ESA’s Clean Space targets orbital debris and greener environment
Next year’s Hollywood film Gravity features George Clooney stranded in orbit by cascading space junk. The threat is genuine, with debris levels rising steadily. ESA’s new Clean Space initiative is developing methods of preserving near-Earth space – and the terrestrial environment, too.
70% of all catalogued objects are in low-Earth orbit (LEO), which extends to 2000 km above the Earth's surface. To observe the Earth, spacecraft must orbit at such a low altitude. The spatial density of objects increases at high latitudes.
Responding to public environmental concerns, Clean Space aims to reduce the environmental effect of Europe’s space activities, cutting waste and pollution on Earth and in orbit.
Industry is contributing to ESA’s draft plans for developing Clean Space technologies: new tools to assess environmental effects, more eco-friendly replacements for materials and techniques, and ways to halt the production of more space debris and bring down existing debris levels.
Mr Dordain, ESA Director General
ESA Director General Jean-Jacques Dordain emphasises that implementing Clean Space is a major objective of Agenda 2015, the Agency’s upcoming action plan: “If we are convinced that space infrastructure will become more and more essential, then we must transmit the space environment to future generations as we found it, that is, pristine.”
“We can therefore say that Clean Space is not a new programme, but instead a new way of designing all of ESA’s programmes. I would like ESA to become a model agency in this respect.
“We will not succeed alone; we will need everyone’s help. The entire space sector has to be with us.”
ESTEC, ESA’s technical centre in Noordwijk, the Netherlands, hosted a Clean Space workshop in June, jointly organised by ESA and industry body Eurospace.
Clean space: eco-design and green technologies workshop
Earth: cleaning up space projects
On Earth, Clean Space involves evaluating the environmental impact of future space projects, as well as monitoring the likely effects of forthcoming legislation on the space industry – environmental law being an extremely fast-moving field.
Life-cycle assessment will be important for evaluating the environmental effects of space technologies, from their initial design and manufacture to their end-of-life.
In the workshop, Environmental consultancy BIO Intelligence Services described the current wide employment of life-cycle assessment in other industrial sectors.
Arcam AB's skull implant produced by additive manufacturing
Environmental friendliness often goes hand-in-hand with increased efficiency – offering industry competitive advantage.
Novel manufacturing processes such as ‘additive manufacturing’, where structures are built up in layers, or ‘friction stir welding’, where lower weld temperatures use less materials and energy to do a better job.
Reducing the need for often costly waste disposal is another win–win: rocket maker Safran is working on a biological method of breaking down toxic solid-propellant waste.
So far, about 200 explosions and at least 5 collisions in space have occured. Further explosions and collisions are very likely. The explosions are mainly caused by onboard energy sources, either due to pressure build-up in propellant tanks, battery explosions, or the ignition of hypergolic fuels. Each explosion creates thousands of small debris objects. The most prominent collision event and the first known one between two catalog objects was in 1996 between the Cerise Satellite and a fragment of an Ariane upper stage explosion.
Space: cleaner means safer
In Gravity, runaway orbital collisions fill low-Earth orbit with a lethal debris cloud.
In real life, of the 6000 satellites launched during the Space Age, less than 1000 remain operational. The rest are derelict and prone to fragment as leftover fuel or batteries explode.
Orbiting at 7.5 km/s or more, even a 2 cm screw has sufficient ‘lethal diameter’ to take out a satellite.
The workshop discussed various means of minimising future debris production, such as tethers or sails to help drag abandoned satellites out of low orbit within 25 years.
Satellite reentry also needs to be a safer process – sometimes entire chunks of satellites have hit the ground intact. New ‘design for demise’ concepts aim to prevent that.
But even if all space launches stop tomorrow, simulations show that debris levels will keep growing. Active removal is also needed, including robotic missions to repair or deorbit satellites.
Source: European Space Agency
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