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نوشته شده در جمعه نهم فروردین 1392ساعت 7:46 توسط aryan jamshidi|


Mir (Russian: Мир, IPA) space station


Mir (Russian: Мир, IPA: [ˈmʲir]; lit. Peace or World) was a space station that operated in low Earth orbit from 1986 to 2001, owned at first by the Soviet Union and then by Russia. Mir was the first modular space station and was assembled in orbit from 1986 to 1996. It had a greater mass than that of any previous spacecraft. It held the record for the largest artificial satellite orbiting the Earth until that record was surpassed by the International Space Station after Mir's deorbit on 21 March 2001. Mir served as a microgravity research laboratory in which crews conducted experiments in biology, human biology, physics, astronomy, meteorology and spacecraft systems in order to develop technologies required for the permanent occupation of space.


The station was the first consistently inhabited long-term research station in space and was operated by a series of long-duration crews. The Mir programme held the record for the longest uninterrupted human presence in space, at 3,644 days, until 23 October 2010 (when it was surpassed by the ISS), and it currently holds the record for the longest single human spaceflight, of Valeri Polyakov, at 437 days 18 hours. Mir was occupied for a total of twelve and a half years of its fifteen-year lifespan, having the capacity to support a resident crew of three, and larger crews for short-term visits.


A cluster of cylindrical modules with projecting feathery solar arrays and a space shuttle docked to the lower module. In the background is the blackness of space, and, in the lower right corner, Earth.
Space Shuttle Atlantis docked to Mir on STS-71

Following the success of the Salyut programme, Mir represented the next stage in the Soviet Union's space station programme. The first module of the station, known as the core module or base block, was launched in 1986, and was followed by six further modules, all launched by Proton rockets (with the exception of the docking module). When complete, the station consisted of seven pressurised modules and several unpressurised components. Power was provided by several photovoltaic arrays mounted directly on the modules. The station was maintained at an orbit between 296 km (184 mi) and 421 km (262 mi) altitude and traveled at an average speed of 27,700 km/h (17,200 mph), completing 15.7 orbits per day.


On 5 May 1986, they undocked from Mir for a day-long journey to Salyut 7. They spent 51 days there and gathered 400 kg of scientific material from Salyut 7 for return to Mir. While Soyuz T-15 was at Salyut 7, the unmanned Soyuz TM-1 arrived at the unoccupied Mir and remained for 9 days, testing the new Soyuz TM model. Soyuz T-15 redocked with Mir on 26 June and delivered the experiments and 20 instruments, including a multichannel spectrometer. The EO-1 crew spent their last 20 days on Mir conducting Earth

The station was launched as part of the Soviet Union's manned spaceflight programme effort to maintain a long-term research outpost in space, and, following the collapse of the USSR, was operated by the new Russian Federal Space Agency (RKA). As a result, the vast majority of the station's crew were Soviet or Russian; however, through international collaborations, including the Intercosmos, Euromir and Shuttle-Mir programmes, the station was made accessible to astronauts from North America, several European nations and Japan. The cost of the Mir programme was estimated by former RKA General Director Yuri Koptev in 2001 as $4.2 billion over its lifetime (including development, assembly and orbital operation). The station was serviced by Soyuz spacecraft, Progress spacecraft and U.S. Space Shuttles, and was visited by astronauts and cosmonauts from 12 different nations.


Mir
A view of Mir backdropped by the limb of the Earth. In view are four cylindrical modules covered in white insulation arranged in a cross shape about a small, central sphere. Another module projects backward from this sphere, and a small module is attached to the far end of that. Each module is sprouting various solar arrays, cranes and other spindly equipment, with Soyuz and Progress spacecraft docked to the forward and aft ports of the complex.
Mir on 9 February 1998 as seen from the departing Space Shuttle Endeavour during STS-89
A vaguely trapezoid blue patch with rounded corners, bordered by a thick red line. A star made up of two red and yellow arrowheads sits in the middle on top of an angular white spiral which comes to form a globe shape in the centre. The letters 'Мир' are visible in white to the top left of the patch.
Mir insignia
Station statistics
COSPAR ID 1986-017A
Call sign Mir
Crew 3
Launch 20 February 1986 – 23 April 1996
Launch pad LC-200/39, and LC-81/23, Baikonur Cosmodrome
LC-39A,
Kennedy Space Center
Reentry 23 March 2001
05:59 UTC
Mass 129,700 kg
(285,940 lbs)
Length 19 m (62.3 ft)
from the core module to Kvant-1
Width 31 m (101.7 ft)
from Priroda to the docking module
Height 27.5 m (90.2 ft)
from Kvant-2 to Spektr
Pressurised volume 350 m³
Atmospheric pressure c.101.3 kPa (29.91 inHg, 1 atm)
Perigee 354 km (189 nmi) AMSL \bar{x} \!\,
Apogee 374 km (216 nmi) AMSL \bar{x} \!\,
Orbital inclination 51.6 degrees
Average speed 7,700 m/s
(27,700 km/h, 17,200 mph)
Orbital period 91.9 minutes \bar{x} \!\,
Orbits per day 15.7 \bar{x} \!\,
Days in orbit 5,519 days
Days occupied 4,592 days
Number of orbits 86,331
Statistics as of 23 March 2001
(unless noted otherwise)
]
Configuration
The main components of Mir shown as a line diagram, with each module highlighted in a different colour.
Station elements as of May 1996.



