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114-464: Electroluminescence is the result of radiative recombination of electrons and holes in a material, usually a semiconductor . The excited electrons release their energy as photons – light. Prior to recombination, electrons and holes may be separated either by doping the material to form a p-n junction (in semiconductor electroluminescent devices such as light-emitting diodes ) or through excitation by impact of high-energy electrons accelerated by

228-518: A Saturn IB . This was originally planned for April 1967, to be followed by the first crewed flight later that year. But the LM's development problems had been underestimated, and LM-1's flight was delayed until January 22, 1968, as Apollo 5 . At that time, LM-2 was held in reserve in case the LM-1 flight failed, which did not happen. LM-3 now became the first crewed LM, again to be flown in low Earth orbit to test all

342-404: A capacitor where the dielectric between the outside plates is a phosphor that gives off photons when the capacitor is charged. By making one of the contacts transparent, the large area exposed emits light. Electroluminescent automotive instrument panel backlighting, with each gauge pointer also an individual light source, entered production on 1960 Chrysler and Imperial passenger cars, and

456-442: A hole . It is an important parameter in optoelectronics where radiative recombination is required to produce a photon; if the non-radiative life time is shorter than the radiative, a carrier is more likely to recombine non-radiatively. This results in low internal quantum efficiency . In Shockley-Read-Hall recombination ( SRH ), also called trap-assisted recombination , the electron in transition between bands passes through

570-631: A soft robotic system. Three six-layer HLEC panels were bound together to form a crawling soft robot, with the top four layers making up the light-up skin and the bottom two the pneumatic actuators. The discovery could lead to significant advances in health care, transportation, electronic communication and other areas. Radiative recombination In solid-state physics of semiconductors , carrier generation and carrier recombination are processes by which mobile charge carriers ( electrons and electron holes ) are created and eliminated. Carrier generation and recombination processes are fundamental to

684-616: A throttleable Descent Propulsion System (DPS) engine with four hypergolic propellant tanks. A continuous-wave Doppler radar antenna was mounted by the engine heat shield on the bottom surface, to send altitude and rate of descent data to the guidance system and pilot display during the landing. Almost all external surfaces, except for the top, platform, ladder, descent engine and heat shield, were covered in amber, dark (reddish) amber, black, silver, and yellow aluminized Kapton foil blankets for thermal insulation. The number 1 (front) landing leg had an attached platform (informally known as

798-591: A Reaction Control System (RCS) for attitude and translation control, which consisted of sixteen hypergolic thrusters similar to those used on the Service Module, mounted in four quads, with their own propellant supply. A forward extravehicular activity hatch provided access to and from the lunar surface, while an overhead hatch and docking port provided access to and from the Command Module. Internal equipment included an environmental control (life support) system;

912-530: A Saturn V, the telescope was mounted on a hinged arm and controlled from inside the MDA. Only the octagonal shape of the telescope container, solar panels and the Apollo Telescope Mount name were kept, though there was no longer any association with the LM. The Apollo LM Truck (also known as Lunar Payload Module) was a stand-alone LM descent stage intended to deliver up to 11,000 pounds (5.0 t) of payload to

1026-486: A Sylvania electroluminescent display panel as part of its display-keyboard interface ( DSKY ). Powder phosphor-based electroluminescent panels are frequently used as backlights for liquid crystal displays . They readily provide gentle, even illumination for the entire display while consuming relatively little electric power. This makes them convenient for battery-operated devices such as pagers, wristwatches, and computer-controlled thermostats, and their gentle green-cyan glow

1140-487: A VHF communications system with two antennas for communication with the Command Module; a unified S-band system and steerable parabolic dish antenna for communication with Earth; an extravehicular activity antenna resembling a miniature parasol which relayed communications from antennas on the astronauts' Portable Life Support Systems through the LM; primary (PGNCS) and backup (AGS) guidance and navigation systems; an Alignment Optical Telescope for visually determining

1254-482: A conduction band electron loses energy and re-occupies the energy state of an electron hole in the valence band. These processes must conserve quantized energy crystal momentum , and the vibrating lattice which plays a large role in conserving momentum as in collisions, photons can transfer very little momentum in relation to their energy. Recombination and generation are always happening in semiconductors, both optically and thermally. As predicted by thermodynamics ,

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1368-402: A consortium including Planar Systems. Thick-film dielectric electroluminescent technology ( TDEL ) is a phosphor -based flat panel display technology developed by Canadian company iFire Technology Corp. TDEL is based on inorganic electroluminescent (IEL) technology that combines both thick-and thin-film processes. The TDEL structure is made with glass or other substrates, consisting of

1482-531: A crew; and Apollo 9 with a crew. A third test flight in low lunar orbit was Apollo 10 , a dress rehearsal for the first landing, conducted on Apollo 11 . The Apollo 13 lunar module functioned as a lifeboat to provide life support and propulsion to keep the crew alive for the trip home, when their CSM was disabled by an oxygen tank explosion en route to the Moon. The six landed descent stages remain at their landing sites; their corresponding ascent stages crashed into

1596-577: A crewed command and service module , named the Apollo Telescope Mission (ATM). This idea was later transferred to the original wet workshop design for the Skylab orbital workshop and renamed the Apollo Telescope Mount to be docked on a side port of the workshop's multiple docking adapter (MDA). When Skylab changed to a "dry workshop" design pre-fabricated on the ground and launched on

