Quirks & Quarks·Analysis

Falling rocket booster points to lack of regulations on space junk

Bob McDonald's blog: There are no international laws to control potentially dangerous orbital debris.

Bob McDonald's blog: There are no international laws to control potentially dangerous orbital debris

Low Earth Orbit or LEO, the region within 2000 km of the Earth's surface, has the highest concentration of space debris. Depending on distance, objects will orbit for days to centuries before re-entry. (NASA)

As the world waits for an uncontrolled Chinese rocket booster to fall from space, it is a reminder that we currently have no international laws to regulate the problem of orbital debris.

The odds of anyone being struck by the remains of the 22-tonne rocket booster that is due to fall out of orbit in the next few days are extremely low. Most of the rocket will disintegrate in the upper atmosphere, so only pieces of it are likely to make it to the ground. The Earth is mostly covered by water, so the chances are good that those pieces will fall into an ocean. No one has ever been killed by debris falling from space in the 65 years we've been launching rockets.

But the world's governments may need to consider how much longer we're willing to play those odds.

Just because we've been getting away with it for so long is not likely to be seen as a justification to keep doing it. Think of someone on the roof of a tall building throwing car parts over the edge. The odds of one of them hitting a pedestrian down below in the head might be low, but the threat they pose is something the public certainly demands our authorities deal with.

For most of the history of space flight, disposable rockets have been the mainstay. Rockets have to reach insane speeds to achieve orbit, close to 30,000 km/h, which is literally faster than a speeding bullet. That requires a huge amount of fuel. In fact, most of the mass of a rocket on the launch pad is fuel, which is burned at such a ferocious rate the tanks run dry in a matter of minutes. 

An empty fuel tank is dead weight, so rather than drag it into space, typically it's just discarded and the mission carries on with a second rocket stacked on top to carry the payload into orbit. Sometimes there is a third stage for missions to the moon or other planets. All of these used stages are discarded along the way and either allowed to drop into the ocean, burn up in the atmosphere or allowed to drift in space.  There's also the problem of abandoned, defunct or damaged satellites in slowly decaying orbits. 

As a result, it's estimated that there are more than 500,000 bits of space debris as large as a marble or more — perhaps a hundred million as big as a millimetre across — in Earth orbit.  These can threaten other spacecraft, astronauts and, occasionally for the largest chunks, people on the ground.

Space agencies, especially in recent decades, have tried to be responsible about disposing of this debris. Usually, larger pieces are directed to fall over oceans. The huge, orange external fuel tanks of the space shuttles were dropped into the Indian Ocean on every flight. In 2001, the Russian space station Mir was driven into the atmosphere in a remote location over the South Pacific. The current situation of a large object falling uncontrollably from space is actually quite rare.

The U.S. Skylab space station launched in the 1970s re-entered the Earth's atmosphere in 1979 scattering debris over sparsely populated Western Australia. (NASA)

Reusable boosters, pioneered by private rocket company SpaceX, which use their rocket engines to return and land on either on a drone ship at sea or back on landing pads at Cape Canaveral, Fla., are a significant step in avoiding the problem of errant space debris. However, their upper stages are not recovered. In fact it's suspected that a SpaceX second stage burning up in the atmosphere was responsible for a spectacular light show seen in the skies above southwestern B.C. in March. There were no reports of debris reaching the ground.

It would be in everyone's best interest to take responsibility for what goes up, to make sure that when it comes down it does so safely.  The U.S. has established national practices that require operators, including the military, to plan for safe disposal of orbital debris. The other spacefaring nations, including Russia, China and the European Union have similar national guidelines.  

But there are no international treaties and, as a result, no international repercussions for doing a bad job at this — apart, perhaps, from the bad press China might get if their falling booster does land in an unfortunate place. 

The Long March 5B Y2 rocket, carrying the core module of China's space station Tianhe, takes off from Wenchang Space Launch Center in Hainan province, China, on April 29. (China Daily via Reuters )

Let's hope we don't wait until an innocent pedestrian is fatally struck by a falling turbopump before we clean up the garbage flying over our heads.

ABOUT THE AUTHOR

Bob McDonald is the host of CBC Radio's award-winning weekly science program, Quirks & Quarks. He is also a science commentator for CBC News Network and CBC-TV's The National. He has received 12 honorary degrees and is an Officer of the Order of Canada.

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