Final days and deorbit

The crew of EO-27, consisting of Viktor Afanasyev and Jean-Pierre Haigneré arrived in Soyuz TM-29 on 22 February 1999 alongside Ivan Bella, who returned to Earth with Padalka in Soyuz TM-28. The crew carried out three EVAs to retrieve experiments and deploy a prototype communications antenna on Sofora. Meanwhile, on 1 June it was announced that the deorbit of the station would be delayed by six months to allow time to seek alternative funding to keep the station operating. The rest of the expedition was spent preparing the station for its deorbit; a special analogue computer was installed and each of the modules, starting with the docking module, was mothballed in turn and sealed off. The crew loaded their results into Soyuz TM-29 and departed Mir on 28 August 1999, ending a run of continuous occupation of the station which had lasted for eight days short of ten years. The station's gyrodynes and main computer were shut down on 7 September, leaving Progress M-42 to control Mir and refine the station's orbital decay rate.

Near the end of its life, there were plans for private interests to purchase Mir, possibly for use as the first orbital television/movie studio. The privately funded Soyuz TM-30 mission by MirCorp, launched on 4 April 2000, carried two crew members, Sergei Zalyotin and Aleksandr Kaleri, to the station for two months to do repair work with the hope of proving that the station could be made safe. This was, however, to be the last manned mission to Mir - while Russia was optimistic about Mir's future, its commitments to the International Space Station project left no funding to support the aging station.

Mir's deorbit was carried out in three stages. The first stage involved waiting for atmospheric drag to reduce the station's orbit to an average of 220 kilometres (140 mi). This began with the docking of Progress M1-5, a modified version of the Progress-M carrying 2.5 times more fuel in place of supplies. The second stage was the transfer of the station into a 165 × 220 km (103 × 137 mi) orbit. This was achieved with two burns of Progress M1-5's control engines at 00:32 UTC and 02:01 UTC on 23 March 2001. After a two-orbit pause, the third and final stage of Mir's deorbit began with the burn of Progress M1-5's control engines and main engine at 05:08 UTC, lasting a little over 22 minutes. Reentry into Earth's atmosphere (100 km/60 mi AMSL) of the 15-year-old space station occurred at 05:44 UTC near Nadi, Fiji. Major destruction of the station began around 05:52 UTC and most of the unburned fragments fell into the South Pacific Ocean around 06:00 UTC. A single piece of the Mir's remains was discovered near Boston, Massachusetts.

نوشته شده در شنبه بیست و هشتم دی 1392ساعت 18:22 توسط aryan jamshidi|

McDonnell Douglas X-36

 

X-36

X-36 in flight

 

 

 

 

 

 

 

 

 

 

 

 

The X-36 was built to 28% scale of a possible fighter aircraft, and controlled by a pilot in a ground station virtual cockpit with a view provided by a video camera mounted in the nose of the aircraft.

For control, a canard forward of the wing was used as well as split ailerons and an advanced thrust vectoring nozzle for directional control. The X-36 was unstable in both pitch and yaw axis, so an advanced digital fly-by-wire control system was put in place to stabilize the aircraft.

First flown on May 17, 1997, it made 31 successful research flights. It handled very well, and the program is reported to have met or exceeded all project goals. McDonnell Douglas merged with Boeing in August 1997 while the test program was in progress; the aircraft is sometimes referred to as the Boeing X-36.

The X-36 possessed high maneuverability that would be ideal for use as a fighter. Despite its potential suitability, and highly successful test-program, there have been no reports regarding the X-36's development as of 2010.

Survivors

  • One X-36 is at the National Museum of the United States Air Force at Wright-Patterson Air Force Base near Dayton, Ohio. It arrived on July 16, 2003, the same day as the Boeing Bird of Prey. It is displayed in the Museum's Research & Development Gallery.
  • Another X-36 is displayed inside the Air Force Test Flight Center Museum at Edwards Air Force Base in California

    General characteristics

     

    Performance

  • نوشته شده در دوشنبه بیست و یکم مرداد 1392ساعت 21:10 توسط aryan jamshidi|

    McDonnell Douglas F-15 Eagle

    F-15 Eagle

    USAF F-15C during an Operation Noble Eagle patrol

     

     

     

     

     

     

     

     

     

     

    The McDonnell Douglas (now Boeing) F-15 Eagle is a twin-engine, all-weather tactical fighter designed by McDonnell Douglas to gain and maintain air superiority in aerial combat. It is considered among the most successful modern fighters, with over 100 aerial combat victories with no losses in dogfights. Following reviews of proposals, the United States Air Force selected McDonnell Douglas' design in 1967 to meet the service's need for a dedicated air superiority fighter. The Eagle first flew in July 1972, and entered service in 1976.

    Since the 1970s, the Eagle has been exported to Israel, Japan, Saudi Arabia, and other nations. The F-15 was originally envisioned as a pure air superiority aircraft. Its design included a secondary ground-attack capability that was largely unused. The design proved flexible enough that an all-weather strike derivative, the F-15E Strike Eagle, was later developed, and entered service in 1989. The F-15 Eagle is expected to be in service with the U.S. Air Force past 2025.

