Tiny bursts of electrical energy caused by collisions of objects no wider than a pencil lead could one day allow pieces of space debris smaller than one millimeter in diameter to be tracked, reducing the danger to spacecraft in Earth orbit.
As more and more satellites are launched into orbit, the potential danger of space debris also increases. According to NASA, there are already over 25,000 objects larger than 10 cm (4 in) in diameter orbiting the Earth and when the scale is reduced the numbers become a tad hair raising. Between 1 and 10 cm, the estimate grows to about 500,000. Push that down to 1 mm and it comes to 100 million and that was in January 2022. In all, some estimates come out to 170 million bits of debris weighing in at 9,000 tonnes all up.
Some of this debris is made up of dead satellites and the rockets that launched them. Others are a mixed lot made up of miscellaneous flotsam and jetsam like nuts and bolts, bits of rocket plumbing, and even lost astronaut tool bags. Space agencies around the world pour money into tracking these objects but they are the tip of the proverbial iceberg.
The most disturbing problem is the very tiny bits – especially from early space missions that didn't enjoy technology aimed at minimizing space debris. Added to this are the results of accidental collisions of satellites and the detritus of irresponsible anti-satellite weapon tests by some countries and the numbers add up. Some of these are the size of a paint fleck, but a paint fleck traveling at 22,000 mph (35,000 km/h) can cause as much damage as a rifle bullet.
Unfortunately, small debris is very hard to detect and track because they don't reflect enough sunlight or radar signal to be detected. As an alternative, researchers at the University of Michigan are looking at a different principle.
What they found is that when two particles, even small ones, collide in space, they give off a cloud of gas and debris fragments that generate a burst of static electricity that charges up the fragments. The initial collision can not only be detected, but when the charged fragments briefly pass close to one another they arc a tiny spark between them.
According to the team, if two pieces of aluminum collide at orbital speeds, the resulting electrical burst can be detected by a 26-m (85-ft) radio antenna on Earth as well as the larger, more sensitive dishes of NASA's Deep Space Network (DSN).
While the idea has been sustained as a concept, there's still work to do before it becomes a practical tracking system. There are a number of factors that control the frequency of the electrical signals and there's also the problem of background radio signals and the attenuation caused by the debris signals passing through the Earth's atmosphere.
The next step will be to search for actual signals from space using the DSN and to look at data from hypervelocity experiments at the Naval Research Laboratory and NASA’s Ames Research Center. In addition, the team will carry out experiments using lasers to launch varieties of debris at different orbital velocities to build up a database of electrical emissions.
"We want to know if an object is hard or soft because that will impact how it orbits and how damaging it can be," said Mojtaba Akhavan-Tafti, an assistant research scientist in climate and space sciences and engineering.
Source: University of Michigan