A Free Template from Joomlashack

A Free Template from Joomlashack

แบบสำรวจ

ท่านกำลังใช้ระบบปฏิบัติการ (OS) อะไรอยู่ ?
 

Search

ผู้เข้าเว็บขณะนี้

เรามี 64 บุคคลทั่วไป ออนไลน์
The Danger of Space Junk PDF พิมพ์ อีเมล
เขียนโดย Administrator   
วันพุธที่ 20 เมษายน 2016 เวลา 08:22 น.

Space  Junk

Space  Junk

 
 
 
 





 

 

          Space  junk is the collection of defunct man-made objects in space – old satellites, spent rocket stages, and fragments from disintegration, erosion, and collisions – including those caused by debris itself.
 
 
 
As of July 2013, there are over 170 million debris smaller than 1 cm (0.4 in). From one to ten cm at ~670,000, larger debris at 29,000. As of 2009, 19,000 debris over 5 cm (2 in) are tracked. Below 2000 km debris are denser than meteoroids; mostly dust from solid rocket motors, surface erosion debris like paint flakes, and frozen coolant from RORSAT nuclear-powered satellites. They cause damage akin to sandblasting, especially to solar panels and optics like telescopes or star trackers that can not be covered with a ballistic Whipple shield (unless it is transparent).
 
 
For comparison, the International Space Station orbits in the 300–400 kilometres (190–250 mi) range and the 2009 satellite collision and 2007 antisat test occurred at 800 to 900 kilometres (500 to 560 mi). The ISS has Whipple shielding, however known debris with a collision chance over 1/10000 are avoided by maneuvering the spacecraft.
 
 
Beyond a critical density, Kessler syndrome ensues — a runaway chain reaction of collisions exponentially increasing the amount of debris. This affects useful polar-orbiting bands, increases the cost of protection for missions and destroys live satellites. Whether it is already underway is debated. The measurement, mitigation and potential removal of debris are conducted by some participants in the space industry.

 
 
Space  Junk

 

 
 

 Size

 

There are over 170 million pieces of debris smaller than 1 cm (0.39 in) as of July 2013. There are approximately ~670,000 pieces from one to ten cm. The current count of large debris (defined as 10 cm across or larger[5]) is 29,000. The technical measurement cutoff is ~3 mm (0.12 in). Over 98 percent of the 1,900 tons of debris in low Earth orbit (as of 2002) was accounted for by about 1,500 objects, each over 100 kg (220 lb). Total mass is mostly constant despite addition of many smaller objects, since they reenter the atmosphere sooner. Using a 2008 figure of 8,500 known items, it is estimated at 5,500 t (12,100,000 lb).
 
 
 
 
 
 
 

Low Earth orbit


In LEO there are few "universal orbits" which keep spacecraft in particular rings (in contrast to GEO, a single widely used orbit). The closest are sun-synchronous orbits that keep a constant angle between the Sun and the orbital plane; they are polar, meaning they cross over the polar regions. LEO satellites orbit in many planes, up to 15 times a day, causing frequent approaches between objects (the density of objects is much higher in LEO).
 
 
 
Orbits are further changed by perturbations (which in LEO include unevenness of the Earth's gravitational field), and collisions can occur from any direction. For these reasons, the Kessler syndrome applies mostly to the LEO region; impacts occur at up to 16 km/s (twice the orbital speed) if head-on - the 2009 satellite collision occurred at 11.7 km/s, creating much spall in the critical size range. These can cross other orbits and lead to a cascade effect. A large-enough collision (e.g. between a space station and a defunct satellite) could make low Earth orbit impossible.
 
 
Manned missions are mostly at 400 km (250 mi) and below, where air drag helps clear zones of fragments. Atmospheric expansion as a result of space weather raises the critical altitude by increasing drag; in the 90s, it was a factor in reduced debris density. Another was fewer launches by Russia; the USSR made most of the launches in the 1970s and 1980s.
 

 
 

 


 Space  Junk
 
 

Higher altitudes

 

 
At higher altitudes, where air drag is less significant, orbital decay takes longer. Slight atmospheric drag, lunar perturbations, Earth's gravity perturbations, solar wind and solar radiation pressure can gradually bring debris down to lower altitudes (where it decays), but at very high altitudes this may take millennia. Although high-altitude orbits are less commonly used than LEO and the onset of the problem is slower, the numbers progress toward the critical threshold more quickly.
 
