The retracted study, authored by Dimov Stojce Ilcev of the University of Johannesburg, had set out to describe the contemporary architecture of satellite Global Ship Tracking systems, the networks that carry their data, and the equipment used aboard vessels and ashore. Global Ship Tracking is a field that sits at the intersection of satellite communications, radio-navigation and maritime operations, and the paper formed part of a body of work by the same author on positioning and tracking solutions for maritime applications. According to the retraction notice, however, the journal determined that the article was redundant, because its content substantially duplicated material that had already appeared in print elsewhere.

The specifics laid out in the retraction note are unusually detailed. The Editor-in-Chief identified overlaps between nine figures in the retracted article and figures in three earlier works: a 2016 book by the same author introducing ship satellite tracking systems, a 2021 Springer volume arising from the first international conference on maritime education and development, and a 2022 article on the architecture of positioning and tracking solutions for maritime applications published in TransNav, the International Journal on Marine Navigation and Safety of Sea Transportation. The retraction note maps each overlap individually, naming the corresponding figures in each of the three earlier publications.

According to the notice, Figure 1 of the retracted paper appears to overlap with Figure 1 of the 2016 book, Figure 3 of the 2021 conference volume, and Figure 9.1 of the 2022 TransNav article. Figure 2 of the retracted paper appears to overlap with Figure 2 of the 2016 book, Figure 4 of the 2021 volume, and Figure 9.2 of the TransNav article. Figure 4 of the retracted paper appears to overlap with Figure 3 of the 2016 book and Figure 9.3 of the TransNav article, and to partially overlap with Figures 7 and 8 of the 2021 volume. Figure 6 of the retracted paper appears to overlap with Figure 4 of the 2016 book and Figure 9.4 of the TransNav article, and partially overlaps with Figure 12 of the 2021 volume.

The pattern continues through the remainder of the flagged figures. Figure 8 of the retracted article appears to overlap with Figure 5 of the 2016 book and Figure 9.5 of the TransNav article, with partial overlap of Figure 15 in the 2021 volume. Figure 10 appears to overlap with Figure 16 of the 2021 volume. Figure 11 appears to overlap with Figure 6 of the 2016 book and Figure 9.6 of the TransNav article. Figure 14 partially overlaps with Figure 8 of the 2016 book and Figure 9.8 of the TransNav article, while Figure 15 partially overlaps with Figure 9 of the 2016 book and Figure 9.9 of the TransNav article. In total, the notice documents repeated reuse of illustrative material across at least three publications by the same author, a practice that journals generally treat as redundant publication when the overlap is not transparently disclosed.

Retraction decisions of this kind follow a well-established process in scholarly publishing. When concerns about overlap, duplication or integrity are raised after publication, the journal’s editors typically investigate, often in consultation with the publisher’s research integrity group and, where appropriate, the author’s institution. Authors are given the opportunity to respond to the concerns and to explain or justify any similarities. In this case, the retraction note records that the author was asked to clarify the similarities in content but did not provide a satisfactory explanation. The Editor-in-Chief therefore retracted the article, stating that it was redundant. The notice adds that the author did not respond to correspondence from the editors regarding the retraction itself.

The technical subject matter of the retracted paper remains an active and consequential area of research, which is part of why the case draws attention. Satellite-based ship tracking relies on constellations and networks that allow vessels to be located, identified and monitored across the open ocean, far beyond the reach of coastal radar and terrestrial automatic identification system base stations. Modern maritime tracking architectures typically combine satellite communications links, positioning services and shore-based data networks to deliver continuous vessel monitoring for safety, security, search and rescue, fleet management and regulatory compliance. Equipment aboard ships must integrate transceivers, antennas and processing units with navigation systems, while shore infrastructure aggregates and distributes tracking data to operators and authorities.

