New Framework Sorts Rocket Parts by Failure Risk to Make Reusable Launch Vehicles Cheaper

Reusable launch vehicles have become the defining technology of the modern space economy, promising to slash the cost of reaching orbit by flying the same hardware mission after mission. Yet the economics of reusability rest on a deceptively simple question that operators must answer after every flight: which components can safely fly again, and which need attention before the next launch? A new study published in the International Journal of Aeronautical and Space Sciences by Ho-Beom Park, Joo-Ho Choi, and Hae-Sung Yoon of Korea Aerospace University tackles this question head-on, proposing a systematic reusability assessment procedure designed to bring rigor and cost discipline to the maintenance of reusable launch vehicles, or RLVs.

The researchers argue that the economic promise of reusability cannot be realized unless reliability, operability, and cost-effectiveness are engineered into the vehicle from the earliest design phase. Retrofitting a maintenance philosophy onto a finished rocket, they contend, leads to inefficiency and unnecessary expense. Their starting point is an observation drawn from decades of experience with high-reliability mechanical systems such as aerospace engines: it is neither practical nor economical to re-evaluate the reusability of every single component after every mission. Some parts degrade quickly and predictably, others fail rarely, and still others show no meaningful wear at all. Treating them all identically wastes resources on components that need little scrutiny while potentially under-serving those that need the most.

To resolve this, the team built an integrated maintenance framework that classifies components into four categories based on the severity and frequency of their failures, using NASA engine data as the evidentiary foundation. Components are sorted into On-Condition, Hard-Time, Servicing-Lubrication, and Non-Significant groups, each carrying a corresponding level of maintenance activity. The classification approach draws on the principles of reliability-centered maintenance, a discipline formalized in the aviation industry and popularized by John Moubray’s influential 1997 work, which holds that maintenance policies should be dictated by the failure characteristics of each item rather than by a uniform schedule applied across the board.

The On-Condition category is the most demanding. These are components whose health cannot be guaranteed by a fixed calendar or usage limit alone, but must instead be verified through inspection and measurement before each subsequent flight. For these parts, the researchers apply condition-based maintenance, an approach in which sensors and diagnostic algorithms determine whether a component retains sufficient remaining useful life, commonly abbreviated RUL, to fly again. The Hard-Time category covers items with well-defined life limits that are replaced or overhauled after a set number of cycles regardless of apparent condition, while Servicing-Lubrication items require routine replenishment and upkeep. Non-Significant components, finally, are those whose failure history and consequences justify minimal dedicated maintenance activity.

As a representative case study for the On-Condition class, the authors selected the fuel supply system of a launch vehicle, the subsystem that typically demands the most intensive maintenance effort. The fuel supply system is a natural choice for such scrutiny: it comprises turbopumps, valves, lines, and pressurization hardware operating under extreme pressures, cryogenic temperatures, and violent vibration, and a failure here can be catastrophic. The paper develops a detailed scenario for assessing the effective remaining useful life of components within this system, showing how sensor data gathered during and after a flight can be fed into a condition-based maintenance workflow to produce a defensible go or no-go decision for the next launch.

The scenario rests on a foundation of failure mode and effect analysis, a structured engineering method for enumerating the ways a component can fail, the mechanisms behind those failures, and their consequences. By pairing this analysis with sensor-based health monitoring, the framework links each critical failure mode to observable physical indicators, such as pressure anomalies, temperature excursions, or vibration signatures, that can be tracked across flights. Prognostics and health management, the broader field to which this work contributes, has matured rapidly in recent years, with techniques ranging from Kalman filter-based fault detection to particle-filter diagnosis of rocket engine startup transients appearing throughout the recent literature on liquid propellant engines.

What distinguishes the Korean team’s contribution is its insistence on a complete, rational procedure rather than an isolated technique. Previous studies have advanced individual pieces of the puzzle, including model-based and data-driven simulators for rocket engine health management, multi-physics system-level modeling for electromechanical actuators, and reliability-centered maintenance frameworks designed to cope with operational uncertainty. By assembling maintenance classification, reusability assessment, and a concrete sensor-based evaluation scenario into a single coherent workflow, the new paper offers launch operators a template they can adapt to their own vehicles. The authors anticipate that this integrated procedure will enhance both the cost-effectiveness and the reliability of RLVs, directly supporting the ambitions of the so-called New Space era.

The stakes are considerable. Launch cost analysis has repeatedly shown that the price of reaching space is the dominant constraint on the growth of the commercial space industry, and reusable systems are the most credible path to orders-of-magnitude reductions. Regulatory frameworks are evolving in parallel, with the United States Federal Aviation Administration’s Part 450 rules establishing launch and reentry licensing requirements that implicitly demand rigorous mission assurance practices from reusable vehicle operators. Standards guidance for the structural, propulsion, mechanical, and dynamics aspects of reusable launch vehicles has been developed within the aerospace community, and studies of mission assurance standards for both expendable and reusable vehicles highlight how much depends on disciplined post-flight evaluation. A repeatable, component-level reusability assessment procedure gives operators and regulators alike a common engineering language for those decisions.

The research is also notable for its provenance. It results from the Commissioned Research Project on the Advancement of the Korean Launch Vehicle Program, hosted by the Korea Aerospace Research Institute with funding from the Korea AeroSpace Administration, with additional support from the National Research Foundation of Korea and the Brain Korea 21 FOUR project at Korea Aerospace University. As Korea develops its own launch capabilities, including the KSLV-II program whose 75-ton engine system has been the subject of prior reliability modeling, the transfer of maintenance science from commercial aviation into launch vehicle engineering reflects a maturing domestic space sector preparing for reusable systems of its own.

For the industry at large, the message of the study is that reusability is not a binary property of a rocket but a property that must be assessed, component by component, flight after flight, with the intensity of scrutiny matched to the risk each part carries. The fuel supply system, sitting at the sharp end of that risk, illustrates the approach in action: sensors watch for the signatures of degradation, condition-based maintenance converts those observations into estimates of remaining useful life, and only components with demonstrated margin are cleared to fly again. If frameworks of this kind take hold, the vision of rockets operating more like airliners, turned around quickly and cheaply with maintenance targeted precisely where the data says it is needed, moves one step closer to routine reality, and the cost curve that has already transformed access to orbit may bend further still.

Subject of Research: Reusability assessment and condition-based maintenance of reusable launch vehicles

Article Title: Assessment Procedure of Reusability of Reusable Launch Vehicles (RLVs) and Sensor-Based Evaluation Scenario in Fuel Supply System

Article References: Park, H.-B., Choi, J.-H., & Yoon, H.-S. (2026). Assessment Procedure of Reusability of Reusable Launch Vehicles (RLVs) and Sensor-Based Evaluation Scenario in Fuel Supply System. International Journal of Aeronautical and Space Sciences. https://doi.org/10.1007/s42405-026-01305-5

Image Credits: AI Generated

DOI: 10.1007/s42405-026-01305-5

Keywords: reusable launch vehicles, reusability assessment, condition-based maintenance, remaining useful life, fuel supply system, prognostics and health management, reliability-centered maintenance, failure mode and effect analysis, rocket engine maintenance, New Space, launch costs, aerospace engineering