    Origins

    Following studies in 1964–1965, the U.S. Air Force developed requirements for an air superiority fighter in October 1965. Then on 8 December 1965, the service issued a request for proposals (RFP) for the new fighter. The request called for both air-to-air and air-to-ground capabilities. Eight companies responded with proposals. In the following study phase, four of these companies developed some 500 design concepts. Typical designs featured variable-sweep wings, weighed over 60,000 lb (27,200 kg), included a top speed of Mach 2.7 and a thrust-to-weight ratio of 0.75. The designs were not accepted by the Air Force as they compromised fighter qualities for ground attack qualities. Acceptance of the Energy-Maneuverability (E-M) theory by the Air Force led to a change in requirements for improved maneuverability by the spring 1967. The design mission weight was reduced to 40,000 lb (18,100 kg), top speed reduced to Mach 2.3–2.5 and thrust-to-weight ratio increased to 0.97.

    In 1967 U.S. intelligence was surprised to find that the Soviet Union was producing a large fighter aircraft, the MiG-25 'Foxbat'. It was not known in the West at the time that the MiG-25 was designed as a high-speed interceptor, not an air superiority fighter, so its primary asset was speed, not maneuverability. The MiG-25's huge tailplanes and vertical stabilizers (tail fins) hinted at a very maneuverable aircraft, which worried the Air Force that its performance might be better than its U.S. counterparts. In reality, the MiG's large fins and stabilators were necessary to prevent the aircraft from encountering inertia coupling in high-speed, high-altitude flight.[citation needed]

    The McDonnell Douglas F-4 Phantom II of the USAF, U.S. Navy and U.S. Marine Corps was the only fighter with enough power, range, and maneuverability to be given the primary task of dealing with the threat of Soviet fighters while flying with visual engagement rules. As a matter of policy, the Phantoms could not engage targets without positive visual identification, so they could not engage targets at long ranges, as designed. Medium-range AIM-7 Sparrow missiles, and to a lesser degree even the AIM-9 Sidewinder, were often unreliable and ineffective at close ranges where it was found that guns were often the only effective weapon. The Phantom did not originally have any guns or cannons, but experience in Vietnam led to the addition of an internally mounted cannon in later versions

    F-X program

    There was a clear need for a new fighter that overcame the close-range limitation of the Phantom while retaining long-range air superiority. After rejecting the U.S. Navy VFX program (which led to the F-14 Tomcat) as being unsuited to its needs, the U.S. Air Force issued its own requirements for the F-X (read as Fighter-Unknown, sometimes referred to as Fighter-Experimental), a specification for a relatively lightweight air superiority fighter. The requirements called for single-seat fighter having a maximum take-off weight of 40,000 lb (18,100 kg) for the air-to-air role with a maximum speed of Mach 2.5 and a thrust to weight ratio of nearly 1 at mission weight. Four companies submitted proposals, with the Air Force eliminating General Dynamics and awarding contracts to Fairchild Republic, North American Rockwell, and McDonnell Douglas for the definition phase in December 1968. The companies submitted technical proposals by June 1969. The Air Force announced the selection of McDonnell Douglas on 23 December 1969. The winning design resembled the twin-tailed F-14, but with fixed wings. It would not be significantly lighter or smaller than the F-4 that it would replace.

     

    Front view of an F-15C. Note the conformal FAST PACK fuel tanks on the trailers

    General characteristics

    Performance

    نوشته شده در یکشنبه ششم مرداد 1392ساعت 22:25 توسط aryan jamshidi|

     

    Interesting Facts About The International Space Station

     

     
    Russian solar arrays, backlit by sunset.
    mounted pairs of USOS solar arrays
     
     
     

    350 kilometers up in space orbits the The International Space Station (ISS). It was launched back in 1998 and it’s been the home of astronauts since, making it one the longest uninterrupted human space flight mission to date. It beat the old record of almost 10 years (or 3,634 days) held by the Russian space station Mir. It is definitely an interesting place, and today we’re going to bring 10 interesting facts about the ISS.

     

    A side-on view of the ISS showing a Space Shuttle docked to the forward end, an ATV to the aft end and Soyuz & Progress spacecraft projecting from the Russian segment.

     

    The ISS is a joint project of 5 space agencies which include US space agency NASA, Russian Federal Space Agency (RKA), Japan Aerospace Exploration Agency (JAXA), European Space Agency (ESA) and the Canadian space agency (CSA). Over a 100,000 people across the world have collaborated to make the ISS possible.

     

    3rd Brightest Object In The Night Sky

     

    As the ISS passes over head, it sometimes captures sunlight which makes the ISS shine really bright. It’s the 3rd brightest object in the night sky, the only things brighter than the ISS are the Sun and the Moon. It has an apparent magnitude (a measure of how bright things are in the sky) of -5.6, Venus, which is the brightest planet in the night sky, has an apparent magnitude just below -5.

    You Can See It From Earth

     

    The ISS is visible to 90% of the population. You can go out and see it! There are plenty of websites and astronomy apps out there that let you know when the ISS is going to make a visible pass in your area, and help you track the current location of the ISS.

