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Ranger 8

Ranger 8

Ranger 8 was designed to achieve a lunar impact trajectory and to transmit high-resolution photographs of the lunar surface during the final minutes of flight up to impact. The spacecraft carried six television vidicon cameras, 2 wide angle (channel F, cameras A and B) and 4 narrow angle (channel P) to accomplish these objectives. The cameras were arranged in two separate chains, or channels, each self-contained with separate power supplies, timers, and transmitters so as to afford the greatest reliability and probability of obtaining high-quality video pictures. No other experiments were carried on the spacecraft.

Spacecraft design

Rangers 6, 7, 8, and 9 were the so-called Block 3 versions of the Ranger spacecraft. The spacecraft consisted of a hexagonal aluminum frame base 1.5 m across on which was mounted the propulsion and power units, topped by a truncated conical tower which held the TV cameras. Two solar panel wings, each 739 mm wide by 1537 mm long, extended from opposite edges of the base with a full span of 4.6 m, and a pointable high gain dish antenna was hinge mounted at one of the corners of the base away from the solar panels. A cylindrical quasiomnidirectional antenna was seated on top of the conical tower. The overall height of the spacecraft was 3.6 m. Propulsion for the mid-course trajectory correction was provided by a 224 N thrust monopropellant hydrazine engine with 4 jet-vane vector control. Orientation and attitude control about 3 axes was enabled by 12 nitrogen gas jets coupled to a system of 3 gyros, 4 primary Sun sensors, 2 secondary Sun sensors, and an Earth sensor. Power was supplied by 9792 Si solar cells contained in the two solar panels, giving a total array area of 2.3 square meters and producing 200 W. Two 1200 watt.hour AgZnO batteries rated at 26.5 V with a capacity for 9 hours of operation provided power to each of the separate communication/TV camera chains. Two 1000 watt.hour AgZnO batteries stored power for spacecraft operations. Communications were through the quasiomnidirectional low-gain antenna and the parabolic high-gain antenna. Transmitters aboard the spacecraft included a 60 W TV channel F at 959.52 MHz, a 60 W TV channel P at 960.05 MHz, and a 3 W transponder channel 8 at 960.58 MHz. The telecommunications equipment converted the composite video signal from the camera transmitters into an RF signal for subsequent transmission through the spacecraft high-gain antenna. Sufficient video bandwidth was provided to allow for rapid framing sequences of both narrow- and wide-angle television pictures.

Mission Profile

The Atlas 196D and Agena B 6006 boosters performed nominally, injecting the Agena and Ranger 8 into an Earth parking orbit at 185 km altitude 7 minutes after launch. Fourteen minutes later a 90 second burn of the Agena put the spacecraft into lunar transfer trajectory, and several minutes later the Ranger and Agena separated. The Ranger solar panels were deployed, attitude control activated, and spacecraft transmissions switched from the omniantenna to the high-gain antenna by 21:30 UT. On 18 February at a distance of 160,000 km from Earth the planned mid-course maneuver took place, involving reorientation and a 59 second rocket burn. During the 27 minute maneuver, spacecraft transmitter power dropped severely, so that lock was lost on all telemetry channels. This continued intermittently until the rocket burn, at which time power returned to normal. The telemetry dropout had no serious effects on the mission. A planned terminal sequence to point the cameras more in the direction of flight just before reaching the Moon was cancelled to allow the cameras to cover a greater area of the Moon's surface. Ranger 8 reached the Moon on February 20 1965. The first image was taken at 9:34:32 UT at an altitude of 2510 km. Transmission of 7,137 photographs of good quality occurred over the final 23 minutes of flight. The final image taken before impact has a resolution of 1.5 meters. The spacecraft encountered the lunar surface in a direct hyperbolic trajectory, with incoming asymptotic direction at an angle of -13.6 degrees from the lunar equator. The orbit plane was inclined 16.5 degrees to the lunar equator. After 64.9 hours of flight, impact occurred at 09:57:36.756 UT on 20 February 1965 in Mare Tranquillitatis at approximately 2.67 degrees N, 24.65 degrees E. (The impact site is listed as about 2.72 N, 24.61 E in the initial report "Ranger 8 Photographs of the Moon".) Impact velocity was slightly less than 2.68 km/s. The spacecraft performance was excellent.

External link

- [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19780007206_1978007206.pdf Lunar impact: A history of Project Ranger (PDF) 1977] 8

Spacecraft

, 2004.]] A spacecraft is a vehicle that travels through space. Spacecraft include robotic or unmanned space probes as well as manned vehicles. The term is sometimes also used to describe artificial satellites, which have similar design criteria.

Overview

The term spaceship is generally applied only to spacecraft capable of transporting people. A space suit has at times been called a miniature spacecraft or spaceship, emphasizing its purpose of keeping its wearer alive while traveling in the vacuum of outer space. The spacecraft is one of the primal elements in science fiction. Numerous short stories and novels are built up around various ideas for spacecraft. Some hard science fiction books focus on the technical details of the craft, while others treat the spacecraft as a given and delve little into its actual implementation.

Examples of past or existing spacecraft

Manned
- Apollo Spacecraft
- Gemini Spacecraft
- International Space Station
- Mir
- Mercury Spacecraft
- Shuttle Buran
- Shenzhou Spacecraft
- Space Shuttle
- Soyuz Spacecraft
- SpaceShipOne
- Voskhod Spacecraft
- Vostok Spacecraft Unmanned
- Cassini-Huygens
- Cluster
- Deep Space 1
- Genesis
- Mars Exploration Rover
- Mars Global Surveyor
- Mars Pathfinder
- Pioneer 10
- Pioneer 11
- Progress
- SOHO
- Stardust
- Viking 1
- Viking 2
- Voyager 1
- Voyager 2
- WMAP

Spacecraft under development

- Crew Exploration Vehicle
- Kliper
- Automated Transfer Vehicle
- H-II Transfer Vehicle
- Ansari X Prize (incl. a list of spacecraft in various stages of completion as of 2005) The US Space Command, according to its "Long Range Plan", is currently planning to develop a weaponized spaceship, which has yet to be announced.[http://www.fas.org/spp/military/docops/usspac/]

External links

- [http://science.hq.nasa.gov/missions/phase.html NASA: Space Science Spacecraft Missions]
- [http://www.skyrocket.de/space/ Gunter's Space Page - Complete information on spacecraft]
- [http://www.cinespaceships.net/ Cinespaceships - Database on spaceships in movie]
- ja:宇宙船

Video camera tube

In older video cameras, prior to the 1990s, a video camera tube or pickup tube was used instead of a charge-coupled device (CCD). Several types were in use from the 1930s to the 1980s. They operate in a somewhat similar manner to cathode ray tubes, which display pictures, but are instead used to capture images that are projected onto them through the camera lens system.

Image dissector

The image dissector was invented by Philo Farnsworth, one of the pioneers of electronic television, in 1927. It is a type of cathode ray tube occasionally employed as a camera in industrial television systems. The image dissector had very poor light sensitivity, and was useful only where scene illumination exceeded 200 foot-lamberts, but it was ideal for high light levels such as when engineers wanted to monitor the bright, hot interior of an industrial furnace. Due to its lack of sensitivity, the image dissector was mainly used only to scan film and other transparencies in TV broadcasting. It was, however, the beginning of the electronic TV age. Image: Orthicon_Vidicon_side_by_side.jpg The image dissector sees the outside world through a glass lens, which focuses an image through the clear glass wall of the tube onto a special plate which is coated with a layer of caesium oxide. When light strikes caesium oxide, the material emits electrons, somewhat like a mirror that reflects an image made of electrons, rather than light. This invisible electron reflection is aimed at a small detector circuit which captures the electrons, so that at a given instant electrons from a single small point in the image pass through the aperture to an electron multiplier; this is similar in principle to the image orthicon. Scanning currents, very much like those of other cameras, pass through the external deflection coils. In this case the entire electron image is deflected, rather than a narrow beam of electrons. The portion of the image which is deflected into the aperture produces the video at a given instant. Electrons emitted from the remaining portion of the tube are wasted, rather than stored on the target as in the image orthicon. The image dissector has no storage characteristic, which accounts in part for its low sensitivity (approximately 3000 lux).

The iconoscope

Vladimir Zworykin patented the idea, in May 1931, of projecting an image on a special plate which was covered with a chemical photoemissive mosaic consisting of granules of material, a pattern comparable to the receptors of the human eye. Emission of photoelectrons from each granule in proportion to the amount of light resulted in a charge image being formed on the mosaic. Each granule, together with the conductive plate behind the mosaic, formed a small capacitor, all of these having a common plate. An electron beam was then swept across the face of the plate from an electron gun, discharging the capacitors in succession; the resulting changes in potential at the metal plate constituted the picture signal. Unlike the image dissector the Zworykin model was much more sensitive, to about 75 000 lux. It was also easier to manufacture and produced a very clear image.

Vidicon

A vidicon tube (sometimes called a hivicon tube) is a video camera tube in which the target material is made of antimony trisulfide (Sb₂S₃). The terms vidicon tube and vidicon camera are often used indiscriminately to refer to video cameras of any type. The principle of operation of the vidicon camera is typical of other types of video camera tubes. S The vidicon is a storage-type camera tube in which a charge-density pattern is formed by the imaged scene radiation on a photoconductive surface which is then scanned by a beam of low-velocity electrons. The fluctuating voltage coupled out to a video amplifier can be used to reproduce the scene being imaged. The electrical charge produced by an image will remain in the face plate until it is scanned or until the charge dissipates. Pyroelectric photocathodes can be used to produce a vidicon sensitive over a broad portion of the infrared spectrum.

