Source: NASA
Executive Summary
Purpose
This report presents a cost-benefit analysis of various approaches to debris remediation, which refers to any action taken to reduce the risks posed by orbital debris by moving, removing, or reusing it. A thorough understanding of the near-term costs and benefits of different remediation approaches can inform decision-making regarding R&D investment and policy creation in this field.
Background
Orbital debris, including abandoned vehicle stages, non-functional satellites, and fragments resulting from collisions or explosions, hinders the use of space upon which critical infrastructure of the U.S. economy relies, such as communications, national security, financial exchanges, transportation, and climate monitoring. Debris increases the costs of space operations by requiring efforts to shield against or maneuver around it, threatens the safety of astronauts and satellites, limits the ability to launch spacecraft, and may eventually make entire orbits unusable.
The 2021 National Orbital Debris Research and Development Plan outlines three broad methods for reducing the risks associated with debris: 1) mitigate the creation of new debris; 2) improve the tracking and characterization of debris; and 3) remediate debris that has already been generated. The costs and benefits of debris mitigation and tracking are fairly well understood, but significant uncertainties exist regarding the costs and benefits of debris remediation.
In the past, motivations for performing debris remediation have been related to ensuring the safety of spacecraft conducting civilian, commercial or national security missions, fulfilling moral responsibility to other operators, or preserving the sustainability of the space environment for future generations. Although these motivations are valid, the cost of remediation is not well-known, and the benefits associated with it may not materialize for many years. Given the substantial upfront expenditures required to develop and deploy remediation capabilities and the potential delay in receiving benefits, these motivations do not appear to be sufficient to incentivize immediate action.
Therefore, we conducted a cost-benefit analysis to determine whether the near-term risks imposed by debris, summed over all U.S. spacecraft operators, are greater than the costs of remediation.
Cost-Benefit Analysis Approach
To perform this analysis, we began by estimating the costs associated with orbital debris. We created a model for economic risks imposed on satellite operators, incorporating a simplified version of a commercially available tool that estimates the number of warnings, maneuvers, and collisions a satellite will have with space debris. We also gathered cost data from discussions with spacecraft operators, subject matter experts, and the literature.
We then estimated the benefits of performing debris remediation by analyzing two scenarios. For large debris remediation, we estimated the benefits of removing the 50 statistically most-concerning derelict objects in LEO (McKnight et al. 2021), while for small debris remediation, we estimated the benefits of removing 100,000 pieces of 1-10 cm debris from 450-850 km altitude.
In both scenarios, all debris is assumed to be remediated upfront, and benefits accrue over the following years. While this is not how debris would be remediated in reality, it removes the complexity of calculating benefits associated with slowly remediating debris and has little effect on the costs of remediation. Our assessments of the relative costs and benefits among remediation approaches are unlikely to change substantially if this assumption is removed.
To identify a prioritized number of approaches for debris remediation, we engaged with subject matter experts and the literature. For large debris remediation, we analyzed five approaches: removing debris by controlled reentry into the ocean; removing debris by uncontrolled reentry; moving debris with lasers or sounding rocket for just-in-time collision avoidance (JCA); and recycling debris by converting its material into propellant. For small debris remediation, we analyzed three approaches, including using ground-based or space-based lasers to nudge debris and using a physical sweeper to impact debris.
For each approach, we estimated the development and operational costs to remediate a single piece of debris and applied these per-debris costs to the debris remediation scenarios to estimate the total cost of using each approach to achieve the benefits of the scenario.