    Solar Power

    The International Space Station gets all its energy from the Sun. Its got over 250,000 solar cells that provide. Laid side-to-side the solar panels span an acre, and they can generate up to 110 killowatts -that’s enough to power 55 homes.

    Multiple Sunsets

     

    Since the ISS orbits the earth at a speed of 7 km/s, it takes it around 90 minutes to complete one orbit. Astronauts on-board the ISS can see the sunrise 16 times and watch the sunset 17 times.

    The Price Tag

     

    It’s estimated that the ISS cost around $100 billion to complete, making the ISS the most expensive single object ever built. The price comes close the entire amount of money spent on the Apollo moon missions.

    700,000 Images Downloaded Every Month

    700,000 images are downloaded every month by teachers, students and scientists from “The Gateway to Astronaut Photography of Earth”, NASA’s website that hosts all the images taken by the astronauts on the ISS. They issue a weekly top 10 list, you can go ahead and check it out here.

    Dodging Bullets

    There’s tons of space debris out in orbit, and the ISS has to constantly watch out for that. NASA keeps track of all space debris in the Space Station’s path, and keeps the astronauts alert about possible hazards. If things get tight, the astronauts are prepared to escape in a Soyuz capsule. The hazardous environment in orbit makes the ISS a dangerous place to work for scientists and astronauts.

    Mir-2

    The International Space Station is based on Mir 2, successor of the Mir Space Station, that was in development back in 1976. Some of the modules used in the ISS were originally designed for the Mir-2. The Zvezda module was originally designed to be the core of Mir-2.

    You can Spend A Week In The ISS

    Space Adventures is a company that sends civilians into space for a premium price: $20-30 million. That’s correct, if you could afford the insane price tag, you could  go to the International Space Station. So far, only 7 civilians have gone to the Space Station. Dennis Tito was the first civilian in space, he spent eight days in orbit on-board the ISS.

     

    A short, cylindrical module, covered in white insulation, suspended in space on the end of a white robotic arm. A smaller white cylinder is attached at one end, and a folded square radiator is mounted at the other. Antennas and poles project from the module, and the Earth forms the backdrop.
    The Cupola's design has been compared to the Millennium Falcon from the motion picture Star Wars.
    Dmitri Kondratyev and Paolo Nespoli in the Cupola. Background left to right, Progress M-09M, Soyuz TMA-20, the Leonardo module and HTV-2.

    If you can’t afford a trip to the ISS, you can at least own a cool scale model of the International Space Station on Amazon

    نوشته شده در پنجشنبه بیستم تیر 1392ساعت 21:57 توسط aryan jamshidi|

    Why is the Sky Blue

     

    When you look up to the sky on a clear and sunny day, you see that the sky appears bright blue.  You become mesmerized by its beauty and start to ask yourself why the sky is blue.  But as the day passes and sunset arrives, you look up and see that the bright blue sky has turned into a combination of reds, oranges, and pinks.  Why is that?  What makes the sky blue?

    Before we can explain the answer to you, there are some basic things you have to know about the colors of light, light waves and the atmosphere in order to understand the reason why the sky is blue.

    Colors of Light

    Light is actually composed of several colors, and not just white.  You can see the different colors by using a prism to split the light.  If you don’t have a prism, just look up when you see a rainbow and you can see that light is actually a combination of red, blue, green, yellow, violet, and many more.

    All these colors have different frequencies, wavelengths, and energies.  In the visible spectrum, violet has the shortest wavelength, meaning it has the highest frequency along with energy.  Red, on the other hand, has the longest wavelength, lowest frequency and lowest energy.

    Light Waves

    Light is a type of energy that travels or radiates in waves. Their energy depends on two things: its frequency and its wavelength.  Frequency is the total number of light waves that pass by for every second, while wavelength is the distance amid the crests or tops of the waves.  They are indirectly proportional, meaning the longer the wavelength, the lower the frequency and the less energy it possesses.

    Why is the Sky Blue

    They sky is blue because of Rayleigh scattering.  The molecules in the atmosphere scatter the different wavelengths of light coming from the sun.  Air molecules like nitrogen and oxygen molecules reflect those with shorter wavelengths like violet, blue or green much better than the longer wavelengths like red, orange or yellow.  That is why wherever you look in the sky, you can see scattered blue light overhead.

    نوشته شده در پنجشنبه بیستم تیر 1392ساعت 21:9 توسط aryan jamshidi|

    خوب سلام

    امروز میخوام با یک خاصیت مواد درآیرودینامیک آشناتون کنم

    به تایپ کردنش میرزه

    تا بحال فکر کردید که چرا وقتی دستتون رو توی آب فرو میبرید دستتون خیس میشه؟

    یا چرا بادبادک ها در ارتفاع نزدیک زمین باید بکشیدش تا بالا بره اما وقتی که یه اندازه بالا رفت دیگه نیاز به کشیدن نداره و خود به خود اوج میگیره؟

    اینا همش بر میگرده به خاصیت ویژه ای در سیالات به نام ویسکوزیته.