Orthicon

infrared The image orthicon tube or simply orthicon tube was common until the 1960s. It replaced the iconoscope, which required a great deal of light to work adequately. A properly constructed image orthicon could take television pictures by candlelight due to the more ordered light-sensitive area and the presence of an electron multiplier at the base of the tube, which operated as a high-efficiency amplifier. It also had a logarithmic light sensitivity curve similar to the human eye, so the picture looked more natural. Its defect was that it tended to flare if a shiny object in the studio caught a reflection of a light, generating a dark halo around the object on the picture. Image orthicons were used extensively in the early color television cameras, where their increased sensitivity was essential to overcome their very inefficient optical system. An engineer's nickname for the tube was the "immy", which later was feminized to become the "Emmy".

Plumbicon

Plumbicon is a registered trademark of Philips. Mostly used in broadcast camera applications. These tubes have low output, but a high signal-to-noise ratio. surface: PbO Led Oxide

Saticon

Saticon is a registered trademark of Hitachi also produced by Thomson. surface: SeAsTe Selenium Arsenic Tellurium

Pasecon

Pasecon is a registered trademark of Heimann. surface: CdSe Cadmium selenide

Newvicon

Newvicon is a registered trademark of Matsushita. The Newvicon tubes were characterized by high light sensitivity. surface: ZnSe, ZnCdTe Zinc Selenide, Zinc Cadmium Telluride

External links

- [http://www.acmi.net.au/AIC/IMAGE_ORTHICON.html Orthicon brief history, description and diagram]
- [http://www.bealecorner.com/trv900/index.html informational site on video]
- [http://members.chello.nl/h.dijkstra19 The Cathode Ray Tube site] Category:Vacuum tubes

Ranger program

The Ranger program of unmanned space missions was the first United States attempt to obtain close-up images of the lunar surface. The Ranger spacecraft were designed to fly straight down towards the Moon and send images back until the moment of impact. Ranger was originally designed, beginning in 1959, in three distinct phases, called "blocks." Each block had different mission objectives and progressively more advanced system design. The JPL mission designers planned multiple launches in each block, to maximize the engineering experience and scientific value of the mission and to assure at least one successful flight. Total research, development, launch, and support costs for the Ranger series of spacecraft (Rangers 1 through 9) was approximately $170 million.

Block 1 missions

JPL Block 1, consisting of two spacecraft launched into Earth orbit in 1961, was intended to test the Atlas/Agena launch vehicle and spacecraft equipment without attempting to reach the Moon. Most elements of spacecraft technology taken for granted today were untested before Ranger. Perhaps the most important of these was three-axis attitude stabilization, meaning that the spacecraft is fixed in relation to space instead of being stabilized by spinning. This would permit pointing large solar panels at the Sun, a large antenna at Earth, and cameras and other directional scientific sensors at their appropriate targets. Rocket propulsion carried aboard the spacecraft was another critically important new technology, needed for accurate targeting at the Moon or distant planets. In addition, two-way communication and closed-loop tracking, requiring spacecraft and ground system development, and the use of on-board computing and sequencing combined with commands from the ground, all had to be developed and tried out in flight. Unfortunately, problems with the early version of the launch vehicle left Ranger 1 and Ranger 2 in short-lived, low-Earth orbits in which the spacecraft could not stabilize themselves, collect solar power, or survive for long.

Block 2 missions

Ranger 2 Block 2 of the Ranger project launched three spacecraft to the Moon in 1962, carrying a TV camera, a radiation detector, and a seismometer in a separate capsule slowed by a rocket motor and packaged to survive its low-speed impact on the Moon’s surface. The three missions together demonstrated good performance of the Atlas/Agena B launch vehicle and the adequacy of the spacecraft design, but unfortunately not all on the same attempt. Ranger 3 was launched into deep space, but an inaccuracy put it off course and it missed the Moon entirely. Ranger 4 had a perfect launch, but the spacecraft was completely disabled. The project team tracked the seismometer capsule to impact just out of sight on the lunar far side, validating the communications and navigation system. Ranger 5 missed the Moon and was disabled. No significant science information was gleaned from these missions. The craft weighed 331 kg.

Block 3 missions

Ranger's Block 3 embodied four launches in 1964-65. These spacecraft boasted a television instrument designed to observe the lunar surface during the approach; as the spacecraft neared the Moon, they would reveal detail smaller than the best Earth telescopes could show, and finally details down to dishpan size. The first of the new series, Ranger 6, had a flawless flight, except that the television system was disabled by an in-flight accident and could take no pictures. Ranger 6 The next three Rangers, with a redesigned television, were completely successful. Ranger 7 photographed its way down to target in a lunar plain, soon named Mare Cognitum, south of Copernicus crater. It sent more than 4,300 pictures from six cameras to waiting scientists and engineers. The new images revealed that craters caused by impact were the dominant features of the Moon's surface, even in the seemingly smooth and empty plains. Great craters were marked by small ones, and the small with tiny impact pockmarks, as far down in size as could be discerned -- about 50 centimeters (16 inches). The light-colored streaks radiating from Copernicus and a few other large craters turned out to be chains and nets of small craters and debris blasted out in the primary impacts. In February 1965, Ranger 8 swept an oblique course over the south of Oceanus Procellarum and Mare Nubium, to crash in Mare Tranquillitatis where Apollo 11 would land 4½ years later. It garnered more than 7,000 images, covering a wider area and reinforcing the conclusions from Ranger 7. About a month later, Ranger 9 came down in the 90 km diameter (75 mile) crater Alphonsus. Its 5,800 images, nested concentrically and taking advantage of very low-level sunlight, provided strong confirmation of the crater-on-crater, gently rolling contours of the lunar surface. Thus, after a long trouble-plagued start that taught the system engineers a great deal and the scientists virtually nothing, Project Ranger finished with three flights that greatly advanced the lunar scientists' knowledge of the surface and whetted their appetites for a closer look.

The Ranger spacecraft

Each Ranger spacecraft had 6 cameras on board. The cameras were fundamentally the same with differences in exposure times, fields of view, lenses, and scan rates. The camera system was divided into two channels, P (partial) and F (full). Each channel was self-contained with separate power supplies, timers, and transmitters. The F-channel had 2 cameras: the wide-angle A-camera and the narrow angle B-camera. The P-channel had four cameras: P1 and P2 (narrow angle) and P3 and P4 (wide angle). The final F-channel image was taken between 2.5 and 5 s before impact (altitude about 5 km) and the last P-channel image 0.2 to 0.4 s before impact (altitude about 600 m). The images provided better resolution than was available from Earth based views by a factor of 1000. Total research, development, launch, and support costs for the Ranger series of spacecraft (Rangers 1 through 9) was approximately $170 million.

Mission list

- Block 1
- Ranger 1, launched 23 August 1961, lunar prototype, launch failure
- Ranger 2, launched 18 November 1961, lunar prototype, launch failure
- Block 2
- Ranger 3, launched 26 January 1962, lunar probe, spacecraft failed, missed moon
- Ranger 4, launched 23 April 1962, lunar probe, spacecraft failed, impact
- Ranger 5, launched 18 October 1962, lunar probe, spacecraft failed, missed
- Block 3
- Ranger 6, launched 30 January 1964, lunar probe, impact, cameras failed
- Ranger 7
- Launched 28 July 1964
- Impacted Moon 31 July 1964 at 13:25:49 UT
- Latitude 10.35 S, Longitude 339.42 E - Mare Cognitum
- Ranger 8
- Launched 17 February 1965
- Impacted Moon 20 February 1965 at 09:57:37 UT
- Latitude 2.67 N, Longitude 24.65 E - Mare Tranquillitatis (Sea of Tranquility)
- Ranger 9
- Launched 21 March 1965
- Impacted Moon 24 March 1965 at 14:08:20 UT
- Latitude 12.83 S, Longitude 357.63 E - Alphonsus crater

External links

- [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19780007206_1978007206.pdf Lunar Impact: A History of Project Ranger (PDF) 1977]
- [http://history.nasa.gov/SP-4210/pages/Cover.htm Lunar Impact: A History of Project Ranger (HTML)] Both links lead to a whole book on the program. For the HTML one, scroll down to see the table of contents link.

Aluminium

x Aluminium or aluminum (Symbol Al) (see the spelling section below) is a silvery and ductile member of the poor metal group of chemical elements. Its atomic number is 13. Aluminium is found primarily as the ore bauxite and is remarkable for its resistance to oxidation (due to the phenomenon of passivation), its strength, and its light weight. Aluminium is used in many industries to make millions of different products and is very important to the world economy. Structural components made from aluminium are vital to the aerospace industry and very important in other areas of transportation and building in which light weight, durability, and strength are needed.

