The Cost/Benefit Of Orbital Debris Removal

Space News is reporting today that last Friday (March 10), NASA released a cost/benefit analysis study (pdf warning) of various methods for clearing near-Earth space of debris from rocket and satellite operations.  The study, released by NASA’s Office of Technology, Policy and Strategy, examined the costs of several approaches to removing both large and small debris and the benefits they offered to satellite operators by reducing the number of avoidance maneuvers and losses of satellites damaged or destroyed by debris collisions.  They billed it as "the most rigorous cost-benefit analysis to date of orbital debris remediation," noting that previous debris removal analyses had largely focused on emphasizing sustainability and the “moral responsibility” of doing so.

The topic of space junk comes up and I know I've done some coverage of it.  The most recent article I posted, last December, concluded with an expert (from a startup company, so someone with financial interest in making it sound dire) ended with predictions that in the next 10 years, "we are going to lose the ability to use certain orbits because the carrying capacity is going to get saturated by objects and junk;" and "we will see a loss of human life by (1) school-bus sized objects reentering and surviving reentry and hitting a populated area, or (2) people riding on this wave of civil and commercial astronauts basically having their vehicle getting scwhacked by an unpredicted piece of junk." 

Given that, the study from NASA is a bit surprising in saying, "some methods of removing orbital debris could pay for themselves within a decade by reducing the costs and risks borne by satellite operators."  It will take 10 years for it to pay for itself?  That long?  The astrodynamicist who made those last predictions made it sound like we don't have 10 years. 

The analysis, which looked at both the cost of establishing various approaches to removing debris as well as the costs incurred by satellite operators from debris, found the most effective approaches involved ground- and space-based lasers to remove large amounts of small debris between 1 and 10 centimeters across. Both laser systems would create benefits that exceed their costs within a decade.

The other effective approaches involved “just-in-time collision avoidance” involving the largest debris objects, using rockets or lasers to nudge such debris to avoid collisions with satellites or other debris. Such approaches could have net benefits almost immediately, or no more than a few decades in a worst-case assessment.

The authors acknowledged that the general perception is that such lasers are weapons or that they could be used as weapons.  They state the power of debris-removal lasers would be too low, by a factor of 1,000, to be effective as a weapon against active satellites, “though perceptions may be harder to navigate.”  

They then go on to say that forcing reentry of larger debris objects (think upper stages of boosters) could break even in as little as 20 to 25 years, but in worst-case scenarios might take close to a century to yield benefits. The study found similar time frames for “sweeper” spacecraft that would physically remove small debris. It also examined recycling debris by turning it into propellant, but found breakeven times of a few decades, in part because of large upfront research and development costs for the technology.

There's a lot of interesting things in this paper, including moments of "is that all?" or "huh."  Granted this is limited to US interests only but they found the estimated annual costs to US launch operators of only $58 million a year.  That's less than the cost of one launch on just about any orbital rocket and includes all military as well as civil operational satellites, like Landsat and weather satellites.  I believe that includes the burgeoning field of internet via space, like Starlink, OneWeb and coming systems like Kuiper. 

“We found that most satellite operators do not incur much cost from conjunction assessments or collision avoidance maneuvers,” said Bhavya Lal, NASA associate administrator for technology, policy and strategy, in a speech at the American Astronautical Society’s Goddard Memorial Symposium March 10 that coincided with the release of the report. “The key takeaway here is that the risk to satellite operators need not increase at the same rate as orbital debris increases.”

Still, the fastest payoff (cost to benefit) was a decade.  When does that decade start?  While the observation that to be a weapon a laser would have to be about 1000x the power they're talking about for clearing out small debris, what about aiming it?  Naturally, being "fully trained in the four rules" of gun handling, I think of the aiming accuracy to affect a "few cubic inches" of junk up 300 or so miles, more specifically, Rule 4: "be sure of your target and know what's behind it."  Now think that there are estimates that put the number of pieces of orbital debris about the size of a blueberry (which can't be tracked by radar from the ground) in the hundreds of thousands of pieces.  

Sounds like a space-based laser is called for.  Maybe that decade could start in a decade - at best?

An illustration of objects and space debris in Earth orbit.  Credit: ESA/ID&Sense/ONiRiXEL, CC BY-SA 3.0 IGO

NASA said they plan to organize a roundtable among various launch industry and satellite operators to get feedback on the study before starting a second phase that will improve the model and incorporate even smaller debris.