1710-669: A dramatization of that mission starring Tom Hanks , Kevin Bacon , and Bill Paxton , was filmed using realistic spacecraft interior reconstructions of the Aquarius and the Command Module Odyssey . In 2013 in the television show Arrested Development , a fictionalized version of Howard is depicted as having the Apollo 11 "LEM" in his office, which his character claims was used to fake the 1969 moon landing . The development and construction of

1824-451: A great distance. In principle, EL lamps can be made in any color. However, the commonly used greenish color closely matches the peak sensitivity of human vision, producing the greatest apparent light output for the least electrical power input. Unlike neon and fluorescent lamps, EL lamps are not negative resistance devices so no extra circuitry is needed to regulate the amount of current flowing through them. A new technology now being used

1938-421: A material at thermal equilibrium will have generation and recombination rates that are balanced so that the net charge carrier density remains constant. The resulting probability of occupation of energy states in each energy band is given by Fermi–Dirac statistics . The product of the electron and hole densities ( n {\displaystyle n} and p {\displaystyle p} )

2052-588: A much heavier, complete Apollo spacecraft on the Moon. Once the decision had been made to proceed using LOR, it became necessary to produce a separate craft capable of reaching the lunar surface and ascending back to lunar orbit. In July 1962, eleven firms were invited to submit proposals for the LEM. Nine companies responded in September, answering 20 questions posed by the NASA RFP in a 60-page limited technical proposal. Grumman

2166-410: A new energy state (localized state) created within the band gap by a dopant or a defect in the crystal lattice ; such energy states are called traps . Non-radiative recombination occurs primarily at such sites. The energy is exchanged in the form of lattice vibration, a phonon exchanging thermal energy with the material. Since traps can absorb differences in momentum between the carriers, SRH

2280-407: A photon with the same properties as the incident photon , in terms of phase , frequency , polarization , and direction of travel. Stimulated emission together with the principle of population inversion are at the heart of operation of lasers and masers . It has been shown by Einstein at the beginning of the twentieth century that if the excited and the ground level are non degenerate then

2394-425: A proportionality constant B r to eliminate the ∝ {\displaystyle \propto } sign: R r = B r n p {\displaystyle R_{r}=B_{r}np} If the semiconductor is in thermal equilibrium, the rate at which electrons and holes recombine must be balanced by the rate at which they are generated by the spontaneous transition of an electron from

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2508-471: A second, forward docking port, allowing the LEM crew to take an active role in docking with the CSM. As the program continued, there were numerous redesigns to save weight, improve safety, and fix problems. First to go were the heavy cockpit windows and the seats; the astronauts would stand while flying the LEM, supported by a cable and pulley system, with smaller triangular windows giving them sufficient visibility of

2622-435: A strong electric field (as with the phosphors in electroluminescent displays ). It has been recently shown that as a solar cell improves its light-to-electricity efficiency (improved open-circuit voltage), it will also improve its electricity-to-light (EL) efficiency. Electroluminescent technologies have low power consumption compared to competing lighting technologies, such as neon or fluorescent lamps. This, together with

2736-546: A suit-puncture hazard to the astronauts, as the probes tended to break off and protrude upwards from the surface.) Equipment for the lunar exploration was carried in the Modular Equipment Stowage Assembly (MESA), a drawer mounted on a hinged panel dropping out of the lefthand forward compartment. Besides the astronaut's surface excavation tools and sample collection boxes, the MESA contained a television camera with

2850-470: A thick-film dielectric layer and a thin-film phosphor layer sandwiched between two sets of electrodes to create a matrix of pixels. Inorganic phosphors within this matrix emit light in the presence of an alternating electric field. Color By Blue (CBB) was developed in 2003. The Color By Blue process achieves higher luminance and better performance than the previous triple pattern process, with increased contrast, grayscale rendition, and color uniformity across

2964-403: A tripod; as the commander opened the MESA by pulling on a lanyard while descending the ladder, the camera was automatically activated to send the first pictures of the astronauts on the surface back to Earth. A United States flag for the astronauts to erect on the surface was carried in a container mounted on the ladder of each landing mission. The Early Apollo Surface Experiments Package (later

3078-431: Is a constant ( n o p o = n i 2 ) {\displaystyle (n_{o}p_{o}=n_{i}^{2})} at equilibrium, maintained by recombination and generation occurring at equal rates. When there is a surplus of carriers (i.e., n p > n i 2 {\displaystyle np>n_{i}^{2}} ), the rate of recombination becomes greater than

3192-434: Is a multistep process wherein a carrier falls into defect-related wave states in the middle of the bandgap. A trap is a defect capable of holding a carrier. The trap emission process recombines electrons with holes and emits photons to conserve energy. Due to the multistep nature of trap emission, a phonon is also often emitted. Trap emission can proceed by use of bulk defects or surface defects. Non-radiative recombination

3306-408: Is a process in phosphors and semiconductors , whereby charge carriers recombine releasing phonons instead of photons. Non-radiative recombination in optoelectronics and phosphors is an unwanted process, lowering the light generation efficiency and increasing heat losses. Non-radiative life time is the average time before an electron in the conduction band of a semiconductor recombines with

3420-415: Is a so-called Lambertian radiator : unlike with neon lamps, filament lamps, or LEDs, the brightness of the surface appears the same from all angles of view; electroluminescent light is not directional. The light emitted from the surface is perfectly homogeneous and is well-perceived by the eye. EL film produces single-frequency (monochromatic) light that has a very narrow bandwidth, is uniform and visible from

