hydrogen, while not hypergolic, is an explosive hazard. Fluorine and the hydrogen fluoride (HF) in the exhaust are very toxic, which damages the environment, makes work around the launch pad difficult, and makes getting a launch license that much more difficult. The rocket exhaust

2523-493: Is inversely proportional to specific fuel consumption (SFC) by the relationship I sp = 1/( g o ·SFC) for SFC in kg/(N·s) and I sp = 3600/SFC for SFC in lb/(lbf·hr). An example of a specific impulse measured in time is 453 seconds, which is equivalent to an effective exhaust velocity of 4.440 km/s (14,570 ft/s), for the RS-25 engines when operating in a vacuum. An air-breathing jet engine typically has

2610-572: Is not degraded by lower temperatures. The fuel cell units are often designed as drop-in replacements. In the International Energy Agency ’s 2022 Net Zero Emissions Scenario, hydrogen is forecast to account for 2% of rail energy demand in 2050, while 90% of rail travel is expected to be electrified by then (up from 45% today). Hydrogen’s role in rail would likely be focused on lines that prove difficult or costly to electrify. In March 2015, China South Rail Corporation (CSR) demonstrated

2697-476: Is produced from feedstocks such as natural gas and biomass or electrolyzed from water. A suggested benefit of large-scale deployment of hydrogen vehicles is that it could lead to decreased emissions of greenhouse gases and ozone precursors. However, as of 2014, 95% of hydrogen is made from methane . It can be produced by thermochemical or pyrolitic means using renewable feedstocks, but that is an expensive process. Renewable electricity can however be used to power

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2784-417: Is produced using natural gas. Hydrogen can be produced from water by electrolysis at working efficiencies of 65–70%. Hydrogen can be made by chemical reduction using chemical hydrides or aluminum. Current technologies for manufacturing hydrogen use energy in various forms, totaling between 25 and 50 percent of the higher heating value of the hydrogen fuel, used to produce, compress or liquefy, and transmit

2871-408: Is proportional to the effective exhaust velocity. A spacecraft without propulsion follows an orbit determined by its trajectory and any gravitational field. Deviations from the corresponding velocity pattern (these are called Δ v ) are achieved by sending exhaust mass in the direction opposite to that of the desired velocity change. When an engine is run within the atmosphere, the exhaust velocity

2958-410: Is reduced by atmospheric pressure, in turn reducing specific impulse. This is a reduction in the effective exhaust velocity, versus the actual exhaust velocity achieved in vacuum conditions. In the case of gas-generator cycle rocket engines, more than one exhaust gas stream is present as turbopump exhaust gas exits through a separate nozzle. Calculating the effective exhaust velocity requires averaging

3045-409: Is related to the thrust , or forward force on the rocket by the equation: F thrust = v e ⋅ m ˙ , {\displaystyle F_{\text{thrust}}=v_{\text{e}}\cdot {\dot {m}},} where m ˙ {\displaystyle {\dot {m}}} is the propellant mass flow rate, which is the rate of decrease of

3132-452: Is that it may be used for rockets, where all the reaction mass is carried on board, as well as airplanes, where most of the reaction mass is taken from the atmosphere. In addition, giving the result as a unit of time makes the result easily comparable between calculations in SI units, imperial units, US customary units or other unit framework. The English unit pound mass is more commonly used than

3219-470: Is the force supplied by the engine and depends on the amount of reaction mass flowing through the engine. Specific impulse measures the impulse produced per unit of propellant and is proportional to the exhaust velocity. Thrust and specific impulse are related by the design and propellants of the engine in question, but this relationship is tenuous. For example, LH 2 /LO 2 bipropellant produces higher I sp but lower thrust than RP-1 / LO 2 due to

3306-503: Is the high effective exhaust velocity compared to kerosene / LOX or UDMH / NTO engines. According to the Tsiolkovsky rocket equation , a rocket with higher exhaust velocity uses less propellant to accelerate. Also the energy density of hydrogen is greater than any other fuel. LH2/LOX also yields the greatest efficiency in relation to the amount of propellant consumed, of any known rocket propellant. A disadvantage of LH2/LOX engines