    در حقیقت وقتی دستتون رو توی آب فرو میبرید آب به دستتون میچسبه

    اگه بخوایم ی معادل فارسی برای ویسکوزیته بگیم بیشتر به چسبندگی شباهت داره

    آب با خاصیت ویسکوزیته ای که داره به دستتون میچسبه

    این خاصیت در مورد هوا هم وجود داره

    هوای نزدیک زمین میشه گفت که به زمین چسبیده و ساکنه پس برای بلا رفتن بادبادک باید بهش نیرو وارد کنید، هرچه که از زمین فاصله میگیریم چسبندگی کمتره و هوا جریان داره و بادبادک در هوای جریان دار ارتفاع اوج میگیره

    در بدن انسان هم همینطوره ، هوا به بدن انسان در لایه های نزدیک به پوست میشه گفت که چسبیده و ساکنه

    وقتی که انسان سردش میشه دیدید که موهای بدنش سیخ میشه

    در حقیقت خدای بزرگمون از ویسکوزیته برای گرم نگه داشتن بدن انسان استفاده میکنه

    موهای بدنتون سیخ میشه تا لایه هوایی رو که بدن چسبیده هم بیشتر کنه و به دام بندازه و اطراف بدن این لایه هوای گرم رو نگه داره و هم اینکه انتقال حرارتی رو بین این لایه و هوای عبوری کمتر کنه تا ما دیرتر سردمون بشه

    دنیا و هر نفسی که میکشیم پر از شگفتی و نمایش قدرت خداوند بزرگه

    کاش بیشتر بدونیم

    بدونیم که چی هستیم و کجاییم

    نوشته شده در چهارشنبه دوازدهم تیر 1392ساعت 20:26 توسط aryan jamshidi|

    آیا میدانید به همراه یك صندلی اجكت(صندلی نجات خلبان هواپیمای جنگنده) چه چیزهایی وجود دارد؟

     

    - شكلات.

    3-یك كلت.

    4-یك كلت منور.

    5- یك قایق بادی مخصوص دراپ در آب.

    6-یك قلاب ماهی گیری.

    7-یك دستگاه شبیه كباب پز برای طبخ غذا.

    8-یك پودر مخصوص كه اگر خلبان در آب دراپ كند با ریختن آن پودر كوسه ها دور می شوند.

    9-بسته ی كمك های اولیه.

    10-چاقوی معروف و بسیار تیز MC 1 كه حتی قادر به بریدن مفتول فلزی می باشد.

    11-آینه برای علامت دادن در روز.

    12-یك تشك بادی كه اگر خلبان بالای جنگل دراپ كند.این تشك اطراف بدن او را می پوشاند تا به خلبان آسیبی نرسد.

    13-قرص تصفیه آب

    معروف ترین شركت سازنده ی صندلی اجكت شركت Martin Backer می باشد.

    نوشته شده در چهارشنبه پنجم تیر 1392ساعت 23:22 توسط aryan jamshidi|

    دانستني‌هاي جالب درباره كره زمين

     

    خورشيد را 9 سياره احاطه كرده‌اند كه در بين آنها كره زمين از نظر فاصله با خورشيد، سومين كره است و از چهار سياره داخلي بزرگ‌تر است.

    از پنج سياره بيروني، چهار تاي آنها از كره زمين بزرگ‌تر هستند. زمين در مداري گردش مي‌كند كه هيچ وقت از 5/91 ميليون مايل به خورشيد نزديك‌تر نمي‌شود و از 5/94 ميليون مايل دورتر نمي‌شود.

    جالب‌تر اينجا است كه اين مدار تقريباً دايره مانند است و اگر غير از اين بود زندگي روي كره زمين غير ممكن مي‌شد زيرا حيوانات و گياهان در زمستان از سرما يخ مي‌زنند و در تابستان از گرما كباب مي‌شدند. ‏

    زمين در مقايسه با كائنات يك كره جوان و جديد است با اين حال زمين حدود 5/4 هزار ميليون سال عمر دارد. كشف اين موضوع از بررسي‌هاي انجام شده توسط راديواكتيو كه در تعيين عمر سنگ‌ها از آن استفاده مي‌شود، به دست آمده است.

    تمامي عناصر راديواكتيو همانند اورانيوم كه براي عكس العمل تعيين شده به كار مي‌رود، به عناصر مختلف در ميزان ثابتي، تغيير شكل مي‌دهند.

    به وسيله اندازه گرفتن اين دو، يعني مقدار عنصر راديواكتيو اصلي و عنصر راديواكتيو تغيير شكل يافته، مي‌توان عمر تشكيل سنگ را حساب كرد. قديمي‌ترين سنگ‌هايي كه تا كنون به دست آمده‌اند حدود 3 هزار ميليون سال عمر داشته‌اند ولي به طور يقين زمين سال‌هاي طولاني قبل از اين كه سطح سنگ‌ها شروع به تشكيل يافتن كنند، وجود داشته است. ‏

    اگر چه ستاره شناسان و سياره شناسان چندين تئوري درباره چگونگي بوجود آمدن زمين و بقيه سيارات منظومه شمسي ارائه داده‌اند ولي هنوز شك و ترديد فراواني در رابطه با مبدأ تشكيل زمين وجود دارد.