Because the field advances through incremental architectural descriptions, diagrams of system configurations carry particular weight in the literature. Network topologies, signal flow diagrams and equipment schematics are the currency through which researchers communicate how tracking systems are assembled and how data moves between ships, satellites and ground stations. When such figures are reused across multiple publications without adequate disclosure, the scholarly record can overstate the amount of new technical information being contributed. Journals such as Aerospace Systems, which covers aerospace technology and astronautics alongside related systems analysis, treat transparent novelty as a condition of publication, and redundant publication undermines that condition even when the underlying engineering content is not itself in dispute.

The retraction also illustrates the mechanics of how the modern scholarly record self-corrects. The retraction note is linked to the original article through its own digital object identifier, 10.1007/s42401-026-00558-y, distinct from the DOI of the retracted paper, 10.1007/s42401-024-00314-0. The original article remains findable, but it now carries the retraction notice, and citation services flag its status so that readers and indexing databases can distinguish retracted work from the standing literature. The publisher’s notice also records that Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations, a standard disclaimer, and notes that no data was obtained for the retraction note itself.

For researchers and practitioners in maritime satellite tracking, the practical takeaway is procedural rather than technical. The retracted paper’s descriptions of Global Ship Tracking systems, networks and equipment can no longer be cited as a novel contribution, and readers seeking that material are directed by the retraction notice’s reference list to the earlier publications where overlapping content first appeared, including the 2016 introduction to ship satellite tracking systems, the 2021 conference proceedings volume, and the 2022 TransNav article on positioning and tracking architectures for maritime applications. The case serves as a reminder that even in specialist engineering fields, where diagrams and system descriptions may legitimately recur across a career’s worth of work on the same technology, journals expect each paper to make clear what is new, to disclose prior publication of overlapping material, and to respond to editorial inquiries. When those expectations are not met, the retraction mechanism, however blunt, remains the primary tool the scientific community has for keeping the record accurate.

Subject of Research: Retraction of a paper on satellite Global Ship Tracking systems architecture due to redundant publication

Article Title: Retraction Note: Contemporary architecture of the satellite Global Ship Tracking (GST) systems, networks and equipment

Article References: Ilcev, D. S. (2026). Retraction Note: Contemporary architecture of the satellite Global Ship Tracking (GST) systems, networks and equipment. Aerospace Systems. https://doi.org/10.1007/s42401-026-00558-y

Image Credits: AI Generated

DOI: 10.1007/s42401-026-00558-y

Keywords: retraction, Global Ship Tracking, satellite communications, maritime navigation, Aerospace Systems, research integrity, redundant publication, duplicate figures, Springer Nature, ship tracking systems, editorial ethics, scholarly publishing

Compliant mechanisms have become increasingly attractive for small spacecraft, where every gram and every moving part must justify its existence. Instead of relying on bearings and hinges, which add mass and can seize in the vacuum of space, a compliant mechanism achieves motion through the elastic deformation of its own structure. The trade-off is that the material itself must endure repeated strain, and its mechanical properties are strongly temperature dependent. For polymers such as polylactic acid, a biodegradable thermoplastic often used in additive manufacturing, stiffness can shift dramatically across a modest temperature range. That is why the research team, building on their earlier investigation of heat exchange in a hinge fitting based on a variable-stiffness compliant mechanism for small spacecraft, treats thermal uniformity not as a cosmetic detail but as a governing design requirement.

The heart of the new method is a film resistive heater, a thin layer in which electric current flows along printed conductive traces and dissipates heat through Joule heating. In a conventional design, the trace width is constant, which means the heat generated per unit length is also roughly constant. But the way that heat spreads and escapes from the film is not uniform: edges, corners and regions near structural features lose heat at different rates, so a constant-width trace inevitably produces a patchy temperature field. The researchers’ insight was to let the baseline design’s own temperature map, measured with an infrared camera, dictate how the trace width should vary across the film. Where the surface runs cold, the trace narrows and resistance rises, boosting local heat generation; where the surface runs hot, the trace widens, lowering resistance and damping the power delivered there.