3393-520: Is the low density and low temperature of liquid hydrogen, which means bigger and insulated and thus heavier fuel tanks are needed compared to methane, although methane is more polluting. This increases the rocket's structural mass which reduces its delta-v accordingly. Another disadvantage is the poor storability of LH2/LOX-powered rockets: Due to the constant hydrogen boil-off, the rocket must be fueled shortly before launch, which makes cryogenic engines unsuitable for ICBMs and other rocket applications with

3480-401: Is the product of the average specific gravity of a given propellant mixture and the specific impulse. While less important than the specific impulse, it is an important measure in launch vehicle design, as a low specific impulse implies that bigger tanks will be required to store the propellant, which in turn will have a detrimental effect on the launch vehicle's mass ratio . Specific impulse

3567-478: Is the second, as values are identical regardless of whether the calculations are done in SI , imperial , or US customary units. Nearly all manufacturers quote their engine performance in seconds, and the unit is also useful for specifying aircraft engine performance. The use of metres per second to specify effective exhaust velocity is also reasonably common. The unit is intuitive when describing rocket engines, although

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3654-427: Is water vapor. In 1807 François Isaac de Rivaz designed the first hydrogen-fueled internal combustion engine . In 1965, Roger E. Billings, then a high school student, converted a Model A to run on hydrogen. In 1970 Paul Dieges patented a modification to internal combustion engines which allowed a gasoline-powered engine to run on hydrogen. Mazda has developed Wankel engines burning hydrogen, which are used in

3741-831: The German Aerospace Center are pursuing hydrogen as fuel for crewed and uncrewed aeroplanes. In February 2008 Boeing tested a crewed flight of a small aircraft powered by a hydrogen fuel cell. Uncrewed hydrogen planes have also been tested. For large passenger aeroplanes, The Times reported that "Boeing said that hydrogen fuel cells were unlikely to power the engines of large passenger jet aeroplanes but could be used as backup or auxiliary power units onboard." In July 2010, Boeing unveiled its hydrogen-powered Phantom Eye UAV , powered by two Ford internal-combustion engines that have been converted to run on hydrogen. As of 2019 hydrogen fuel cells are not suitable for propulsion in large long-distance ships but are being considered as

3828-525: The Mazda RX-8 Hydrogen RE . The advantage of using an internal combustion engine, like Wankel and piston engines, is the lower cost of retooling for production. Hydrogen fuel cells are relatively expensive to produce, as their designs require rare substances, such as platinum , as a catalyst . In 2014, former European Parliament President Pat Cox estimated that Toyota would initially lose about $ 100,000 on each Mirai sold. In 2020, researchers at

3915-602: The Space Shuttle to run the fuel cells that power the electrical systems. The byproduct of the fuel cell is water, which is used for drinking and other applications that require water in space. As of 2021 , there were two hydrogen cars publicly available in select markets: the Toyota Mirai and the Hyundai Nexo . The Honda Clarity was produced from 2016 to 2021. Hydrogen combustion cars are not commercially available. In

4002-596: The Suzuki Burgman fuel-cell scooter and the FHybrid . The Burgman received "whole vehicle type" approval in the EU. The Taiwanese company APFCT conducted a live street test with 80 fuel-cell scooters for Taiwan's Bureau of Energy. Hydrogen auto rickshaw concept vehicles have been built by Mahindra HyAlfa and Bajaj Auto. Autostudi S.r.l 's H-Due is a hydrogen-powered quad, capable of transporting 1-3 passengers. A concept for

4089-466: The Toyota Mirai (2014–), the first commercially produced dedicated fuel cell electric vehicle (FCEV), and the Hyundai Nexo (2018–). The Honda CR-V e:FCEV became available, for lease only, in very limited quantities in 2024. As of 2019, 98% of hydrogen is produced by steam methane reforming , which emits carbon dioxide . It can be produced by electrolysis of water , or by thermochemical or pyrolytic means using renewable feedstocks , but

