Space 4.0 refers to the profound reconfiguration of the global space arena from predominantly state-led, vertically integrated arrangements toward heterogeneous, networked ecosystems. In this open and diversified environment, established space agencies and aerospace incumbents now interact with commercial companies, small and medium-sized enterprises, entrepreneurial ventures, research organizations, and actors from adjacent technological fields. Innovation increasingly unfolds across geographical, organizational, and institutional boundaries, and the capacity of heterogeneous actors to combine complementary knowledge has become the decisive resource. For countries with developing space sectors, such as Greece—classified by the European Innovation Scoreboard 2024 as a Moderate Innovator, ranking 24th among the 27 EU Member States and performing at 77.5 percent of the EU average—access to institutional interfaces, regulatory frameworks, and transnational programmes is critical for capability formation and integration into European and international networks.

The theoretical anchor of the study is multidimensional proximity, a framework long used to explain knowledge circulation and interaction among heterogeneous actors. Geographical proximity enables co-presence and direct interaction; cognitive proximity facilitates mutual understanding through compatible knowledge bases and interpretative repertoires; social proximity stabilizes expectations and supports knowledge exchange through trust; organizational proximity promotes coordinated action through shared routines and governance arrangements; and institutional proximity provides normative and regulatory alignment that reduces ambiguity. The researchers treat these dimensions not as static attributes but as a dynamic governance mechanism performing three interrelated functions: coordination, uncertainty reduction, and knowledge co-creation. Crucially, insufficient relatedness may impede communication and coordination, whereas excessive similarity may reduce novelty and contribute to cognitive or relational lock-in.

The empirical setting is the Greek Space 4.0 ecosystem, organized around a limited number of institutional and industrial nodes, most notably the Corallia si-Cluster. At the time of the study, the cluster comprised more than 70 Greek firms, academic and research centers, public-sector bodies, and civil-society actors active in space technologies and applications, working in areas including Earth observation and remote sensing, aerospace electronics and embedded systems, satellite communications, and on-board software. The ecosystem is strongly embedded in European programmes and cross-border coordination frameworks, with European Space Agency initiatives such as the Greek National Satellite Space Project illustrating the importance of EU-supported funding and coordinated engagement among Greek industry, academia, national authorities, and ESA.

Methodologically, the study employs a qualitative case-study design grounded in constructivist grounded theory principles. The researchers conducted 22 semi-structured interviews with representatives of si-Cluster firms and research organizations directly engaged in Space 4.0 collaborative projects. The initial data-collection phase took place during 2019–2020, and the material was updated during 2024–2025 to incorporate sector developments. Eight interviews were conducted face-to-face and 14 remotely, ranging from 26 to 120 minutes with an average duration of approximately 60 minutes. The 29-question protocol used the five proximity dimensions as sensitizing concepts to examine partner selection, coordination practices, trust formation, institutional compatibility, and spatial distance management, explicitly distinguishing between domestic and international partnerships. Interview material was analyzed through thematic coding in NVivo, combining deductive structuring around the five dimensions with inductive pattern identification and constant comparison across four iterative stages, progressing from individual dimensions to recurring configurations, interaction mechanisms, functional effects, and the proximity profile.

The findings are striking in their rejection of spatial determinism. Participants consistently stressed that co-location, cluster membership, or national affiliation did not automatically generate effective cooperation. Collaborative viability instead depended on shared interpretive frameworks, compatible procedures, institutional clarity, and reliable communication practices. Cognitive proximity emerged as the most influential dimension, with respondents noting that speaking the same language, both in terms of knowledge and culture, is decisive, and that a shared scientific language is a fundamental prerequisite for effective communication. Such compatibility underpinned knowledge co-creation, mutual understanding, and absorptive capacity, often determining whether partnerships progressed beyond initial exploratory exchanges. Conversely, differences in technical interpretation and difficulties in codifying tacit knowledge constrained knowledge exchange even where partners shared broad project objectives.

Organizational proximity proved equally consequential, particularly in projects requiring tightly coordinated workflows and interdependent technical tasks. Respondents emphasized that cognitive alignment had to be complemented by established coordination routines, clear communication channels, and flexible yet coherent procedural structures, with defined hierarchical channels for institutional matters and immediate resolution of everyday issues. These issues were especially pronounced in international partnerships, where differences in organizational cultures and operational logics frequently generated friction. Social proximity became evident through trust, familiarity, prior acquaintance, and ease of interpersonal communication; in domestic partnerships, pre-existing familiarity reduced the relational effort required to establish credible engagement, while abroad, participants noted, you must clearly demonstrate who you are. Trust was described as a condition enacted through continued interaction rather than assumed in advance, though several respondents regarded it as a contingent rather than constitutive coordination resource in relationships involving foreign partners.

