About 22,000 items of space junk - from defunct satellites to spent rocket engines, metal fragments and other things larger than 10cm - are floating in space, 600km above Earth.
They pose a risk of colliding with more than 1,200 operational satellites, even as more satellites are launched every year.
Singapore start-up Astroscale has spotted a business opportunity in garbage collection in space. It is developing technology to remove debris at a fraction of current costs.
Now Japanese venture capital firm Jafco and other Japanese entrepreneurs have pledged US$7.7 million (S$10.4 million) to help it develop its technology.
The company was founded here in 2013 by Japanese entrepreneur Nobu Okada, 43, who told The Sunday Times it is believed to be the first space-related start-up to receive funding outside of the US.
The company is essentially developing an adhesive strong enough to stick to metal, carbon and other material.
The adhesive will be applied to a junk removal vehicle nicknamed "Boy", a powerful device measuring about 30cm by 40cm.
Six Boys will be taken to space on a mothership called "Mother". The latter will be sent close to an item of junk before a Boy is launched to grab the debris with its sticky surface.
Boy and junk will then be sent back towards Earth. "When they re-enter Earth's atmosphere, a lot of heat is generated and they will burst into flames, burning up completely," said Mr Okada.
Mr Okada, previously a management consultant with McKinsey and an IT entrepreneur, hopes to demonstrate his technology in a pilot project in 2017.
Boy and Mother are being developed in Astroscale's engineering office in Tokyo. "I tried to develop it in Singapore but there aren't enough space engineers here," he said.
He said Singapore is the right place for his company.
"Singapore is friendly to all countries, especially the United States, Russia and China, which launch the most satellites. We're seen as a neutral party which makes it easier for us to do business," he said.
About 200 new satellites are launched each year to orbit between 500km and 900km above sea level.
"Space is getting crowded. If the space debris is not removed, accidents can happen, which add to more debris," said Mr Okada.
It could also mean that spacecraft attempting to go beyond 900km will have to penetrate the wall of space junk, he added.
Space junk varies in size from 6m-long pieces weighing upwards of 100kg to 10cm items weighing a mere 1mg.
"A collision with a 10cm fragment is dangerous because these things are travelling at 27,360km per second. Even paint flecks at that speed can damage a satellite," said Mr Okada.
Astroscale is one of two space-related start-ups in Singapore.
The other is Kacific Broadband Satellites, which aims to provide broadband Internet via satellites to remote places like the Pacific islands.
Space debris is a major issue for international space agencies.
Associate Professor Low Kay Soon, director of the Satellite Research Centre at Nanyang Technological University, said there has been no attempt so far to clean up the junk.
Many items of debris have been in space for more than 20 years, and some have dropped from their orbits and burnt while re-entering Earth's atmosphere.
Prof Low said the risk of mishaps is low but in 2009, there was a collision between an active American commercial satellite called Iridium and a defunct Russian satellite called Kosmos and that incident added to the junk in space.
"We get forewarnings of possible collisions and we try to steer clear of any mishap," said Prof Low, who is in charge of NTU's satellite called X-Sat, launched in 2011.
Norad, the North American Aerospace Defence Command, which tracks all space debris bigger than a softball, and which also assigns all satellites an identification number, provides information on near misses to owners and operators.
The United Nations is trying to get countries that launch satellites to be responsible for their removal too, but cost and time are key issues, Prof Low said.
Mr Okada said it has been estimated that it will cost about US$500 million to remove 10 large objects from space.
He hopes to make it cost less. "I'm bringing the costs down to one-tenth of this cost," he said.
This article was first published on April 19, 2015.
Get a copy of The Straits Times or go to straitstimes.com for more stories.