Properties

transport Aluminium is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. Aluminium is nontoxic (as the metal) nonmagnetic and non-sparking. Pure aluminium has a tensile strength of about 49 megapascals (MPa) and 700 MPa if it is formed into an alloy. Aluminium is about one-third as dense as steel or copper; is malleable, ductile, and easily machined and cast; and has excellent corrosion resistance and durability due to the protective oxide layer. It is also nonmagnetic and nonsparking and is the second most malleable metal (after gold) and the sixth most ductile. ductile

Applications

Whether measured in terms of quantity or value, the use of aluminium exceeds that of any other metal except iron, and it is important in virtually all segments of the world economy. Pure aluminium has a low tensile strength, but readily forms alloys with many elements such as copper, zinc, magnesium, manganese and silicon. When combined with thermo-mechanical processing these aluminium alloys display a marked improvement in mechanical properties. Aluminium alloys form vital components of aircraft and rockets as a result of their high strength to weight ratio. When aluminium is evaporated in a vacuum it forms a coating that reflects both visible light and radiant heat. These coatings form a thin layer of protective aluminium oxide that does not deteriorate as silver coatings do. In particular, nearly all modern mirrors are made using a thin reflective coating of aluminium on the back surface of a sheet of float glass. Telescope mirrors are also coated with a thin layer of aluminium, but are front coated to avoid internal reflections even though this makes the surface more susceptible to damage. Telescope Diet Coke.]] Some of the many uses for aluminium are in:
- Transportation (automobiles, airplanes, trucks, railroad cars, marine vessels, etc.)
- Packaging (cans, foil, etc.)
- Water treatment
- Construction (windows, doors, siding, building wire, etc.
- Consumer durable goods (appliances, cooking utensils, etc.)
- Electrical transmission lines (aluminium conductors are half the weight of copper for equal conductivity and lower in price[http://www.metalprices.com])
- Machinery.
- Although non-magnetic itself, aluminium is used in MKM steel and Alnico magnets.
- Super purity aluminium (SPA, 99.980% to 99.999% Al) is used in electronics and CDs.
- Powdered aluminium is commonly used for silvering in paint. Aluminium flakes may also be included in undercoat paints, particularly wood primer — on drying, the flakes overlap to produce a water resistant barrier.
- Anodised aluminium is more stable to further oxidation, and is used in various fields of construction.
- Most modern computer CPU heat sinks are made of aluminium due to its ease of manufacture and good heat conductivity. Copper heat sinks are smaller although more expensive and harder to manufacture. Aluminium oxide, alumina, is found naturally as corundum (rubies and sapphires), emery, and is used in glass making. Synthetic ruby and sapphire are used in lasers for the production of coherent light. Aluminium oxidises very energetically and as a result has found use in solid rocket fuels, thermite, and other pyrotechnic compositions. Aluminium is also a superconductor, with a superconduting critical temperature of 1.2 Kelvin.

Engineering use

Improper use of aluminium can result in problems, particularly in contrast to iron or steel, which appear "better behaved" to the intuitive designer, mechanic, or technician. The reduction by two thirds of the weight of an aluminium part compared to a similarly sized iron or steel part seems enormously attractive, but it should be noted that it is accompanied by a reduction by two thirds in the stiffness of the part. Therefore, although direct replacement of an iron or steel part with a duplicate made from aluminium may still give acceptable strength to withstand peak loads, the increased flexibility will cause three times more deflection in the part. Where failure is not an issue but excessive flex is undesirable due to requirements for precision of location or efficiency of transmission of power, simple replacement of steel tubing with similarly sized aluminium tubing will result in a degree of flex which is undesirable; for instance, the increased flex under operating loads caused by replacing steel bicycle frame tubing with aluminium tubing of identical dimensions will cause misalignment of the power-train as well as absorbing the operating force. To increase the rigidity by increasing the thickness of the walls of the tubing increases the weight proportionately, so that the advantages of lighter weight are lost as the rigidity is restored. Aluminium can best be used by redesigning the part to suit its characteristics; for instance making a bicycle of aluminium tubing which has an oversize diameter rather than thicker walls. In this way, rigidity can be restored or even enhanced without increasing weight. The limit to this process is the increase in susceptibility to what is termed "crippling" failure, where the deviation of the force from any direction other than directly along the axis of the tubing causes folding of the walls of the tubing. For instance, a common aluminium soft drink can should be able to support an enormous weight directly along its axis; in practice, however, the walls of the can buckle, crumple, and/or fold up under even a mild force, due to minute deviations from the precise axial direction, making possible the common pastime of flattening an empty can by slamming it against one's forehead. The latest models of the Corvette automobile, among others, are a good example of redesigning parts to make best use of aluminium's advantages. The aluminium chassis members and suspension parts of these cars have large overall dimensions for stiffness but are lightened by reducing cross-sectional area and removing unneeded metal; as a result, they are not only equally or more durable and stiff as the usual steel parts, but they possess an airy gracefulness which most people find attractive. Similarly, aluminium bicycle frames can be optimally designed so as to provide rigidity where required, yet have flexibility in terms of absorbing the shock of bumps from the road and not transmitting them to the rider. The strength and durability of aluminium varies widely, not only as a result of the components of the specific alloy, but also as a result of the particular manufacturing process; for this reason, it has from time to time gained a bad reputation. For instance, a high frequency of failure in many early aluminium bicycle frames in the 1970s resulted in just such a poor reputation; with a moment's reflection, however, the widespread use of aluminium components in the aerospace and automotive high performance industries, where huge stresses are undergone with vanishingly small failure rates, proves that properly built aluminium bicycle components should not be unusually unreliable, and this has subsequently proved to be the case. Similarly, use of aluminium in automotive applications, particularly in engine parts which must survive in difficult conditions, has benefited from development over time. An Audi engineer commented about the V12 engine, producing over 500 horsepower (370 kW), of an Auto Union race car of the 1930s which was recently restored by the Audi factory, that the aluminium alloy of which the engine was constructed would today be used only for lawn furniture and the like. Even the aluminium cylinder heads and crankcase of the Corvair, built as recently as the 1960s, earned a reputation for failure and stripping of threads in holes, even as large as spark plug holes, which is not seen in current aluminium cylinder heads. Often, aluminium's sensitivity to heat must also be considered. Even a relatively routine procedure such as welding is complicated by the fact that aluminium will melt long before it gets even dully red hot; therefore, unlike steel or iron, where the experienced welder can know from its hue how close the metal is to the melting point, welding aluminium requires a degree of expertise incorporating an almost intuitive sense of the metal's temperature, or else the part suddenly and without warning melts into a puddle. Aluminium also will accumulate internal stresses and strains under conditions of overheating; while not immediately obvious, the tendency of the metal to "creep" under sustained stresses results in delayed distortions, for instance the commonly observed warping or cracking of aluminium automobile cylinder heads after an engine is overheated, sometimes as long as years later, or the tendency of welded aluminium bicycle frames to gradually twist out of alignment from the stresses accumulated during the welding process. For this reason, many uses of aluminium in the aerospace industry avoid heat altogether by joining parts using adhesives; this was also used for some of the early aluminium bicycle frames in the 1970s, with unfortunate results when the aluminium tubing corroded slightly, loosening the bond of the adhesive and leading to failure of the frame. Stresses from overheating aluminium can be relieved by heat-treating the parts in an oven and gradually cooling, in effect annealing the stresses; this can also result, however, in the part becoming distorted as a result of these stresses, so that such heat-treating of welded bicycle frames, for instance, results in a significant fraction becoming misaligned. If the misalignment is not too severe, once cooled they can be bent back into alignment with no negative consequences; of course, if the frame is properly designed for rigidity (see above), this will require enormous force.

Household wiring

Because of its high conductivity and relatively low price compared to copper at the time, aluminium was introduced for household electrical wiring to a large degree in the United States in the 1960s. Unfortunately, many of the wiring fixtures at the time were not designed to accept aluminium wire. More specifically:
- The greater coefficient of thermal expansion of aluminium, causes the wire to expand and contract relative to the dissimilar metal screw connection, eventually loosening the connection.
- Pure aluminium has a tendency to "creep" under steady sustained pressure (to a greater degree as the temperature rises), again producing a degree of looseness in an initially tight connection.
- Galvanic corrosion from the dissimilar metals increases the electrical resistance of the connection. In combination, these properties caused connections between electrical fixtures and aluminium wiring to overheat which resulted in several fires. As a result, aluminium household wiring has become unpopular, and in many jurisdictions is not permitted in very small sizes in new construction. However, aluminium wiring can be safely used with fixtures whose connections are designed to avoid loosening and overheating. Older fixtures of this type are marked "Al/Cu", and newer ones are marked "CO/ALR". Otherwise, aluminium wiring can be terminated by crimping it to a short "pigtail" of copper wire, which can be treated as any other copper wire. A properly done crimp, requiring high pressure produced by the proper tool, is tight enough not only to eliminate any thermal expansion of the aluminium, but also to exclude any atmospheric oxygen and thus prevent corrosion between dissimilar metals. New alloys are used for aluminium building wire today in combination with aluminium terminations. Connections made with these standard industry products are as safe and reliable as copper connections. :See also:Aluminum wire