    هر كدام از اين تئوري‌ها بايد شامل اين واقعيت باشد كه تمامي سياره‌هاي بزرگ‌تر در مدار دايره مانندي در اطراف خورشيد گردش مي‌كنند و اين مدارها تقريباً در يك سطح نزديك هم قرار مي‌گيرند. حقيقت ديگري كه بايد توضيح داده شود اين است كه تمامي كرات در يك جهت به دور خورشيد مي‌چرخند و آن در جهتي است كه خورشيد به تناوب دور مي‌زند.

    حتي عجيب‌تر اين كه فاصله كرات مختلف از خورشيد از نظر رياضي به وسيله يك معادله ساده با هم نسبت دارند و به نام قانون «باد» ناميده مي‌شود. البته ممكن است اين فقط يك تصادف و اتفاق باشد يا احتمال دارد رابطه با مبدأ اصلي منظومه شمسي داشته باشد. ‏

    در اينجا دو تئوري اصلي به وجود مي‌آيد يكي اين كه يك رشته طولاني از بخار داغ به وسيله نيروي جاذبه سياره ديگري كه از نزديكي خورشيد مي‌گذشته از خورشيد جدا شده و پايين افتاده است سپس به تدريج بخار داغ، خنك و منقبض شده و تبديل به گلوله‌هاي جامدي شده است كه همان كرات هستند.

    تئوري ديگر كه احتمال بيشتري دارد عبارت است از اين كه در اصل يك توده بخار و غبار وجود داشته كه در حال چرخش دايره مانند بوده است.

    چرخش‌ها و گردبادهاي اين توده تكامل حاصل كرده و هسته‌هاي مركزي كرات ايجاد شده است. هر كدام از اين هسته‌ها به تدريج بزرگ‌تر شدند زيرا نيروي جاذبه آنها هر زمان بيشتر و بيشتر اجسامي را كه در فضاي لايتناهي اطرافشان پراكنده بودند به طرف خود جذب مي‌كردند.

    خورشيد در مركز اين دايره‌اي كه بخار و غبار به صورت ابر تيره در آمده واقع شده بود، زمين يكي از گرد بادها بوده است.‏

    كره زمين با سرعت 5/18 مايل در ثانيه به دور خورشيد در حال حركت است. همانند تمامي اجسام ديگري كه در مدارهاي هيأت، حركت و راهشان از قوه ميل به مركز پيروي مي‌كنند درست همانند پوست حلزون بسيار بزرگي كه روي يك نخ نامريي قرار داشته باشد.

    همان طور كه كره دور مي‌شود نيروي ميل به مركز به وسيله كشش نيروي جاذبه زمين بين خورشيد و كره زمين ايجاد مي‌شود. اگر كره زمين از دور زدن باز بايستد روي خورشيد سقوط خواهد كرد. ‏

    خوشبختانه در فضا بخار آن قدر وجود ندارد كه گردش زمين را آهسته كند و فقط از اندازه مدار زمين به طور بسيار ملايمي كاسته مي‌شود.‏

    زمين در فضا به شكل مارپيچ در حال حركت است به علاوه اين كه كره زمين از مغرب به مشرق روي محور خودش هر بيست و چهار ساعت يك بار مي‌چرخد.‏‎ ‎اندازه گيري‌هاي جديد صورت گرفته نشان مي‌دهند كه محور شمالي جنوبي كره زمين جنبش نسبتاً مختصر و نامنظمي دارد. همچنين ساعت‌هاي بسيار دقيق نشان مي‌دهند كه طول روزها به طور بسيار ملايمي تغيير مي‌كند.

    البته به عقيده بسياري از صاحب نظران اين طولاني شدن ملايم روزها به دليل زياد شدن جزر و مدهاي انرژي محرك گردش زمين است. البته اساس جزر و مدهاي دريا به واسطه كشش نيروي جاذبه ماه است.‏

    خوشبختي بشري كه روي زمين زندگي مي‌كند در اين است كه زمين تندتر نمي‌چرخد وگرنه وقتي كه نيروي گريز از مركز از نيروي جاذبه بيشتر مي‌شد زمين و تمامي متعلقاتش در فضا پخش مي‌شدند. ‏

    يك نكته جالب در مورد زمين اين است كسي كه روي خط استوا زندگي مي‌كند در واقع از كسي كه در هر يك از قطب‌هاي زمين است تندتر حركت مي‌كند. حركت زمين در خط استوا تندتر از دو قطب است.‏

    اندازه گيري‌هايي كه روي حركت و جنبش ستاره‌هاي كوچك مصنوعي كه به وسيله راكت به فضا پرتاب شده‌اند نشان مي‌دهند كه نه فقط زمين در دو قطب كمي پهن‌تر است بلكه كمي هم به شكل گلابي است.

    زمين يگانه كره‌اي است كه روي آن اقيانوس وجود دارد و داراي هوايي به نسبت چهار پنجم ازت و يك پنجم اكسيژن است. همچنين زمين شامل هسته مركزي مذابي است به قطر 3 هزار مايل و به طور قطع حرارت مركز آن چندين هزار درجه سانتي گراد است.

