Misplaced Pages

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40-602: The RQ-3 DarkStar was designed as a " high-altitude endurance UAV", and incorporated stealth aircraft technology to make it difficult to detect, which allowed it to operate within heavily defended airspace, unlike the Northrop Grumman RQ-4 Global Hawk , which is unable to operate except under conditions of air supremacy . The DarkStar was fully autonomous: it could take off, fly to its target, operate its sensors, transmit information, return and land without human intervention. Human operators, however, could change

80-455: A dead man's switch to preclude unmonitored operation. Aviation fuel can cause severe environmental damage; all fueling vehicles must carry equipment to control fuel spills. Fire extinguishers must be present at any fueling operation. Airport firefighting forces are specially trained and equipped to handle aviation fuel fires and spills. Aviation fuel must be checked daily and before every flight for contaminants such as water or dirt. Avgas

120-445: A radio relay , for oceanography or earth imaging , for border security , maritime patrol and anti- piracy operations, disaster response , or agricultural observation . While reconnaissance aircraft have been capable of reaching high altitudes since the 1950s, their endurance is limited. One of the few operational HALE aircraft is the Northrop Grumman RQ-4 Global Hawk . There are many solar powered, lightweight prototypes like

160-722: A 5 pounds (2.3 kilograms) payload. By August 2002, US company Worldwide Aeros was building a stratospheric demonstrator for the Korea Aerospace Research Institute , as a part the South Korean HAA development program. By April 2004, stratospheric airships were being developed in USA, UK, Canada, Korea and Japan. In May 2004, the Japan Aerospace Exploration Agency shown its test airship in Taiki, Hokkaido ,

200-575: A crash shortly after takeoff. A modified, more stable design (the RQ-3A) first flew on June 29, 1998, and made a total of five flights before the program was canceled just prior to the sixth and final flight planned for the airworthiness test phase. Two additional RQ-3As were built, but never made any flights before program cancellation. The "R" is the Department of Defense designation for reconnaissance; "Q" means unmanned aircraft system. The "3" refers to it being

240-1023: A debate in the UK Parliament , the forgone tax income due to the exemption of tax on aviation fuel was estimated at £10 billion annually. The planned inclusion of international aviation into the European Union Emission Trading Scheme in 2014 has been called an "illegal tax" by countries including the US and China , which cite the Chicago Convention. Fuels have to conform to a specification in order to be approved for use in type certificated aircraft. The American Society for Testing and Materials (ASTM) developed specifications for automobile gasoline as well as aviation gasoline. These specifications are ASTM D910 and ASTM D6227 for aviation gasoline and ASTM D439 or ASTM D4814 (latest revision) for automobile gasoline. Aviation fuel generally arrives at

280-655: A density of jet fuel around 6.7 lb/US gal, 8.02 lb/ imp Gal or 0.8 kg/L. Specific cases are: Aviation fuels consist of blends of over two thousand chemicals, primarily hydrocarbons ( paraffins , olefins , naphthenes , and aromatics ), additives such as antioxidants and metal deactivators, biocides, static reducers, icing inhibitors, corrosion inhibitors, and impurities. Principal components include n-heptane and isooctane . Like other fuels, aviation fuel for spark-ignited piston engines are described by their octane rating . Alcohol, alcohol mixtures, and other alternative fuels may be used experimentally, but alcohol

320-408: A faster flowrate. Because of the danger of confusing the fuel types, precautions are taken to distinguish between avgas and jet fuel beyond clearly marking all containers, vehicles, and piping. The aperture on fuel tanks of aircraft requiring avgas cannot be greater than 60  millimetres in diameter. Avgas is often dyed and is dispensed from nozzles with a diameter of 40 mm (49 mm in

360-432: A high-pressure hose is attached and fuel is pumped in at 275  kPa (40  psi ) and a maximum of 310 kPa (45 psi) for most commercial aircraft. Pressure for military aircraft, especially fighters, ranges up to 415 kPa (60 psi). Air being displaced in the tanks is usually vented overboard through a single vent on the aircraft. Because there is only one attachment point, fuel distribution between tanks

400-1156: A part of its Stratosphere Platform Project. A geostationary balloon satellite (GBS) flies in the stratosphere (60,000 to 70,000 ft (18 to 21 km) above sea level) at a fixed point over the Earth's surface. At that altitude the air has 1/10 of its density is at sea level . A GBS could be used to provide broadband Internet access over a large area. One prior project was the Google 's Project Loon , which envisioned using helium-filled high-altitude balloons . Aviation fuel Aviation fuels are petroleum -based fuels , or petroleum and synthetic fuel blends, used to power aircraft . They have more stringent requirements than fuels used for ground use, such as heating and road transport , and contain additives to enhance or maintain properties important to fuel performance or handling. They are kerosene -based ( JP-8 and Jet A-1 ) for gas turbine-powered aircraft. Piston-engined aircraft use leaded gasoline and those with diesel engines may use jet fuel (kerosene). By 2012, all aircraft operated by

