On September 22, 2020, NASA and the U. S. Space Command announced that they were tracking an unidentified piece of space debris that appeared to be hurtling toward the International Space Station (ISS). It was predicted to pass by within only a few kilometers, dangerously too close to chance, at 5:21 p.m. CT. The astronauts boarded the Soyuz spacecraft “out of an abundance of caution,” and NASA controllers fired thrusters to redirect the ISS out of the debris’ trajectory. The object — later identified as a piece of a Japanese rocket launched back in 2018 — whizzed by the ISS at 14.6 km/s (more than 30,000 mph). Crisis averted.
|The International Space Station. Image Credit: © NASA.|
Since the successful launch of Sputnik in 1957, nearly ten thousand satellites have been sent to space. They’re joined in orbit by thousands of spent rocket bodies, fuel tanks, nuts, bolts, and other broken
pieces of metal, and things astronauts have accidentally lost on spacewalks. (Oops!) Some estimates suggest that there are upwards of a hundred million bits of space debris larger than a millimeter. If you want to include objects the size of a micron, that estimate jumps to a hundred trillion.
Space has become a cluttered, uncontrollable mess.
The space debris problem we have today has been a concern since the dawn of the Space Age but was first formalized in 1978 by NASA astrophysicist Donald J. Kessler. In a paper for the Journal of Geophysical Research titled, “Collision frequency of artificial satellites: The creation of a debris belt,” Kessler developed a mathematical model to predict the rate at which a “belt of debris” would form around Earth. (Think Saturn’s rings, but instead made of garbage). “As the number of artificial satellites in earth orbit increases, the probability of collisions between satellites also increases,” he argues. This idea of a cascading chain of collisions between objects in low-Earth orbit is now referred to as the Kessler syndrome. This scene from the 2013 movie Gravity demonstrates the concept:
In 2009, Kessler’s collision fears became a reality. On February 10, two satellites collided with one another at a speed of 26,000 mph: one, Iridium 33, was an active U. S. communications satellite, and the other, Kosmos 2251, was a defunct Russian military communications satellite. It was the first hypervelocity collision of its kind, and it caused an enormous amount of debris and threatened the Hubble Space Telescope. Within 10 days of the incident, NASA estimated that at least 1,000 pieces of debris larger than 10 cm were a direct consequence of the collision. These pieces have since collided and multiplied, and you can see all tracked debris from the accident on stuffin.space, shown below.
Jack Bacon, a senior scientist at NASA, reacted bluntly to the 2009 collision: “The Kessler syndrome is in effect. We’re in a runaway environment, and we won’t be able to use space in the future if we don’t start dealing with this now.”
|The debris from the 2009 Iridium 33 Collision. Image Credit: Screenshot from stuffin.space.|
AstriaGraph, developed by Dr. Moriba Jah — who describes himself as a “space environmentalist” — and colleagues at the University of Texas at Austin is a visualization tool that draws on numerous databases to map orbital trajectories of space debris. “I want to make space a place that is safe to operate, that is free and useful for future generations,” he said. On October 2, 2020, IBM, in partnership with Dr. Jah, published two new open-source artificial intelligence projects to help track space junk. Such progress in the field of “space-traffic management” is an encouraging sign that we may be able to clean up space.
|Screenshot of AstriaGraph. Image Credit: spacewatch.global.|
So many things in (and out of) this world may be invisible but are nevertheless impactful on our daily lives. Space debris is yet another example. GPS, the internet, cell phones, and other global communication networks rely on functioning space technologies, and increasing amounts of space debris put these infrastructures at risk. Additionally, it may become even more difficult or impossible to pursue launches and space missions in the future. It seems as though we’re well-past due to take out our space trash.
“What’s going on in this video? Our science teacher claims that the pain comes from a small electrical shock, but we believe that this is due to the absorption of light. Please help us resolve this dispute!”
(We’ve since updated this article to include the science behind vegan ice cream. To learn more about ice cream science, check out The Science of Ice Cream, Redux)
Over at Physics@Home there’s an easy recipe for homemade ice cream. But what kind of milk should you use to make ice cream? And do you really need to chill the ice cream base before making it? Why do ice cream recipes always call for salt on ice?