Jason Held rekindled his love for space while lying in a ditch in Bosnia in 1996, where he was one of 16,500 US troops deployed on a peacekeeping mission at the end of the Bosnian War.
Then a lieutenant, he says he had "nothing to do but to watch the two armies put their guns away." So he signed up for a class in undergraduate biology through an army education program, taking the books to the ditch and passing the hours by studying.
"It wasn't hard but it was fun, and so then I did a physics class," he said.
"Then I started buying some academic books on magnetics, and began thinking about energy distribution and how to create force and thrust for space objects."
In 2004, Held began his PhD in robotics at the University of Sydney, and eventually founded the university's space engineering laboratory, where he led a space satellite project and worked on rocket engines.
Today, he leads the company Saber Astronautics in Sydney, where he has built technology he believes can be used to rid space of debris, one of the most pressing issues for space programs worldwide.
At least a couple of times every year, the International Space Station maneuvers to avoid a potentially catastrophic collision with space junk.
While estimations vary, there are about 4,000 active and inactive satellites in space. They are at risk of being hit by the approximately half a million bits of floating space debris, ranging in size from micro-millimeters to two double-decker buses.
"What everyone is realizing is this is a growing problem, though nobody gave a shit in the early days of space exploration," Held says.
"Why would they? There wasn't a lot out there. If you think of the early days of aviation you didn't need air traffic control. It took a few plane accidents before air traffic control was put in place.
"People are now starting to see congestion up in space, and if a satellite is up there and it deactivates for some reason while up there and you can't move it, you have a giant bullet flying around at 8 kilometers per second."
But Held hopes the device created by him and his team will be able to eliminate some of this junk and drag it back down into the atmosphere where it will combust. Called the DragEN, the yo-yo like device weighs just under 100 grams and can be attached to spacecraft and satellites. When activated, the DragEN unspools hundreds of meters of string made of a conductive material that gathers electric and magnetic forces as it travels through the earth's magnetic field . This force drags the satellite back towards Earth and into the atmosphere, where it will combust.
Left to gravity alone, satellites can take decades to re-enter the atmosphere and combust.
Held isn't sure how long it will take for a satellite attached to the DragEN to combust. He hopes to find out soon -- the Indian Space Research Organization will trial it in space for the first time on a satellite launch planned for later this year.
"The satellite mission is to take photos of the earth and downlink photos," Held says.
"At the end of its mission, the team will release the DragEN tether, which will start dragging the satellite back to Earth. We are all very interested to learn how DragEN unspools in space and how quickly or slowly it takes to come back down."
Held isn't alone in the race to tackle space junk. While Australia isn't a big player in building spacecraft systems, it is an important collector of data and information from space. Australian researchers are using this information to monitor roughly 29,000 pieces of space junk, and warn of collisions.
Addressing the issue has become a matter of international urgency, as satellites worth billions of dollars are under threat from collisions. They are being sent into space at a far greater rate than they are being destroyed.
Eventually, satellites will be dragged down into the earth's atmosphere, where they will burn up, or extra fuel can be used to blast them into the atmosphere more quickly. But for the communication and weather satellites found in the geostationary orbit 35,000km from the earth, this requires a lot of fuel and is prohibitively expensive. These satellites are more commonly blasted into a graveyard orbit, more than 36,000km above the earth and of no operational use. But even these orbits are becoming overcrowded.
Professor Craig Smith is the chief executive and technical director for the Australian aerospace technology company Electro Optic Systems. He is leading a team of scientists and engineers at the Space Environment Research Center in trying to create a high-powered, high-precision laser that can push space junk out of the way to avoid a collision. There is also hope the lasers could eventually be used to destroy chunks of junk.
His team, based at Mt Stromlo Observatory near Canberra, hopes to have an operational laser ready to demonstrate within the next three years, and is working closely with the US to build it.
"The issue is, we have to be able to project the laser beam through the atmosphere without it being dispersed," he says.
