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Wednesday, February 3, 2016

Earth-orbiting space debris surrounds us

 by Mark Ollig

As I write this sentence, there are thousands of various-sized fragments, some traveling over 22,000 mph, circling around our planet.

NASA calls these fragments “space debris,” defined as: “man-made objects in orbit about the Earth which no longer serve a useful purpose.”

In other words: space junk.

Examples of orbital space debris include:

• Derelict (abandoned) spacecraft.

• Separated fuel stages from launch vehicles.

• Debris created by spacecraft or upper rocket stage explosions or collisions.

• Solid-rocket motor emission particles.

Even small flecks of paint from rockets and satellites, because of their fast orbital rate of speed, are considered space debris, and could do damage if they struck another object in space.

Of course, our planet’s atmosphere protects us, and would burn up much, if not all, space debris upon its re-entry.

While researching space debris, I was surprised to learn there’s such a large amount of it.

Currently, over 21,000 pieces of space debris, each averaging 4 inches in size, are orbiting the Earth.

The estimated amount of space debris measuring three-fourths of an inch to 4 inches, and traveling at 17,500 mph, is numbered at 500,000.

I was amazed to find out over 100 million individual space debris particles; each measuring less than three-fourths of an inch, are orbiting around our planet.

The US Space Surveillance Network monitors orbiting space debris larger than 4 inches.

Its ground radar is capable of tracking space objects as small as one-tenth of an inch.

NASA said upon a spacecraft’s return to Earth, it would be inspected for surface space debris impacts as small as 3/64 of an inch.

I viewed a photograph of a triple paned, glass windshield from a space shuttle which was damaged from an impact caused by a tiny piece of space debris.

The surface of the glass had a visible shattered area, and a small pitted crater about a quarter-inch wide.

It looked like a speeding bullet had struck bullet-proof glass – but did not get through.

Most of the space debris is located within 1,243 miles of our planet’s surface, with the largest debris clusters inside 467 to 500 miles.

While thinking of all the space debris out there, my thoughts turned to the Earth-orbiting International Space Station (ISS).

The ISS’s orbit averages 250 miles above the Earth.

Although it’s below much of the clustered space debris, there have been occasions when the space station needed to use its thruster engines to avoid possible collisions with debris crossing its orbital path.

NASA has stated: “The ISS is the most heavily shielded spacecraft ever flown.”

The shielding protecting the crew’s livable compartments, and the high-pressure tanks of the ISS, can withstand an impact of space debris as large as nearly one-half inch.

About once a year, the ISS will maneuver away from a piece of space debris it has a problematical chance of being struck by.

To view in real-time where the ISS is presently located, its current speed, altitude, and geographical surface locations the crew would be seeing, visit:

The duration of time in which space debris will orbit around our planet, before its eventual entry into Earth’s atmosphere, varies.

NASA says objects in a higher altitude will remain in orbit longer than those in a lower altitude; this sounds logical to me.

Space debris in orbit within 373 miles above the Earth, will take several years before re-entering the planet’s atmosphere.

An object orbiting around 500 miles above the planet, will take decades before its orbit decays, and it falls back to the surface.

Space debris orbiting the Earth at 620 miles will take centuries before it drops back down to us.

Many telecommunication and weather-related satellites, orbit the Earth at distances averaging 2,200 miles.

NASA says these satellites are relatively safe from being impacted by any space debris at such a high altitude.

Operators of these satellites will normally “boost” them into a higher orbit towards the end of their useable life-cycle, sending them further away from the Earth, and thus greatly diminishing their chances of becoming a projectile which could collide with working satellites.

However, there have been incidents of Earth-orbiting satellites colliding with one another.

The most noted collision occurred Feb. 10, 2009, when a US Iridium communications satellite and an abandoned Russian Cosmos satellite crashed into each another.

So, what is NASA doing to address all this Earth-orbiting space junk?

They began the NASA Orbital Debris Program Office at the Johnson Space Center, in Houston, TX.

This program has recommended reducing the launching of too many unnecessary objects into Earth’s orbit.

They also admit cleaning up the thousands of pieces of floating space debris above our planet is a “technical and economic challenge.”

Russia, China, Japan, and the European Space Agency, have also issued guidelines for reducing orbital space debris.

Ideas have been suggested for removing the space debris.

In 2011, Japan’s space agency suggested using a “magnetic net” to capture drifting space debris.

The US Government Orbital Debris Mitigation Standard Practices was approved in 2001.

Design enhancements in a satellite’s physical structure to better withstand small space-debris impacts was one improvement suggested.

The NASA Orbital Debris Program’s website is:

Photo source: NASA Orbital Debris Program Office.