 
 
Many communications satellites are in geostationary orbits (GEO), clustering over specific targets and sharing the same orbital path. Although velocities are low between GEO objects, when a satellite becomes derelict (such as Telstar 401) it assumes a geosynchronous orbit; its orbital inclination increases about .8° and its speed increases about 100 miles per hour (160 km/h) per year. Impact velocity peaks at about 1.5 km/s (0.93 mi/s). Orbital perturbations cause longitude drift of the inoperable spacecraft and precession of the orbital plane. Close approaches (within 50 meters) are estimated at one per year. The collision debris pose less short-term risk than from an LEO collision, but the satellite would likely become inoperable. Large objects, such as solar-power satellites, are especially vulnerable to collisions.
 
 
 
Although the ITU now requires proof a satellite can be moved out of its orbital slot at the end of its lifespan, studies suggest this is insufficient. Since GEO orbit is too distant to accurately measure objects under 1 m (3 ft 3 in), the nature of the problem is not well known. Satellites could be moved to empty spots in GEO, requiring less maneuvering and making it easier to predict future motion. Satellites or boosters in other orbits, especially stranded in geostationary transfer orbit, are an additional concern due to their typically high crossing velocity.
 
 
 
 
 
Despite efforts to reduce risk, spacecraft collisions have occurred. The European Space Agency telecom satellite Olympus-1 was struck by a meteoroid on 11 August 1993 and eventually moved to a graveyard orbit. On 24 July 1996 Cerise, a French microsatellite in a Sun-synchronous LEO, was hit by fragments of an Ariane-1 H-10 upper-stage booster which had exploded in November 1986. On 29 March 2006, the Russian Express-AM11 communications satellite was struck by an unknown object and rendered inoperable;   its engineers had enough contact time with the satellite to send it into a graveyard orbit.
 
 

 
 
 
 
From Wikipedia, the free encyclopedia
 
 
 

The Danger of Space  Junk

The Danger of Space  Junk 

 

 

 

 

 BBC Horizon  The Trouble with Space Junk (Part 1)

 

 

           In 2014, the International Space Station had to move three times to avoid lethal chunks of space debris and there is an increasing problem of satellites mysteriously breaking down. With first-hand accounts from astronauts and experts, Horizon reveals the scale of the problem of space junk. Our planet is surrounded by hundreds of millions of pieces of junk moving at 17,000 miles per hour. Now the US government is investing a billion dollars to track them, and companies around the world are developing ways to clear up their mess - from robot arms to nets and harpoons. Horizon investigates the science behind the hit film Gravity and discovers the reality is far more worrying than the Hollywood fiction.

 

 

 

 The International Space Station

 





 

BBC Horizon  The Trouble with Space Junk (Part 2)

 

           Killer Space Junk In 2014 the International Space Station had to move three times to avoid lethal chunks of space debris, while satellites are mysteriously breaking down. With first-hand accounts from astronauts and experts, Killer Space Junk reveals the scale of the problem of space junk. Our planet is surrounded by hundreds of millions of pieces of junk moving at 17 000 miles per hour. Now the US government is investing a billion dollars to track them, and companies around the world are developing ways to clear up their mess – from robot arms, to nets, to harpoons.

 

 

 

 

 
 
 
 


  
แก้ไขล่าสุด ( วันเสาร์ที่ 14 พฤษภาคม 2016 เวลา 08:03 น. )
 

คอมเมนต์คอมเมนต์  

 
0 #157 Kandice 2019-07-18 08:02
You are sso interesting! I do not think I have
read something like this before. So gooid to find somebody
with genuine thoughts on this topic. Really.. many thanks for starting this up.
This website is one thing that is required on the web, sojeone with some originality!


My page ... alt mandiriqq: http://mandiriqq.host
อ้างอิง
 
 
0 #156 Darlene 2019-07-17 14:33
Hello, yes this post is genuinely pleasant and I have
learned lot of things from it regarding blogging. thanks.