440-430: A wide margin. Compressed natural gas (CNG) and liquified natural gas (LNG) are fuel feedstocks that aircraft may use in the future. Studies have been done on the feasibility of using natural gas and include the "SUGAR Freeze" aircraft under NASA's N+4 Advanced Concept Development program (made by Boeing's Subsonic Ultra Green Aircraft Research (SUGAR) team). The Tupolev Tu-155 was an alternative fuel testbed which

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480-524: Is a gas turbine fuel used in propeller and jet aircraft and helicopters. It has a low viscosity at low temperature, has limited ranges of density and calorific value , burns cleanly, and remains chemically stable when heated to high temperature. Aviation gasoline , often referred to as "avgas" or 100-LL (low-lead), is a highly refined form of gasoline for aircraft, with an emphasis on purity, anti-knock characteristics and minimization of spark plug fouling. Avgas must meet performance guidelines for both

520-878: Is a long endurance , high altitude aircraft able to offer observation or communication services similarly to artificial satellites . Mostly unmanned aerial vehicles (UAVs), they remain aloft through atmospheric lift, either aerodynamic like airplanes , or aerostatic like airships or balloons . High-altitude long endurance (HALE) military drones can fly above 60,000 ft (18,000 m) over 32 hours, while civil HAPS are radio stations at an altitude of 20 to 50 km above waypoints, for weeks. High-altitude, long endurance flight has been studied since at least 1983, and demonstrator programs since 1994. Hydrogen and solar power have been proposed as alternatives to conventional engines. Above commercial air transport and wind turbulence, at high altitudes, drag as well as lift are reduced. HAPS could be used for weather monitoring, as

560-467: Is a mix of extremely refined kerosene and burns at temperatures at or above 49 °C (120 °F). Kerosene-based fuel has a much higher flash point than gasoline-based fuel, meaning that it requires significantly higher temperature to ignite. It is a high-quality fuel; if it fails the purity and other quality tests for use on jet aircraft, it is sold to ground-based users with less demanding requirements, such as railroads. Avgas ( av iation gas oline)

600-404: Is either automated or it is controlled from a control panel at the fueling point or in the cockpit. An early use of pressure refueling was on the de Havilland Comet and Sud Aviation Caravelle . Larger aircraft allow for two or more attachment points; however, this is still referred to as single-point refueling, as either attachment point can refuel all of the tanks. Multiple attachments allow for

640-452: Is fairly lengthy. Alternatives to conventional aviation fuel available in the near term include aviation biofuel and synthetically created fuel (aka "e-jet"). These fuels are collectively referred to as "Sustainable Aviation Fuel" (SAF). The production of aviation fuel falls into two categories: fuel suitable for turbine engines and fuel suitable for spark-ignition piston engines. There are international specifications for each. Jet fuel

680-812: Is not permitted in any certified aviation fuel specification. In Brazil, the Embraer Ipanema EMB-202A is a version of the Ipanema agricultural aircraft with a modified Lycoming IO-540-K1J5 engine so as to be able to run on ethanol . Other aircraft engines that were modified to run on 100% ethanol were several other types of Lycoming engines (including the Lycoming 235N2C, and Lycoming IO-320 ) and certain Rotax engines. The Convention on International Civil Aviation (ICAO) (Chicago 1944, Article 24) exempts air fuels already loaded onto an aircraft on landing (and which remain on

720-516: Is that a local aviation fuel tax would cause increased tankering , where airlines carry extra fuel from low tax jurisdictions. This extra weight increases fuel burn, thus a local fuel tax could potentially increase overall fuel consumption. To avoid increased tankering, a worldwide aviation fuel tax has been proposed. Australia and the United States oppose a worldwide aviation fuel tax, but a number of other countries have expressed interest. During

760-477: Is used by small aircraft, light helicopters and vintage piston-engined aircraft. Its formulation is distinct from the conventional gasoline (UK: petrol , or "aviation spirit" in this context) used in motor vehicles which is commonly called mogas or autogas in aviation context. Although it comes in many different grades, its octane rating is higher than that for "regular" motor gasoline. Alternatives to conventional fossil-based aviation fuels, new fuels made via

