FAA proposes rule to limit lifetime of upper stages in orbit

WAILEA, Hawaii — The Federal Aviation Administration has proposed new regulations that would require commercial launch providers to dispose of upper stages from their launches to mitigate the growth of orbital debris.

The FAA released the draft rule Sept. 20, which will be formally published in the Federal Register in the coming days. That publication will start a 90-day public comment period.

The rule would require companies with FAA commercial launch licenses to choose from one of five approaches for removing upper stages from congested orbits on future launches, ranging from placing them into graveyard orbits to contracting with a third party to handle the disposal.

The FAA said the rule is motivated by the growth of orbital debris. “Historically, the largest contributor to orbital debris was the explosion of upper stages,” the document states. Those explosions came from batteries that exploded or propellant tanks that burst, leading to past regulations that call for “passivization” of upper stages by venting propellant tanks and discharging batteries after completing their missions.

However, the size and mass of upper stages also poses hazards from collisions with other space objects. “The strength of upper stage structures, along with their mass and size, pose a risk of catastrophic collisions that would create substantial amounts of orbital debris,” the document states.

The proposed regulation would require commercial launch operators to choose one of five approaches to removing upper stages from key orbits. The most straightforward is to have the stage perform a controlled reentry over an unpopulated region, like the ocean, which the regulation would require be completed within 30 days of launch.

A second approach would be to send the stage out of Earth orbit completely by placing it into a heliocentric orbit around the sun. That would be primarily for launches sending payloads beyond Earth orbit and, the document acknowledges, and would be “prohibitively costly” for other missions.

The proposal would allow upper stages to go into certain “disposal” orbits outside of the commonly used low, medium and geostationary Earth orbits. Those orbits would have to be stable for at least 100 years and avoid those commonly used orbits.

The rule would allow launch operators to elect to use uncontrolled reentries of upper stages, provided that those stages, if left in LEO, reenter no more than 25 years after launch — although the FAA said it wanted feedback on shortening that timeframe to as little as five years — and limit the risk of casualties to people in the ground. Upper stages could alternatively be left in highly elliptical, stable orbits that would take up to 200 years to reenter, but the proposal notes that few commercial launches send payloads to orbits where that would be an option.

The last option would be to allow the launch operator to contract with another company to retrieve the debris no more than five years after launch, either moving the debris into a disposal orbit or performing a controlled reentry. While no such active debris removal systems are in service today, several companies are working on such systems that include the ability to remove upper stages.

While the key section of the proposed rule governs disposal of upper stages, it has several other provisions. One section limits the amount of debris from upper stages released during “normal operations” of the stage, like payload adapter components. Another sets a 1-in-1,000 threshold for the risk of a collision between space objects at least 10 centimeters across and the upper stage over the planned orbital lifetime of the upper stage.

Space sustainability experts at the AMOS Conference here said that while they had not yet reviewed the full proposal, they were encouraged by the FAA’s approach, including giving launch operators several options to dispose of stages in a timely manner that could help incentivize development of active debris removal systems.

“I love it,” said Darren McKnight, senior technical fellow at LeoLabs, which operates a network of commercial radars for tracking objects in low Earth orbit. The key, he said, is that the regulation is simple, traceable and behavior-based. “I think regulators have a responsibility to make it simple.”

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