Featured Research

from universities, journals, and other organizations

The End Is Mir: Heaviest Thing Orbiting Our Planet Other Than The Moon Itself Returns To Earth

Date:
March 22, 2001
Source:
NASA/Marshall Space Flight Center
Summary:
When the space station Mir returns to Earth over the remote South Pacific this week, it will be big news. And rightly so. The 135-ton Russian outpost is the heaviest thing orbiting our planet other than the Moon itself. During its 15-year stint in space, Mir has set endurance and space-adventure records that are going to be hard to beat.

When the space station Mir returns to Earth over the remote South Pacific this week, it will be big news. And rightly so. The 135-ton Russian outpost is the heaviest thing orbiting our planet other than the Moon itself. During its 15-year stint in space, Mir has set endurance and space-adventure records that are going to be hard to beat.

But among scientists who monitor the near-Earth environment, an encounter with a 135 ton object from space is, well.... all in a day's work.

"Asteroids weighing as much as Mir hit Earth perhaps 10 times each year," says Bill Cooke, a member of the Space Environments team at the Marshall Space Flight Center's Engineering Directorate. "We know this because we observe the flashes of the explosions in the upper atmosphere via Department of Defense satellites."

Just last year a 200-ton asteroid startled Canadians with a sonic boom and a brilliant fireball as it disintegrated above the Yukon territory. Scientists later recovered a smattering of meteorites from nearby Lake Tagish, none larger than a few hundred grams.

"If a [rocky] asteroid with the same mass as Mir hit the ground it would explode like a few kilotons of TNT, gouging out a crater about the size of a football field," noted Cooke. However, Mir will never make it that close to the ground. As Cooke explained, "the atmosphere is very good protection and it breaks up meteorites and other space objects well before impact."

Indeed, if Mir were an asteroid, it wouldn't merit classification as a potentially hazardous one. In the cosmic scheme of things, Mir is simply too small.

Nevertheless, scientists expect the space station to put on a good show when it returns.

Mir is put together much like an erector set. It's a beautiful but gangly-looking assortment of solar arrays, laboratories and living quarters -- obviously not designed for aerodynamic flight through the atmosphere. The station will quickly fall apart as it descends toward Earth.

"We expect Mir to break into six or more main pieces when it hits the atmosphere," says Nicholas Johnson, chief scientist and program manager for orbital debris studies at NASA's Johnson Space Center. Each piece will resemble a blazing meteor that spits smaller fireballs as the pieces crumble and burn.

Cosmonauts assembled Mir piece-by-piece during a busy ten year period beginning in 1986. The station's modules include the voluminous Core, Mir's original 20-ton segment that harbors the crew's living quarters; plus Spektr, a 19-ton science laboratory famous for its 1997 collision with a Progress spacecraft; and the 19-ton Priroda Earth observatory, launched only five years ago.

Five of Mir's modules are still pressurized with air inside for humans. When they explode, sky watchers (mainly sea birds) could witness a once-in-a-lifetime display as incandescent fragments streak across the sky.

"Of Mir's 135 tons, the Russians say about 20 tons might reach the surface -- mostly in small pieces," noted Johnson.

Even now Mir is sinking 1.5 km each day because of atmospheric drag. Left to itself, the station would naturally plunge to Earth from its 250 km orbit no later than March 28th. But that would be an uncontrolled descent. Instead, Mir will be guided to its final resting place by a Progress spacecraft attached to the station.

On March 22nd Russian ground controllers plan to fire the Progress's engines when Mir is at apogee -- its greatest distance from Earth. "The engine firing will move perigee [Mir's closest approach to our planet] to a point inside the atmosphere over the south Pacific," explained Johnson. "That's where the station's fragments will land."

"With a controlled deorbit it doesn't matter if 20 tons or the whole 135 tons reaches the surface -- the risk to people or property should be essentially zero," says Johnson. Mir's descent is certainly safer than the many uncontrolled encounters we experience with Mir-weight asteroids each year.