800-404: Is used on smaller planes, helicopters, and all piston-engine aircraft. Overwing fueling is similar to car fueling — one or more fuel ports are opened and fuel is pumped in with a conventional pump. Underwing fueling, also called single-point refueling or pressure refueling where not dependent on gravity, is used on larger aircraft and for jet fuel exclusively. For pressure refueling,

840-786: The Design and experimental results for a high-altitude, long-endurance airfoil report proposed applications as a radio relay , for weather monitoring or cruise missile targeting . The NASA ERAST Program (Environmental Research Aircraft and Sensor Technology) was started in September 1994 to study high-altitude UAVs, and was terminated in 2003. In July 1996, the USAF Strikestar 2025 report forecast HALE UAVs maintaining air occupation with 24 hours flights. The Defense Airborne Reconnaissance Office made demonstrations of long-endurance UAV craft. In September 1996, Israel Aircraft Industries detailed

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880-736: The NASA Pathfinder / Helios , or the Airbus Zephyr that can fly for 64 days; few are as advanced as these. Conventional aviation fuels have been used in prototypes since 1970 and can fly for 60 hours like the Boeing Condor . Hydrogen aircraft can fly even longer, a week or longer, like the AeroVironment Global Observer . Stratospheric airships are often presented as a competing technology. However few prototypes have been built and none are operational. Among balloons specifically,

920-459: The U.S. Air Force had been certified to use a 50-50 blend of kerosene and synthetic fuel derived from coal or natural gas as a way of stabilizing the cost of fuel. Jet fuel is a clear to straw-colored fuel, based on either an unleaded kerosene (Jet A-1), or a naphtha - kerosene blend (Jet B). Similar to diesel fuel , it can be used in either compression ignition engines or turbine engines . Jet-A powers modern commercial airliners and

960-754: The biomass to liquid method (like sustainable aviation fuel ) and certain straight vegetable oils can also be used. Fuels such as sustainable aviation fuel have the advantage that few or no modifications are necessary on the aircraft itself, provided that the fuel characteristics meet specifications for lubricity and density as well as adequately swelling elastomer seals in current aircraft fuel systems. Sustainable aviation fuel and blends of fossil and sustainably-sourced alternative fuels yield lower emissions of particles and GHGs. They are, however, not being used heavily, because they still face political, technological, and economic barriers, such as currently being more expensive than conventionally produced aviation fuels by

1000-404: The 5 billion people lacking it, either with 11,000 airplane UAVs or with balloons like Google's Project Loon . Reconnaissance aircraft like the late 1950s Lockheed U-2 could fly above 70,000 ft (21,000 m) and the 1964 SR-71 above 80,000 ft (24,000 m). The twin-turbofan powered Myasishchev M-55 reached an altitude of 21,360 m (70,080 ft) in 1993, a variant of

1040-524: The DarkStar's flight plan and sensor orientation through radio or satellite relay. The RQ-3 carried either an optical sensor or radar, and could send digital information to a satellite while still in flight. It used a single airbreathing jet engine of unknown type for propulsion. One source claims it used a Williams-Rolls-Royce FJ44-1A turbofan engine. The first prototype made its first flight on March 29, 1996, but its second flight, on April 22, 1996, ended in

1080-560: The M-17 first flown in 1982, which reached 21,830 m (71,620 ft) in 1990. Unmanned Stratospheric airships are designed to operate at very high 60,000 to 75,000 feet (18.3 to 22.9 km) altitudes during weeks, months or years. Subjected to ultraviolet damage , ozone corrosion and challenging station keeping, they can be solar-powered with energy storage for the night. The first stratospheric powered airship flight took place in 1969, reaching 70,000 feet (21 km) for 2 hours with

1120-628: The United States). Jet fuel is clear to straw-colored, and is dispensed from a special nozzle called a J spout or duckbill that has a rectangular opening larger than 60 mm diagonally, so as not to fit into avgas ports. However, some jet and turbine aircraft, such as some models of the Astar helicopter, have a fueling port too small for the J spout, and thus require a smaller nozzle. In recent years, fuel markets have become increasingly volatile. This, along with rapidly changing airline schedules and

1160-408: The air, it can accumulate static electricity . If this is not dissipated before fueling, an electric arc could occur and ignite fuel vapors. To prevent this, aircraft are electrically bonded to the fueling apparatus before fueling begins, and are not disconnected until after fueling is complete. Some regions require the aircraft and/or fuel truck to be grounded too. Pressure fueling systems incorporate