History

The oldest suspected (although unprovable) reference to aluminium is in Pliny the Elder's Naturalis Historia: One day a goldsmith in Rome was allowed to show the Emperor Tiberius a dinner plate of a new metal. The plate was very light, and almost as bright as silver. The goldsmith told the Emperor that he had produced the metal from ordinary clay. He also assured the Emperor that only he, himself, and the gods knew how to produce this metal from clay. The Emperor became very interested, and, as a financial expert, he was also worried. He feared that all his treasures of gold and silver would fall in value if people started producing this bright metal from clay. Therefore, instead of giving the goldsmith the recognition the latter had anticipated, he ordered him to be beheaded. [http://www.findarticles.com/p/articles/mi_m2843/is_n3_v19/ai_16836663 Notes] - [http://www.world-aluminium.org/history/antiquity.html Source] The ancient Greeks and Romans used salts of this metal as dyeing mordants and as astringents for dressing wounds, and alum is still used as a styptic. Further Joseph Needham suggested finds in 1974 showed the ancient Chinese used aluminium (see the link for "Notes" above). In 1761 Guyton de Morveau suggested calling the base alum 'alumine'. In 1808, Humphry Davy identified the existence of a metal base of alum, which he named (see Spelling below for more information on the name). Friedrich Wöhler is generally credited with isolating aluminium (Latin alumen, alum) in 1827 by mixing anhydrous aluminium chloride with potassium. However, the metal had been produced for the first time two years earlier in an impure form by the Danish physicist and chemist Hans Christian Ørsted. Therefore almanacs and chemistry sites often list Øersted as the discoverer of aluminium.[http://www.chemicalelements.com/elements/al.html#isotopes Source] Still it would further be P. Berthier who discovered aluminium in bauxite ore and successfully extracted it. The Frenchman Henri Saint-Claire Deville improved Wöhler's method in 1846 and described his improvements in a book in 1859, chief among these being the substitution of sodium for the considerably more expensive potassium. The American Charles Martin Hall of Oberlin, OH applied for a patent (400655) in 1886 for an electrolytic process to extract aluminium using the same technique that was independently being developed by the Frenchman Paul Héroult in Europe. The invention of the Hall-Héroult process in 1886 made extracting aluminium from minerals cheaper, and is now the principal method in common use throughout the world. Upon approval of his patent in 1889, Hall, with the financial backing of Alfred E. Hunt of Pittsburgh, PA, started the Pittsburgh Reduction Company, renamed to Aluminum Company of America in 1907, later shortened to Alcoa. Alcoa Aluminium was selected as the material to be used for the apex of the Washington Monument, at a time when one ounce cost twice the daily wages of a common worker in the project. [http://www.tms.org/pubs/journals/JOM/9511/Binczewski-9511.html Source] Germany became the world leader in aluminium production soon after Adolf Hitler seized power. By 1942, however, new hydroelectric power projects such as the Grand Coulee Dam gave the United States something Nazi Germany could not hope to compete with, namely the capability of producing enough aluminium to manufacture sixty thousand warplanes in four years. [http://www.phpsolvent.com/wordpress/?page_id=341]

Natural occurrence

Although aluminium is an abundant element in Earth's crust (believed to be 7.5% to 8.1%), it is very rare in its free form and was once considered a precious metal more valuable than gold. Napoleon III of France had a set of aluminium plates reserved for his finest guests. Others had to make do with gold ones. Aluminium has been produced in commercial quantities for just over 100 years. Aluminium was, when it was first discovered, extremely difficult to separate from its ore. Aluminium is among the most difficult metals on earth to refine, despite the fact that it is one of the planet's most common. The reason is that aluminium is oxidised very rapidly and that its oxide is an extremely stable compound that, unlike rust on iron, does not flake off. The very reason for which aluminium is used in many applications is why it is so hard to produce. Recovery of this metal from scrap (via recycling) has become an important component of the aluminium industry. Recycling involves simply melting the metal, which is far less expensive than creating it from ore. Refining aluminium requires enormous amounts of electricity; recycling it requires only 5% of the energy to produce it. A common practice since the early 1900s, aluminium recycling is not new. It was, however, a low-profile activity until the late 1960s when the exploding popularity of aluminium beverage cans finally placed recycling into the public consciousness. Other sources for recycled aluminium include automobile parts, windows and doors, appliances, containers and other products. Aluminium is a reactive metal and it is hard to extract it from its ore, aluminium oxide (Al₂O₃). Direct reduction, with carbon for example, is not economically viable since aluminium oxide has a melting point of about 2000°C. Therefore, it is extracted by electrolysis — the aluminium oxide is dissolved in molten cryolite and then reduced to the pure metal. By this process, the actual operational temperature of the reduction cells is around 950 to 980°C. Cryolite was originally found as a mineral on Greenland, but has been replaced by a synthetic cryolite. Cryolite is a mixture of aluminium, sodium, and calcium fluorides: (Na₃AlF₆). The aluminium oxide (a white powder) is obtained by refining bauxite, which is red since it contains 30 to 40% iron oxide. This is done using the so-called Bayer process. Previously, the Deville process was the predominant refining technology. The electolytic process replaced the Wöhler process, which involved the reduction of anhydrous aluminium chloride with potassium. Both of the electrodes used in the electrolysis of aluminium oxide are carbon. Once the ore is in the molten state, its ions are free to move around. The reaction at the negative cathode is :Al³⁺ + 3e^- → Al Here the aluminium ion is being reduced (electrons are added). The aluminium metal then sinks to the bottom and is tapped off. At the positive electrode (anode) oxygen gas is formed: :2O^2- → O₂ + 4e^- This carbon anode is then oxidised by the oxygen. The anodes in a reduction must therefore be replaced regularly, since they are consumed in the process: :O₂ + C → CO₂ Contrary to the anodes, the cathodes are not consumed during the operation, since there is no oxygen present at the cathode. The carbon cathode is protected by the liquid aluminium inside the cells. Cathodes do erode, mainly due to electrochemical processes. After 5 to 10 years, depending on the current used in the electrolysis, a cell has to be reconstructed completely, because the cathodes are completely worn. Aluminium electrolysis with the Hall-Héroult process consumes a lot of energy, but alternative processes were always found to be less viable economically and/or ecologically. The world-wide average specific energy consumption is approximately 15±0.5 kilowatt-hours per kilogram of aluminium produced (52 to 56 MJ/kg). The most modern smelters reach approximately 12.8 kW·h/kg (46.1 MJ/kg). Reduction line current for older technologies are typically 100 to 200 kA. State-of-the-art smelters operate with about 350 kA. Trials have been reported with 500 kA cells. Electric power represents about 20 to 40% of the cost of producing aluminium, depending on the location of the aluminium smelter. Smelters tend to be located where electric power is plentiful and inexpensive, such as South Africa, the South Island of New Zealand, Australia, China, Middle-East, Russia, Iceland and Quebec in Canada. China is currently (2004) the top world producer of aluminium. Suriname depends on aluminium exports for 70% of its export earnings.[http://www.cia.gov/cia/publications/factbook/geos/ns.html#Econ]

Isotopes

Aluminium has nine isotopes, whose mass numbers range from 23 to 30. Only Al-27 (stable isotope) and Al-26 (radioactive isotope, t_1/2 = 7.2 × 10⁵ y) occur naturally, however Al-27 has a natural abundance of 100%. Al-26 is produced from argon in the atmosphere by spallation caused by cosmic-ray protons. Aluminium isotopes have found practical application in dating marine sediments, manganese nodules, glacial ice, quartz in rock exposures, and meteorites. The ratio of Al-26 to beryllium-10 has been used to study the role of transport, deposition, sediment storage, burial times, and erosion on 10⁵ to 10⁶ year time scales. Cosmogenic Al-26 was first applied in studies of the Moon and meteorites. Meteorite fragments, after departure from their parent bodies, are exposed to intense cosmic-ray bombardment during their travel through space, causing substantial Al-26 production. After falling to Earth, atmospheric shielding protects the meteorite fragments from further Al-26 production, and its decay can then be used to determine the meteorite's terrestrial age. Meteorite research has also shown that Al-26 was relatively abundant at the time of formation of our planetary system. Possibly, the energy released by the decay of Al-26 was responsible for the remelting and differentiation of some asteroids after their formation 4.6 billion years ago.

Clusters

In the journal Science of 14 January 2005 it was reported that clusters of 13 aluminium atoms (Al₁₃) had been made to behave like an iodine atom; and, 14 aluminium atoms (Al₁₄) behaved like an alkaline earth atom. The researchers also bound 12 iodine atoms to an Al₁₃ cluster to form a new class of polyiodide. This discovery is reported to give rise to the possibility of a new characterisation of the periodic table: superatoms. The research teams were led by Shiv N. Khanna (Virginia Commonwealth University) and A. Welford Castleman Jr (Penn State University). [http://www.science.psu.edu/alert/Castleman1-2005.htm]

Precautions

Aluminium is one of the few abundant elements that appears to have no beneficial function in living cells, but a few percent of people are allergic to it — they experience contact dermatitis from any form of it: an itchy rash from using styptic or antiperspirant products, digestive disorders and inability to absorb nutrients from eating food cooked in aluminium pans, and vomiting and other symptoms of poisoning from ingesting such products as Rolaids , Amphojel, and Maalox (antacids). In other persons, aluminium is not considered as toxic as heavy metals, but there is evidence of some toxicity if it is consumed in excessive amounts, although the use of aluminium cookware, popular because of its corrosion resistance and good heat conduction, has not been shown to lead to aluminium toxicity in general. Excessive consumption of antacids containing aluminium compounds and excessive use of aluminium-containing antiperspirants are more likely causes of toxicity. It has been suggested that aluminium may be linked to Alzheimer's disease, although that research has recently been refuted; aluminium accumulation may be a consequence of the Alzheimer's damage, not the cause. In any event, if there is any toxicity of aluminium it must be via a very specific mechanism, since total human exposure to the element in the form of naturally occurring clay in soil and dust is enormously large over a lifetime. Care must be taken to prevent aluminium from coming into contact with certain chemicals that can cause it to corrode quickly. For example, just a small amount of mercury applied to the surface of a piece of aluminium can break up the normal aluminium oxide barrier usually present. Within a few hours, even a heavy structural beam can be significantly weakened. For this reason, mercury thermometers are not allowed on many airliners, as aluminium is a common structural component in aircraft.

