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Recently, in the space market, there has been a rapid reduction in the launch price. The major reason for this is that a few commercial companies began to enter the space market about ten years ago, which has changed the space market from monopolization to competition and accelerated the adoption of commercial efficiency in technology and management. Also, SpaceX made a breakthrough by successfully recovering the first stage of its launch vehicle in 2016, thereby opening the door to reusable launch vehicles. They have declared their intention to significantly reduce satellite launch costs in the future by utilizing the potential of reusable launch vehicles. In this study, we calculate the total launch cost required to place a single satellite into Low Earth Orbit (LEO) and compare the launch costs for three different payload capacity scenarios, investigating how payload capacity affects the cost-effectiveness of reusable launch vehicles. The launch cost is broken down into development costs, production costs, reuse costs, operational costs, fixed costs, and insurance costs, with cost estimation equations utilized based on cost calculation models such as TRANSCOST.

Hydrogen peroxide (H2O2) is a dense, storable oxidizer, but its suitability for high-energy upper stages is limited. This study evaluates liquid hydrogen–hydrogen peroxide (LH2/H2O2) as an alternate propellant using KSLV-II as the reference vehicle. Propulsion performance was analyzed with NASA CEA and RPA, while staging and MER methods assessed system-level effects. The results show that the specific impulse decreases from 465 s (LH2/LOX) to 372~382 s with H2O2, but structural efficiency improves as the coefficient drops from 0.162 to 0.099~0.102. The payload capacity increases compared with Jet A-1/LOX yet remains below that of LOX. These findings clarify both the advantages and limitations of H2O2 as an upper-stage oxidizer.

With the cost-saving benefits of reusable launch vehicles (RLVs), South Korea is pursuing the application of reusability technologies to KSLV-III. While SpaceX currently reuses only the first stage of Falcon 9, the Starship program aims for full-stage recovery, motivating further examination of second-stage reuse. This study extends the scope of the analysis to medium-class launch vehicles and evaluates the feasibility of second-stage reuse for two vehicle scales. The performance losses associated with three recovery methods—vertical landing, parachute, and fly-back—are quantitatively assessed using conceptual-level recovery system design and simplified mass modeling. For KSLV-III, a conceptual expendable medium-class launch vehicle capable of delivering a 10-ton payload to a 200 km low Earth orbit (LEO) was designed using an algebraic modeling approach. Based on this reference design, the recovery methods were evaluated for both medium-class and super-heavy-class vehicles. Results of the present order-of-magnitude conceptual trade study show that, for medium-class vehicles, the parachute provides the highest performance, followed by fly-back, while vertical landing yields the lowest. For super-heavy vehicles, the parachute remains the most effective, but vertical landing becomes the second-best option, with fly-back exhibiting the lowest performance. As the vehicle scale increases, parachute effectiveness declines, fly-back performance improves, and vertical landing shows the greatest performance gains. However, parachute becomes impractical for super-heavy vehicles due to structural limitations, making vertical landing the most viable option. In contrast, medium-class vehicles do not necessarily require vertical landing, and the optimal recovery strategy should be chosen based on vehicle structural characteristics and mission objectives. This study provides insights that support the selection of efficient recovery strategies during the early design phase of RLVs.

Bifurcation of the characteristic cells into multiple smaller cells and decay of those cells into single large characteristic cell is observed frequently. In the present study the bifurcation phenomenon of the detonation front is investigated for marginally unstable detonations using decomposition technique. Numerical analysis is carried out with detailed chemical kinetics for detonation propagation in H2/O2 mixtures at 10 kPa. The dynamic characteristics of the instability at the detonation front, such as the local oscillation frequency and the coherent spatial structure of the oscillation are also studied with dynamic mode decomposition (DMD) technique. The coherent structures of the primary and secondary detonation cells are analyzed during the cell bifurcation process and the mechanism in which the secondary cells are formed is investigated. It is demonstrated that the modal analysis categorizes the instability phenomena clearly and can be effectively utilized to identify the origin and source of the instability.

