Cost-Benefit Analysis of Debris Risk Reduction Portfolios

Orbital debris is defined as all human-made, nonfunctional objects, including fragments and other elements, that are in Earth’s orbit or are reentering the atmosphere. These debris increase the costs of space operations by requiring efforts to shield against or maneuver around debris, threaten the safety of astronauts and satellites, hinder the launch of new spacecraft, and may eventually make entire orbits unusable.

A wide range of actions have been proposed to address risks from orbital debris, from mitigating their creation to removing existing objects. The effectiveness of these actions has typically been assessed in isolation. This includes previous work by the authors— referred to here as Phase 1 (Colvin, Karcz and Wusk 2023) and Phase 2 (Locke, et al. 2024)—to assess the costs and benefits of performing debris remediation, mitigation, and tracking on operationally relevant timescales. In reality, no risk-reducing action will be applied by itself, as operational norms naturally evolve, or policymakers consider parallel interventions. Ignoring interdependencies is a key gap in our objective to build a capability that can (1) complete rigorous calculations of the net present value of each action, (2) identify an economically efficient portfolio of actions to reduce risk, and (3) quantitatively analyze policies related to space sustainability.

This work assesses the effectiveness of different portfolios of risk-reducing actions, accounting for the interdependencies among actions. The analysis uses the models developed in Phase 1 and Phase 2 to analyze combinations of remediation, mitigation, and tracking actions and identify economically efficient portfolios of actions. We demonstrate that our approach of measuring risks in dollars facilitates identification of complementarities and substitution potential between actions. These, in turn, generate novel results about technology development priorities given budget and other constraints.