Dodging Space Debris in the Depths of Space

Today’s successful SpaceX Falcon-9 launch of 46 Starlink satellites from Vandenburg Space Force Base in California follows hard on the heels of this past Tuesday’s launch of 52 Starlink satellites from Cape Canaveral, Fla. It’s the second of seven launches scheduled this month as SpaceX continues to relentlessly expand its global internet network.

Fully reusable Falcon-9 first-stage boosters are retrieved immediately after launch, and the process of refurbishing begins even before the payloads reach their final orbits. With a ready inventory of affordable and reusable rockets, SpaceX has increased its launch cadence over three short years from monthly to weekly and now every few days. Averaging fifty satellites per launch, that’s a lot of metal in low Earth orbit.

And that’s just from SpaceX. Although Elon Musk pretty much owns low Earth orbit, not to mention more than half of all functional satellites orbiting Earth (Starlink will account for over 3,000 by the end of this month), there are other players. Dozens of space agencies and communications conglomerates are actively placing and expanding their own orbital networks.

“There’s a lot of stuff up there.”

But SpaceX’s “satellites” aren’t one-off shiny Sputnik spheres with spiky antennas, or car-size custom-built signal relays and observation platforms. They are smallish, mass-produced space vehicles weighing in at around 550 pounds each, equipped with global navigation systems, proximity approach warning protocols, and autonomous collision avoidance technology. Once positioned into a preliminary transfer orbit (around the average height of the International Space Station), solar panels deploy to power up Krypton Hall ion propulsion thrusters and boost the craft to operating altitude. The relatively low orbits (over sixty times closer to Earth than traditional communication satellites) ensure optimal low-latency and high-speed broadband internet service. They also squeeze the Starlink constellation into compact shells of whirling metal between 300 and 400 miles above our planet. Not impenetrable—but still.

There’s a lot of stuff up there.

In March of last year, NASA signed a 13-page Joint Spaceflight Safety Agreement with SpaceX to help regulate low Earth orbit traffic patterns and enhance the safety of spacecraft as they attempt to launch through the various shells of Starlink satellites.

The Krypton Hall thrusters that allow the Starlink sats to maneuver into their assigned orbits also allow them to avoid incoming spacecraft—either autonomously or through ground-control command. Under the NASA/SpaceX agreement, SpaceX “has the conn” when it comes to clearing a path for potential collision courses. Presumably, other agencies/space companies have negotiated or can negotiate similar protocols.

Of course, there is a lot of junk up there too—almost fifty years’ worth of derelict rockets, boosters, bits and pieces of solar panels, defunct satellites, nuts and bolts and tools lost while assembling space labs and space stations, even flakes of paint. It’s no joke. Millions of pieces of high-tech debris hurtle above the Earth at speeds exceeding 18,000 miles per hour. And that’s just the accidental and relatively benign stuff.

Back in 2007 the Red Chinese tested anti-satellite weapon (ASAT) technology by blasting one of its own decommissioned satellites out of orbit. The strike unleashed a swath of over 2,000 “trackable” pieces of shrapnel (golf-ball-size or bigger) and another 150,000 smaller bits. Fifteen years later, the Chinese ASAT test still accounts for almost one-third of the space debris routinely tracked by the U.S. Space Force as a potential threat to the International Space Station (ISS).

In 2019, India tested its own ASAT, destroying a purpose-built Indian Space Research Organization (ISRO) target satellite and scattering wreckage just below what is now Starlink’s preliminary transfer orbit. In September 2020 the ISS had to perform emergency maneuvers three times to avoid space debris.

In December 2020, in collaboration with U.S. Space Command, NASA published the Spacecraft Conjunction Assessment and Collision Avoidance Best Practices Handbook to “improve global awareness of space activity” and to “share lessons-learned regarding close approach coordination and mitigation.” While tailored to address satellite constellations of 100 or more assets, by extrapolation these “best practices” embrace probes, interplanetary missions, and space debris.

Last year a Russian ASAP interceptor took out the huge (4,000-pound) derelict COSMOS 1408 satellite. The resulting wreckage forced NASA to cancel at least one ISS space walk and prompted SpaceX to alter some Starlink orbits. The Commercial Space Operations Center (COMSPOC) has reported over 6,000 “close approaches” with the Russian debris field, affecting 841 Starlink satellites.

America has demonstrated its own fair share of destructive ASAT tests but has since “learned the error of their ways.” Last April, Vice President Kamala Harris renounced “direct ascent” anti-satellite missile testing, seeking “to establish this as a new international norm for responsible behavior in space.” Last month the White House went a step further, issuing a National Orbital Debris Implementation Plan incorporating a section on debris remediation. Lots of talk and not much action, but it is a start.

Starlink has five orbital groups or shells, each one assigned a distinct orbital path and distinct orbital inclination. This month’s launches are populating a shell that is unfortunately within the path of successive ASAT debris fields.

It’s a two-way street.

In 2019, the European Space Agency (ESA) had to fire the thrusters on Earth observation satellite Aeolus to avoid a potential collision with a Starlink satellite. Last year, Starlink rival OneWeb claimed a near miss with a Starlink asset. Just last December, Red China complained that they’d had to move their Tianhe space station to avoid close approaches by Starlink-2305 and Starlink-2305.

Back in 1978 NASA scientist Donald J. Kessler postulated a scenario in which the density of objects in low Earth orbit becomes so high that collisions between objects cause cascades in which each collision generates space debris that sequentially enhances the likelihood of further collisions. Now termed the Kessler effect, modeling results indicate that the debris environment is already unstable, with successive collisions generating fragments faster than atmospheric drag can remove them, making the use of satellites difficult for generations to come.

The U.S. Space Command’s 18th Space Defense Squadron out of Vandenburg SFB is responsible for monitoring space traffic. When stood up, Space Command was tracking 25,000 pieces of space debris. Now they’re tracking over 47,000, and they really aren’t staffed for that. Space Policy Directive 3 directs the Commerce Department’s Office of Space Commerce to take over civil space traffic management from Space Force by 2024.

By then, the number of satellites and space platforms will have increased exponentially—as will the inevitable generation of space junk.

NASA, ESA, ISRO, ROSCOMOS, Red China’s CNSA, and all other national space agencies, civilian space companies, and communications corporations all have a vested interest in dealing with Kessler effect risks. And plans are afoot—or at least, contracts have been awarded.

The ESA awarded the world’s first contract to begin removing space debris to Swiss space company ClearSpace—calling for positive progress by 2025. The U.S. Space Command’s Orbital Prime project is awarding study contracts for technologies focused on satellite life extension through repair and refueling, and debris removal. The Australian Neumann Space company is working with Japanese start-up Astroscale to capture space debris, and U.S. companies Nanorocks and Cislunar to store and cut debris and smelt debris for potential fuel.

Red China’s Shijian-21 “space debris mitigation satellite” has docked with a decommissioned Chinese satellite and parked it in a “high graveyard orbit.” It didn’t work (the defunct satellite returned toward its original orbit), and skeptics have assigned less peaceful capabilities for the so-called space tug, but the PR was profitable.

Northrup Grumman has at least notional plans for a space junk recycler on their drawing boards.

Meanwhile, SpaceX continues to maneuver around rival satellite constellations, government spacecraft, and space junk, as it doggedly populates low Earth orbit fifty or so satellites at a time.



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