3534-407: Is based on multispectral phosphors that emit light from 600 to 400   nm depending on the drive frequency; this is similar to the color-changing effect seen with aqua EL sheet but on a larger scale. Electroluminescent devices are fabricated using either organic or inorganic electroluminescent materials. The active materials are generally semiconductors of wide enough bandwidth to allow the exit of

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3648-576: Is common in the technological world. EL backlights require relatively high voltage (between 60 and 600 volts). For battery-operated devices, this voltage must be generated by a boost converter circuit within the device. This converter often makes a faintly audible whine or siren sound while the backlight is activated. Line-voltage-operated devices may be activated directly from the power line; some electroluminescent nightlights operate in this fashion. Brightness per unit area increases with increased voltage and frequency. Thin-film phosphor electroluminescence

3762-419: Is replaced by the density of trapped electrons/holes N t ( 1 − f t ) {\displaystyle N_{t}(1-f_{t})} . R n t = B n n N t ( 1 − f t ) {\displaystyle R_{nt}=B_{n}nN_{t}(1-f_{t})} Where N t {\displaystyle N_{t}}

3876-481: Is significant only in direct bandgap materials. This process is also known as bimolecular recombination . This type of recombination depends on the density of electrons and holes in the excited state, denoted by n ( t ) {\displaystyle n(t)} and p ( t ) {\displaystyle p(t)} respectively. Let us represent the radiative recombination as R r {\displaystyle R_{r}} and

3990-728: Is the density of trap states and f t {\displaystyle f_{t}} is the probability of that occupied state. Considering a material containing both types of traps, we can define two trapping coefficients B n , B p {\displaystyle B_{n},B_{p}} and two de-trapping coefficients G n , G p {\displaystyle G_{n},G_{p}} . In equilibrium, both trapping and de-trapping should be balanced ( R n t = G n {\displaystyle R_{nt}=G_{n}} and R p t = G p {\displaystyle R_{pt}=G_{p}} ). Then,

4104-456: Is the dominant recombination process in silicon and other indirect bandgap materials. However, trap-assisted recombination can also dominate in direct bandgap materials under conditions of very low carrier densities (very low level injection) or in materials with high density of traps such as perovskites . The process is named after William Shockley , William Thornton Read and Robert N. Hall , who published it in 1952. Even though all

4218-470: Is the name for the process of electrons jumping down from the conduction band to the valence band in a radiative manner. During band-to-band recombination, a form of spontaneous emission , the energy absorbed by a material is released in the form of photons. Generally these photons contain the same or less energy than those initially absorbed. This effect is how LEDs create light. Because the photon carries relatively little momentum , radiative recombination

4332-451: Is the principle of operation in laser diodes . Besides light excitation, carriers in semiconductors can also be generated by an external electric field, for example in light-emitting diodes and transistors . When light with sufficient energy hits a semiconductor, it can excite electrons across the band gap. This generates additional charge carriers, temporarily lowering the electrical resistance of materials. This higher conductivity in

4446-587: Is the rate at which excess holes Δ p {\displaystyle \Delta p} disappear Solve this differential equation to get a standard exponential decay where p max is the maximum excess hole concentration when t = 0. (It can be proved that p max = G L B n 0 {\displaystyle p_{\max }={\frac {G_{L}}{Bn_{0}}}} , but here we will not discuss that). When t = 1 B n 0 {\displaystyle t={\frac {1}{Bn_{0}}}} , all of

4560-887: Is then obtained from the rate of both type of events according to: 1 τ = 1 τ r + 1 τ n r {\displaystyle {\frac {1}{\tau }}={\frac {1}{\tau _{r}}}+{\frac {1}{\tau _{nr}}}} From which we can also define the internal quantum efficiency or quantum yield, η {\displaystyle \eta } as: η = 1 / τ r 1 / τ r + 1 / τ n r = radiative recombination total recombination ≤ 1. {\displaystyle \eta ={\frac {1/\tau _{r}}{1/\tau _{r}+1/\tau _{nr}}}={\frac {\text{radiative recombination}}{\text{total recombination}}}\leq 1.} Band-to-band recombination

4674-498: The Apollo Lunar Surface Experiments Package ), was carried in the opposite compartment behind the LM. An external compartment on the right front panel carried a deployable S-band antenna which, when opened looked like an inverted umbrella on a tripod. This was not used on the first landing due to time constraints, and the fact that acceptable communications were being received using the LM's S-band antenna, but

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4788-582: The Lunar Landing Research Vehicle (LLRV), which used a gimbal-mounted vertical jet engine to counter five-sixths of its weight to simulate the Moon's gravity, in addition to its own hydrogen peroxide thrusters to simulate the LM's descent engine and attitude control. Successful testing of two LLRV prototypes at the Dryden Flight Research Center led in 1966 to three production Lunar Landing Training Vehicles (LLTV) which along with

4902-617: The command and service module (CSM) with legs folded, inside the Spacecraft-to-LM adapter (SLA) attached to the S-IVB third stage of the Saturn V rocket. There it remained through Earth parking orbit and the trans-lunar injection (TLI) rocket burn to send the craft toward the Moon. Soon after TLI, the SLA opened; the CSM performed a maneuver whereby it separated, turned around, came back to dock with

5016-561: The command module Columbia splashed down in the Pacific Ocean, completing President John F. Kennedy's goal : "...before this decade is out, of landing a man on the Moon and returning him safely to the Earth". This was followed by landings by Apollo 12 (LM-6 Intrepid ) and Apollo 14 (LM-8 Antares ). In April 1970, the Apollo 13 LM-7 Aquarius played an unexpected role in saving the lives of