An unstable shock-induced combustion (SIC) case around a hemispherical projectile has been numerically studied which experimentally produced a regular oscillation. Comparison of detailed H2/O2 reaction mechanisms is made for the numerical simulation of SIC with higher-order numerical schemes intended for the use of the code for the hypersonic propulsion and supersonic combustion applications. The simulations show that specific reaction mechanisms are grid-sensitive and produce spurious reactions in the high-temperature region, which trigger artificial instability in the oscillating flow field. The simulations also show that specific reaction mechanisms develop such spurious oscillations only at very fine grid resolutions. The instability mechanism is investigated using the dynamic mode decomposition (DMD) technique and the spatial structure of the decomposed modes are further analyzed. It is found that the instability triggered by the high-temperature reactions strengthens the reflecting compression wave and pushes the shock wave further and disrupts the regularly oscillating mechanism. The spatial coherent structure from the DMD analysis shows the effect of this instability in different regions in the regularly oscillating flow field.

Background Understanding the processes underlying carbon storage and balance is critical for equipping the terrestrial biosphere to respond to contemporary climatic challenges. However, ecosystem-level estimates and distribution of net primary productivity (NPP), a metric for evaluating forest carbon cycling patterns and dynamics, remain constrained by uneven empirical observations between above- and belowground fractions. We herein quantified the rate and composition of NPP for four stands characteristic of the cool-temperate deciduous ( Larix kaempferi , LK; Quercus mongolica , QM) and evergreen ( Pinus densiflora , PD; Pinus koraiensis , PK) forests of South Korea over a complete annual cycle (2022–2023). Variations in dynamic NPP compartments, particularly (1) canopy litterfall by stand and season and (2) fine root production by stand, diameter class, and depth interval, were further characterized using litter traps and ingrowth cores, respectively. Results Total NPP varied from 1226 ± 101 to 1796 ± 154 g m −2  yr −1 , with 78–84% allocated aboveground and 16–22% belowground. LK and QM exhibited total NPP up to 46% higher than PD and PK. Both litterfall and fine root production differed considerably across stands, decreasing in the order of QM > PK > PD > LK for litterfall and QM & PD > LK & PK for fine root production. Litterfall peaked in autumn, similar to the leaf phenological rhythm of many temperate deciduous species. In contrast, fine root production showed a negative vertical distribution with depth, which is consistent with decreasing nutrient availability and increasing mechanical impedance along the soil profile. Conclusions By disentangling the contribution levels and dynamic patterns of each NPP compartment, our findings demonstrate a strong inclination toward aboveground NPP investment when belowground resources are not limiting. In other words, an adequate nutrient supply enables plants to modify their priority allocation from fine root maintenance to internal resource transport, leaf production, canopy expansion, reproduction, and other critical aboveground functions. Such information underscores the necessity for forest management strategies that target soil fertility to strengthen not only canopy productivity and CO 2 sequestration but also ecosystem resilience by reinforcing allocation patterns that sustain high NPP and safeguard forests against shifting climate conditions.

Urbanization and associated forest conversions have given rise to a continuum of native (forest fragments) and modified (artificial grasslands and perennial ecosystems) land-use types. However, little is known about how these shifts affect soil and fine-root compartments that are critical to a functioning carbon and nutrient circulation system. In this study, soil physicochemical properties, fine-root mass, and vertical distribution patterns were investigated in four representative urban land-use types: grassland (ZJ), perennial agroecosystem (MP), broadleaf deciduous forest patch (QA), and coniferous evergreen forest patch (PD). We quantified the fine-root mass in the upper 30 cm vertical profile (0–30 cm) and at every 5 cm depth across three diameter classes (<2 mm, 2–5 mm, and <5 mm). Soil physicochemical properties, except for phosphorus, nitrogen, ammonium nitrogen, and sodium cations, varied significantly across land-use types. The total root biomass (<5 mm) decreased in the order of QA (700.3 g m−2) > PD (487.2 g m−2) > ZJ (440.1 g m−2) > MP (98.3 g m−2). The fine-root mass of ZJ and MP was correlated with soil nutrients, which was attributed to intensive management operations, while the fine-root mass of QA and PD had a significant relationship with soil organic matter due to the high inputs from forest litter. Very fine roots (<2 mm) presented a distinct decremental pattern with depth for all land-use types, except for MP. Very fine roots populated the topmost 5 cm layer in ZJ, QA, and PD at 52.1%, 49.4%, and 39.4%, respectively. Maintaining a woody fine-root system benefits urban landscapes by promoting soil stabilization, improving ground infiltration rates, and increasing carbon sequestration capacity. Our findings underscore the importance of profiling fine-root mass when assessing urban expansion effects on terrestrial ecosystems.