Spelling

Etymology / Nomenclature history

In 1808, Humphry Davy originally proposed the name alumium while trying to isolate the new metal electrolytically from the mineral alumina. In 1812 he changed the name to aluminum to match its Latin root. The same year, an anonymous contributor to the Quarterly Review objected to aluminum, and proposed the name aluminium. :Aluminium, for so we shall take the liberty of writing the word, in preference to aluminum, which has a less classical sound. (Q. Review VIII. 72, 1812) This had the advantage of conforming to the -ium suffix precedent set by other newly discovered elements of the period: potassium, sodium, magnesium, calcium, and strontium (all of which Davy had isolated himself). Nevertheless, -um spellings for elements were not unknown at the time: platinum, which had been known to Europeans since the 16th century, molybdenum, which was discovered in 1778, and tantalum, which was discovered in 1802, all have spellings ending in -um. Curiously, the United States adopted the -ium for most of the 19th century with aluminium appearing in Webster's Dictionary of 1828. However in 1892 Charles Martin Hall used the -um spelling in an advertising handbill for his new efficient electrolytic method for the production of aluminium, despite using the -ium spelling in all of his patents filed between 1886 and 1903. It has consequently been suggested that the spelling on the flyer was a simple spelling mistake rather a deliberate choice to use the -um spelling. Hall's domination of production of the metal ensured that the spelling aluminum became the standard in North America, even though the Webster Unabridged Dictionary of 1913 continued to use the -ium version. In 1926, the American Chemical Society officially decided to use aluminum in its publications, and American dictionaries typically label the spelling aluminium as a British variant.

Present day spelling

In the English-speaking world, the spellings (and associated pronunciations) aluminium and aluminum are both in common use in both scientific and nonscientific contexts. In the United States, the spelling aluminium is largely unknown, and the spelling aluminum predominates. Elsewhere in the English-speaking world the spelling aluminium predominates, and the spelling aluminum is largely unknown. However, in Canada both spellings are common, due to the multiple influences on the language of its proximity to the United States, its British colonial past and the large number of native French speakers. Outside English, the "ium" spelling is widespread: the word is aluminium in French and German, and identical or similar forms are used in many other languages. Consequently it is the more common of the two spellings in global terms, even though there may be more users of aluminum in the English-speaking world. The International Union of Pure and Applied Chemistry (IUPAC) adopted aluminium as the standard international name for the element in 1990, but three years later recognised aluminum as an acceptable variant. Hence their periodic table includes both, but places aluminium first [http://www.iupac.org/reports/periodic_table/index.html]. IUPAC officially prefers the use of aluminium in its internal publications, although several IUPAC publications use the spelling aluminum.[http://www.iupac.org/cgi-bin/htsearch?sort=score&restrict=www.iupac.org%2Fpublications%2Fci&config=htdig&restrict=&exclude=www.iupac.org%2Fgoldbook%2F&words=aluminum&submit=]

Chemistry

Oxidation state 1

- AlH is produced when aluminium is heated at 1500 °C in an atmosphere of hydrogen.
- Al₂O is made by heating the normal oxide, Al₂O₃, with silicon at 1800 °C in a vacuum.
- Al₂S can be made by heating Al₂S₃ with aluminium shavings at 1300 °C in a vacuum. It quickly disproportionates to the starting materials. The selenide is made in a parallel manner.
- AlF, AlCl and AlBr exist in the gaseous phase when the tri-halide is heated with aluminium.

Oxidation state 2

- Aluminium suboxide, AlO can be shown to be present when aluminium powder burns in oxygen.

Oxidation state 3

- Fajans rules show that the simple trivalent cation Al³⁺ is not expected to be found in anhydrous salts or binary compounds such as Al₂O₃. The hydroxide is a weak base and aluminium salts of weak bases, such as carbonate, can't be prepared. The salts of strong acids, such as nitrate, are stable and soluble in water, forming hydrates with at least six molecules of water of crystallization.
- Aluminium hydride, (AlH₃)_n, can be produced from trimethylaluminium and an excess of hydrogen. It burns explosively in air. It can also be prepared by the action of aluminium chloride on lithium hydride in ether solution, but cannot be isolated free from the solvent.
- Aluminium carbide, Al₄C₃ is made by heating a mixture of the elements above 1000 °C. The pale yellow crystals have a complex lattice structure, and react with water or dilute acids to give methane. The acetylide, Al₂(C₂)₃, is made by passing acetylene over heated aluminium.
- Aluminium nitride, AlN, can be made from the elements at 800 °C. It is hydrolysed by water to form ammonia and aluminium hydroxide.
- Aluminium phosphide, AlP, is made similarly, and hydrolyses to give phosphine.
- Aluminium oxide, Al₂O₃, occurs naturally as corundum, and can be made by burning aluminium in oxygen or by heating the hydroxide, nitrate or sulfate. As a gemstone, its hardness is only exceeded by diamond, boron nitride and carborundum. It is almost insoluble in water.
- Aluminium hydroxide may be prepared as a gelatinous precipitate by adding ammonia to an aqueous solution of an aluminium salt. It is amphoteric, being both a very weak acid, and forming aluminates with alkalis. It exists in various crystalline forms.
- Aluminium sulfide, Al₂S₃, may be prepared by passing hydrogen sulfide over aluminium powder. It is polymorphic.
- Aluminium fluoride, AlF₃, is made by treating the hydroxide with HF, or can be made from the elements. It consists of a giant molecule which sublimes without melting at 1291 °C. It is very inert. The other trihalides are dimeric, having a bridge-like structure.
- Organo-metallic compounds of empirical formula AlR₃ exist and, if not also giant molecules, are at least dimers or trimers. They have some uses in organic synthesis, for instance trimethylaluminium.
- Alumino-hydrides of the most electropositive elements are known, the most useful being lithium aluminium hydride, Li[AlH₄]. It decomposes into lithium hydride, aluminium and hydrogen when heated, and is hydrolysed by water. It has many uses in organic chemistry. The aluminohalides have a similar structure.

Aluminium in popular culture

- In the film Star Trek IV: The Voyage Home, Scotty devises the fictional material transparent aluminum.

References

- [http://periodic.lanl.gov/elements/13.html Los Alamos National Laboratory – Aluminum]
- [http://www.worldwidewords.org/articles/aluminium.htm World Wide Words] A history of the spelling of aluminium from a British viewpoint.
- Oxford English Dictionary Entries "aluminum" and "aluminium", available by subscription. [http://www.oed.com]

External links

- [http://www.webelements.com/webelements/elements/text/Al/index.html WebElements.com – Aluminium]
- [http://www.world-aluminium.org/ World Aluminium]
- [http://www.indexmundi.com/en/commodities/minerals/aluminum/aluminum_table12.html World production of primary aluminum, by country]
- [http://www.saanet.org/kashipur/docs/seenalum.htm Social and Environmental Impact of the Aluminium Industry]
- [http://153rd.com/sam/as/physics/aluminium/normal/redirect.html Sam's Aluminium Information Site] Patents
- US[http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/srchnum.htm&r=1&f=G&l=50&s1=400664.WKU.&OS=PN/400664&RS=PN/400664 400664] – Process of reducing aluminum from its floride salts by electrolysis – C. M. Hall Category:Chemical elements Category:Poor metals Category:Pigments Category:Pyrotechnic chemicals Category:Rocket fuels ko:알루미늄 ja:アルミニウム simple:Aluminium th:อะลูมิเนียม

Antenna

- In biology, antenna (plural: antennae) refers to the sensing organs of several arthropods.
- In electronics, antenna (plural: antennas) refers to the component designed to send and receive radio waves - also called an aerial
- Antenna, also known as ANT1, is a Greek-language terrestrial channel.
- In astronomy, The Antennae is the name of two colliding galaxies NGC 4038 and NGC 4039.
- In astronomy, antenna may be a reference to a radio telescope.

- Antena 3 is also a Spanish terrestrial television channel from Spain. ja:アンテナ

Megahertz

Megahertz (MHz, or megacycle per second in ancient nomenclature) is the name given to one million (10⁶) hertz, a measure of frequency. One megahertz simply means "one million per second" (1,000,000/s). The unit may be applied to any periodic event – for example, a CPU clock might be said to operate at a rate expressed in megahertz. Electromagnetic waves oscillate at rates which may be expressed in megahertz.

Megahertz in radio

When used in the context of radio, MHz refers to the number of oscillations of electromagnetic waves per second. Several parts of the radio spectrum fall into the MHz range.

Megahertz in computing

Most CPUs are labeled in terms of their clock speed expressed in megahertz or gigahertz (10⁹ hertz)). The number of megahertz refers to the frequency of the CPU's master clock signal ("clock speed"). Various computer buses, such as memory buses connecting the CPU and system RAM, also transfer data using clock signals operating at frequencies in the megahertz range.

