The weak bursts of electrical energy produced by the collision of objects no larger than the width of a pencil lead could one day help the aerospace community track space debris less than one millimeter in diameter, thereby reducing the danger to spacecraft in Earth orbit. As more satellites are put into orbit, the potential danger from space debris increases.
According to the National Aeronautics and Space Administration (NASA), there are currently more than 25,000 objects larger than 10 centimeters (4 inches) in diameter orbiting the Earth. Between 1 cm and 10 cm, this is estimated to increase to approximately 500,000. If you shrink it to 1 mm, it will be 100 million. This is still the number in January 2022. It is estimated that there are a total of 170 million pieces of debris near the Earth, with a total weight of 9,000 tons.
Some of the debris consists of dead satellites and the rockets that launched them. Others are a mixture of nuts and bolts, fragments of rocket tubing, and even miscellaneous items like a lost astronaut tool bag. Space agencies around the world invest heavily in tracking these objects, but they are just the tip of the proverbial iceberg.
The biggest concern was very tiny debris -- especially from early space missions, because the technology designed to minimize space debris didn't yet exist. In addition, there are increasing amounts of debris resulting from accidental satellite collisions and from irresponsible anti-satellite weapons testing by some countries. Some of these fragments are only the size of paint splotches, but a paint splotch traveling at 22,000 miles (35,000 kilometers) per hour can cause as much damage as a rifle bullet.
Unfortunately, small debris is difficult to detect and track because they don't reflect enough sunlight or radar signals to be detected. As an alternative, researchers at the University of Michigan are working on a different principle.
They found that when two particles, even small ones, collide in space, they release a cloud of gas and debris, creating a burst of static electricity that charges the debris. Not only can the initial collision be detected, but when the charged fragments briefly approach each other, tiny sparks of electricity are produced between them.
According to the research team, if two pieces of aluminum collided at orbital speeds, the resulting electrical pulses could be detected by radio antennas 26 meters (85 feet) high on Earth, as well as larger, more sensitive antennas on NASA's Deep Space Network (DSN).
While the idea has gained support as a concept, there is still much work to be done before it becomes a practical tracking system. There are many factors that control the frequency of electrical signals, as well as attenuation caused by background radio signals and signals from debris traveling through the Earth's atmosphere.
The next steps will be to use DSN to search for actual signals from space and look at data from ultra-high-speed experiments at the Naval Research Laboratory and NASA's Ames Research Center. In addition, the team will conduct experiments using lasers to launch various fragments at different orbital velocities to build a database of electrical emissions.
"We want to know whether an object is hard or soft because that will affect its orbit and how destructive it is," said Mojtaba Akhavan-Tafti, assistant research scientist in Climate and Space Science and Engineering.