1200-453: The aircraft) from import taxes. Bi-lateral air services agreements govern the tax exemption of aviation fuels. In the course of an EU initiative, many of these agreements have been modified to allow taxation. A motion for a European Parliament resolution on a European Strategy for Low-emission Mobility has stated that "the possibilities for harmonised international measures for kerosene taxation for aviation" needs to be explored. A worry

1240-499: The airport via pipeline systems, such as the CEPS . It is then pumped over and dispensed from a tanker or bowser . The fuel is then driven up to parked aircraft and helicopters . Some airports have pumps similar to filling stations to which aircraft must taxi. Some airports have permanent piping to parking areas for large aircraft. Aviation fuel is transferred to an aircraft via one of two methods: overwing or underwing. Overwing fueling

Lockheed Martin RQ-3 DarkStar - Misplaced Pages Continue

1280-542: The design of a HALE UAV. In 2002, Preliminary reliability design of a solar-powered high-altitude very long endurance unmanned air vehicle was published. The European Union CAPECON project aimed to develop HALE vehicles, while the Polish Academy of Sciences proposed its PW-114 concept that would fly at 20 km (66,000 ft) for 40 hours. Luminati Aerospace proposed its Substrata solar-powered aircraft that would fly in formation like migratory geese to reduce

1320-614: The desire to not carry excess fuel on board aircraft, has increased the importance of demand forecasting. In March 2022, Austin's Austin-Bergstrom International Airport came close to running out of fuel, potentially stranding aircraft. Common forecasting techniques include tracking airline schedules and routes, expected distance flown, ground procedures, fuel efficiency of each aircraft and the impact of environmental factors like weather and temperature. Any fueling operation can be very dangerous, and aviation operations have characteristics which must be accommodated. As an aircraft flies through

1360-404: The hydrogen fuel itself, largely negating the weight to energy advantage of hydrogen fuel over hydrocarbon fuels. Hydrogen has a severe volumetric disadvantage relative to hydrocarbon fuels, but future blended wing body aircraft designs might be able to accommodate this extra volume without greatly expanding the wetted area . Even if finally practical, the industry timeline for adopting hydrogen

1400-535: The most well known high-endurance project was Google Loon , using helium-filled high-altitude balloons to reach the stratosphere. Loon was ended in 2021. In 1983, Lockheed produced A Preliminary Study of solar powered aircraft and Associated Power Trains for the NASA , as long endurance flight could be compared to suborbital spacecraft. In 1984 was published the Design of Long Endurance Unmanned Airplanes Incorporating Solar and fuel cell propulsion report. In 1989,

1440-499: The power required for the trailing aircraft by 79%, allowing smaller airframes to remain aloft indefinitely up to a latitude of 50°. Atmospheric satellites could be used for weather monitoring, as a radio relay , for oceanography or earth imaging like an orbital satellite for a fraction of the cost. Other uses include border security , maritime patrol and anti- piracy operations, disaster response , or agricultural observation . They could bring internet connectivity to

1480-536: The rich mixture condition required for take-off power settings and the leaner mixtures used during cruise to reduce fuel consumption. Aviation fuel can be used as CNG fuel. Avgas is sold in much lower volume than jet fuel, but to many more individual aircraft operators; whereas jet fuel is sold in high volume to large aircraft operators, such as airlines and militaries. The net energy content for aviation fuels depends on their composition. Some typical values are: In performance calculations, airliner manufacturers use

1520-772: The third of a series of purpose-built unmanned reconnaissance aircraft systems. Although the RQ-3 was terminated on January 28, 1999, a July 2003 Aviation Week and Space Technology article reported in April 2003 that a derivative of the RQ-3 had been used in the 2003 invasion of Iraq . There has been no independent confirmation. General characteristics Performance Aircraft of comparable role, configuration, and era Related lists High-Altitude Long Endurance A high-altitude platform station ( HAPS , which can also mean high-altitude pseudo-satellite or high-altitude platform systems ), also known as atmospheric satellite ,

1560-460: Was fuelled on LNG. The low specific energy of natural gas even in liquid form compared to conventional fuels gives it a distinct disadvantage for flight applications. Hydrogen can be used largely free of carbon emissions , if it is produced with power from renewable energy like wind and solar power . Some development of technology for hydrogen-powered aircraft started after the millennium and gained track since about 2020, but as of 2022

1600-479: Was still far away from outright aircraft product development. Hydrogen fuel cells do not produce CO 2 or other emissions (besides water). However, hydrogen combustion does produce NO x emissions. Cryogenic hydrogen can be used as a liquid at temperatures below 20 K. Gaseous hydrogen involves pressurized tanks at 250–350 bar. With materials available in the 2020s, the mass of tanks strong enough to withstand this kind of high pressure will greatly outweigh

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