My web blog: alt pokerpelangi: http://indopokerpelangi.com
อ้างอิง
 
 
0 #155 Gordon 2019-07-17 13:38
The Ball of Whacks contains 30 "Whack pieces" which they
can use to generate a variety of shapes. How
do you think definitely will feel about it? The new version is expected to aunch
in the fall, for around $50.

Stop by my weblog: 918kiss software: http://www.circuito.ws/__media__/js/netsoltrademark.php?d=superslot.app
อ้างอิง
 
 
0 #154 Calvin 2019-07-14 04:58
Use internet sites carefully bby using all the safety rules.
Yes, onlline trading can be higyly highly effective. You can make room for more displays by
applying retail dispplay systems since ggridwall or slatwall.


my web blog: mobile slot game: https://medicine.ekmd.huji.ac.il/En/publications/Publications/Pages/Abstract.aspx?pid=11656&src=http://918kiss.poker/casino-games/74-ace333
อ้างอิง
 
 
0 #153 Carina 2019-07-13 15:38
Except it a lot easier if he continues single. Shopping
at Kiddie Book Online just isn't easy but comparatively cheap also.

Because Landing Tours are much more time consuming,
a cost-free lunch is included.

Look at my blog; live poker stream: http://www.kartaly.surnet.ru/?a%5B%5D=%3Ca+href%3Dhttps%3A%2F%2Fkslot.app%2Findex.php%2Fgames%2Fntc33%3Entc33%3C%2Fa%3E
อ้างอิง
 
 
0 #152 Corine 2019-07-12 11:55
Earlier search engines had regarding link structures alone.
It has been the #1 hottest-selling product 918kiss apk for pc: http://www.pabili.com/__media__/js/netsoltrademark.php?d=www.killerknuts.com%2Fgroups%2Ftop-ten-reasons-for-gambling-online-296132611%2F home based business final results.
Try it, can not regret.
อ้างอิง
 
 
0 #151 Johnny 2019-07-10 11:27
Communicatfe with them personally, whether always be on a second messenger service or on the telephone.
Initially ask yourself, whether you are good, reliable, honest, friendly or
hardworking person.

myweb page :: virgin live blackjack: http://C.H.Er.Ie.Mon.T.Gom.Er.Y.323.7.8@Ca.Ta.L.I.N.Al.Aws.On.01.7.5@kcns.kr/?a%5B%5D=%3Ca+href%3Dhttps%3A%2F%2F918kiss.poker%2Fcasino-games%2F68-ntc33-newton-casino%3Entc33%3C%2Fa%3E
อ้างอิง
 
 
0 #150 Edison 2019-07-09 23:46
Hi there, I want to subscribe for this website to take
latest updates, thus where can i do it please help out.

Look at my site; feel more
enjoyable: http://sopadipuhiqu.mihanblog.com/post/comment/new/55/fromtype/postone/fid/1496942118593986267ca13/atrty/1496942118/avrvy/0/key/efbcfe79ca88707d42ef22f85d5d3c7f/
อ้างอิง
 
 
0 #149 Derrick 2019-07-09 03:28
Doing so carefully and thouyghtfully will deliver you an ever-increasing
stream of visitors and profits. SEO is not easy and what makes it
doubly hard is the eever changing pace of things.
General items are harder to sell than niche items.


my web site: mega casino slots: http://918.credit/casino-games/mega888
อ้างอิง
 
 
0 #148 Valarie 2019-07-08 14:15
Thank you for every other excellent post. Where else may anybody get that type of information in such a perfect
way of writing? I've a presentation next week, and I am at the search for such information.

My web page :: kartupoker: https://viewbookmarks.com/story.php?title=becoming-a-texas-hold-em-shark
อ้างอิง
 
 
0 #147 Irma 2019-07-07 19:37
Wiill nott increase your odds of being described.

Run promotions on website running for prizes on regularly.
Forum marketing is a well-known strategy for ramping your current traffic.



Here is my blog post - sky 777: http://918.credit/downloads/88-download-sky777-for-android-and-ios
อ้างอิง
 

เพิ่มคอมเมนต์ใหม่

 


Joomla 1.5 Templates by Joomlashack