No one knows more about dumping spacecraft in the remote Pacific than the Russians. Since 1978 they've deorbited 80 Progress spacecraft and five Salyut space stations in the same area. "Two Progress spacecraft have gone down there already this year," says Johnson. "Mir, which is attached to a Progress, will be the third."

"The most recent space station to descend over the Pacific was Salyut 6," he added. "That weighed 40 tons and came down in July of 1982. The deorbiting technique is exactly the same -- Mir's just a bit bigger."

Mir's dazzling finale won't be seen by many people, but perhaps that's just as well. The twenty tons of Mir-bits that scatter across the Pacific will be traveling 100 to150 mph when they reach the water -- a bit too fast for comfort!

Fortunately, there's still time to see Mir from the safety of your own back yard. The rapidly-moving space station reflects sunlight and if you're outside at the right moment -- usually near local dusk or dawn -- Mir will appear as bright as a streaking first or second magnitude star. Science@NASA's online satellite tracking utility, JPass written by Patrick Meyer, can tell you when and where to look (see: http://liftoff.msfc.nasa.gov/RealTime/JPass/20/).

Russia's fabled space station is easy to see, but don't wait --because the end of Mir ... is near.


Story Source:

The above story is based on materials provided by NASA/Marshall Space Flight Center. Note: Materials may be edited for content and length.


Cite This Page:

NASA/Marshall Space Flight Center. "The End Is Mir: Heaviest Thing Orbiting Our Planet Other Than The Moon Itself Returns To Earth." ScienceDaily. ScienceDaily, 22 March 2001. <www.sciencedaily.com/releases/2001/03/010322074514.htm>.
NASA/Marshall Space Flight Center. (2001, March 22). The End Is Mir: Heaviest Thing Orbiting Our Planet Other Than The Moon Itself Returns To Earth. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2001/03/010322074514.htm
NASA/Marshall Space Flight Center. "The End Is Mir: Heaviest Thing Orbiting Our Planet Other Than The Moon Itself Returns To Earth." ScienceDaily. www.sciencedaily.com/releases/2001/03/010322074514.htm (accessed July 25, 2014).

Share This




More Space & Time News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: ISS Cargo Ship Launches in Kazakhstan

Raw: ISS Cargo Ship Launches in Kazakhstan

AP (July 23, 2014) The Progress 56 cargo ship launched from the Baikonur Cosmodrome in Kazakhstan Wednesday. NASA says it will deliver cargo and crew supplies to the International Space Station. (July 23) Video provided by AP
Powered by NewsLook.com
Raw: Cargo Craft Undocks from Space Station

Raw: Cargo Craft Undocks from Space Station

AP (July 22, 2014) A Russian Soyuz cargo-carrying spacecraft undocked from the International Space Station on Monday. The craft is due to undergo about ten days of engineering tests before it burns up in the Earth's atmosphere. (July 22) Video provided by AP
Powered by NewsLook.com
NASA Ceremony Honors Moon Walker Neil Armstrong

NASA Ceremony Honors Moon Walker Neil Armstrong

AP (July 21, 2014) NASA honored one of its most famous astronauts Monday by renaming a historic building at the Kennedy Space Center in Florida. It now bears the name of Neil Armstrong, the first man to walk on the moon. (July 21) Video provided by AP
Powered by NewsLook.com
Neil Armstrong's Post-Apollo 11 Life

Neil Armstrong's Post-Apollo 11 Life

Newsy (July 19, 2014) Neil Armstrong gained international fame after becoming the first man to walk on the moon in 1969. But what was his life like after the historic trip? Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

    Health News

      Environment News

        Technology News



          Save/Print:
          Share:

          Free Subscriptions


          Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

          Get Social & Mobile


          Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

          Have Feedback?


          Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
          Mobile: iPhone Android Web
          Follow: Facebook Twitter Google+
          Subscribe: RSS Feeds Email Newsletters
          Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins