As the Space Age turns 60 years old next year, the amount of junk in Earth orbit continues to grow. Derelict satellites still in orbit date all the way to Vanguard 1, launched by the United States in 1958. From old rocket boosters to tools lost during spacewalks, low Earth orbit is getting crowded. This is not only hazardous to satellites, which have fallen prey to debris impacts in the past, but presents a growing danger for astronauts as well. Many scientists fear what’s known as the Kessler Syndrome, a tipping point where the density of orbital debris becomes self-propagating, and one destructive impact leads to many more. Is such an “ablation cascade” unavoidable? Here are five key issues concerning space debris.
5. The Amount of Space Junk is Growing Exponentially
NASA estimates there are more than a half-million pieces of debris the size of a marble or larger orbiting the Earth. The U.S. Joint Space Operations Center tracks more than 21,000 pieces of space junk that is 2 inches or larger; that’s roughly the size of a tennis ball. Yet both figures represent a tiny fraction of the 170 million pieces of debris larger than 1 millimeter estimated to be in orbit. And the amount of debris continues to grow. The collision of the defunct Russian Kosmos-2251 satellite with the U.S. commercial satellite Iridium-33 over Siberia in early 2009 highlighted this issue in a dramatic fashion, littering low Earth orbit with more than 2,000 pieces of debris, many of which will stay in orbit for years. The old method of simply waiting for objects to reenter the atmosphere on their own and burn up isn’t working, as debris keeps accumulating in orbit.
Meanwhile, the U.S. and Russia are the two main players in so-called Space Situational Awareness. That can be defined as the comprehensive knowledge of space objects and the ability to track, understand and predict their future location. While little is known about Russia’s capabilities, the U.S. orbital debris tracking system is aging. Lockheed Martin has a $914 million contract to build the next-generation Space Fence. The S-band radar system will be capable of tracking 200,000 objects, and have twice the range of the current system. It’s expected to begin limited operations in 2018 and be fully functional by 2022.
4. Astronauts and the ISS Are at Increased Risk
While the movie Gravity sensationalized the idea of space debris out of control, the risk is real. Such debris travels at a velocity of up to 17,500 mph and can pack a tremendous punch. The International Space Station is often moved to avoid space junk, but even a tiny pea-sized piece of debris zips along faster than a bullet, and would make for a very bad day for a space-walking astronaut, with absolutely no warning. And damage to the ISS due to debris impacts has already been observed: in 2013, astronauts noted a small “bullet hole” in one of the solar arrays of the ISS, caused by either a micrometeorite or space junk.
Astronauts have also observed pitting from debris impacts, and engineers noticed similar “sand-blasting” effects on the windows of the space shuttles on return to the Earth; some of these “cracked windshields,” so to speak, resulted from collisions with tiny paint chips (!). Ground controllers monitor debris that may threaten the ISS, and occasionally astronauts have to make “Debris Avoidance Maneuvers” to move away from a potential impact. There’s always a bit of uncertainty with close passes; on several occasions astronauts aboard the ISS have had to sit out a pass that was too close to call inside their Soyuz space capsule, ready to evacuate and head back to Earth at a moment’s notice if necessary.
3. Many New Sources of Debris Are Emerging
In the good old days, the U.S. and the Soviet Union were the only space-faring nations, and everyone played by semi-accepted rules. More than a dozen countries now have the capability to launch rockets into space, with some of the newest players including Iran and North Korea. Many more nations build satellites to launch on carriers with Russia, the United States and the European Union. Schools and private individuals can now field small CubeSats in space through crowd-funding platforms like Kickstarter. Researchers are obviously excited about these relatively low-cost, easy-access ways to put their experiments in orbit. But what becomes of these projects in the end? A study in NASA’s Orbital Debris Quarterly News — yes, there really is such a publication — found that roughly 20 percent of the CubeSats launched in the previous decade were not designed to deorbit after their “retirement.” That means they’ll end up as orbital debris, possibly for decades. This issue will need to be addressed. In the long term, it’s possible, probably likely, that every new satellite fielded would be required to have a way to safely deorbit at the end of its lifespan. The NanoSail D2 mission in 2010-2011 demonstrated just such a system, deploying a solar sail to speed up reentry.
2. Could a Debris Impact in Earth Orbit Spark a War?
Imagine this scenario: A Russian satellite that regularly crosses the U.S. in its orbital path is suddenly destroyed. Russian President Vladimir Putin is furious and immediately denounces the U.S. for its actions; he puts his country on a war alert. Military experts are already pondering these types of scenarios. An orbital debris impact destroying a spy satellite could certainly be mistaken as an intentional “first strike” by a nation seeking to blind the cyber eyes of another, triggering a counterstrike and possibly even a war. The biggest danger is in low-Earth orbit, where the density of space debris is the highest, although even critical satellites in geosynchronous orbits aren’t totally immune. This problem is reminiscent of the detection of meteor strikes versus nuclear weapons tests during the Cold War. Information sharing between nations is vital to assure that damage to a satellite isn’t mistaken for a first strike.
Then there are the dilemmas posed by the mounting militarization of space. For example, China carried out an anti-satellite missile test against one of its own satellites in 2007, adding to the debris in low Earth orbit. The U.S. demonstrated a similar capability when it shot down its own failing reconnaissance satellite in early 2008. Ground observers spotted the Russian satellite Kosmos 2504 maneuvering in 2015, and some analysts suspect the Russians may be testing some new sat-killer technology in orbit.
1. Strange Ideas Emerging to Clean up Earth Orbit
There are plenty of ideas out there to deal with orbital debris, ranging from the easily implemented to the exotic. The Swiss firm EPFL has developed a satellite, CleanSpaceOne, designed to eliminate and deorbit obsolete satellites. It’s set for launch in 2018. Other ideas are still on the drawing board. One idea posed by Star Inc. is to place house-sized “space nets” in orbit, with its ElectroDynamic Debris Eliminator. Another idea is to zap space junk with ground-based lasers in an effort to change a target’s velocity and speed up reentry; the U.S. Air Force has researched such a “space broom” approach for decades. Still another idea pioneered by Raytheon is known as the Space Debris Elimination system, and would send puffs of air in the path of space debris in an effort to induce reentry.