5130-412: The landing gear , the LM was withdrawn to a safe distance, then rotated until the descent engine was pointed forward into the direction of travel. A 30-second descent orbit insertion burn was performed to reduce speed and drop the LM's perilune to within about 50,000 feet (15 km) of the surface, about 260 nautical miles (480 km) uprange of the landing site. As the craft approached perilune,

5244-404: The valence band they become hole traps. The distinction between shallow and deep traps is commonly made depending on how close electron traps are to the conduction band and how close hole traps are to the valence band. If the difference between trap and band is smaller than the thermal energy k B T it is often said that it is a shallow trap . Alternatively, if the difference is larger than

5358-419: The vibrating crystal lattice itself , it can flow freely among the nearly empty conduction band energy states. Furthermore, it will also leave behind a hole that can flow like a physically charged particle. Carrier generation describes processes by which electrons gain energy and move from the valence band to the conduction band, producing two mobile carriers; while recombination describes processes by which

5472-411: The "porch") in front of the ascent stage's extravehicular activity hatch and a ladder, which the astronauts used to ascend and descend between the cabin to the surface. The landing pad of each leg incorporated a 67-inch-long (1.7 m) surface contact sensor probe, which signaled the commander to switch off the descent engine. (The probe was omitted from the number 1 leg of every landing mission, to avoid

5586-691: The 1960s, Sylvania's Electronic Systems Division in Needham, Massachusetts developed and manufactured several instruments for the Apollo Lunar Module and Command Module using electroluminescent display panels manufactured by the Electronic Tube Division of Sylvania at Emporium, Pennsylvania . Raytheon in Sudbury, Massachusetts manufactured the Apollo Guidance Computer , which used

5700-572: The LLRV's were used to train the astronauts at the Houston Manned Spacecraft Center. This aircraft proved fairly dangerous to fly, as three of the five were destroyed in crashes. It was equipped with a rocket-powered ejection seat, so in each case the pilot survived, including the first man to walk on the Moon, Neil Armstrong . LM-1 was built to make the first uncrewed flight for propulsion systems testing, launched into low Earth orbit atop

5814-602: The LM became the most reliable component of the Apollo–Saturn space vehicle . The total cost of the LM for development and the units produced was $ 21.65 billion in 2016 dollars, adjusting from a nominal total of $ 2.29 billion using the NASA New Start Inflation Indices. Ten lunar modules were launched into space. Of these, six were landed by humans on the Moon from 1969 to 1972. The first two flown were tests in low Earth orbit : Apollo 5 , without

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5928-413: The LM's ascent engine fired, leaving the descent stage on the Moon's surface. After a few course correction burns, the LM rendezvoused with the CSM and docked to transfer the crew and rock samples. Having completed its job, the ascent stage was separated. The Apollo 10 ascent stage engine was fired until its fuel was used up, sending it past the Moon into a heliocentric orbit . The Apollo 11 ascent stage

6042-454: The LM, replaced the hatches and docking equipment, unfolded and locked its landing legs, and separated from the CSM, flying independently. The commander operated the flight controls and engine throttle, while the Lunar Module pilot operated other spacecraft systems and kept the commander informed about systems status and navigational information. After the command module pilot visually inspected

6156-418: The Lunar Module from lunar orbit to the Moon's surface. During takeoff, the spent descent stage was used as a launch pad for the ascent stage which then flew back to the command module , after which it was also discarded. Overseen by Grumman , the LM's development was plagued with problems that delayed its first uncrewed flight by about ten months and its first crewed flight by about three months. Regardless,

6270-470: The Lunar Module, and extracted it from the S-IVB. During the flight to the Moon, the docking hatches were opened and the Lunar Module pilot entered the LM to power up temporarily and test all systems except propulsion. The Lunar Module pilot performed the role of an engineering officer, monitoring the systems of both spacecraft. After achieving a lunar parking orbit, the commander and LM pilot entered and powered up

6384-423: The Moon following use. One ascent stage (Apollo 10's Snoopy ) was discarded in a heliocentric orbit after its descent stage was discarded in lunar orbit. The other three LMs were destroyed during controlled re-entry in the Earth's atmosphere: the four stages of Apollo 5 and Apollo 9 each re-entered separately, while Apollo 13's Aquarius re-entered as a unit. At launch, the lunar module sat directly beneath

6498-557: The Moon for an uncrewed landing. This technique was intended to deliver equipment and supplies to a permanent crewed lunar base . As originally proposed, it would be launched on a Saturn V with a full Apollo crew to accompany it to lunar orbit and guide it to a landing next to the base; then the base crew would unload the "truck" while the orbiting crew returned to Earth. In later AAP plans, the LPM would have been delivered by an uncrewed lunar ferry vehicle. The 1995 Ron Howard film Apollo 13 ,

6612-516: The Moon's surface during the United States' Apollo program . It was the first crewed spacecraft to operate exclusively in the airless vacuum of space, and remains the only crewed vehicle to land anywhere beyond Earth. Structurally and aerodynamically incapable of flight through Earth's atmosphere, the two-stage Lunar Module was ferried to lunar orbit attached to the Apollo command and service module (CSM), about twice its mass. Its crew of two flew

6726-439: The abbreviation as ( / l ɛ m / ) instead of the letters "L-M". Comparing landing on the Moon to "a hovering operation", Gus Grissom said in 1963 that although most early astronauts were fighter pilots, "now we're wondering if the pilot making this first moon landing shouldn't be a highly experienced helicopter pilot". To allow astronauts to learn lunar landing techniques, NASA contracted Bell Aerosystems in 1964 to build

