August 2005
Space Debris
CDI Fact Sheet
Theresa Hitchens
thitchens@cdi.org

 
“As the number of objects in Earth orbit increases, the likelihood of accidental collisions will also increase. Currently, hundreds of close approaches (i.e., passes within less than 1 kilometer) between cataloged objects occur on a daily basis.  If future spacecraft and rocket bodies are not removed from LEO within a moderate amount of time after then end of a mission, e.g., within 25 years, the rate of accidental collisions will increase markedly later in the this century.”

“The Orbital Debris Quarterly News,” April 2005, NASA Orbital Debris Program Office, Johnson Space Center, Houston, Tex.

Space-faring nations are well aware of the dangers caused by space debris – from inactive satellites to discarded rocket stages to nuts and bolts left in orbit.  Space debris is the inevitable consequence of the global uses of space; every space launch will create some amount and form of debris, just as every kind of transportation on Earth creates some amount and form of pollution.

Even tiny pieces of debris such as paint flecks or bolts can damage or destroy a satellite or spacecraft, due to the tremendously high speeds of orbital objects (some 10 kilometers per second in Low Earth Orbit). Space scientists universally agree there is already too much orbital debris, particularly in the most heavily used orbits. Unfortunately, the amount of space debris is increasing rather than decreasing as more nations and commercial entities seek the economic and military benefits provided by satellites.

Indeed, space debris is now of such a concern that there is an effort underway, with NASA playing a leading role, to create U.N.-sanctioned international guidelines for space operators designed to minimize the creation of debris during routine space operations.

For these reasons, it is worrisome that the U.S. Air Force, in its efforts to establish what the service terms as “space dominance” and “space control,” is considering the possible uses of anti-satellite weapons (ASATs) that would create vast amounts of space debris.  U.S. Air Force documents envision “disabling” or “destroying” enemy satellites using air-launched missiles and ground- and space-based ASATs that would shatter their targets into many bits through high-speed impacts, as well as ground-, air- and space-based laser systems that would “toast” a satellite into a giant hunk of space junk.  At a time when scientists are already concerned that failure to slow current rates of debris creation could result in parts of space becoming too dangerous for satellites to use, Air Force plans to include debris-creating weapons in its space control arsenal seem short-sighted at the least, and deliberately negligent at the worst.  Given that the U.S. military is the world’s largest consumer of space-provided data and services, from communications to Earth imagery to precision-guidance for weapons provided by the U.S. Global Positioning System satellite network, and thus has the most to lose in space, the Air Force should reconsider this dangerous strategy.

Some Basic Facts about Space Debris

  • The U.S. Air Force currently tracks about 13,400 objects in space, of which only between 6 and 7 percent are active satellites. The rest is debris.
     
  • Not all space debris can be located and tracked with current capabilities. The Air Force’s Space Surveillance Network – the best in the world – can see objects down to 10 centimeters (the size of a baseball) in diameter in LEO, where the Space Shuttle, the International Space Station (ISS), most Earth imaging satellites, and satellites providing mobile communications reside); and down to about 1 meter in diameter in Geosynchronous Orbit (GEO, where most of the world’s communications and broadcast satellites reside).
     
  • There are more than 100,000 pieces of smaller, untrackable debris, down to the size of a marble (1 centimeter in diameter) in orbit; and possibly trillions of pieces smaller yet.  Scientists estimate that there is about 4 million pounds of space junk in LEO alone.
     
  • Even tiny pieces of debris can damage or destroy satellites, the Space Shuttle, the ISS, or penetrate astronaut suits. Debris in LEO travel at 10 times the speed of a rifle bullet; a marble-sized bit of junk would slam into a satellite with the force equal to a 1-ton safe hitting the ground if dropped from a five-story building. Indeed, a tiny paint fleck put a pit in the window of the Challenger Space Shuttle during Sally Ride’s historic first mission.
     
  • The amount of space junk is increasing by about 5 percent per year; meaning that by the end of the century a satellite in GEO will have a 40 percent chance of being struck during its operational life-time.
  • NASA has found that of the 20 problems most likely to cause the loss of a Space Shuttle, 11 involve debris.
     
  • NASA data shows a current risk of a “catastrophic” debris strike to the Shuttle of 1 in 200. By comparison, the lifetime risk of a U.S. citizen dying in a car accident is about 1 in 100; the risk of dying in an attack with a firearm, about 1 in 325; the risk of dying in a fire, about 1 in 1,116.
     
  • While debris in LEO eventually de-orbits and most burns up in the Earth’s atmosphere (unfortunately, sometimes very large pieces of debris actually hit the Earth intact), debris in GEO remains on orbit, and thus a threat to spacecraft there, forever.
     
  • The 1985 test of an ASAT missile fired from a U.S. F-15 fighter at a U.S. Air Force satellite named Solwind resulted in more than 250 pieces of space debris that took 17 years to clear out of LEO.  One piece of that debris came within a mile of the ISS.
     
  • Most space-faring nations have incorporated into national legislation and regulations requirements for space operators designed to limit debris creation. NASA and the Federal Communications Commission have been leaders in this arena, with the United States currently setting the highest bar in the battle against space junk.  Indeed, as noted above, the U.N. Committee on the Peaceful Uses of Outer Space is now working on development of an international code of conduct in hopes of slowing the creation of space debris.


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