A primary cilium is an antenna-like structure on the cell surface that plays a crucial role in sensory perception and signal transduction. Mitochondria, the ‘powerhouse’ of the cell, control cell survival, and death. The cellular ability to remove dysfunctional mitochondria through mitophagy is important for cell survival. We show here that mitochondrial stress, caused by respiratory complex inhibitors and excessive fission, robustly stimulates ciliogenesis in different types of cells including neuronal cells. Mitochondrial stress-induced ciliogenesis is mediated by mitochondrial reactive oxygen species generation, subsequent activation of AMP-activated protein kinase and autophagy. Conversely, abrogation of ciliogenesis compromises mitochondrial stress-induced autophagy, leading to enhanced cell death. In mice, treatment with mitochondrial toxin, MPTP elicits ciliary elongation and autophagy in the substantia nigra dopamine neurons. Blockade of cilia formation in these neurons attenuates MPTP-induced autophagy but facilitates dopamine neuronal loss and motor disability. Our findings demonstrate the important role of primary cilia in cellular pro-survival responses during mitochondrial stress.

Background The psychometric properties of the Korean Short Form-12 Health Survey, version 2 (SF-12 v2) have not been assessed in the general population. Therefore, the aim of our study was to evaluate the psychometric properties of the Korean version of the SF-12 v2 in the general population and to provide SF-12 v2 domain scores according to the general characteristics of the study population. Methods A total of 1,000 participants from the general Korean population were recruited using a multistage quota sampling method. Psychometric properties were evaluated by descriptive statistics, validity, reliability, and exploratory factor analysis. Results Item convergent and discriminant validity met the criteria established by the instrument developer. In the known-group comparison, male gender, age <60 years, high educational status, and absence of any comorbidity were significantly associated with high scale scores. The reliability of all SF-12 v2 items was 0.88. Conclusions The findings of this study generally support the idea that the Korean SF-12 v2 is a feasible, valid, and reliable instrument for assessing health-related quality of life in the general population. The SF-12 v2 seems to be a viable alternative health-related quality of life instrument for the Korean population.

Purpose This study aimed to estimate Korean preference weights for EQ-5D-5L based on values elicited from Korean population by applying the EuroQol Valuation Technology (EQ-VT) program and the standard protocol by the EuroQol Group. Methods The multistage quota sampling method was used to recruit 1085 subjects from the general population in Korea. Each respondent valuated 10 health states using the composite time trade-off (cTTO) and 7 health states using discrete choice experiment. The EQ-VT program was developed by the EuroQol Group and translated into Korean with the Korean research team. Computer-assisted, face-to-face interviews were conducted. A range of predictive models were explored using cTTO. The most appropriate model was determined after assessing goodness of fit, logical consistency, and parsimony. Results Of 3206 contacted, 1085 subjects completed interviews (33.8 %) and 1080 were used for modeling. A model with dummy variables for each level of severity and dimension and a term that picked up whether any dimension in the state was at level 4 or 5 was selected as the best predictive model. All coefficients of the final model were statistically significant and logically consistent. In addition, it was parsimonious. This model had mean absolute error of 0.027, and the absolute error for all 86 health states was below 0.1. Conclusions The final model built in this study appears to predict the utilities of the states which were valuated directly. This model could be used to interpolate quality weights for all EQ-5D-5L health states.