4176-597: The chemical energy of hydrogen to mechanical energy , either by reacting hydrogen with oxygen in a fuel cell to power electric motors or, less commonly, by hydrogen internal combustion . Hydrogen burns cleaner than fuels such as gasoline or methane but is more difficult to store and transport because of the small size of the molecule. As of the 2020s hydrogen light duty vehicles, including passenger cars, have been sold in small numbers due to competition with battery electric vehicles . As of 2021 , there were two models of hydrogen cars publicly available in select markets:

4263-404: The effective exhaust velocity while reducing the actual exhaust velocity. Again, this is because the mass of the air is not counted in the specific impulse calculation, thus attributing all of the thrust momentum to the mass of the fuel component of the exhaust, and omitting the reaction mass, inert gas, and effect of driven fans on overall engine efficiency from consideration. Essentially,

4350-442: The effective exhaust velocity . As the SI system is mass-based, this type of analysis is usually done in meters per second. If a force-based unit system is used, impulse is divided by propellant weight (weight is a measure of force), resulting in units of time (seconds). These two formulations differ from each other by the standard gravitational acceleration ( g 0 ) at the surface of the earth. The rate of change of momentum of

4437-675: The Space Shuttle engines. A variety of other rocket propulsion methods, such as ion thrusters , give much higher specific impulse but with much lower thrust; for example the Hall-effect thruster on the SMART-1 satellite has a specific impulse of 1,640 s (16.1 km/s) but a maximum thrust of only 68 mN (0.015 lbf). The variable specific impulse magnetoplasma rocket (VASIMR) engine currently in development will theoretically yield 20 to 300 km/s (66,000 to 984,000 ft/s), and

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4524-493: The U.S. Army has been testing the commercial Chevrolet Colorado ZH2 on its U.S. bases to determine the viability of hydrogen-powered vehicles in military mission tactical environments. ENV develops electric motorcycles powered by a hydrogen fuel cell, including the Crosscage and Biplane . Other manufacturers as Vectrix are working on hydrogen scooters. Finally, hydrogen-fuel-cell-electric-hybrid scooters are being made such as

4611-800: The US to that time due to a risk of fuel leaks and fire from a faulty "pressure relief device". Toyota launched the world's first dedicated mass-produced fuel cell vehicle (FCV), the Mirai , in Japan at the end of 2014 and began sales in California, mainly the Los Angeles area and also in selected markets in Europe, the UK, Germany and Denmark later in 2015. The car has a range of 312 mi (502 km) and takes about five minutes to refill its hydrogen tank. The initial sale price in Japan

4698-516: The US. As of 2024, approximately 50,000 hydrogen forklifts are in operation worldwide (the bulk of which are in the U.S.), as compared with 1.2 million battery electric forklifts that were purchased in 2021. Most companies in Europe and the US do not use petroleum powered forklifts, as these vehicles work indoors where emissions must be controlled and instead use electric forklifts. Fuel-cell-powered forklifts can be refueled in 3 minutes. They can be used in refrigerated warehouses, as their performance

4785-537: The University of Copenhagen's Department of Chemistry are developing a new type of catalyst that they hope will decrease the cost of fuel cells. This new catalyst uses far less platinum because the platinum nano-particles are not coated over carbon which, in conventional hydrogen fuel cells, keeps the nano-particles in place but also causes the catalyst to become unstable and denatures it slowly, requiring even more platinum. The new technology uses durable nanowires instead of

4872-408: The actual exhaust speed is much lower, so the kinetic energy the exhaust carries away is lower and thus the jet engine uses far less energy to generate thrust. While the actual exhaust velocity is lower for air-breathing engines, the effective exhaust velocity is very high for jet engines. This is because the effective exhaust velocity calculation assumes that the carried propellant is providing all

4959-437: The automobile companies developing hydrogen cars had switched their focus to battery electric vehicles. By 2020, all but three automobile companies had abandoned plans to manufacture hydrogen cars. The Honda CR-V e:FCEV became available, for lease only, in very limited quantities in 2024. A significant number of the public hydrogen fuel stations in the California are not able to dispense hydrogen. In 2024, Mirai owners filed