To turn this intuition into a rigorous design rule, the authors defined the local trace width using a power law governed by a spatial-modulation parameter they call alpha. Rather than hand-tuning the geometry, they computed the steady-state temperature field with a two-dimensional sheet heat-transfer model for candidate values of alpha and selected the value that minimized the standard deviation of the predicted temperature. This choice of objective is deliberate. The standard deviation captures how tightly the temperature values cluster around their mean, so minimizing it directly quantifies the goal of spatial uniformity. The two-dimensional sheet model is a pragmatic simplification: it treats the heater as a thin conducting sheet with distributed heat input and losses, avoiding the cost of a full three-dimensional conjugate simulation while retaining the physics needed to compare design variants.

A crucial step in the study was a sensitivity analysis of the principal model parameters. Any optimization is only as trustworthy as the model behind it, and the team examined how the calculated optimum responds to uncertainty in the inputs that drive the heat-transfer calculation. This analysis matters for practical deployment, because material properties of additively manufactured polymers can vary between batches and printing conditions, and the thermal characterization of such materials is an active research area. By showing how the result shifts when key parameters change, the authors give future designers a way to judge how much confidence to place in a predicted geometry before committing to fabrication.

The experimental validation is where the study becomes particularly convincing. Using the optimized value of alpha, the researchers fabricated a heater with the modified conductive-trace geometry and tested it under the same steady-state conditions used in the modeling. The measured temperature standard deviation fell to 8.23 degrees Celsius, matching the predicted value of 7.75 degrees Celsius to within approximately 5.8 percent. That level of agreement between a relatively simple two-dimensional model and a physical experiment is notable, and it suggests the method can be iterated quickly: model, optimize, print, and verify, without the expense of full computational fluid dynamics or three-dimensional thermal simulation at every step.

Equally important is the second contribution buried in the paper: an algorithm for reconstructing a numerical temperature field from a pseudocolor thermographic image. Infrared cameras typically present their output as a false-color map, and extracting reliable numbers from those colors is complicated by the camera’s palette, its resolution and the way colors are quantized on screen. The team’s reconstruction algorithm converts the pseudocolor image back into a quantitative temperature field, achieving a mean absolute error of 0.509 degrees Celsius and a root-mean-square error of 0.623 degrees Celsius, while the relative difference in the temperature standard deviation was only about 0.06 percent. In practice, this means researchers can mine temperature data from published thermographs or archived imagery, not just from raw camera files, which broadens the method’s usefulness for design studies and comparative analysis.

The broader context for this work is the growing field of thermal design optimization, in which topology optimization and related techniques are used to distribute conductive material, heat loads or cooling channels in the most effective arrangement. Previous studies have applied such methods to heat exchangers and to conduction problems with design-dependent heat loads, and the present paper extends that spirit to a flexible, printed heating element whose geometry is constrained by the electrical path it must provide. Because the trace width is expressed through a smooth power law with a single modulation parameter, the optimization remains parametric rather than fully free-form, which keeps the problem tractable and the resulting geometry manufacturable with standard film-printing techniques.

For small spacecraft, the implications are concrete. Thermal control is a persistent challenge for satellites that cycle between intense solar illumination and frigid eclipse, and compliant mechanisms used in deployable structures, hinges or variable-stiffness joints need their temperature kept within workable bounds for their materials to perform as designed. A heater whose temperature field is engineered to be uniform can protect polymer components from localized overheating, reduce thermal gradients that drive unwanted deformation, and simplify the thermal budget of the overall system. The authors note that the approach applies to the design of heaters for compliant mechanisms with improved spatial temperature uniformity under the steady-state conditions they investigated, and the method relies only on a baseline temperature measurement, a simple heat-transfer model and a one-parameter search.

