Coming to terms with a load of old rubbish
12 July 2010
Some eighteen months ago I reported in this column on the growing menace of space junk – the vast quantities of debris in orbit around the earth, from microscopic particle to full-size redundant satellite. The issue came strongly into focus following the first widely reported incident in January 2009 of the collision between the US commercial ‘Iridium’ satellite and a defunct Russian ‘Cosmos’ military communications craft over Siberia. With an estimated 6,000 manmade satellites - from the fully-functioning to the spent hulk - currently in orbit around the earth, the risk of collisions and their ensuing hazards has long been a cause for concern.
The US military authorities are said to track around 18,000 pieces of ‘space junk’ - a figure that suddenly jumped by an estimated 600 pieces of significant size (100mm diameter or more) following the Iridium collision. Unknown are the countless numbers of much smaller particles that may have sufficient momentum to damage manned craft such as the International Space Station and scientific instruments like the Hubble orbiting telescope. High time the hand-wringing gave way to the next stage – one of actively removing as much of this junk as possible from the earth’s exosphere in order to avoid catastrophic outcomes.
For years, the world’s space agencies have been addressing the need for debris removal and they remain open to ideas from the wider engineering and academic communities as to how this might be accomplished. Indeed, there appears to be no shortage of schemes. The latest of these is a proposal put forward by a team of eleven astronautics and space engineering MSc students from Cranfield University. Their project, entitled ‘Debris Removal in Low Earth Orbit’ (DR LEO) was presented at the first European workshop on Active Debris Removal at the French Space Agency (CNES) in Paris last month.
The Cranfield students have designed and costed a mission that would remove up to ten tonnes of debris from low earth orbit per year using a spacecraft with a robotic arm. Its aim is to capture Arianne 4 rocket bodies that were abandoned in space after they had fulfilled their purpose of placing satellites in orbit, and that are now orbiting from pole to pole at an altitude of about 800km. These captured rocket bodies would be brought back into the earth’s atmosphere over a safe location where they would disintegrate with the heat generated during re-entry. Cranfield’se five-month project seeks to remove five large non-functional space craft per year at an orbital altitude range of 700 to 2,000km.
At a conference organised by NASA and DARPA (the US Defense Advanced Research Projects Agency) at the end of last year, the US companies, Star Technology & Research and Tether Applications proposed an Electro-dynamic Debris Eliminator (EDDE) that uses solar powered electro-dynamic thrusters to manoeuvre a long, lightweight craft from which large nets are deployed to ‘capture’ pieces of debris, targeted using real time video under ground control. Objects are then dragged to an orbit of approximately 320km above the earth’s surface, which reduces their orbit life to just a few months. The companies claim that each propellant-less EDDE vehicle would be capable of removing 400 times its own mass (a total of 40 tons) per year in this manner, returning time after time to retrieve objects without need for refuelling.
Other proposals include the use of lasers and even ballistic techniques using water or foams as the payload medium. But then there is a political facet to all this: in terms of national interests, ’debris removal’ might easily be misconstrued as ‘satellite removal’. One man’s junk is inevitably another’s scientific or military asset. All these techniques, no matter how carefully controlled, in themselves pose a hazard to other legitimately orbiting objects. If we are to avoid what some believe is already upon us – ‘collision cascading’, a scenario proposed by NASA scientist, Donald Kessler more than thirty years ago – then a systematic and internationally agreed (and financed) approach to clearing low earth orbit space must eventually be put to the test.
From ‘space junk’ to ‘garbage islands’
Coming down to earth with a bump, it will come as no surprise to readers that we also have a pretty huge junk problem here on the surface of our planet, too, and I’m not referring to landfill. As far back as the 1950s, scientists observed an accumulation of industrial and domestic plastic debris in an area of the Pacific corresponding to the confluence of ocean currents. It has been building ever since and is now reportedly covering an area twice the size of the State of Texas. Other accumulations have been observed in the Atlantic and Indian Oceans.
These so-called ‘garbage islands’ pose a great threat to marine fauna and toxins released as the plastics break down are reputedly entering the human food chain. A number of high profile environmental campaigns have sought to bring this phenomenon to the wider public attention. Perhaps the most adventurous to date has been David de Rothschild’s ‘Plastiki’ expedition, which set sail earlier this year in a boat made virtually entirely from recycled plastics. Currently, it has almost completed its journey across the Pacific from San Francisco to Sydney.
More recently, the world’s second largest manufacturer of domestic appliances, Electrolux, announced its intention to gather plastic from these floating islands of waste, to recycle and ultimately reuse it to manufacture cases for a limited line of vacuum cleaners. The ‘Vac from the Sea’ project, like Plastiki, is aimed at raising awareness of the fact that around ten per cent of the 250 million tonnes of plastic the world produces every year ends up in the sea.
Electrolux has managed to get its green range vacuum cleaners up to 70 per cent recycled plastic but the company’s ultimate vision is 100 per cent, and for all of its ranges. The main barrier to taking the next step and increase the share of recycled plastic in home appliances, however, is the uncertain supply of recycled raw material. Electrolux believes that to fix the imbalance in supply and demand and get the cycle working, overall consumer perception must change and barriers to recycling become lower.
“This issue is much too important to leave to politicians,” says Electrolux VP, Cecilia Nord. “Companies, consumers and politicians are equally accountable for the situation. Since our company delivers appliances to millions of homes, we have an opportunity to raise awareness and affect consumer decisions. There are plastic islands, some several times the size of the state of Texas, floating in our oceans. Yet on land, we struggle to get hold of enough recycled plastics to meet the demand for sustainable vacuum cleaners. What the world needs now is a better plastic karma”.
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