Agena

: For the Agena star, see Hadar. The Agena was a rocket upper stage developed by Lockheed for the ill-fated WS-117L US reconnaissance satellite program. It lived on to see extensive use as the upper stage/spacecraft for the Corona spy satellite program and as an upper stage on the Thor, Atlas, and Titan boosters. It was also used by the manned Gemini program to practice rendezvous and docking (see Agena Target Vehicle). Agena Target Vehicle It was 5 feet (1.5 m) in diameter, three axis stabilized (for the benefit of the reconnaissance system cameras) and its Bell 8096 engine produced 16,000 lbf (71 kN) thrust using hydrazine (UDMH) and nitrogen tetroxide as propellants. The engine could be restarted multiple times in orbit. This engine started life as the power plant for the canceled rocket-propelled nuclear warhead pod for the Convair B-58 Hustler bomber. Agena was thus known as Hustler early in its development. There were at least three versions of the Agena: ; A : 69 kN thrust Bell 8048 engine, 120 second burn time, used on Thor and Atlas. ; B : 71 kN thrust Bell 8081 engine, 240 second burn time, used on Thor and Atlas. Launched early SAMOS and MIDAS military satellites and the Ranger lunar probes. ; C : Proposed but never built. ; D : 71 kN thrust Bell 8096 engine, 265 second burn time, used on Thor, Atlas, and Titan. Launched early KH-7 GAMBIT spy satellites and the two Mariner Mars probes. As a military reconnaissance spacecraft, much information on the project remains classified. The final Agena launch was of an Agena D on 12 February 1987, configured as the upper stage of a Titan 34B [http://www.designation-systems.net/dusrm/app1/rm-81.html]. Category:Space launch vehicles

Altitude

For other uses see Altitude (disambiguation) Altitude is the elevation of an object from a known level or datum, called zero level. Most often this level is defined as the absolute sea level, but it can vary. In aviation, the term altitude is used to describe elevation above mean sea level, the term height refers to elevation above a ground reference point and the term flight level is the elevation according to a standard pressure altimeter setting. Atmospheric pressure decreases with altitude. In North America and the UK altitude is usually measured in feet. Everywhere else in the world the altitude is measured in metres.
- High altitude = 1500m – 3500m
- Very High altitude = 3500m – 5500m
- Extreme altitude = 5500m – above
- Troposphere — 8 km (above poles) – 18 km (above equator).
- Tropopause
- Stratosphere — 10km (above poles) 50 km (above equator),contains the Ozone layer
- Mesosphere — 50 km – 80 km
- Thermosphere — 100–200 km (1000°–1500° K)
- Exosphere — 500 km – 10,000km (outer space)

Altitude records

- 19 September, 1783 — 500m (1,700ft) animal carrying Montgolfier hot-air balloon.
- 15 October, 1783 — 26m (84ft) Pilâtre de Rozier in a Montgolfier tethered balloon.
- 1 December, 1783 — 2.7km Professor Charles and assistant Robert in Charliere, his hydrogen-filled balloon.
- 1784 — 4km Pilâtre de Rozier and the chemist Proust in a Montgolfier.
- 18 July, 1803 — 7.28km Etienne Gaspar Robertson and Lhoest in a balloon.
- 1839 — 7.9km Charles Green and Spencer Rush in a free balloon.
- 5 September, 1862 — 9km Coxwell and English physicist Glaisher in a balloon.
- 4 December, 1894 — 9.155km German meteorologist Berson in an airship.
- 31 July, 1901 — 10.8km German meteorologist Berson and Süring in a free balloon.

Trajectory

A trajectory is an imagined trace of positions followed by an object moving through space. Some common examples of trajectories: (i) the path taken by a falling body, and (ii) the orbit of a spacecraft. A particular trajectory may be described mathematically either by the geometry of the entire trajectory (i.e. the set of all positions taken by the object), or as the position of the object as function of time. A familiar example is a projectile launched under the influence of only a uniform gravitational force field. A rock thrown on the practically airless surface of the Moon is a good approximation. In this case, the trajectory takes the shape of a parabola, provided the rock is not thrown too far. More generally, the precise trajectory of a projectile requires taking into account nonuniform gravitational forces and other forces such as drag and wind. This is the focus of the discipline of ballistics. A projectile, such as a baseball, when thrown through the air, is influenced by both gravity and aerodynamics. More generally, trajectory refers to the ordered set of intermediate states assumed by a dynamical system as a result of time evolution. The word trajectory is also often used metaphorically, for instance, to describe an individual's career.

Physics of trajectories

One of the remarkable achievements of Newtonian mechanics was the derivation of the laws of Kepler, in the case of the gravitational field of a single point mass (representing the Sun). The trajectory is a conic section, like an ellipse or a parabola. This agrees with the observed orbits of planets and comets, to a reasonably good approximation. Although if a comet passes close to the Sun, then it is also influenced by other forces, such as the solar wind and radiation pressure, which modify the orbit, and cause the comet to eject material into space. Newton's theory later developed into the branch of theoretical physics known as classical mechanics. It employs the mathematics of differential calculus (which was, in fact, also initiated by Newton, in his youth). Over the centuries, countless scientists contributed to the development of these two disciplines. Classical mechanics became a most prominent demonstration of the power of rational thought, i.e. reason, in science as well as technology. It helps to understand and predict an enormous range of phenomena. Trajectories are but one example. Consider a particle of mass

m

, moving in a potential field

V

. Physically speaking, mass represents inertia, and the field

V

represents external forces, of a particular kind known as "conservative". That is, given

V

at every relevant position, there is a way to infer the associated force that would act at that position, say from gravity. Not all forces can be expressed in this way, however. The motion of the particle is described by the second-order differential equation :

m \frac = -\nabla V(\vec(t))

with

\vec = (x, y, z)

On the right-hand side, the force is given in terms of

\nabla V

, the gradient of the potential, taken at positions along the trajectory. This is the mathematical form of Newton's second law of motion: mass times acceleration equals force, for such situations.

Example: Uniform gravity, no drag or wind

The case of uniform gravity, disregarding drag and wind, yields a trajectory which is a parabola. To model this, one chooses

V = m g z

, where

g

(gee) is the so-called acceleration of gravity. This gives the equations of motion :

\frac = \frac = 0

\frac = - g

Simplifications are made for the sake of studying the basics. The actual situation, at least on the surface of Earth, is considerably more complicated than this example would suggest, when it comes to computing actual trajectories. By deliberately introducing such simplifications, into the study of the given situation, one does, in fact, approach the problem in a way that has proved exceedingly useful in physics. The present example is one of those originally investigated by Galileo Galilei. To neglect the action of the atmosphere, in shaping a trajectory, would (at best) have been considered a futile hypothesis by practical minded investigators, all through the Middle Ages in Europe. Nevertheless, by anticipating the existence of the vacuum, later to be demonstrated on Earth by his collaborator Evangelista Torricelli, Galileo was able to initiate the future science of mechanics. And in a near vacuum, as it turns out for instance on the Moon, his simplified parabolic trajectory proves essentially correct. Relative to a flat terrain, let the initial horizontal speed be

v_h

, and the initial vertical speed be

v_v

. It will be shown that, the range is

2v_h v_v/g

, and the maximum altitude is

/2g

. The maximum range, for a given total initial speed

v

, is obtained when

v_h=v_v

, i.e. the initial angle is 45 degrees. This range is

v^2/g

, and the maximum altitude at the maximum range is a quarter of that.

Derivation

The equations of motion may be used to calculate the characteristics of the trajectory. Let: :

t \;

be the time into the flight of the projectile :

d_h(t) \;

be the horizontal displacement at time t :

d_v(t) = z \;

be the vertical displacement at time t :

v_h \;

be the horizontal velocity (which is constant) :

v_v \;

be the initial vertical velocity upwards :

v \;

be the initial speed :

v_v(t) \;

be the vertical velocity at time t Along the horizontal dimension,

v_h

is a constant and thus by the equations of motion, :

d_h(t)=v_h t \;

(Equation 1) The vertical distance, or altitude follows the equations of motion for constant negative acceleration

g

: :

d_v=v_vt-

(Equation 2) :

v_v = \frac d_v(t) = v_v-gt

(Equation 3: velocity equation which is the derivative of equation 2) The range of the projectile occurs when

d_v(t)

is zero again and intercepts the ground. This occurs when

d_v

in equation 2 is zero: :

0=v_vt-

Solving this for time

t

gives the time of the projectile's flight: :

t=

(Equation 4: "hang time" of projectile) The maximum range occurs when equation 4 is substituted into equation 1: :

d_h(t) =  =  =

(Equation 5: range of projectile) The maximum altitude for a given trajectory occurs when the vertical velocity is zero. Thus set equation 3 to zero: :

0=v_v-gt \;

Solving for

t

t=

This can be substituted into equation 2 to give the maximum altitude: :

d_v(max)=v_v ( ) -  \frac 1 2 g(  )^2 =

(Equation 6: maximum altitude of projectile) Thus, not surprisingly, for a given initial speed the attained altitude is highest if the initial velocity was straight up. This altitude is twice the attained altitude when the range is maximized.

Derivation in polar coordinates

In terms of angle of elevation

\theta

and initial speed

v

: :

v = \sqrt

v_h=v \cos \theta \;

v_v=v \sin \theta \;

Substituting into Equation 1 gives: :

d_h=v_h t = vt \cos \theta \;

(Equation 1a) Substituting into Equation 2 gives: :

d_v=v_vt-  =  ( v \sin \theta ) t -

(Equation 2a) Taking the derivative gives the vertical velocity: :

v_v=\frac d_v = \frac (v \sin \theta) t -  = v \sin \theta -gt

(Equation 3a: vertical velocity) Hang time calculated above in equation 4 may be expressed in terms of angle of elevation: :

t= =

(Equation 4a) Equation 4a may be substituted into Equation 1a to get the horizontal distance or range: :

d_h=v_h t =  =v () \cos \theta =

Now using the trigonometric identity for

2 \sin \theta \cos \theta = sin 2 \theta

: :

d_h=

(Equation 5a: range of projectile) This may be solved for angle

\theta

to give the "angle" equation to hit a target at range

d_h

: :

=  \frac 1 2 \sin^ (  )

(Equation 7: angle of projectile launch) Note that the sine function is such that there are two solutions for

\theta

for a given range

d_h

. Physically, this corresponds to a direct shot versus a mortar shot up and over obstacles to the target. The maximum altitude for a given range may be determined by setting the vertical velocity to zero in equation 3a and solving for

t

: :

0= v \sin \theta -gt \;

t= \frac

(rearrange and solve for

t

) Now substitute into the vertical height equation 2a: :

d_v = (v \sin \theta) t - \frac = (v \sin \theta)(\frac ) - \frac  = \frac - \frac = \frac

(Equation 6a: max altitude for a given launch angle)

