Monday, March 13, 2023

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.




  1. Much of this debris will deorbit and burn up in the atmosphere...eventually. But not all of it. And the time frame involved is pretty significant. In the mean time near earth orbit just gets more and more cluttered with debris. Eventually this debris will create such a significant hazard to satellites and manned missions that something will HAVE to be done about it. The only question is what and how much it will cost. Sadly there is no magical means of space propulsion to allow vehicles to do such a job simply or efficiently. That means it will be a complex, expensive and difficult task to deal with.

  2. When I worked for GEODSS back in '03 there were over 3000 "objects" we were tracking in orbit.

    With the Chinese throwing all their crap up there it has gotten two orders of magnitude worse since then. Let's make sure and deorbit OUR junk over top of THEM.

    Who's with me?

    1. The only stuff that can be deliberately deorbited are functional satellites that still have fuel. Most of the debris up there doesn't fall into that category. In fact a huge percentage of it is detritus. Pieces left over from things that are no longer intact. That stuff will come down where, when at random times and places...if it ever deorbits at all.

    2. Considering China drops boosters on their own population, it's hard to think they'd care about deorbiting junk onto them. Unless they want to claim victimhood.

  3. As a general comment, I would hope that "cost:benefit analysis" would consider (for example) the cost of not only the damage to things on orbit from debris, but the costs of the giant space laser to push things around - or whatever hardware they expect to develop to go up there and do it. It would include costs of losing certain orbits. It would include the costs of doing things vs. the costs of doing nothing.

    1. Wouldn't a laser create more pieces, just smaller? Vaporizing a small part of a chunk of material with heat is not a clean cut. Some of the resulting pieces would be too small to track.

    2. I don't think that's what they're doing. They seem to be using the pressure from the light to slow down the junk, making it drop into a lower orbit so that it gets caught in the atmosphere sooner.

      Light pressure is a very different idea for most people.

    3. Why space based? A ground based laser has as much power as it wants, and as much cooling capacity as it wants. Ground based telescopes at high-altitude sites can point at things effectively through the atmosphere at high elevation angles.


    4. I should have emphasized that the NASA report didn't say space-based, it was something I thought of. That was mostly from the perspective of using it pointed closer to the horizon rather than straight up. I've heard stories of lasers heating the air enough to change the direction the beam is aimed, by minutes of arc. That's a lot over a few miles.

  4. First time I read about this was Ben Bova's (R.I.P.) Kinsman series. He didn't quite live to see his SF turn to reality . . . .

  5. OK, I haven't done the math but if you launch into low westerly orbit tons of liquid nitrogen, wouldn't it temporarily increase the (very low) atmospheric presure and create drag to remove microparticles?

  6. At the rate he's going, Musk will begin the cleanup, and charge per pound recovered.
    Anyone who doesn't pay up, gets it de-orbited over their own population.

    "Nice capitol you've got there. Be a shame if 2-ton satellites started flaming into it at the speed of heat, wouldn't it?"

    Even China will cough up under those circumstances, and he'll turn a profit the first year.