The study also illustrates a quiet trend in modern aerospace engineering: the fusion of measurement, modeling and manufacturing into a single design loop. Thermographic data is no longer just a diagnostic record; it becomes the input that shapes the next design iteration. With the reconstruction algorithm bridging the gap between colorful camera images and quantitative fields, and with a validated model linking trace geometry to temperature uniformity, the workflow described by the Moscow Aviation Institute team offers a template that other laboratories could adopt for any resistive heating application where uniformity matters, from de-icing surfaces to temperature-controlled flexures. As additive manufacturing continues to put complex, customized geometries within reach, methods like this one show that the smartest design decisions can come from listening carefully to what the material itself reports about its own temperature.

Subject of Research: Parametric optimization of conductive-trace geometry in film resistive heaters for compliant mechanisms using thermographic temperature data

Article Title: Parametric optimization of conductive-trace geometry in a film heater for a compliant mechanism based on thermographic data

Article References: Kurguzov, A. V., Trakhman, R. A., Ermakov, V. Y., & Tufan, A. (2026). Parametric optimization of conductive-trace geometry in a film heater for a compliant mechanism based on thermographic data. Aerospace Systems. https://doi.org/10.1007/s42401-026-00557-z

Image Credits: AI Generated

DOI: 10.1007/s42401-026-00557-z

Keywords: compliant mechanism, film resistive heater, parametric optimization, conductive-trace width, infrared thermography, temperature field, spatial temperature uniformity, small spacecraft, heat transfer modeling, additive manufacturing, polylactic acid, aerospace systems

The research, conducted by H. R. Alimohammadi and H. Naseh of the Aerospace Research Institute in Tehran and F. Ommi of Tarbiat Modares University, focuses on the design optimization of a thrust chamber for the RD-161 propulsion system. The team set out with two objective functions at the center of the work: specific impulse, which measures how efficiently propellant is converted into thrust, and thrust-to-weight ratio, which captures how much acceleration an engine can deliver for the mass it adds to the vehicle. These two quantities are widely regarded as the defining figures of merit for liquid-propellant engines, and they frequently pull the design in opposite directions. A chamber shaped for maximum exhaust velocity may end up heavy; a lightweight design may sacrifice combustion efficiency.

To formalize the problem, the researchers identified seven input variables that govern the geometry and operating conditions of the chamber: the propellant consumption ratio, the combustion chamber pressure, the contraction area ratio between the chamber cross-section and the throat, the expansion pressure ratio across the nozzle, two geometric ratios describing the convergence of the chamber walls, and the contraction angle itself. Together, these parameters define a vast multidimensional design space in which even a modest number of candidate configurations quickly becomes computationally overwhelming. Evaluating every possible combination with high-fidelity physics simulations would require an impractical amount of time and computing resources, which is precisely the bottleneck the surrogate approach is designed to remove.

A surrogate model, sometimes called a metamodel, is essentially a fast mathematical approximation of a slower, more expensive simulation. Instead of running a full physics-based analysis for every candidate design, engineers run a strategically chosen subset of simulations and then fit a statistical model that interpolates the results across the entire design space. The quality of the surrogate depends critically on how those sample points are selected, which is where the Design of Experiments methodology comes in. In this study, the team carried out 46 different numerical experiments on the RD-161 propulsion system, varying the seven input parameters according to a structured experimental plan. Of those 46 runs, 39 produced results that were approved and found compatible with the problem constraints, forming the data foundation on which the response surfaces were built.

From that approved dataset, the researchers drew response surface curves and derived the corresponding objective function equations that link the seven input variables to the two performance outputs. Response surfaces are a powerful visualization and analysis tool because they reveal not just the optimum point but the entire topology of the design landscape: where performance rises steeply, where it plateaus, and where design variables interact in ways that a one-at-a-time sensitivity study would miss. The team then applied the Analysis of Variance, or ANOVA, to quantify how much of the variation in specific impulse and thrust-to-weight ratio could be attributed to each input factor and their combinations. According to the published results, the ANOVA demonstrated that the model is capable of predicting the responses adequately within the limits of the input parameters, a crucial validation step before any optimization can be trusted.