Maximum range

Given the above range and altitude equations, the maximum range and altitude may be determined. Both equations for the range, equations 5 and 5a may be used to determine the maximum range by setting their derivatives to zero. For equation 5, range of the projectile is a function of

v_h

and

v_v

such that

v_v^2+v_h^2=v^2

where v is the total initial velocity and is constant. Thus, the range may be expressed as a function of

v_v

by solving for

v_h

: :

v_h=\sqrt

(Equation 8) And substituting

v_h

into equation 5: :

d_h= =

The maximum

d_h

may be determined by calculating the derivative and setting it to zero. The derivative is calculated as follows: :

\frac d_h= \frac

= (2 \sqrt +2v_v \frac \sqrt

(application of product rule) ::

= (2 \sqrt +2v_v \frac \frac)

(application of chain rule) ::

= (2 \sqrt +2v_v (\frac ) 2v_v)

(derivative of square root) ::

= (2 \sqrt - \frac)

(simplify second term) Set to zero and solve for

v

: :

0= (2 \sqrt - \frac)

\sqrt=\frac

v^2-^2=v_v^2

v^2=2v_v^2

(Equation 9) Thus maximum range occurs when

v^2

2v_v^2

and this can be substituted back into equation 8: :

v_h=\sqrt=\sqrt=\sqrt=v_v

Thus the maximum range occurs when

v_h=v_v

. The actual maximum range may now be calculated by substituting

v_h=v_v

and equation 9 into equation 5: :

d_h =   =  =  =

Maximum range in polar coordinates

The same conclusion may be drawn by starting with equation 5a. :

\frac d_h = \frac

= \frac  \frac \sin 2 \theta \frac

(application of chain rule) ::

= \frac (\cos 2 \theta) 2 \quad

Set to zero and solve for

\theta

: :

0= \frac (\cos 2 \theta) 2

0=\cos 2 \theta \quad

Now cosine is zero at

\pi \over 2

: :

2 \theta=\frac \pi 2

(also directly clear from equation 5a, it gives the maximum possible sine value of 1) :

_ = \frac \pi 4

radians Thus the maximum range occurs when the angle is 45 degrees. The actual maximum range may now be calculated by substituting 45 degrees into equation 5a: :

d_h== =

Maximum altitude at maximum range

Equations 6 and 6a may be used to calculate the maximum altitude at the maximum range. Equation 9 may be substituted into equation 6: :

d_v=\frac=\frac=\frac

Likewise 45 degrees may be substituted into equation 6a: :

d_v=\frac=\frac=\frac

As a parabola

Equations 1 and 2 are parametric equations that describe a parabola. They may be rearranged into the more familiar quadratic form by solving equation 1 for

t

and substituting into equation 2: :

t=\frac

(rearrange equation 1 for

t

) Substituting this into equation 2: :

d_v=v_vt- \frac=v_v(\frac)-\frac=-\frac(d_h)^2 + \frac(d_h)

This is now in the form :

y=ax^2+bx+c \quad

where :

y=d_v, x=d_h, a=-g/, b=v_v/v_h, c=0

. This is the form of a parabola and thus the trajectory is a parabola. Likewise equations 1a and 2a can be rearranged into quadratic form. Equation 1a may be rearranged to: :

t=\frac

And this may be substituted into equation 2a: :

d_v=vt \sin \theta - \frac=v \sin \theta \frac - \frac

Now

\tan \theta=\sin \theta / \cos \theta

, so: :

d_v=-\fracd_h^2 +  d_h \tan \theta

(Equation 10) This is again now in the form

y=ax^2+bx+c

where

y=d_v

x=d_h

a=-g/

b=\sin \theta / \cos \theta

and

c=0

demonstrating that this is a parabola. The quadratic formula gives the location of the intersection of the parabola and the x-axis. This is where the projectile trajectory starts and ends and thus may be used directly to calculate the range. In terms of rectilinear coordinate systems: :

d_h=\frac=\frac = \frac=0, \frac

This is the same result as equation 5 above. In polar coordinates and using the trigonometric identity

2 \sin \theta \cos \theta = \sin 2 \theta

, the intersections are: :

d_h=\frac=\frac =0, \frac = 0, \frac = 0, \frac

This is the same result as in equation 5a above. Similarly, the vertex of the parabola is the maximum altitude for a given range.

Uphill/downhill in uniform gravity in a vacuum

Given a hill angle

\alpha

and launch angle

\theta

as before, it can be shown that the range along the hill

R_s

forms a ratio with the original range

R

along the imaginary horizontal, such that: :

\frac =(1-\tan \theta \tan \alpha)\sec \alpha

(Equation 11) In this equation, downhill occurs when

\alpha

is between 0 and -90 degrees. For this range of

\alpha

we know:

\tan(-\alpha)=-\tan \alpha

and

\sec ( - \alpha ) = \sec \alpha

. Thus for this range of

\alpha

R_s/R=(1+\tan \theta \tan \alpha)\sec \alpha

. Thus

R_s/R

is a positive value meaning the range downhill is always further than along level terrain. This makes perfect sense as it is expected that gravity will assist the projectile, giving it greater range. While the same equation applies to projectiles fired uphill, the interpretation is more complex as sometimes the uphill range may be shorter or longer than the equivalent range along level terrain. Equation 11 may be set to

R_s/R=1

(i.e. the slant range is equal to the level terrain range) and solving for the "critical angle"

\theta_

: :

1=(1-\tan \theta \tan \alpha)\sec \alpha \quad \;

\theta_=\arctan((1-\csc \alpha)\cot \alpha) \quad \;

Equation 11 may also be used to develop the "rifleman's rule" for small values of

\alpha

and

\theta

(i.e. close to horizontal firing, which is the case for many firearm situations). For small values, both

\tan \alpha

and

\tan \theta

have a small value and thus when multiplied together (as in equation 11), the result is almost zero. Thus equation 11 may be approximated as: :

\frac =(1-0)\sec \alpha

And solving for level terrain range,

R

R=R_s \cos \alpha \

"Rifleman's rule" Thus if the shooter attempts to hit the level distance R, s/he will actually hit the slant target. "In other words, pretend that the inclined target is at a horizontal distance equal to the slant range distance multiplied by the cosine of the inclination angle, and aim as if the target were really at that horizontal position."[http://www.snipertools.com/article4.htm]

Derivation based on equations of a parabola

The intersect of the projectile trajectory with a hill may most easily be derived using the trajectory in parabolic form in Cartesian coordinates (Equation 10) intersecting the hill of slope

m

in standard linear form at coordinates

(x,y)

: :

y=mx+b \;

(Equation 12) where in this case,

y=d_v

x=d_h

and

b=0

Substituting the value of

d_v=m d_h

into Equation 10: :

m x=-\fracx^2 +   \frac x

x=\frac(\frac-m)

(Solving above x) This value of x may be substituted back into the linear equation 12 to get the corresponding y coordinate at the intercept: :

y=mx=m \frac (\frac-m)

Now the slant range

R_s

is the distance of the intercept from the origin, which is just the hypoteneuse of x and y: :

R_s=\sqrt=\sqrt

=\frac \sqrt

=\frac (\frac-m) \sqrt

Now

\alpha

is defined as the angle of the hill, so by definition of tangent,

m=\tan \alpha

. This can be substituted into the equation for

R_s

: :

R_s=\frac (\frac-\tan \alpha) \sqrt

Now this can be refactored and the trigonometric identity for

\sec \alpha = \sqrt

may be used: :

R_s=\frac(1-\frac\tan\alpha)\sec\alpha

Now the flat range

R=v^2\cos 2 \theta / g = 2v^2\cos\theta\sin\theta

by the previously used trigonometric identity and

\sin\theta/\cos\theta=tan \theta

so: :

R_s=R(1-\tan\theta\tan\alpha)\sec\alpha \;

\frac=(1-\tan\theta\tan\alpha)\sec\alpha

Solar panel

with solar hot water panels on the roof.]] Solar panels are devices for capturing the energy in sunlight. The term solar panel can be applied to either solar hot water panels (usually used for providing domestic hot water) or solar photovoltaic panels (providing electricity).

Current Development

Right now, countless corporations and institutions are developing ways to increase the practicality of solar power. While private companies conduct much of the research and development in this area, colleges and universities also work on solar-powered devices, especially solar-powered vehicles. Solar-powered cars have commonly appeared at many car and technology shows, and now solar boats are an interesting application of the technology. Colleges and Universities compete against each other for superiority in this field of technology. They meet in competitions such as the [http://www.solarsplash.com/ Solar Splash]competition in North America, or the [http://www.frisiannuonsolarchallenge.com/ Frisian Nuon Solar Challenge] in Europe. In 2005 the most important issue with Solar Panels is the cost, which has been coming down to about $3-4 (US) a watt. Also grid tied systems are the largest growth area. In the USA, with incentives from States, power companies and in 2006 and 7 from the Federal government growth will continue to climb. Net-metering lets you get credit for any extra power you send back into the grid. Most is true net-metering with even prices for you to equal what you get charged, a few only give avoided cost at about 1/3 what they charge you. In Germany you get paid 8 times what the power company charges you. That large premium has made a huge demand in solar panels for that area. As manufacturers increase production the cost will continue to drop in the years to come. The price of silicon used for most panels is now being pressed and the price has increased. This has caused developers to start using other materials and thinner silicon to keep cost down. Renewable energy like solar PV gets less costly as we use and buy more.

