Saturday, January 27, 2018

Lasers to Clear-Away Space Junk?

                                                                      
This graphic shows how a ground-based laser system may be able to clear-away space junk by de-orbiting the particles.
(Graphic Source: Wired Magazine < https://www.wired.com/2011/10/space-junk-laser/ >)

By Glenn A. Walsh
Reporting for SpaceWatchtower

Can lasers be used to clear-away space junk? For more than 20 years, scientists have been considering using ground-based lasers to solve an increasing problem for satellites and other spacecraft in Earth orbit. Now, the Chinese are proposing to use space-based lasers to solve the problem.

No, we are not talking about completely incinerating space junk with laser beams, as phaser beams on the popular science-fiction television and motion picture series, Star Trek, are often seen to incinerate targets. The idea is to affect the orbit of the particular piece of space junk, so the heating of the object by a laser beam either moves the object to an orbit that does not threaten operating satellites, moves it to an orbit where it will eventually de-orbit and burn-up in the atmosphere, or both. Some people refer to such a ground-based laser system as a “Laser Broom.”

Space junk or space debris has been in orbit, just above Earth's atmosphere, since the dawn of the Space Age in 1957, when Russia orbited the first artificial satellites, Sputnik 1 & 2. This was followed soon-after by the first American satellite, Explorer 1. Wednesday marks the 60th anniversary of the launch of Explorer 1.

Since then, the United States, Russia, and China have sent both crewed and uncrewed spacecraft into Earth orbit. Thirteen other nations and the European Union have also sent uncrewed satellites into orbit. And, more recently, private firms such as SpaceX have started sending uncrewed spacecraft into orbit, with the prospect of sending crewed spacecraft in the not-too-distant future.

After more than 60 years, many obsolete and unused satellites, as well as spent rocket boosters and other auxiliary apparatus, remain in orbit. And, through collisions of some of these objects, small and even more dangerous artificial space particles now exist in orbit.

February of 2009 saw the first collision between an active satellite (Iridium satellite-telephone communications satellite) and a defunct satellite (Russian Cosmos weather satellite). Such collisions were predicted in 1978 by NASA scientist Donald Kessler, and hence this new phenomena is known as the Kessler Syndrome.

The cluttering of orbits with such particles from space collisions was predicted, by the Kessler Syndrome, to eventually make certain orbits quite unsafe for new satellites, and hence, unusable by space-faring nations. The danger is that much of this space junk travels at speeds of nearly 17,000 miles per hour or 7.5 kilometers per second.

Tiny particles, such as even a flake of paint, from some previous space missions, traveling at those kind of speeds, can be hazardous to satellites, the International Space Station (ISS), and particularly to someone outside a spacecraft conducting an extra-vehicular activity (EVA - ie. a space-walk). The ISS is clad in special shielding to protect the orbital laboratory from small impacts often received from orbiting space debris. And, to avoid the larger orbiting particles, sometimes the Space Station is moved out-of-the-way.

Even in low Earth orbit, much of this space junk could remain in orbit for years or even centuries. In geo-synchronous orbit (approx. 22,236 statute miles / 35,786 kilometers above the Earth; an orbit that mimics the rotation rate of the Earth), space junk could remain in orbit indefinitely, as there is minimal friction to create drag and slow the space junk. Many communications satellites are placed in geo-synchronous orbits, so they appear to stay above one part of the Earth at all times.

In 1996, NASA and the U.S. Air Force, in a study titled Project ORION, suggested using ground-based lasers to nudge space junk out-of-the-way or toward de-orbiting. These would be very powerful lasers (5 kilowatts in power, costing around $800,000 a piece), which would vaporize surface material on target space debris, to drive it toward the atmosphere where it would burn-up.

Scientists noted that such a system could also be used to move active satellites into more advantageous orbits. This would reduce the need for such satellites to be launched with additional rocket propellent, saving weight and money

Such a laser system, including operating system and telescope, would cost in the tens of millions of dollars. Scientists believe such a system could engage about 10 pieces of space junk per day. However, such powerful lasers could be seen as a threat to orbiting spacecraft of other nations.

In 2015, a team of scientists from Japan's RIKEN research lab proposed sending a laser cannon to the ISS, to clear-away space junk in low Earth orbit. Mounted on the ISS, the project would begin with a much weaker laser, about 10 watts of power firing 100 laser pulses a second. Eventually, according to the researchers, a dedicated space junk-cleaning satellite could house a 500,000-watt laser, which could pulse 50,000 times per second. Again, a major obstacle to this proposal is the fear that this space-based laser cannon could have military applications.

In a scientific research paper issued this month, Chinese researchers are also proposing a powerful space-based laser to clean-up space junk. The paper titled, “Impacts of orbital elements of space-based laser station on small scale space debris removal” published in the February issue of Optik – International Journal for Light and Electron Optics, was produced by scientists at the Chinese Air Force Engineering University.

It is, perhaps, appropriate that China concentrate on the removal of space debris. China created a great deal of space debris in 2007, with an anti-satellite missile test on an old Chinese satellite. This one test created thousands of new pieces of junk in low Earth orbit, the most severe fragmentation in the history of space debris. One fragment seems to have damaged a Russian spacecraft in 2013.

However, there is great skepticism as to whether space junk is all China is interested in, regarding space-based lasers. A U.S. Congressional commission, the U.S.-China Economic Security and Review Commission, reported last year that China is very interested in shooting-down U.S. satellites.

Internet Links to Additional Information ---

Laser: Link >>> https://en.wikipedia.org/wiki/Laser

Space Junk or Space Debris: Link >>> https://en.wikipedia.org/wiki/Space_debris

Laser Broom: Link >>> https://en.wikipedia.org/wiki/Laser_broom

Daley, Jason. "Amateur Astronomer Finds Long-Lost NASA Satellite." 

Smithsonian Magazine 2018 Jan. 29.


Palmer, David. "Satellite 'License Plates' Could Prevent a Disaster in Low Earth Orbit."
Blog: The Crux.
Discover Magazine 2017 Dec. 18.
Link >>> http://blogs.discovermagazine.com/crux/2017/12/18/satellite-license-plates/#.Wm7cHnlG3IV

Related Blog Posts ---

"New USAF 'Space Fence' to Track Space Junk by 2019." 2014 May 10.

Link >>> http://spacewatchtower.blogspot.com/2014/05/new-usaf-space-fence-to-track-space.html

 

"Sequestration: Cuts to USAF 'Space Fence' Tracking Space Junk ?" 2013 April 16.

Link >>> http://spacewatchtower.blogspot.com/2013/04/sequestration-cuts-to-usaf-space-fence.html


Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss.
             2018 January 27.

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