Scientists warn of ‘tipping point’ as debris breaks up; legal hurdles as agencies explore nets and probes
The amount of junk in space is rising exponentially, with continuous collisions between abandoned equipment, spent rockets and other debris creating ever growing clouds of dangerous fragments, an influential report warned on Thursday.
The report, commissioned by NASA, says the quantity of hazardous material circling the Earth has reached a “tipping point” and poses a real and increasing danger to satellites and the International Space Station.
It suggests developing a clean-up strategy, which could include catching debris with nets, magnets or giant umbrellas.
The U.S. National Research Council was asked to review the space agency’s meteoroid and orbital debris programmes last April following a request from the White House. Meteoroids are particles or larger lumps of rock in the solar system.
“The current space environment is growing increasingly hazardous to spacecraft and astronauts,” said Donald Kessler, chair of the committee responsible for the report and a retired head of NASA’s orbital debris programme. “NASA needs to determine the best path forward for tackling the multifaceted problems caused by meteoroids and orbital debris that put human and robotic space operations at risk.” While the report, Limiting future collision risk to spacecraft, found NASA had used available resources wisely, the authors raised concerns that the agency’s programmes had no overall management or budget and that most programmes were run by one person, making them vulnerable to staff changes.
Objects in space ranging from the huge upper stages of Russian rockets to tiny particles of liquid coolant are tracked by ground based radars operated by NASA and other space agencies. About half a million fragments and objects larger than a centimetre are in low orbit around Earth. There are tens of millions of particles larger than a millimetre.
Even minuscule specks of debris can cause serious damage to spacecraft and satellites because of the immense speeds at which they travel.
“The average impact velocity is 10km per second,” Kessler said. “And at 2km per second, the energy of the collision is equivalent to the particle’s mass in TNT.” The potential threat from space debris became more pressing after China destroyed an orbiting weather satellite with a missile in 2007 as part of an anti-satellite test, and two satellites collided over Siberia in 2009.
These events more than doubled the amount of catalogued fragmentation debris in space, which had remained almost constant for the previous 20 years.
The report adds that NASA may have to launch operations to remove space junk from orbit, or find other ways to reduce the dangers posed by debris.
Since the NASA space shuttle was retired, there are no tried and tested means to remove defunct satellites and other space junk from orbit.
Several companies and agencies are exploring ways to clean up the space environment, with techniques that range from capturing the junk in lightweight nets to launching probes that latch on to debris and steer it into the atmosphere, where it will burn up.
Any programme aimed at removing space junk is likely to face serious legal hurdles, because current principles restrict countries to salvaging only their own objects. NASA estimates that about 30% of space junk can be attributed to the United States. In anticipation of future clean-up operations, 12 countries set up the Inter-Agency Space Debris Co-ordination Committee in 1993 to oversee the programme.
“The cold war is over, but the acute sensitivity regarding satellite technology remains,” said George Gleghorn, the report’s co-author and chief engineer for the TRW Space and Technology Group.
Although NASA had identified the need for removing debris, the agency and U.S. government had not fully examined the economic, technological, political, and legal considerations, the report added.
“The longer you wait to do this the more expensive it’s going to be. Given the economy, we’ll probably end up putting it off, but that’s really not very wise. This scenario of increasing space debris will play out even if we don’t put anything else in orbit,” Kessler said.
Satellite and spacecraft manufacturers routinely build additional shields to protect against debris strikes, but there is a trade-off between safety and weight. The International Space Station (ISS) has shields designed to withstand strikes from centimetre-sized objects, but satellites are less well protected.
Mission controllers can alter the orbits of the ISS and some satellites to avoid collisions, but this is not always effective.
In 2009, satellite operators might have been able to prevent the satellite collision over Siberia, but the defunct Russian Cosmos satellite involved was ranked 16th on a list of objects the US Iridium satellite was most likely to strike.
“Any avoidance move would have been to avoid something else,” Kessler said.
Copyright: Guardian News & Media 2011 Sidebar Deadly debris - The oldest known piece of space junk is the US Vanguard 1 communications satellite. It was launched in 1958 and failed in 1964.
- The space shuttle was regularly struck by space debris or rock. On average, NASA engineers replaced two damaged windows on every mission.
- A solar panel on the International Space Station (ISS) tore apart after a guide wire was hit by debris.
- In June, the ISS crew were ordered to take shelter in two Soyuz lifeboats after NASA spotted debris approaching.
- In 2007, the pilot of an airliner flying from Chile to New Zealand spotted a defunct Russian spy satellite falling from the sky and noted the sonic boom it made as it passed.
- In 2009, the US space surveillance network tracked 19,000 man-made objects larger than 10 cm in orbit.
Copyright: Guardian News & Media 2011