Institutional proximity became particularly salient in international partnerships, where differences in standards, certification regimes, contractual discipline, and administrative expectations affected collaborative feasibility. Respondents regarded agreement on fundamental rules as a prerequisite for advancing a partnership, warning that the absence of a shared normative and socioeconomic understanding can fragment the entire effort. International engagements often required early examination of regulatory and procedural compatibility at the contracting stage, with misalignment halting collaboration before it began. The si-Cluster itself reduced uncertainty by familiarizing participants with sector-specific regulatory requirements and providing guidance on compliance obligations. Geographical proximity, by contrast, played a modest and highly situational role. Respondents consistently rejected physical co-location as a decisive consideration, observing that what matters is the project itself and that geographical distance on its own is not a deterrent. Cross-border relationships addressed physical separation through digital communication tools, temporary co-presence, and more formalized coordination mechanisms, and in several instances international partners were preferred because they offered superior technical capabilities, more reliable institutional conditions, or greater strategic value.

The analysis reveals that the five dimensions rarely operated in isolation, instead forming recurring configurations with distinct interaction mechanisms. A first pattern linked cognitive and organizational proximity: shared expertise enabled substantive knowledge exchange, yet technical understanding alone could not sustain cooperation without task management, procedural discipline, and compatible routines—the operative mechanism being the translation of shared technical understanding into coordinated action. A second pattern concerned the interplay between social and institutional proximity, particularly in collaborations spanning different regulatory environments: trust-based relations were indispensable for initiating cooperation but proved insufficient when standards, administrative cultures, or certification procedures diverged, so uncertainty was managed through the joint operation of interpersonal assurance and institutional predictability. A third configuration involved geographical proximity interacting with non-spatial dimensions, where physical closeness reinforced existing complementarities only when combined with cognitive, social, or organizational compatibility. The evidence further indicates that proximity configurations evolve across project stages: during early phases, cognitive and social proximity were more prominent as actors assessed technical compatibility and trust, while organizational and institutional proximity became increasingly consequential as projects progressed toward contracting and implementation.

These findings informed the proximity profile, a qualitative diagnostic and normative framework for identifying relational complementarities, vulnerabilities, and alignment requirements in partnership design. Rather than proposing an additional proximity dimension or a quantitative index, the profile redirects attention from isolated dimensions toward the patterns created through their interaction, revealing where complementarities are robust, where vulnerabilities may arise, and where further alignment may be required. It links each dimension to synthesized diagnostic questions, potential implications of insufficient alignment, indicative alignment-building considerations, and relevant project stages—from early technical scoping and shared terminology for cognitive proximity to planned co-presence and hybrid coordination routines for geographical separation. The study positions proximity as a dynamic governance mechanism whose effects arise from interactions among multiple dimensions, with collaborative viability depending on evolving patterns of relational alignment rather than isolated dimensions or geographical concentration. The implications extend to multi-level governance across EU/ESA, national, ecosystem, and project levels, where formal allocation of responsibilities does not by itself ensure coherent implementation; effective translation of programme requirements into project-level arrangements requires sufficient cognitive, organizational, and institutional compatibility among participating actors. For emerging and internationally embedded space economies, the message is clear: effective cooperation need not depend on spatial concentration but may be supported by alternative combinations of alignment, making relational configuration a mechanism enabling participation within distributed innovation ecosystems.

Subject of Research: Science

Article Title: Proximity as a factor of space cluster formation in a European peripheral economy: evidence from the Greek Space 4.0 ecosystem

Article References: Stathaki, H., Skayannis, P., Stamboulis, Y., & Vetsikas, A. (2026). Proximity as a factor of space cluster formation in a European peripheral economy: evidence from the Greek Space 4.0 ecosystem. Frontiers in Political Science, 8, Article 1940774. https://doi.org/10.3389/fpos.2026.1940774

Image Credits: AI Generated

DOI: 10.3389/fpos.2026.1940774

Keywords: Space 4.0, proximity, innovation ecosystems, Greece, si-Cluster, collaboration governance, aerospace, New Space, factor, space, cluster, formation

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