The precision of the fitted model was assessed against independent checks, and the authors report that the outputs showed high accuracy when interpreted and analyzed. With a validated surrogate in hand, the optimization itself could proceed far more efficiently than a brute-force sweep of the design space. The study notes that classical optimization techniques such as Genetic Algorithms and Sequential Quadratic Programming are commonly paired with surrogate models in this domain, allowing search algorithms to evaluate thousands of candidate configurations on the cheap statistical approximation while reserving full simulations for the most promising regions. This combination is what makes multidisciplinary design optimization of rocket engines practical on realistic engineering timescales.

The headline results are striking for a field where gains are often measured in fractions of a percent. Applying the methodology to optimize the thrust chamber, the researchers achieved a 2.8-second increase in specific impulse and an 8.5 percent increase in thrust-to-weight ratio for the chamber itself. When the objective functions were evaluated at the level of the complete engine, the improvements grew even larger: specific impulse rose by 3 seconds and the thrust-to-weight ratio climbed by 12 percent. In the conservative world of liquid-propellant engine design, where flight-proven hardware changes slowly and every design revision must survive rigorous qualification, improvements of this magnitude are considered considerably large, and they illustrate how much performance may be left on the table when chambers are designed by iteration and experience alone rather than systematic global optimization.

The work also sits within a broader movement in propulsion engineering toward simulation-driven, data-rich design. Earlier studies have applied genetic algorithms, particle swarm methods, and mass-based models to liquid rocket engine design problems, and the same research group has previously developed surrogate-based frameworks for optimizing the cooling systems and multidisciplinary robust design of liquid-propellant engines. Regenerative cooling channels, turbine design, and combustion modeling have all been drawn into multidisciplinary optimization frameworks in recent years, reflecting a recognition that the classical separation of engine components into isolated design silos leaves coupled performance gains undiscovered. The surrogate approach presented here extends that trajectory to one of the most consequential components in the entire engine.

What makes the surrogate methodology especially attractive for engineering practice is that it produces not just a single optimized point but an interpretable map of the design space, complete with objective function equations that other teams can reuse and adapt. The response surfaces can expose trade-off frontiers between specific impulse and mass, guiding engineers toward designs that best serve a particular mission profile rather than a generic ideal. The study also underscores the importance of constraint filtering: of the 46 experiments conducted, 7 fell outside the problem constraints and were excluded, a reminder that raw computational sweeps are only as useful as the feasibility boundaries that frame them. Careful constraint definition, the authors’ results suggest, is as essential to credible optimization as the statistical model itself.

For the wider aerospace community, the implications extend beyond the RD-161. As launch providers pursue reusable boosters and satellite operators demand ever more capable propulsion for orbit-raising and station-keeping, the pressure to extract maximum performance from minimum mass will only intensify. Surrogate-based design optimization offers a path to that performance without the prohibitive cost of exhaustive high-fidelity simulation, and the substantial gains reported in this study provide concrete evidence that the approach is ready to move from academic methodology into the engine design offices where the next generation of liquid-propellant engines will take shape. The datasets generated and analyzed in the study are available from the corresponding author on reasonable request, opening the door for other groups to build on the framework.

Subject of Research: Surrogate model development for the design optimization of a liquid-propellant rocket engine thrust chamber

Article Title: A surrogate model development for design optimization of thrust chamber

Article References: Alimohammadi, H. R., Naseh, H., & Ommi, F. (2026). A surrogate model development for design optimization of thrust chamber. Aerospace Systems. https://doi.org/10.1007/s42401-026-00548-0

Image Credits: AI Generated

DOI: 10.1007/s42401-026-00548-0

Keywords: surrogate model, thrust chamber, liquid-propellant engine, design optimization, specific impulse, thrust-to-weight ratio, response surface methodology, ANOVA, Design of Experiments, rocket propulsion, Aerospace Systems, RD-161