    به احتمال زياد قسمت بزرگي از اين حرارت از راديواكتيو معادن داخل زمين حاصل مي‌شود.‏

    قشر زمين يا ورقه رويي آن حدود 25 مايل ضخامت دارد. فاصله بين قله اورست تا «مارياناز ترانش» گودترين نقطه اقيانوس آرام، حدود 12 مايل است و نيز تقريباً 78 درصد سطح زمين از آب پوشيده شده است.‏

    نوشته شده در چهارشنبه پنجم تیر 1392ساعت 22:53 توسط aryan jamshidi|

    مطلب مهمی که باید در مورد جعبه سیاه بگم اینه که این جعبه هرگز سیاه رنگ نبوده

    در آغاز سفید بوده و امروزه به رنگ قرمز یا نارنجی هست تا زودتر و بهتر شناسایی و پیدا بشه

    An example of a flight data recorder; the underwater locator beacon is the small cylinder on the far right. (English translation of warning message: FLIGHT RECORDER DO NOT OPEN)

     

    در هر هواپیما، دو دستگاه ویژه وجود دارد که جزئیات لحظه به لحظه پرواز و مکالمات جاری در کابین خلبان را ثبت می‌کنند. این دو وسیله در جعبه‌های فولادی مخصوصی قرار دارند که به آنها «جعبه سیاه» می‌گویند.

     داخل جعبه‌های سیاه را با موادی عایق‌بندی می‌کنند که تا 1000 درجه گرما را می‌توانند تحمل کنند. ضربه نیز بر این جعبه‌ها تاثیر نمی‌گذارد و آب تا مدتی قابل توجه، به درون آنها نفوذ نمی‌کند.

     جعبه مربوط به ثبت جزئیات پرواز در قسمت دم هواپیما جای دارد- در صورت بروز هر حادثه هوایی یا سقوطی، دم امن‌ترین قسمت هواپیماست. این دستگاه دمای داخل هواپیما، شتاب و جهت پرواز، صدای موتورها، جهت و سرعت وزش باد، ارتفاع پرواز و بسیاری از مشخصات فنی دیگر را هر لحظه ثبت می‌کند.

    مکالمات داخل کابین خلبان، صدای انفجار و صداهای ناشی از هر واقعه دیگری در هواپیما را نیز دستگاه دوم ثبت می‌کند. به این ترتیب، اگرهواپیما دچار حادثه‌ای شود، اختلالی فنی در آن بروز کند. انفجاری در آن صورت گیرد، سقوط کند یا مورد حمله هواپیما ربایان قرار گیرد، با بررسی اطلاعات ضبط شده در جعبه سیاه می‌توان علت وقوع حادثه و سیر جریان‌های رخ داده در هواپیما را بررسی کرد.

    البته جعبه سیاه به هیچ وجه سیاه نیست. بلکه رنگ قرمز روشنی دارد تا پیدا کردن آن در محل حادثه آسان‌تر باشد.

    جعبه سیاه یا ضبط کننده اطلاعات پرواز (به انگلیسی: Flight data recorder یا FDR) در هواپیما ابزاری است که در طول پرواز جهت ذخیره پارامترهای خاصی به کار می‌رود. در بعضی از موارد جعبه سیاه شامل ضبط کننده صدای خلبان (CVR) است.

    با بروز هر سانحه‌ای برای یک هواپیما سوالات زیادی در مورد علت سقوط هواپیما مطرح می‌شود. پاسخ به این سوالات به کمک سیستم‌های FDR و CVR که در مجموع جعبه سیاه نامیده می‌شود، انجام می‌گیرد. این سیستم‌ها که هر یک قیمتی بین ۱۰ تا ۱۵ هزار دلار دارند، جزئیات پرواز را در طول پرواز ضبط می‌کنند.

    سیستم جعبه سیاه علی‌رغم آنچه از نامش پیداست، رنگ نارنجی روشنی دارد. داشتن چنین رنگ شاخصی به همراه نوار انعکاس دهنده متصل شده به بخش خارجی ضبط کننده بعد از وقوع سانحه در پیدا کردن جعبه سیاه بخصوص در هنگام سقوط هواپیما در آب، بسیار موثر است.

    جعبه‌های سیاه معمولاً اطلاعات ۲۵ ساعت آخر پرواز را ضبط می‌کنند. جعبه‌های سیاه قدیمی‌تر از نوارهای مغناطیسی که همانند نوار ضبط صوت عمل می‌کنند، با استفاده از هد الکترومغناطیسی به ثبت اطلاعات می‌پردازند. از سال ۱۹۹۰، سازندگان سیستم جعبه سیاه به سمت استفاده از تکنولوژی‌هایی پیش رفته‌اند که در آن قطعهٔ متحرک وجود نداشته باشد، و جعبه‌های سیاه مدرن بجای نوارهای مغناطیسی بکار رفته در نوع متوسط آن از تراشه‌های حافظهٔ الکترونیکی استفاده می‌کنند.