5046-427: The burned fuel. Next, inert gases in the atmosphere absorb heat from combustion, and through the resulting expansion provide additional thrust. Lastly, for turbofans and other designs there is even more thrust created by pushing against intake air which never sees combustion directly. These all combine to allow a better match between the airspeed and the exhaust speed, which saves energy/propellant and enormously increases

5133-401: The case of a rocket, this means less propellant needed for a given delta- v , so that the vehicle attached to the engine can more efficiently gain altitude and velocity. For engines like cold gas thrusters whose reaction mass is only the fuel they carry, specific impulse is exactly proportional to the effective exhaust gas velocity. In an atmospheric context, specific impulse can include

5220-448: The cathode, three stages in cold start and Nafion ionic conductivity. A parameter, defined as coulomb of charge, was also defined to measure cold start capability. The service life of fuel cells is comparable to that of other vehicles. Polymer-electrolyte membrane (PEM) fuel cell service life is 7,300 hours under cycling conditions. Hydrogen does not exist in convenient reservoirs or deposits like fossil fuels or helium . It

5307-402: The contribution to impulse provided by the mass of external air that is accelerated by the engine, such as by fuel combustion or by external propeller. Jet engines and turbofans breathe external air for both combustion and bypass, and therefore have a much higher specific impulse than rocket engines. For air-breathing engines, only the fuel mass is counted, not the mass of air passing through

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5394-473: The conversion of water into hydrogen: Integrated wind-to-hydrogen ( power to gas ) plants, using electrolysis of water , are exploring technologies to deliver costs low enough, and quantities great enough, to compete with traditional energy sources. The challenges facing the use of hydrogen in vehicles include its storage on board the vehicle. As of September 2023, hydrogen cost $ 36 per kilogram at public fueling stations in California, 14 times as much per mile for

5481-474: The definition of specific impulse as impulse per unit mass of propellant. Specific fuel consumption is inversely proportional to specific impulse and has units of g/(kN·s) or lb/(lbf·h). Specific fuel consumption is used extensively for describing the performance of air-breathing jet engines. Specific impulse, measured in seconds, can be thought of as how many seconds one kilogram of fuel can produce one kilogram of thrust. Or, more precisely, how many seconds

5568-492: The effective exhaust speed of the engines may be significantly different from the actual exhaust speed, especially in gas-generator cycle engines. For airbreathing jet engines , the effective exhaust velocity is not physically meaningful, although it can be used for comparison purposes. Metres per second are numerically equivalent to newton-seconds per kg (N·s/kg), and SI measurements of specific impulse can be written in terms of either units interchangeably. This unit highlights

5655-464: The engine. Air resistance and the engine's inability to keep a high specific impulse at a fast burn rate are limiting factors to the propellant consumption rate. If it were not for air resistance and the reduction of propellant during flight, specific impulse would be a direct measure of the engine's effectiveness in converting propellant mass into forward momentum. The specific impulse in terms of propellant mass spent has units of distance per time, which

5742-638: The entire exit cross section and such velocity profiles are difficult to measure accurately. A uniform axial velocity, v e , is assumed for all calculations which employ one-dimensional problem descriptions. This effective exhaust velocity represents an average or mass equivalent velocity at which propellant is being ejected from the rocket vehicle." The two definitions of specific impulse are proportional to one another, and related to each other by: v e = g 0 ⋅ I sp , {\displaystyle v_{\text{e}}=g_{0}\cdot I_{\text{sp}},} where This equation

5829-435: The exhaust gases having a lower density and higher velocity ( H 2 O vs CO 2 and H 2 O). In many cases, propulsion systems with very high specific impulse—some ion thrusters reach 10,000 seconds—produce low thrust. When calculating specific impulse, only propellant carried with the vehicle before use is counted. For a chemical rocket, the propellant mass therefore would include both fuel and oxidizer . In rocketry,

5916-451: The first 200 of the bikes are to be provided to journalists covering the 45th G7 summit in Biarritz , France. In 2020, Alles over Waterstof developed a 2-wheel hydrogen powered stand-up scooter. The stand-up scooter has a range of over 20 km on 15 grams of hydrogen. It uses a swappable 1 litre 200 bar hydrogen cylinder. In 2021 the company developed a hydrogen powered cargo-bike, using

