07 February 2017

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Explained Space Junk,Orbital Debris 1st attempt to clean space junk failed

Explained Space Junk or Orbital Debris First attempt to clean space junk failed
What is space junk or what is Orbital Debris

What is space junk or debris?
Space debris encompasses both natural (meteoroid) and artificial (man-made) particles. Meteoroids are in orbit about the sun, while most artificial debris is in orbit about the Earth. Hence, the latter is more commonly referred to as orbital debris.

Every time satellites collide, they create debris that then crashes with other debris to create even more debris, and so on. If these collisions progress unchecked, the amount of debris in low Earth orbit will make space travel a difficult task.

Orbital debris, or “space junk,” is anything manmade that’s orbiting around the Earth and is no longer being used, according to NASA. This includes old launch vehicles, spacecraft and even flecks of paint.

Orbital debris (duh-bree) is "junk" in space. It is pieces of spacecraft. Humans have been launching objects into space for more than 50 years.

Most of the "junk" has fallen back toward Earth. About once a day, something falls back to Earth. Some of these objects have landed on Earth. Since most of Earth's surface is water, objects usually fall there. Other objects burn up in the atmosphere. But many of the objects are still in orbit around Earth.

Debris can be as small as tiny flecks of paint from a spacecraft. Large debris could be satellites that are no longer working. A lot of orbital debris comes from explosions of objects in orbit. These are often parts of rockets.

How Big Is Orbital Debris?
On one extreme, debris can be as small as tiny flecks of paint or bits of metal that have come off spacecraft. On the other, large debris could be an entire satellite that is no longer working. The most common source of orbital debris larger than 1 centimeter (0.39 inches) is the explosion of objects orbiting Earth. These are often rocket upper stages. They can contain fuel or high-pressure fluids.

Why Is Orbital Debris Important?
Most "space junk" is moving very fast. It can reach speeds of 4.3 to 5 miles per second. Five miles per second is about 18,000 miles per hour. That's almost seven times faster than a bullet. Since it is moving so quickly, a tiny piece of orbital debris can cause a lot of damage. A piece of debris the size of a marble could hit as hard as a bowling ball going 300 miles per hour.

How Much Debris Is in Orbit?
Scientists keep track of the debris in orbit. They sort it by size. They have found about 13,000 objects bigger than a softball. Scientists believe there are more than 100,000 pieces of orbital debris bigger than a penny. Tens of millions of pieces are smaller than that. Scientists track all debris larger than a softball using radar and telescopes.

To figure out how many pieces of very small debris are in orbit, scientists study the space shuttle. They look for damage from the impacts of debris. When the shuttle returns from space, scientists count how many things hit it. This helps them figure out how many tiny objects are in orbit.

NASA has other ways to learn more about orbital debris. Satellites are brought back to Earth. Scientists then count the number of objects that hit the satellite. One of these satellites was the Long Duration Exposure Facility. It was left in space for over five years. NASA used it to learn about what space does to materials.

How Do Astronauts Stay Safe from Orbital Debris?
NASA knows where larger space debris is. The International Space Station can change its path to stay away from objects that would damage it. Plus, the space station has shields to protect it. The debris hits extra panels instead of important parts. The station can survive impact with small debris.

Spacesuits help protect astronauts from orbital debris. When astronauts go on spacewalks, they wear special suits. The suits include a layer of strong, thin material. This material protects astronauts from impacts. The layer is like a bulletproof vest.

NASA and the DoD cooperate and share responsibilities for characterizing the satellite (including orbital debris) environment. DoD’s Space Surveillance Network tracks discrete objects as small as 2 inches (5 centimeters) in diameter in low Earth orbit and about 1 yard (1 meter) in geosynchronous orbit. Currently, about 15,000 officially cataloged objects are still in orbit. The total number of tracked objects exceeds 21,000. Using special ground-based sensors and inspections of returned satellite surfaces, NASA statistically determines the extent of the population for objects less than 4 inches (10 centimeters) in diameter.

Collision risks are divided into three categories depending upon size of threat. For objects 4 inches (10 centimeters) and larger, conjunction assessments and collision avoidance maneuvers are effective in countering objects which can be tracked by the Space Surveillance Network. Objects smaller than this usually are too small to track and too large to shield against. Debris shields can be effective in withstanding impacts of particles smaller than half an inch (1 centimeter).

There’s a lot of space junk orbiting Earth and in future it will become very big problem for space travel this is the reason now scientist are trying to find methods using which it will become easy to get rid of space junk

More than 500,000 pieces of debris, or “space junk,” are tracked as they orbit the Earth. They all travel at speeds up to 17,500 mph, fast enough for a relatively small piece of orbital debris to damage a satellite or a spacecraft.