    جعبه سیاه پارامترهای پروازی را ضبط می‌کند. حساسه‌های زیادی از قسمتهای مختلف هواپیما از طریق سیم‌کشی به سیستم FDR مرتبط شده‌اند. زمانی که کلیدی روشن یا خاموش می‌شود، عملیات آن توسط سیستم FDR به ثبت می‌رسد. کمیت و بازه اطلاعات ضبط شده توسط این سیستم به میزان زیادی متفاوت بوده و به عمر و اندازه هواپیما وابسته است. طبق استانداردهای هوایی حداقل اطلاعاتی که باید توسط این سیستم ضبط شود شامل موارد زیر است :

    • زمان
    • شتاب عمودی هواپیما
    • موقعیت دستهٔ کنترل پرواز
    • موقعیت پدال کنترل رادِر
    • موقعیت فرمان هواپیما
    • تثبیت کننده وضعیت افقی هواپیما
    • جریان سوخت
    • سرعت
    • ارتفاع فشاری
    • جهت مغناطیسی هواپیما
    • شتاب طبیعی هواپیما
    • روشن و خاموش شدن میکروفون، که زمان ارتباطهای رادیویی برقرار شده توسط خدمه را ضبط می‌کند، و برای تطبیق اطلاعات ضبط شده توسط FDR و CVR بکار می‌رود. سیستم‌های کنونی به منظور بررسی تمامی جهات عملکردی هواپیما تا صدها پارامتر را ضبط می‌کنند.

     flight data recorder -FDR

    A flight data recorder (FDR) (also ADR, for accident data recorder) is an electronic device employed to record any instructions sent to any electronic systems on an aircraft. It is a device used to record specific aircraft performance parameters. Another kind of flight recorder is the cockpit voice recorder (CVR), which records conversation in the cockpit, radio communications between the cockpit crew and others (including conversation with air traffic control personnel), as well as ambient sounds. In this both functions have been combined into a single unit. The current applicable FAA TSO is C124b titled Flight Data Recorder Systems.

    Popularly referred to as a "black box" by the media, the data recorded by the FDR is used for accident investigation, as well as for analyzing air safety issues, material degradation and engine performance. Due to their importance in investigating accidents, these ICAO-regulated devices are carefully engineered and stoutly constructed to withstand the force of a high speed impact and the heat of an intense fire. Contrary to the "black box" reference, the exterior of the FDR is coated with heat-resistant bright orange paint for high visibility in wreckage, and the unit is usually mounted in the aircraft's empennage (tail section), where it is more likely to survive a severe crash. Following an accident, the recovery of the FDR is usually a high priority for the investigating body, as analysis of the recorded parameters can often detect and identify causes or contributing factors

    Design

    The design of today's FDR is governed by the internationally recognized standards and recommended practices relating to flight recorders which are contained in ICAO Annex 6 which makes reference to industry crashworthiness and fire protection specifications such as those to be found in the European Organisation for Civil Aviation Equipment.documents EUROCAE ED55, ED56 fiken A and ED112 (Minimum Operational Performance Specification for Crash Protected Airborne Recorder Systems). In the United States, the Federal Aviation Administration (FAA) regulates all aspects of U.S. aviation, and cites design requirements in their Technical Standard Order, based on the EUROCAE documents (as do the aviation authorities of many other countries).

    After the crash of Gol Transportes Aéreos Flight 1907, Brazilian Air Force personnel recover the flight data recorder of PR-GTD, the Boeing 737-8EH used for the flight, in the Amazon Rainforest in Mato Grosso, Brazil.
     

    Currently, EUROCAE specifies that a recorder must be able to withstand an acceleration of 3400 g (33 km/s²) for 6.5 milliseconds. This is roughly equivalent to an impact velocity of 270 knots (310 mph) and a deceleration or crushing distance of 450 cm. Additionally, there are requirements for penetration resistance, static crush, high and low temperature fires, deep sea pressure, sea water immersion, and fluid immersion.

    Modern day FDRs receive inputs via specific data frames from the Flight Data Acquisition Units (FDAU). They record significant flight parameters, including the control and actuator positions, engine information and time of day. There are 88 parameters required as a minimum under current U.S. federal regulations (only 29 were required until 2002), but some systems monitor many more variables. Generally each parameter is recorded a few times per second, though some units store "bursts" of data at a much higher frequency if the data begins to change quickly. Most FDRs record approximately 17–25 hours worth of data in a continuous loop. It is required by regulations that an FDR verification check (readout) is performed annually in order to verify that all mandatory parameters are recorded.

    This has also given rise to flight data monitoring programs, whereby flights are analyzed for optimum fuel consumption and dangerous flight crew habits. The data from the FDR is transferred, in situ, to a solid state recording device and then periodically analyzed with some of the same technology used for accident investigations. In other cases the data is downloaded from the aircraft's Quick Access Recorder (QAR), either by transfer to a portable solid state recording device or by direct upload to the operator's headquarters via radio or satellite.

    FDRs are usually located in the rear of the aircraft, typically in the tail. In this position, the entire front of the aircraft is expected to act as a "crush zone" to reduce the shock that reaches the recorder. Also, modern FDRs are typically double wrapped, in strong corrosion-resistant stainless steel or titanium, with high-temperature insulation inside. They are usually bright orange. They are designed to emit an underwater locator beacon for up to 30 days, and can operate immersed to a depth of up to 6,000 meters (20,000 ft)

    نوشته شده در جمعه سی و یکم خرداد 1392ساعت 16:7 توسط aryan jamshidi|


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