6003-455: The following equation: F thrust = g 0 ⋅ I sp ⋅ m ˙ , {\displaystyle F_{\text{thrust}}=g_{0}\cdot I_{\text{sp}}\cdot {\dot {m}},} where: I sp in seconds is the amount of time a rocket engine can generate thrust, given a quantity of propellant whose weight is equal to the engine's thrust. The advantage of this formulation

6090-459: The hydrogen by pipeline or truck. Environmental consequences of the production of hydrogen from fossil energy resources include the emission of greenhouse gasses , a consequence that would also result from the on-board reforming of methanol into hydrogen. Hydrogen production using renewable energy resources would not create such emissions, but the scale of renewable energy production would need to be expanded to be used in producing hydrogen for

6177-717: The investment required to build refuelling infrastructure around the world to dispense hydrogen. In addition, leaked hydrogen is an invisible, highly flammable gas and has a global warming effect 11.6 times stronger than CO₂. The rationale for hydrogen vehicles lies in their potential to reduce reliance on fossil fuels, associated greenhouse gas emissions and localised air pollution from transportation. This would require hydrogen to be produced cleanly, for use in sectors and applications where cheaper and more energy efficient mitigation alternatives are limited. Many large rockets use liquid hydrogen as fuel, with liquid oxygen as an oxidizer (LH2/LOX). An advantage of hydrogen rocket fuel

6264-528: The light road vehicle segment, by the end of 2022, 70,200 fuel cell electric vehicles had been sold worldwide, compared with 26 million plug-in electric vehicles. In 2023, 3,143 hydrogen cars were sold in the US compared with 380,000 BEVs. With the rapid rise of electric vehicles and associated battery technology and infrastructure, the global scope for hydrogen's role in cars is shrinking relative to earlier expectations. John Max of Hydrogen Fuel News believes that hydrogen may, however, be used directly, or as

6351-490: The momentum of engine exhaust includes a lot more than just fuel, but specific impulse calculation ignores everything but the fuel. Even though the effective exhaust velocity for an air-breathing engine seems nonsensical in the context of actual exhaust velocity, this is still useful for comparing absolute fuel efficiency of different engines. A related measure, the density specific impulse , sometimes also referred to as Density Impulse and usually abbreviated as I s d

6438-553: The nano-particles. "The next step for the researchers is to scale up their results so that the technology can be implemented in hydrogen vehicles." The problems in early fuel-cell designs at low temperatures concerning range and cold start capabilities have been addressed so that they "cannot be seen as show-stoppers anymore". Users in 2014 said that their fuel cell vehicles continue to operate in temperatures below zero without significantly reducing range. Studies using neutron radiography on unassisted cold-start indicate ice formation in

6525-459: The need for short launch preparations. Overall, the delta-v of a hydrogen stage is typically not much different from that of a dense fuelled stage, but the weight of a hydrogen stage is much less, which makes it particularly effective for upper stages, since they are carried by the lower stages. For first stages, dense fuelled rockets in studies may show a small advantage, due to the smaller vehicle size and lower air drag. LH2/LOX were also used in

6612-465: The only reaction mass is the propellant, so the specific impulse is calculated using an alternative method, giving results with units of seconds. Specific impulse is defined as the thrust integrated over time per unit weight -on-Earth of the propellant: I sp = v e g 0 , {\displaystyle I_{\text{sp}}={\frac {v_{\text{e}}}{g_{0}}},} where In rockets, due to atmospheric effects,

6699-580: The processes are currently expensive. Various technologies are being developed that aim to deliver costs low enough, and quantities great enough, to compete with hydrogen production using natural gas. Vehicles running on hydrogen technology benefit from a long range on a single refuelling, but are subject to several drawbacks including high carbon emissions when hydrogen is produced from natural gas, capital cost burden, high energy inputs in production and transportation, low energy content per unit volume at ambient conditions, production and compression of hydrogen,

6786-414: The reaction mass and all the thrust. Hence effective exhaust velocity is not physically meaningful for air-breathing engines; nevertheless, it is useful for comparison with other types of engines. The highest specific impulse for a chemical propellant ever test-fired in a rocket engine was 542 seconds (5.32 km/s) with a tripropellant of lithium , fluorine , and hydrogen . However, this combination

6873-574: The slug, and when using pounds per second for mass flow rate, it is more convenient to express standard gravity as 1 pound-force per pound-mass. Note that this is equivalent to 32.17405 ft/s2, but expressed in more convenient units. This gives: F thrust = I sp ⋅ m ˙ ⋅ ( 1 l b f l b m ) . {\displaystyle F_{\text{thrust}}=I_{\text{sp}}\cdot {\dot {m}}\cdot \left(1\mathrm {\frac {lbf}{lbm}} \right).} In rocketry,

6960-490: The specific impulse varies with altitude, reaching a maximum in a vacuum. This is because the exhaust velocity isn't simply a function of the chamber pressure, but is a function of the difference between the interior and exterior of the combustion chamber . Values are usually given for operation at sea level ("sl") or in a vacuum ("vac"). Because of the geocentric factor of g 0 in the equation for specific impulse, many prefer an alternative definition. The specific impulse of

7047-415: The two mass flows as well as accounting for any atmospheric pressure. For air-breathing jet engines, particularly turbofans , the actual exhaust velocity and the effective exhaust velocity are different by orders of magnitude. This happens for several reasons. First, a good deal of additional momentum is obtained by using air as reaction mass, such that combustion products in the exhaust have more mass than

7134-446: The vehicle's mass. A rocket must carry all its propellant with it, so the mass of the unburned propellant must be accelerated along with the rocket itself. Minimizing the mass of propellant required to achieve a given change in velocity is crucial to building effective rockets. The Tsiolkovsky rocket equation shows that for a rocket with a given empty mass and a given amount of propellant, the total change in velocity it can accomplish

7221-455: The world's first hydrogen fuel cell-powered tramcar at an assembly facility in Qingdao. Tracks for the new vehicle have been built in seven Chinese cities. In northern Germany in 2018 the first fuel-cell powered Coradia iLint trains were placed into service; excess power is stored in lithium-ion batteries . In 2007, Pearl Hydrogen Power Source Technology Co of Shanghai , China, demonstrated

7308-583: Was Champaign , Illinois, when in 2021 the Champaign–Urbana Mass Transit District ordered two New Flyer XHE60 articulated hydrogen fuel cell buses, with 10 more New Flyer XHE40 buses added in 2024. In 2022, the city of Montpellier , France, cancelled a contract to procure 51 buses powered by hydrogen fuel cells, when it found that "the cost of operation for hydrogen [buses] is 6 times the cost of electricity". A hydrogen internal combustion engine (or "HICE") forklift or HICE lift truck

7395-455: Was about 7 million yen ($ 69,000). Former European Parliament President Pat Cox estimated that Toyota would initially lose about $ 100,000 on each Mirai sold. At the end of 2019, Toyota had sold over 10,000 Mirais. Many automobile companies introduced demonstration models in limited numbers (see List of fuel cell vehicles and List of hydrogen internal combustion engine vehicles ). In 2013 BMW leased hydrogen technology from Toyota , and

7482-440: Was the world's first hydrogen fuel cell vehicle designed for mass production rather than adapting an existing model. Honda established the world's first fuel cell vehicle dealer network in 2008, and at the time was the only company able to lease hydrogen fuel cell vehicles to private customers. The 2013 Hyundai Tucson FCEV , a modified Tucson, was introduced to the market as a lease-only vehicle, and Hyundai Motors claimed it

7569-505: Was the world's first mass-produced hydrogen fuel cell vehicle. However, due to high prices and a lack of charging infrastructure, sales fell far short of initial plans, with only 273 units sold by the end of May 2015. Hyundai Nexo , which succeeded the Tucson in 2018, was selected as the "safest SUV" by the Euro NCAP in 2018, but In October 2024, Hyundai recalled all 1,600 Nexo vehicles sold in

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