Solar hot water

A solar water heater uses the sun's energy to heat a fluid, which is used to transfer the heat to a heat storage vessel. In the home, for example, sanitary hot water would be heated and stored in a hot water cylinder. Panels on the roof have an absorber plate to which fluid circulation tubes are attached. The absorber (usually coated with a dark selective coating) assures the conversion of the sun's radiation into heat, while fluid circulating through the tubes carries the heat away where it can be used or stored. The heated fluid is pumped to a heat exchanger (a coil in the storage vessel or an external heat exchanger) where it gives off its heat and is then circulated back to the panel to be reheated. This provides a simple and effective way of harnessing the sun's energy.

Solar photovoltaics

Solar photovoltaic panels contain arrays of solar cells that convert light into electricity. They are called solar after the sun or "Sol" because the sun is the most powerful source of the light available for use. The solar cells are sometimes called photovoltaic cells, photovoltaic meaning literally "light-electricity". Solar cells or PV cells rely on the photovoltaic effect to absorb the energy of the sun and cause current to flow between two oppositely charged layers. On a bright day, the sun delivers about 1 kW/m² to the Earth's surface. Today's solar panels are known to have an average efficiency of 12 %. This would result in 120 W/m². However, not all days have bright suns and are fortunate enough to be blessed by such energy. At middle northern latitudes, taking the daylight cycle and weather conditions into account, on average 100 W/m² in winter and 250 W/m² in summer reach the ground. With a conversion efficiency of about 12%, one can expect to obtain between 12 and 30 watts per square meter of solar cell. Accordingly, at the current $0.08/kWh, a square meter will generate up to $0.06 per 24 hr day, and a square kilometer (250 acres) would generate up to 30 MW, or $50,000/km²/day. For reference, the unpopulated Sahara desert is over 9 million km², with less cloud cover and better solar angle, giving closer to 50MW/km², or 450TW (terrawatt) total. The Earth's current energy consumption is near 12-13 TW at any given moment (including oil, gas, coal, nuclear, hydro.) The real issue with solar panels is the capital cost, as shown at the net energy gain article, requiring up to over 7 years recovery period before any profit is made, out of a 40+ year useful life. In contrast, nuclear or coal plant recovers its capital cost in under a mere month, not considering the limited fuel supplies and thus fuel cost. Solar energy on Earth is not bound by limited reserves.

Use of solar PVs

Together with a backup battery, they have become routine in certain low-power applications, such as powering buoys or devices in remote areas or simply where connection to the electricity mains would be impractical. The relatively high cost of purchase and installation still prohibits their use in large-scale power generation. Solar PV panels currently make up a very small portion of the world's electricity production. In experimental form they have even been used to power automobiles in races such as the World solar challenge across Australia. Many yachts and land-vehicles use them to charge on-board batteries away from grid power. Large-scale incentive programs, offering financial incentives like the ability to sell excess electricity back to the public grid, have greatly accelerated the pace of solar PV installations in Spain, Germany, Japan, the United States and other countries. Even with these incentives, the start-up costs associated with solar electric panels currently push their likely 'pay-back' period into decades rather than years in applications where conventional "grid" power is readily available. As fossil fuel energy costs climb, production experience and economies of scale reduce prices, and technological advances increase the efficiency of solar cells, this may not be true in the relatively near future. Many installations at this time are motivated by tax incentives and green sensibilities.

World solar power production

Total peak power of installed solar panels is around 2,600 MW as of the end of 2004.

Large PV power plants

Cost of solar photovoltaic panels

Costs of photovoltaic panels seem, in 2005, to be about $1 to $2 per watt in ~400kW quantities. As production rates increase, costs are likely to continue to go down. Installed, costs seem to be in the $3-$7 per watt range.

Theory and construction

See the solar cell article for a description of the conversion of light energy into electrical energy. Crystalline silicon and gallium arsenide are typical choices of materials for solar cells. Gallium arsenide crystals are grown especially for photovoltaic use, but silicon crystals are available in less-expensive standard ingots, which are produced mainly for consumption in the microelectronics industry. Polycrystalline silicon has lower conversion efficiency but also lower cost. When exposed to direct sunlight at 1 AU, a 6-centimeter diameter silicon cell can produce a current of about 0.5 ampere at 0.5 volt. Gallium arsenide is more efficient. Crystalline ingots are sliced into wafer-thin disks, polished to remove slicing damage, dopants are introduced into the wafers, and metallic conductors are deposited onto each surface: a thin grid on the sun-facing side and usually a flat sheet on the other. Solar panels are constructed of these cells cut into appropriate shapes, protected from radiation and handling damage on the front surface by bonding on a cover glass, and cemented onto a substrate (either a rigid panel or a flexible blanket). Electrical connections are made in series-parallel to determine total output voltage. The cement and the substrate must be thermally conductive, because the cells heat up from absorbing infrared energy that is not converted to electricity. Since cell heating reduces the operating efficiency it is desirable to minimize the heating. The resulting assemblies are called solar panels or solar arrays. A solar panel is a collection of solar cells. Although each solar cell provides a relatively small amount of power, many solar cells spread over a large area can provide enough power to be useful. To get the most power, solar panels have to be pointed directly at the sun. It is claimed that if one fourth of the nation's pavement and buildings in cities alone were converted to incorporate solar panels, these could power the entire United States.

Solar panels on spacecraft

Probably the most successful use of solar panels is on spacecraft, including most spacecraft that orbit the Earth and Mars, and spacecraft going to other destinations in the inner solar system. In the outer solar system, the sunlight is too weak to produce sufficient power and radioisotope thermal generators are used. Research is underway to develop solar power satellites: space-based solar plants — satellites with large arrays of photovoltaic cells that would beam the energy to Earth using microwaves or lasers. Japanese and European space agencies have announced plans to develop such power plants in the first quarter of the 21st century. As opposed to chemical rockets, which are powered by a chemical reaction of the propellant, and uses the exhaust gases as reaction mass, some spacecraft propulsion methods have a method of expelling reaction mass powered by electricity. Either solar energy or nuclear energy is used. These methods typically have a higher specific impulse. The amount of reaction mass needed always grows exponentially with the delta-v to be produced, but more mildly if the specific impulse is high (but it should not be too high because for large specific impulse the power needed is proportional to it). With solar power the acceleration that can be produced is very low (much too low for a launch), but enduring. Typical burn times are months instead of minutes. The power the solar panel produces per kg, as an upper limit of the power the spacecraft has at its disposal per kg spacecraft (including solar panels) is an important factor. See also energy needed for propulsion methods. Solar panels need to have a lot of surface area that can be pointed towards the Sun as the spacecraft moves. More exposed surface area means more electricity can be converted from light energy from the Sun. Sometimes, satellite scientists purposefully orient the solar panels to "off point," or out of direct alignment from the Sun. This happens if the batteries are completely charged and the amount of electricity needed is lower than the amount of electricity made. The extra power will just be vented by a shunt into space as heat. Spacecraft are built so that the solar panels can be pivoted as the spacecraft moves. Thus, they can always stay in the direct path of the light rays no matter how the spacecraft is pointed. Spacecraft are usually designed with solar panels that can always be pointed at the Sun, even as the rest of the body of the spacecraft moves around, much as a tank turret can be aimed independently of where the tank is going. A tracking mechanism is often incorporated into the solar arrays to keep the array pointed towards the sun. To date, solar power, other than for propulsion, has been practical for spacecraft operating no farther from the sun than the orbit of Mars. For example, Magellan, Mars Global Surveyor, and Mars Observer used solar power as did the Earth-orbiting, Hubble Space Telescope. For future missions, it is desirable to reduce solar array mass, and to increase the power generated per unit area. This will reduce overall spacecraft mass, and may make the operation of solar-powered spacecraft feasible at larger distances from the sun. The Rosetta space probe, launched March 2, 2004, will use solar panels as far as the orbit of Jupiter (5.25 AU); previously the furthest use was the Stardust spacecraft at 2 AU. Solar power for propulsion is currently used on the European lunar mission SMART-1 with a Hall effect thruster. Solar array mass could be reduced with thin-film photovoltaic cells, flexible blanket substrates, and composite support structures. Solar array efficiency could be improved by using new photovoltaic cell materials and solar concentrators that intensify the incident sunlight. Photovoltaic concentrator solar arrays for primary spacecraft power are devices which intensify the sunlight on the photovoltaics. This design uses a flat lens, called

Ranger 8

Spacecraft design

Mission Profile

External link

Spacecraft

Overview

Examples of past or existing spacecraft

Spacecraft under development

See also

External links

Video camera tube

Image dissector

The iconoscope

Vidicon

Orthicon

Plumbicon

Saticon

Pasecon

Newvicon

External links

Ranger program

Block 1 missions

Block 2 missions

Block 3 missions

The Ranger spacecraft

Mission list

External links

See also

Aluminium

Properties

Applications

Engineering use

Household wiring

History

Natural occurrence

Isotopes

Clusters

Precautions

Spelling

Etymology / Nomenclature history

Present day spelling

Chemistry

Oxidation state 1

Oxidation state 2

Oxidation state 3

Aluminium in popular culture

See also

References

External links

Antenna

Related

Megahertz

Megahertz in radio

Megahertz in computing

See also

Agena

Altitude

Altitude records

See also

Trajectory

Physics of trajectories

Example: Uniform gravity, no drag or wind

Derivation

Derivation in polar coordinates

Maximum range

Maximum range in polar coordinates

Maximum altitude at maximum range

As a parabola

Uphill/downhill in uniform gravity in a vacuum

Derivation based on equations of a parabola

See also

Solar panel

Current Development

Solar hot water

Solar photovoltaics

Use of solar PVs

World solar power production

Large PV power plants

Cost of solar photovoltaic panels

Theory and construction