Self-destructing satellites to tackle space junk

Hundreds of thousands of pieces of machinery and equipment are already in circulation above the Earth’s surface – many of them now obsolete or broken – which pose a threat of collision to other spacecraft.

Now students at Strathclyde University have won backing from European space agencies to investigate the use of inflatable satellites, which can be manipulated from the ground to tumble from orbit when no longer in use. They will burn up as they descend through the atmosphere at great speed, leaving no potentially damaging debris behind.

The team of engineering  students will travel to Sweden later this year to launch a rough prototype to an altitude of 35km, roughly the same height that Austrian skydiver Felix Baumgartner jumped from when he broke the speed of sound late last year.

It is hoped the launch will show that inflatable satellites can be sent up to an altitude  of 2,000km to perform observations on disaster areas or to take atmospheric measurements.

The current models are made from ultra-thin plastic which when inflated form a tough protective barrier around the vulnerable instrumentation within. They are  designed to last just a few months, although versions with chemically hardened skins that will last several years are also being developed.

When their work is scheduled to be over, the structure is programmed to change to a shape that will cause it to slow down to such an extent that it drops out of orbit rather than remain in place above the Earth for decades to come.

Andrew Allan, a 22-year-old Masters student working on the inflatable satellite project, said the current prototype consisted of a number of inflatable pods housing the satellite’s electronics, which are mounted on a 1.5 square metre platform. “This project is about laying the building bricks for this kind of satellite. Hopefully, we can show it’s possible and it’s worthwhile,” Allan said. “It is designed to leave orbit so it will nothing up there and, because it will burn up, nothing will reach the Earth’s surface.”

According to Nasa, there are more than 500,000 pieces of debris, or space junk, which are tracked as they orbit the Earth, many of them made from hardened metals.

In 2009, US and Russian communications satellites  collided in space at an altitude of about 800km over Siberia. The collision added more than 2,000 pieces of trackable debris to the inventory of space junk. The problem of defunct satellite technology was again highlighted in 2011 when large pieces of the six-tonne UARS spacecraft plunged into the Pacific Ocean.

Dr Massimiliano Vasile, the director of Strathclyde’s Advanced Space Concepts Laboratory, said the issue of space debris had become so “compelling” that it could no longer be ignored.

“The estimates about the number of pieces of debris are changing every year,” he said. “The debris can be anything from launch parts to pieces of satellites which have detached or have been involved in a collision. Then there are the satellites themselves.

He added that he was confident a solution would soon be found for dealing with space debris. “I think we’re getting there,” he said. “The problem has become compelling because the impact of not doing something now outweighs the [financial] cost of tackling it.”

The next stage for the Strathclyde students is to travel to Esrange in the far north of Sweden in September for the launch of their prototype. The launch is being made possible by the Experiments for University Students initiative, which is supported by the European Space Agency, the Swedish National Space Board (SNSB) and the German Aerospace Centre (DLR).

At the end of last year, the students attended a selection workshop at the ESA’s Space Research and Technology Centre (ESTEC) near Amsterdam, where their project was accepted on to the initiative.

An inflatable satellite launched in the future would be sent up on a rocket and deployed in low earth orbit. The structure would inflate due to residual air trapped inside before the satellite began to perform its observation tasks.

It is likely the satellite  would remain in orbit for two to 12 months before changing shape to naturally beginning falling back to Earth once its task is complete.