The rising population of space debris increases the potential danger to all space vehicles, but especially to the International Space Station, space shuttles and other spacecraft with humans aboard.

In 1996, a French satellite was hit and damaged by debris from a French rocket that had exploded a decade earlier.

On Feb. 10, 2009, a defunct Russian satellite collided with and destroyed a functioning U.S. Iridium commercial satellite. The collision added more than 2,000 pieces of trackable debris to the inventory of space junk.

China's 2007 anti-satellite test, which used a missile to destroy an old weather satellite, added more than 3,000 pieces to the debris problem.

2013 –
The largest space debris risk in orbit is the derelict ENVISAT satellite. Contact was lost unexpectedly in April 2012. The 85 foot [ 26 meters] derelict is in an orbit where other space objects approach within 600 feet [ 200 meters] of the satellite every year. An impact could generate a devastating chain reaction of debris collisions. ENVISAT is expected to stay in orbit for about 150 years until it eventually falls back into Earth’s atmosphere and burns up.

Has anyone ever been hit by space junk?
The first space junk known to crash to earth happened in 1979. It landed in Western Australia. Nobody was hit.

As per media reports Lottie Williams of Tulsa, Oklahoma, is the only person to have ever actually been hit by space junk. In 1997, she was hit on the shoulder by a piece of what was thought to be the Delta II rocket. The debris was later confirmed to have been part of a fuel tank from a Delta 2 rocket

All the time space debris keeps reentering our atmosphere.
High-speed debris from satellite explosions could cause a catastrophic chain reaction, as seen in the movie "Gravity."

Space Junk Clean Up options?
NASA and other agencies are working on to find the ways to remove space junk, to get rid of space junk.

Jan-Feb 2017
The first attempt to remove space junk failed
The Japanese cable test was the first in-space evaluation of debris-removing technology.

On 28 January, the Japan Aerospace Exploration Agency (JAXA) started an inaugural in-space evaluation of their junk-removing cable technology.

A 700-metre-long metal cable was fitted to an unmanned spacecraft called Kounotori 6, which was on its way back to Earth after delivering supplies to the International Space Station.

The cable was meant to unfurl from the spacecraft, at which point an electric current would pass along its length. The idea was that the current would interact with the Earth’s magnetic field, creating a drag that pulled the spacecraft out of orbit. The spacecraft would then tumble into our atmosphere and become incinerated.

Proponents of such junk-removing cables say that special space vehicles could attach cables to existing pieces of space junk. In addition, each new satellite launched could go up with a cable that could be activated at the end of its working life.

However, Kounotori 6 was unable to release the cable to test its junk-removing potential, and JAXA could not fix the glitch before the spacecraft returned to Earth’s atmosphere
 “We could not extend the cable, but we think it is not because of the cable itself, but some other reasons,” a spokesperson for JAXA told New Scientist. “A detailed analysis is underway.”
 We believe the tether did not get released", leading researcher Koichi Inoue told reporters.

Other Projects –

Phoenix – A robotic servicer spacecraft would chase down derelict satellites and harvest still usable hardware such as dish antenna. The servicer attaches a module that allows that salvaged part to be used for a new mission.
Phoenix is a project of the United States Defense Advanced Research Project Agency.

A robotic janitor spacecraft is launched into orbit from an airplane. The Janitor chases down a target satellite, grapples it and then plunges back into the earth’s atmosphere, destroying itself along with the derelict satellite.
Cleanspace one is a project of the Swiss Ecole Polytechnique Fedrale de Lausanne [ EPFL]

Earth based lasers –
A ground based laser could de-orbit space debris by robbing it of a bit of the momentum it needs to continue orbiting the earth. Light exerts pressure, so to de-orbit an object such as the discarded ASTRO-F satellite lens cap-31 inches [ 80 centimeters] wide and 11 pounds [ 5 kilograms] in mass – a laser beam of about 5 to 10 kilowatts would be shined upon it for about two hours.

Currently, there are several efforts to mitigate the problem:
1-Pieces of space debris are tracked by radar, so that spacecraft can be steered around them.
2-Spacecraft can be built to survive impacts from space debris. This will also protect them from meteoroid impacts.
3-Several of the spacefaring nations have agreed to measures to reduce the number of derelict satellites that could hit working satellites by steering aging satellites into otherwise useless orbits or into paths that will cause them to harmlessly burn up in the atmosphere of the Earth.

Watch Video Space Debris in Motion NASA -

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Tuesday, February 7, 2017

Tags – Explained Space Junk Orbital Junk Remove Importance