April 26, 2012
FEATURE | Demolition
Contractors for Canadian Space Agency to study remediation of low earth orbit
Environmental remediation efforts commonly focus on polluted land and waterways. The past decade has seen increased emphasis on remediating Low Earth Orbit (LEO) — a segment of space located between 160 kilometres and 2,000 kilometres from the Earth’s surface.
NASA estimates that LEO contains 21,000 chunks of orbital debris larger than 10 centimetres in diameter and 500,000 chunks between one and 10 centimetres. The orbit also contains more than 100 million particles smaller than one centimetre. Travelling at an average speed of 10 kilometres per second, each of these particles is capable of impacting other orbiting bodies with a wallop.
The Canadian Space Agency (CSA) is a member of the Inter-Agency Space Debris Coordination Committee, which examines issues surrounding space debris. Last October CSA awarded three $250,000 contracts to two Canadian companies to develop concept studies that might lead to technologies that could help make orbits safer.
MacDonald, Dettwiler and Associates Ltd. (MDA) of Burnaby, B.C. will head up The Clear Sky Project. Under the project, a consortium of Canadian industrial and academic organizations will work to design a robotic vehicle capable of removing space debris.
Under the Canadian On-Orbit Automated Servicing Experiment, MDA will also prepare a concept study for an experimental payload on the International Space Station to demonstrate the technologies and techniques required to capture a satellite for repair, refueling or removal.
The Mission for Orbital Debris Elimination will be led by COM DEV International Ltd., of Cambridge, Ont. The company, which designs and manufactures space satellite hardware, will work with Canadian partners to develop a robotics mission concept to tackle space debris.
“One of the big problems with space debris is that it’s self-propagating,” says Ron Holdway, vice-president, government relations with COM DEV. “When larger pieces of space junk are hit by smaller pieces, it results in a rapid increase in the amount of debris in orbit.”
A case in point: the 2009 collision between U.S. satellite Iridium 33 and defunct Russian satellite Cosmos 2251 that caused $55 million in damage and created almost 2,000 identified chunks of debris.
Holdway notes that a screw, bolt, or pea-sized chunk of debris can cause significant collision damage.
If a robotic spacecraft could sidle up to chunks of debris, they could theoretically be moved into graveyard orbit — a few hundred kilometres beyond the furthest functional satellites at more than 36,000 kilometres from Earth — or sent to a lower orbit where they would burn up in the atmosphere on re-entry.
“Part of our research is identifying the challenges in such an approach,” says Holdway. “People think of trying to grab these things as a simple operation. But you can’t just reach out and grab the debris because it may be spinning and there’s no easy place to grab it.
“Even if you were trying to get up to the same speed, in space speeding up means you orbit higher, while slowing down drops you closer to Earth. These would be complicated manoeuvres that could conceivably take several orbits around the Earth to achieve.”
The European Space Agency is currently experimenting with polyurethane foam that would harden as it’s sprayed to create a connection between the debris and a robot spacecraft. The foam could also be used to increase drag on debris located in LEO, causing it to re-enter the atmosphere more quickly.
Currently, much of the emphasis is on ensuring that no additional debris is introduced into orbit.
“One way of making sure that obsolete satellites don’t continue to become threats is to promote treaty agreements that all satellites will carry enough fuel to take them up to a graveyard orbit,” says Holdway. “The cost of creating satellites with extra fuel capacity far exceeds the cost of replacing a damaged satellite.”
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