What Can We Do with Orbital Debris?
Austin Morris, Director of Engineering
5 minute read
One of the most common questions that we at KMI get when people are first introduced to our business of orbital debris remediation is what do we plan to do once we have captured a piece of debris. Often we are asked if we’ll throw it into the Sun (we’ll get into that in the next paragraph, but the short answer is “No.”) or if we’ll bring it back down to Earth to harvest the materials. The real answer is that there are several possibilities, some more likely than others and some more exciting than others. The goal of this column is to explain some of the potential solutions to this problem and why each one is or is not viable.
So first and foremost, let’s cover a few of the things that we don’t plan to do. As discussed in a previous column, we don’t plan to blow up debris objects. Likewise, in another previous column, I detailed why it is so difficult to bring objects safely back to the ground and why that isn’t the most feasible solution (although companies like Inversion Space are working on methods of streamlining that process and making it feasible for the scenarios in which we do want a controlled reentry). As for throwing debris into the Sun, not only is it unnecessary but it is actually extremely difficult and costly. As it turns out, for the same amount of energy we could either take a single trip to the Sun or take 55 trips to Mars. So those are some of the various things that we are not planning to do. It’s probably about time that I get around to actually answering the title question and explaining what we are planning to do.
Current guidelines and international agreements drive us to examine two of the simplest options. The first option is to simply deorbit captured orbital debris by lowering its altitude until it enters the atmosphere, heats up due to immense air friction, and burns up on reentry (ideally without dragging the capturing spacecraft down with it). This concept has been discussed in a previous KMI column as well. The other simple option is to do the opposite of deorbiting, and instead increase the altitude of the orbital debris to place it into a designated “graveyard orbit,” ensuring that it is well out of the way and won’t make its way back to Earth anytime soon. While both of these options are certainly simple, they are also costly in terms of propellant usage and are wasteful in the sense that they essentially dispose of material that was launched into orbit at significant cost and effort. At KMI, we believe that we can use this material productively, and can do so at a lower propellant cost than deorbiting or boosting to a graveyard orbit.
“Debris” is a term that covers a wide variety of objects in space, ranging from whole, but defunct, satellites and rocket bodies to shards and fragments of former satellites. When it comes to making a significant effort toward stabilizing the orbital environment in terms of debris growth, it is important to remove the largest debris objects as they have the most potential to become numerous pieces of debris if struck by another object. How this plays into what we do with them is that many of these large objects are generally intact, which determines what can be done with them. Let’s consider a hypothetical satellite that gets launched in the near future and has one critical component that shorts out or fails (for example, batteries are notorious for being at risk of early failure). The whole satellite is now seen as useless, akin to blowing a tire and abandoning your whole car. However, if that satellite can be retrieved, then maybe it can be repaired. Let’s take this a step further and say that two of these satellites were launched and both had different critical components fail. We can now look at this as an opportunity to salvage components from one satellite to repair the other, so that rather than having two defunct satellites we can at least have one functional one, with no additional launches. While this scenario may seem like an unlikely occurrence, it becomes significantly more likely when we consider that there are tens of thousands of identical or near-identical satellites planned for launches in the next decade as part of megaconstellations. This is where repurposing components from one satellite to repair another becomes not only possible but optimal.
In addition to repair prospects, there are potential end-uses for repurposing existing components to create new or different satellites, rather than simply slotting it in to replace an identical component on another satellite. For example, if we collected the solar panels from several defunct satellites in orbit and strung them all together, we could potentially create an orbiting solar farm with components that were otherwise considered to be hazardous junk. In this scenario, the solar panels don’t even necessarily have to operate at peak efficiency to be worthwhile, considering that some power generation is still better than no power generation at all, especially when there are unused solar panels ripe for usage relatively nearby.
Looking back toward our hypothetically salvaged satellite, let’s consider that maybe it was struck by another piece of debris or a major radiation event that rendered most of the advanced components useless. In the case of components like solar panels and batteries and computers having no useful life left for repair or repurposing, we can still turn to the option of recycling. At the time of this writing, I can confidently say that satellites and rocket bodies in orbit were constructed under the effects of gravity on Earth and subjected to the extreme forces necessary to launch them into orbit. This generally means that they have some sort of structure built into them onto which the remaining advanced components and circuitry were mounted. For many of these objects, that structure is made up of metal alloys such as aluminum or stainless steel. Leveraging technologies such as the CisLunar Industries Micro Space Foundry, which can melt down materials in orbit and forge them back into raw material, or the Nanoracks Mission Extension Kit, which can turn expended rocket bodies into active space stations, new space infrastructure is enabled, ranging from in-space manufacturing of satellites to new orbiting stations and more.
With these options of repair, repurposing, and recycling available, it makes it seem like deorbiting or boosting to a graveyard orbit isn’t worthwhile. The reality is that in the immediate future, the most important thing to do to secure the orbital environment is to remove debris objects and reduce the risk of collision through whatever means are most available. Deorbiting debris or boosting it into a graveyard orbit may not be the optimal solution, but it is still a step in the right direction. As technologies progress, the question of capability and worth of repair, repurposing, and recycling will likely come down to the cost of retrieving and processing the components (again, referenced in a previous column), which is why KMI and our partners are continually working on streamlining these types of missions and operations to bring these seemingly science-fiction capabilities into the real world. This is how we continue to make progress forward on our mission of #KeepingSpaceClearForAll.
Recommended column to read next: ADR and Adversity