6840-579: The absorption rate W 12 {\displaystyle W_{12}} and the stimulated emission rate W 21 {\displaystyle W_{21}} are the same. Else if level 1 and level 2 are g 1 {\displaystyle g_{1}} -fold and g 2 {\displaystyle g_{2}} -fold degenerate respectively, the new relation is: g 1 W 12 = g 2 W 21 . {\displaystyle g_{1}W_{12}=g_{2}W_{21}.} Trap emission

6954-452: The cabin. The return payload included the lunar rock and soil samples collected by the crew (as much as 238 pounds (108 kg) on Apollo 17), plus their exposed photographic film . The descent stage's primary job was to support a powered landing and surface extravehicular activity. When the excursion was over, it served as the launch pad for the ascent stage. Its octagonal shape was supported by four folding landing gear legs, and contained

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7068-533: The carrier generation rate as G. Total generation is the sum of thermal generation G 0 and generation due to light shining on the semiconductor G L : G = G 0 + G L {\displaystyle G=G_{0}+G_{L}} Here we will consider the case in which there is no illumination on the semiconductor. Therefore G L = 0 {\displaystyle G_{L}=0} and G = G 0 {\displaystyle G=G_{0}} , and we can express

7182-564: The change in carrier density as a function of time as d n d t = G − R r = G 0 − R r {\displaystyle {dn \over dt}=G-R_{r}=G_{0}-R_{r}} Because the rate of recombination is affected by both the concentration of free electrons and the concentration of holes that are available to them, we know that R r should be proportional to np: R r ∝ n p {\displaystyle R_{r}\propto np} and we add

7296-418: The descent engine was started again to begin powered descent. During this time, the crew flew on their backs, depending on the computer to slow the craft's forward and vertical velocity to near zero. Control was exercised with a combination of engine throttling and attitude thrusters, guided by the computer with the aid of landing radar. During braking, the LM descended to about 10,000 feet (3.0 km), then, in

7410-508: The descent propellant tanks were enlarged. A waste storage tank was added to the descent stage, with plumbing from the ascent stage. These upgrades allowed stays of up to 75 hours on the Moon. The Lunar Roving Vehicle was folded up and carried in Quadrant 1 of the descent stage. It was deployed by the astronauts after landing, allowing them to explore large areas and return a greater variety of lunar samples. Weights given here are an average for

7524-493: The designers compromised on four landing legs. In June 1966, the name was changed to Lunar Module (LM), eliminating the word excursion . According to George Low , Manager of the Apollo Spacecraft Program Office, this was because NASA was afraid that the word excursion might lend a frivolous note to Apollo. Despite the name change, the astronauts and other NASA and Grumman personnel continued to pronounce

7638-415: The electron and hole densities when the quasi Fermi level matches the trap energy. In steady-state condition, the net recombination rate of electrons should match the net recombination rate for holes, in other words: R n t − G n = R p t − G p {\displaystyle R_{nt}-G_{n}=R_{pt}-G_{p}} . This eliminates

7752-468: The electrons. At absolute zero temperature, all of the electrons have energy below the Fermi level; but at non-zero temperatures the energy levels are filled following a Fermi-Dirac distribution . In undoped semiconductors the Fermi level lies in the middle of a forbidden band or band gap between two allowed bands called the valence band and the conduction band . The valence band, immediately below

7866-800: The equilibrium carrier densities. Using the mass action law n p = n i 2 {\displaystyle np=n_{i}^{2}} ，with n i {\displaystyle n_{i}} being the intrinsic carrier density, we can rewrite it as R 0 = G 0 = B r n 0 p 0 = B r n i 2 {\displaystyle R_{0}=G_{0}=B_{r}n_{0}p_{0}=B_{r}n_{i}^{2}} The non-equilibrium carrier densities are given by n = n 0 + Δ n , {\displaystyle n=n_{0}+\Delta n,} p = p 0 + Δ p {\displaystyle p=p_{0}+\Delta p} Then

7980-441: The excess energy is converted into heat by phonon emission after the mean lifetime τ n r {\displaystyle \tau _{nr}} , whereas in the former at least part of the energy is released by light emission or luminescence after a radiative lifetime τ r {\displaystyle \tau _{r}} . The carrier lifetime τ {\displaystyle \tau }

8094-479: The excess holes will have disappeared. Therefore, we can define the lifetime of the excess holes in the material τ p = 1 B n 0 {\displaystyle \tau _{p}={\frac {1}{Bn_{0}}}} So the lifetime of the minority carrier is dependent upon the majority carrier concentration. Stimulated emission is a process where an incident photon interacts with an excited electron causing it to recombine and emit

8208-400: The extended missions. [REDACTED] One proposed Apollo application was an orbital solar telescope constructed from a surplus LM with its descent engine replaced with a telescope controlled from the ascent stage cabin, the landing legs removed and four "windmill" solar panels extending from the descent stage quadrants. This would have been launched on an uncrewed Saturn IB, and docked with

8322-436: The final approach phase, down to about 700 feet (210 m). During final approach, the vehicle pitched over to a near-vertical position, allowing the crew to look forward and down to see the lunar surface for the first time. Astronauts flew Apollo spacecraft manually only during the lunar approach. The final landing phase began about 2,000 feet (0.61 km) uprange of the targeted landing site. At this point, manual control

