WAILEA, Hawaii — The Federal Aviation Administration has proposed recent regulations that might require business launch providers to get rid of upper stages from their launches to mitigate the expansion of orbital debris.
The FAA released the draft rule Sept. 20, which can be formally published within the Federal Register in the approaching days. That publication will start a 90-day public comment period.
The rule would require firms with FAA business launch licenses to select from certainly one of five approaches for removing upper stages from congested orbits on future launches, starting from placing them into graveyard orbits to contracting with a 3rd party to handle the disposal.
The FAA said the rule is motivated by the expansion of orbital debris. “Historically, the most important contributor to orbital debris was the explosion of upper stages,” the document states. Those explosions got here from batteries that exploded or propellant tanks that burst, resulting in past regulations that decision for “passivization” of upper stages by venting propellant tanks and discharging batteries after completing their missions.
Nevertheless, the scale and mass of upper stages also poses hazards from collisions with other space objects. “The strength of upper stage structures, together with their mass and size, pose a risk of catastrophic collisions that might create substantial amounts of orbital debris,” the document states.
The proposed regulation would require business launch operators to decide on certainly one of five approaches to removing upper stages from key orbits. Essentially the most straightforward is to have the stage perform a controlled reentry over an unpopulated region, just like the ocean, which the regulation would require be accomplished inside 30 days of launch.
A second approach could be to send the stage out of Earth orbit completely by placing it right into a heliocentric orbit across the sun. That may be primarily for launches sending payloads beyond Earth orbit and, the document acknowledges, and could be “prohibitively costly” for other missions.
The proposal would allow upper stages to enter certain “disposal” orbits outside of the commonly used low, medium and geostationary Earth orbits. Those orbits would need to be stable for no less than 100 years and avoid those commonly used orbits.
The rule would allow launch operators to elect to make use of uncontrolled reentries of upper stages, provided that those stages, if left in LEO, reenter not 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 chance of casualties to people in the bottom. Upper stages could alternatively be left in highly elliptical, stable orbits that might take as much as 200 years to reenter, however the proposal notes that few business launches send payloads to orbits where that might be an option.
The last option could be to permit the launch operator to contract with one other company to retrieve the debris not more than five years after launch, either moving the debris right into a disposal orbit or performing a controlled reentry. While no such energetic debris removal systems are in service today, several firms are working on such systems that include the power to remove upper stages.
While the important thing section of the proposed rule governs disposal of upper stages, it has several other provisions. One section limits the quantity of debris from upper stages released during “normal operations” of the stage, like payload adapter components. One other sets a 1-in-1,000 threshold for the chance of a collision between space objects no less than 10 centimeters across and the upper stage over the planned orbital lifetime of the upper stage.
Space sustainability experts on the AMOS Conference here said that while they’d not yet reviewed the total proposal, they were encouraged by the FAA’s approach, including giving launch operators several options to get rid of stages in a timely manner that might help incentivize development of energetic debris removal systems.
“I like it,” said Darren McKnight, senior technical fellow at LeoLabs, which operates a network of economic radars for tracking objects in low Earth orbit. The important thing, he said, is that the regulation is straightforward, traceable and behavior-based. “I believe regulators have a responsibility to make it easy.”