Space Cadets Out on a Junk-It

There’s still lots of space in outer space, but if you happen to be cruising by Earth, you might bump into a couple of things in the old hood. Oh, the stuff we launched in the 1950s has long since burned up in a fiery descent through the atmosphere, but there are tons of space junk (in addition to the crappy television shows being beamed down from geosynchronous orbit) floating around up there. Most of the articles circling earth will eventually succumb to the Earth’s gravity and will get pulled through our atmosphere, many literally vaporizing by the time the debris hits the surface. But not all.

“A new battery of studies followed as NASA, NORAD and others attempted to better understand exactly what the environment [around Earth] was like. Every one of these studies adjusted the number of pieces of debris in this critical mass zone upward. In 1981,… it was placed at 5,000 objects, but a new battery of detectors in the Ground-based Electro-Optical Deep Space Surveillance system quickly found new objects within its resolution. By the late 1990s it was thought tha t the majority of 28,000 launched objects had already decayed and about 8,500 remained in orbit. By 2005 this had been adjusted upward to 13,000 objects, and a 2006 study raised this to 19,000 as a result of an ASAT test and a satellite collision. In 2011, NASA said 22,000 different objects were being tracked….

“The first major space debris collision was on 10 February 2009... The deactivated 950 kilograms (2,100 lb) Kosmos 2251 and an operational 560 kilograms (1,200 lb) Iridium 33 collided 500 miles (800 km) over northern Siberia. The relative speed of impact was about 11.7 kilometers per second (7.3 mi/s), or approximately 42,120 kilometers per hour (26,170 mph). Both satellites were destroyed and the collision scattered considerable debris, which poses an elevated risk to spacecraft. The collision created a debris cloud, although accurate estimates of the number of pieces of debris is not yet available.” Wikipedia. Small pits on manned orbiters suggest that space debris is everywhere (there are actually an estimated 500,000 “things” floating up there from the size of a marble on up), and for the larger chunks, the shields built into the relevant vehicles aren’t strong enough; the satellites have move to avoid contact.

NASA is acutely aware of the risks that falling space junk poses for all of us, constantly tracking the decay of space objects making the turn, predicting places of impact and preparing for the damage. Their Website tells us more: “Spacecraft that reenter from either orbital decay or controlled entry usually break up at altitudes between 84-72 km due to aerodynamic forces causing the allowable structural loads to be exceeded. The nominal breakup altitude for spacecraft is considered to be 78 km. Large, sturdy, and dense satellites generally break up at lower altitudes. Solar arrays frequently break off the spacecraft parent body around 90-95 km because of the aerodynamic forces causing the allowable bending moment to be exceeded at the array/spacecraft attach point.

“After spacecraft (or parent body) breakup, individual components, or fragments, will continue to lose altitude and receive aeroheating until they either demise or survive to impact the Earth. Spacecraft components that are made of low melting-point materials (e.g., aluminum) will generally demise at higher altitudes than objects that are made of materials with higher melting points (e.g., titanium, stainless steel, beryllium, carbon-carbon). If an object is contained inside of a housing, the housing must demise before the internal object receives significant heating. Many objects have a very high melt temperature such that they do not demise, but some can be so light (e.g., tungsten shims) that they impact with a very low velocity. As a result, the kinetic energy at impact is sometimes under 15 J [light impact], a threshold below which th e probability of human casualty is very low.” Weeeeeeee! 15 J, eh, well, I’m not scared!

The Agency is also working with creating new materials for satellites to make them more likely to burn up on their return to the planet and to create smaller footprints to minimize risk to operating space vehicles: “Orbital debris protection involves conducting hyper-velocity impact measurements to assess the risk presented by orbital debris to operating spacecraft and developing new materials and new designs to provide better protection from the environment with less weight penalty. The data from this work provides the link between the environment defined by the models and the risk presented by that environment to operating spacecraft and provides recommendations on design and operations procedures to reduce the risk as required.”

On June 28^th, Mission Control called The International Space Station around 7:30 EDT and ordered the six astronauts (two Americans, three Russians and one Japanese) “into their Soyuz capsules… Controllers wanted to keep them safe from a piece of orbiting debris. The unidentified object was predicted to pass within 800 or so feet… Even a small piece of junk can do big damage. The astronauts could have undocked in their two Soyuz capsules and returned to Earth, in case of a serious collision.” Washington Post, June 26^th. They got the all-clear about a half hour later. It all happened at 29,000 miles per hour… and the object cleared by 1,100 feet. I’m thinking a movie here… we could call it Crash. Oh, Paul Haggis already did that one… the grounded kind?

I’m Peter Dekom, and if we accumulated that much junk in about 60 years, what’s it gonna look like in 2100?!