8436-413: The final approach. The CSM would then raise its perilune back to the normal 60 nautical miles (110 km). The Extended Lunar Module (ELM) used on the final three "J-class missions" — Apollo 15 , 16 , and 17 — was upgraded to land larger payloads and stay longer on the lunar surface. The descent engine thrust was increased by the addition of a 10-inch (250 mm) extension to the engine bell, and

8550-426: The forbidden band, is normally very nearly completely occupied. The conduction band, above the Fermi level, is normally nearly completely empty. Because the valence band is so nearly full, its electrons are not mobile, and cannot flow as electric current. However, if an electron in the valence band acquires enough energy to reach the conduction band as a result of interaction with other electrons , holes , photons, or

8664-887: The four rates as a function of f t {\displaystyle f_{t}} become: R n t = B n n N t ( 1 − f t ) G n = B n n t N t f t R p t = B p p N t f t G p = B p p t N t ( 1 − f t ) {\displaystyle {\begin{array}{l l}R_{nt}=B_{n}nN_{t}(1-f_{t})&G_{n}=B_{n}n_{t}N_{t}f_{t}\\R_{pt}=B_{p}pN_{t}f_{t}&G_{p}=B_{p}p_{t}N_{t}(1-f_{t})\end{array}}} Where n t {\displaystyle n_{t}} and p t {\displaystyle p_{t}} are

8778-538: The front electrode. The display applications are primarily passive (i.e., voltages are driven from the edge of the display cf. driven from a transistor on the display). Similar to LCD trends, there have also been Active Matrix EL (AMEL) displays demonstrated, where the circuitry is added to prolong voltages at each pixel. The solid-state nature of TFEL allows for a very rugged and high-resolution display fabricated even on silicon substrates. AMEL displays of 1280×1024 at over 1000 lines per inch (LPI) have been demonstrated by

8892-546: The landing site. Later, the redundant forward docking port was removed, which meant the Command Pilot gave up active control of the docking to the Command Module Pilot; he could still see the approaching CSM through a small overhead window. Egress while wearing bulky extra-vehicular activity spacesuits was eased by a simpler forward hatch (32 in × 32 in or 810 mm × 810 mm). The configuration

9006-468: The last four landing missions by using the Service Module engine to perform the initial descent orbit insertion burn 22 hours before the LM separated from the CSM, a practice begun on Apollo 14. This meant that the complete spacecraft, including the CSM, orbited the Moon with a 9.1-nautical-mile (16.9 km) perilune, enabling the LM to begin its powered descent from that altitude with a full load of descent stage propellant, leaving more reserve propellant for

9120-402: The legs of the lander touched the surface, activating the contact indicator light which signaled the commander to shut off the descent engine, allowing the LM to settle onto the surface. On touchdown, the probes would be bent as much as 180 degrees, or even break off. The original design used the probes on all four legs, but starting with the first landing (LM-5 on Apollo 11), the one at the ladder

9234-620: The light. The most typical inorganic thin-film EL (TFEL) is ZnS:Mn with yellow-orange emission. Examples of the range of EL material include: The most common electroluminescent (EL) devices are composed of either powder (primarily used in lighting applications) or thin films (for information displays.) Light-emitting capacitor , or LEC , is a term used since at least 1961 to describe electroluminescent panels. General Electric has patents dating to 1938 on flat electroluminescent panels that are still made as night lights and backlights for instrument panel displays. Electroluminescent panels are

9348-411: The lightest possible configuration. But as any particular leg would have to carry the weight of the vehicle if it landed at a significant angle, this was also the least stable configuration if one of the legs were damaged during landing. The next landing gear design iteration had five legs and was the most stable configuration for landing on an unknown terrain. That configuration, however, was too heavy and

9462-409: The lunar landing, practicing all phases of the mission except powered descent initiation through takeoff. The LM descended to 47,400 feet (9.0 mi; 14.4 km) above the lunar surface, then jettisoned the descent stage and used its ascent engine to return to the CSM. The first crewed lunar landing occurred on July 20, 1969, in the Apollo 11 LM-5 Eagle . Four days later, the Apollo 11 crew in

9576-403: The lunar module is dramatized in the 1998 miniseries From the Earth to the Moon episode entitled "Spider" . This is in reference to LM-3, used on Apollo 9, which the crew named Spider after its spidery appearance. The unused LM-13 stood in during the teleplay to depict LM-3 and LM-5, Eagle , used by Apollo 11. The Apollo 11 Lunar Module Eagle is depicted in the 2018 film First Man ,

9690-951: The new recombination rate R net {\displaystyle R_{\text{net}}} becomes, R net = R r − G 0 = B r n p − G 0 = B r ( n 0 + Δ n ) ( p 0 + Δ p ) − G 0 {\displaystyle R_{\text{net}}=R_{r}-G_{0}=B_{r}np-G_{0}=B_{r}(n_{0}+\Delta n)(p_{0}+\Delta p)-G_{0}} Because n 0 ≫ Δ n {\displaystyle n_{0}\gg \Delta n} and p 0 ≫ Δ p {\displaystyle p_{0}\gg \Delta p} , we can say that Δ n Δ p ≈ 0 {\displaystyle \Delta n\Delta p\approx 0} In an n-type semiconductor, thus Net recombination

9804-524: The occupation probability f t {\displaystyle f_{t}} and leads to the Shockley-Read-Hall expression for the trap-assisted recombination: Apollo Lunar Module The Apollo Lunar Module ( LM / ˈ l ɛ m / ), originally designated the Lunar Excursion Module ( LEM ), was the lunar lander spacecraft that was flown between lunar orbit and

