Amid the growing buildup of space debris, the use of smaller satellites in low Earth orbit (LEO) could ensure an equitable distribution of the limited amount of area near the planet.
How much room is there in space?
Viasat (NASDAQ:VSAT) Executive Chairman Mark Dankberg asked the question during his Oct. 6 keynote speech at Satellite Innovation 2021 in Mountain View, Calif.
“People say it’s infinite but by definition the space near Earth is finite. Low Earth orbit is a limited, rivalrous zero-sum game,” he said, referring to the economic concept that when one person uses a resource, another person is prevented from using it.
Since space “is non-excludable, available to all nations,” Dankberg added, it creates the classic “tragedy of the commons,” in which individuals have incentives to maximize their own gain at the expense of others.
For this reason, certain orbits could be unusable for decades or centuries, Dankberg said, citing the Federal Communications Commission’s description of the Kessler syndrome in its Notice of Proposed Rulemaking, Mitigation of Orbital Debris in the New Space Age, from October 2018. The Kessler syndrome describes a theoretical chain reaction in which debris from one collision creates more collisions, each creating more debris in a cascade of damage, according to the FCC.
However, it’s extraordinary that the FCC said this, “because they have not done anything,” said Dankberg. He described the problem in detail with data from “The Impacts of Large Constellations of Satellites,” a study by independent science advisory group JASON published by the National Science Foundation last January.
Derelict satellites, which Dankberg defined as those that have been rendered uncontrollable by contact with debris, have not broken up into pieces.
The report predicts that a constellation of 30,000 satellites launched to a 600-kilometer orbit would have more than 1,000 collisions in less than 10 years, producing nearly 3,000 derelict satellites. At this point, the total number of satellites in the constellation declines as they go out of service faster than they can be launched.
The problem is worse at an orbit of 1,200 kilometers, Dankberg added, because satellite orbits decay more slowly at that altitude, even though the volume of space is greater.
The JASON-NSF model is optimistic, because it assumes a limited dispersion of debris objects, and assumes that debris decays at the same rate as intact satellites. “These are not errors; they are artifacts of a simplified but meaningful analysis,” Dankberg said. And because there is only a small sample set of actual collisions, there is not much data about what happens in a collision. However, models can be compared to the few collisions that have been tracked and measured.
“People describe me as a curmudgeon, doom and gloom,” Dankberg said. “But I don’t see it that way: I see an opportunity. … We can avoid the Kessler syndrome as long as [the] footprint of each LEO satellite is smaller.”
Given a finite resource, it makes sense to require that satellites be smaller, he added. The LEO ecosystem can support hundreds of thousands of satellites at a size of 12U or smaller. A 12U satellite has a mass of 24 kilograms, according to the U.S. government, though definitions vary.
As for debris removal, Dankberg noted that most debris is currently characterized as untrackable.
“One thing I want people to leave with is that space traffic management is not going to matter if we don’t resolve the debris problem,” he concluded.