"It is challenging. The atmospheric turbulence causes the beam to disperse rather than stay focused on target, so the number of photons landing on the target is reduced, which means we can't propel it as far."
While there is an acute awareness among those working in space-related fields that the levels of space junk are becoming unacceptably high, Smith says it has not been fully realized that the satellites people and businesses depend on can be randomly destroyed by a collision at any time.
"There are satellites worth billions of dollars," he says.
"But it's not just about the cost of the satellites. If some of the satellites were to go offline, it could take a long time to get a replacement up, and many businesses, like the telecommunications industry, are dependent on them.
"It's a serious issue. We have oceans and rivers, and we pollute them until they become almost unusable. We've done exactly the same with space. We've left junk everywhere."
The United Nations Office for Outer Space Affairs has worked with NASA and the European Space Agency to develop a set of guidelines on space debris mitigation. Under the guidelines, when an orbital mission is planned, it must include a strategy to remove the spacecraft from the orbit within 25 years.
But a space archaeologist with Flinders University in Melbourne, Dr Alice Gorman, says the UN guidelines are voluntary and are followed only in about 40% of all space missions.
Gorman, who is on the executive council of the Space Industry Association of Australia, says the more urgent issue is that there is no international agreement on the best way to remove space junk. There is also a risk that removing the junk could be interpreted by other countries as a hostile act if not done carefully.
"It would be perfectly possible for a nation to create a spacecraft that could go into orbit and remove things using a giant net," she says. "The problem is, it might not remove just the junk.
"It might remove a military surveillance satellite from another country. It wouldn't be enough to say: ‘Oops, sorry'. You risk international wrath. So any technology designed to remove space junk from orbit is also an anti-satellite weapon, and this has really held back any binding international agreement on how to deal with this stuff."
Gorman says that while there is a financial and intelligence cost to satellites being damaged or destroyed by space junk, she is concerned about the cultural and heritage value of spacecraft and satellites no longer in use.
She believes there needs to be a space environmental management plan to preserve significant technology and satellites that may have played an important part in history, and does not want to see space junk mindlessly destroyed.
"People think that if there is nothing alive, then there is no moral and ethical obligation towards it," she says.
"I would argue that space is a culturally valuable environment because the manmade objects up there are a record of the development of technology and of contemporary telecommunication."
She uses the example of Vanguard 1, the fourth artificial earth orbital satellite ever launched and the first solar powered satellite. Although communication with it was lost in 1964, about six years after its launch in 1958, it is the oldest satellite still orbiting the earth.
"If you took it out of orbit, it would lose its significance," Gorman says.
"It would no longer be the oldest human object in orbit. There is a huge number of really interesting abandoned and non-functional satellites and spacecraft that tell the story of the space age and how the humans engage with a very challenging space environment, so there should be a well-reasoned and logical decision-making process before destroying them."
Still, the increasing amount of space debris is a pressing global issue, Gorman says. She is "slightly optimistic" that enough can be done to minimize the amount of junk left behind by future space missions.
A paper written in 1978 by NASA scientist Donald Kessler warned that every collision was generating more debris and shrapnel as pieces flew apart on impact. This debris would then collide with other debris and spacecraft, creating even more shrapnel. Eventually space would become impenetrable due to the unstoppable cascade of colliding debris, Kessler wrote, taking out telecommunications systems and preventing future space missions.
"Some say we are at the tipping point of the cascade," Gorman says.
"This was not helped in 2007 when the Chinese fired a ground-based missile into one of their own satellites, and it broke into millions of little pieces. Some people said that alone accelerated us 20 years faster into a cascade situation. It was one of the single most destructive things that happened in earth's orbit.
"People are right to be concerned, and I'm not in the camp of 'she'll be right.' We do need to be proactive.
"My assessment is we haven't yet reached that tipping point. But we need to make some serious progress in the next decade, 20 years tops, if we are going to prevent disaster."