9918-429: The operation of many optoelectronic semiconductor devices , such as photodiodes , light-emitting diodes and laser diodes . They are also critical to a full analysis of p-n junction devices such as bipolar junction transistors and p-n junction diodes . The electron–hole pair is the fundamental unit of generation and recombination in inorganic semiconductors , corresponding to an electron transitioning between

10032-403: The original pre-ELM spec vehicles. For specific weights for each mission, see the individual mission articles. The ascent stage contained the crew cabin with instrument panels and flight controls. It contained its own Ascent Propulsion System (APS) engine and two hypergolic propellant tanks for return to lunar orbit and rendezvous with the Apollo command and service module . It also contained

10146-499: The other particles involved in the process (e.g. photons , electron , or the system of vibrating lattice atoms ). When light interacts with a material, it can either be absorbed (generating a pair of free carriers or an exciton ) or it can stimulate a recombination event. The generated photon has similar properties to the one responsible for the event. Absorption is the active process in photodiodes , solar cells and other semiconductor photodetectors , while stimulated emission

10260-399: The panel. Color By Blue is based on the physics of photoluminescence . High luminance inorganic blue phosphor is used in combination with specialized color conversion materials, which absorb the blue light and re-emit red or green light, to generate the other colors. Electroluminescent lighting is now used as an application for public safety identification involving alphanumeric characters on

10374-505: The potential for long life and full-color electroluminescent displays have been developed. The EL material must be enclosed between two electrodes and at least one electrode must be transparent to allow the escape of the produced light. Glass coated with indium tin oxide is commonly used as the front (transparent) electrode, while the back electrode is coated with reflective metal. Additionally, other transparent conducting materials, such as carbon nanotube coatings or PEDOT can be used as

10488-452: The presence of light is known as photoconductivity . This conversion of light into electricity is widely used in photodiodes . Carrier recombination can happen through multiple relaxation channels. The main ones are band-to-band recombination, Shockley–Read–Hall (SRH) trap-assisted recombination, Auger recombination and surface recombination. These decay channels can be separated into radiative and non-radiative. The latter occurs when

10602-471: The rate of generation, driving the system back towards equilibrium. Likewise, when there is a deficit of carriers (i.e., n p < n i 2 {\displaystyle np<n_{i}^{2}} ), the generation rate becomes greater than the recombination rate, again driving the system back towards equilibrium. As the electron moves from one energy band to another, the energy and momentum that it has lost or gained must go to or come from

10716-409: The recombination events can be described in terms of electron movements, it is common to visualize the different processes in terms of excited electron and the electron holes they leave behind. In this context, if trap levels are close to the conduction band , they can temporarily immobilize excited electrons or in other words, they are electron traps . On the other hand, if their energy lies close to

10830-683: The roof of vehicles for clear visibility from an aerial perspective. Electroluminescent lighting, especially electroluminescent wire (EL wire), has also made its way into clothing as many designers have brought this technology to the entertainment and nightlife industry. From 2006, t-shirts with an electroluminescent panel stylized as an audio equalizer , the T-Qualizer, saw a brief period of popularity. Engineers have developed an electroluminescent "skin" that can stretch more than six times its original size while still emitting light. This hyper-elastic light-emitting capacitor (HLEC) can endure more than twice

10944-409: The spacecraft orientation; rendezvous radar with its own steerable dish antenna; and a system for active thermal control. Electrical storage batteries, cooling water, and breathing oxygen were stored in amounts sufficient for a lunar surface stay of 48 hours initially, extended to 75 hours for the later missions. During rest periods while parked on the Moon, the crew would sleep on hammocks slung across

11058-414: The strain of previously tested stretchable displays. It consists of layers of transparent hydrogel electrodes sandwiching an insulating elastomer sheet. The elastomer changes luminance and capacitance when stretched, rolled, and otherwise deformed. In addition to its ability to emit light under a strain of greater than 480% of its original size, the group's HLEC was shown to be capable of being integrated into

11172-403: The surface, leaving the spacecraft to be only remotely attended by Mission Control. Beginning with Apollo 14 , extra LM propellant was made available for the powered descent and landing, by using the CSM engine to achieve the 50,000-foot (15 km) perilune. After the spacecraft undocked, the CSM raised and circularized its orbit for the remainder of the mission. When ready to leave the Moon,

11286-467: The systems, and practice the separation, rendezvous, and docking planned for Apollo 8 in December 1968. But again, last-minute problems delayed its flight until Apollo 9 on March 3, 1969. A second, higher Earth orbit crewed practice flight had been planned to follow LM-3, but this was cancelled to keep the program timeline on track. Apollo 10 launched on May 18, 1969, using LM-4 for a "dress rehearsal" for

11400-514: The thermal energy, it is called a deep trap . This difference is useful because shallow traps can be emptied more easily and thus are often not as detrimental to the performance of optoelectronic devices. In the SRH model, four things can happen involving trap levels: When carrier recombination occurs through traps, we can replace the valence density of states by that of the intragap state. The term p ( n ) {\displaystyle p(n)}

11514-426: The thinness of the material, has made EL technology valuable to the advertising industry. Relevant advertising applications include electroluminescent billboards and signs. EL manufacturers can control precisely which areas of an electroluminescent sheet illuminate, and when. This has given advertisers the ability to create more dynamic advertising that is still compatible with traditional advertising spaces. An EL film

11628-752: The three astronauts after an oxygen tank in the service module ruptured, disabling the CSM. Aquarius served as a "lifeboat" for the astronauts during their return to Earth. Its descent stage engine was used to replace the crippled CSM Service Propulsion System engine, and its batteries supplied power for the trip home and recharged the Command Module's batteries critical for reentry. The astronauts splashed down safely on April 17, 1970. The LM's systems, designed to support two astronauts for 45 hours (including two depressurization and repressurization cycles, causing loss of oxygen supply), actually stretched to support three astronauts for 90 hours (without pressurization cycles and loss of oxygen). Hover times were maximized on

11742-459: The valence band and the conduction band where generation of an electron is a transition from the valence band to the conduction band and recombination leads to a reverse transition. Like other solids, semiconductor materials have an electronic band structure determined by the crystal properties of the material. Energy distribution among electrons is described by the Fermi level and the temperature of

11856-567: The valence band to the conduction band. The recombination rate R 0 {\displaystyle R_{0}} must be exactly balanced by the thermal generation rate G 0 {\displaystyle G_{0}} . Therefore： R 0 = G 0 = B r n 0 p 0 {\displaystyle R_{0}=G_{0}=B_{r}n_{0}p_{0}} where n 0 {\displaystyle n_{0}} and p 0 {\displaystyle p_{0}} are

11970-486: Was awarded the contract officially on November 7, 1962. Grumman had begun lunar orbit rendezvous studies in the late 1950s and again in 1961. The contract cost was expected to be around $ 350 million. There were initially four major subcontractors: Bell Aerosystems ( ascent engine ), Hamilton Standard (environmental control systems), Marquardt (reaction control system) and Rocketdyne ( descent engine ). The Primary Guidance, Navigation and Control System (PGNCS)

12084-417: Was chiefly designed by Grumman aerospace engineer Thomas J. Kelly . The first LEM design looked like a smaller version of the Apollo command and service module (a cone-shaped cabin atop a cylindrical propulsion section) with folding legs. The second design invoked the idea of a helicopter cockpit with large curved windows and seats, to improve the astronauts' visibility for hover and landing. This also included

12198-585: Was continued successfully on several Chrysler vehicles through 1967 and marketed as "Panelescent Lighting". The Sylvania Lighting Division in Salem and Danvers, Massachusetts , produced and marketed an EL night light, under the trade name Panelescent at roughly the same time that the Chrysler instrument panels entered production. These lamps have proven extremely reliable, with some samples known to be still functional after nearly 50 years of continuous operation. Later in

12312-611: Was developed by the MIT Instrumentation Laboratory ; the Apollo Guidance Computer was manufactured by Raytheon (a similar guidance system was used in the command module ). A backup navigation tool, the Abort Guidance System (AGS), was developed by TRW . The landing gear was manufactured by Héroux . The Apollo Lunar Module was assembled in a Grumman factory in Bethpage, New York . The Apollo Lunar Module

12426-451: Was enabled for the commander, who had enough propellant to hover for up to two minutes to survey where the computer was taking the craft and make any necessary corrections. If necessary, landing could have been aborted at almost any time by jettisoning the descent stage and firing the ascent engine to climb back into orbit for an emergency return to the CSM. Finally, one or more of three 67.2-inch (1.71 m) probes extending from footpads on

12540-777: Was first commercialized during the 1980s by Sharp Corporation in Japan, Finlux (Oy Lohja Ab) in Finland, and Planar Systems in the US. In these devices, bright, long-life light emission is achieved in thin-film yellow-emitting manganese-doped zinc sulfide material. Displays using this technology were manufactured for medical and vehicle applications where ruggedness and wide viewing angles were crucial, and liquid crystal displays were not well developed. In 1992, Timex introduced its Indiglo EL display on some watches. Recently, blue-, red-, and green-emitting thin film electroluminescent materials that offer

12654-698: Was frozen in April 1963, when the ascent and descent engine designs were decided. In addition to Rocketdyne, a parallel program for the descent engine was ordered from Space Technology Laboratories (TRW) in July 1963, and by January 1965 the Rocketdyne contract was cancelled. Power was initially to be produced by fuel cells built by Pratt and Whitney similar to the CSM, but in March 1965 these were discarded in favor of an all-battery design. The initial design had three landing legs,

12768-575: Was left in lunar orbit to eventually crash; all subsequent ascent stages (except for Apollo 13) were intentionally steered into the Moon to obtain readings from seismometers placed on the surface. The Lunar Module (originally designated the Lunar Excursion Module, known by the acronym LEM) was designed after NASA chose to reach the Moon via Lunar Orbit Rendezvous (LOR) instead of the direct ascent or Earth Orbit Rendezvous (EOR) methods. Both direct ascent and EOR would have involved landing

12882-415: Was removed out of concern that the bent probe after landing might puncture an astronaut's suit as he descended or stepped off the ladder. The original extravehicular activity plan, up through at least 1966, was for only one astronaut to leave the LM while the other remained inside "to maintain communications". Communications were eventually deemed to be reliable enough to allow both crew members to walk on

12996-593: Was used on Apollo 12 and 14. A hand-pulled Modular Equipment Transporter (MET), similar in appearance to a golf cart, was carried on Apollo 13 and 14 to facilitate carrying the tools and samples on extended moonwalks. On the extended missions ( Apollo 15 and later), the antenna and TV camera were mounted on the Lunar Roving Vehicle , which was carried folded up and mounted on an external panel. Compartments also contained replacement Portable Life Support System (PLSS) batteries and extra lithium hydroxide canisters on

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