Airframe noise generated at wing trailing edges and high-lift devices, such as flaps, remains a major challenge during landing, with significant contributions in the low-frequency band of 500-1500 Hz. While solid surfaces reflect this acoustic energy, metallic porous materials can effectively absorb it through viscous and thermal dissipation within their internal pore structure. To address this, the present study examines the acoustic absorption characteristics of open-cell AlSi porous cylinders featuring controlled pore diameters between 0.3 mm and 2.25 mm. Measurements were conducted in an acoustic impedance tube according to the ISO 10534-2:2023 standard, using six cylindrical samples (28 mm diameter, 70 mm length). Two sets of measurements were performed for each sample (front and rear faces), and the average values were used. The findings indicate that the normal-incidence sound absorption coefficient α rises as pore size increases, reaching 0.93-0.97 at low frequencies of 500-700 Hz for the samples with the largest pores (1.8-2.25 mm). These results indicate that open-cell AlSi alloys offer strong low-frequencies sound absorption, positioning them as promising options for aeroacoustic noise mitigation, including applications such as porous trailing edge and hybrid flap designs.
Reusable launch vehicles are a key category of next-gen European launchers, as multiple companies are in advanced stages of study and are shifting towards the development of first demonstrators. A worldwide tendency to reduce the costs associated with satellite insertion into low Earth orbits can be observed, together with the existence of a niche in the future European launcher family for reusable small launch vehicles, known as microlaunchers. Multiple recovery methods exist for space launch vehicles; in this study, a return to launch site (RTLS) vertical-landing approach is being prioritized for the recovery of the first stage of a two-stage LOX/methane microlauncher. In 2023, INCAS, with support from the Romanian Nucleu Program, initiated a large study to address the prospect of developing a partially reusable microlauncher. A multidisciplinary optimization (MDO) environment has been developed, which is used in this paper to assess the implications of stage recovery versus the landing location (return to launch site versus downrange recovery) and state whether an RTLS can be feasible for small launchers. The paper will also present some key results from previous studies, such that a clear solution trade-off can be made, together with the quantitative assessment of how different vertical-landing techniques affect the microlauncher specifications.
The topic of reusability in the launch vehicle sector is of current worldwide interest, as a shift from expendable to partially reusable configurations can be observed. Based on the work realized in a nationally funded Nucleu project, INCAS has developed a multidisciplinary optimization environment (MDO algorithm) capable of generating preliminary launcher concepts that also take into account the recovery process needed to reuse key major assemblies, such as the lower stage. The current paper analyzes a set of five key missions of interest (with different launch locations) and their influence on the preliminary definition of a family of partially reusable microlaunchers capable of inserting the same payload (100 kg) into different inclination, low Earth orbits (ranging from almost equatorial to Sun-synchronous orbits). The proposed microlauncher concepts are based on a two-stage constant-diameter architecture, where the first stage is recovered via a downrange, autonomous vertical landing mission, while the upper stage is expendable. The main scope of this paper is to quantify the impact of different key mission requirements on the characteristics of the reusable microlauncher that minimize its lift-off mass. This approach also correlates to the definition of reusable launch vehicle concepts that have reduced the associated costs of development, production, and operation.
This paper presents a study on the thermal behavior of an electro-hydrostatic servo actuator designed to actuate the ailerons of an airliner. The considered servo actuator was designed using existing commercial off-the-shelf components (electric motor, pump, hydraulic cylinder, valves, hydro-accumulator), and the control part was tuned using numerical simulations performed in SIMCENTER/AMESIM. This study begins with the functional parameters of the components used in the design and uses numerical simulations to test the thermal behavior of the components. A continuous stress spectrum of the servo actuator is considered, with the servo actuator located in a compartment inside the wing. Different external conditions are also considered, such as situations where component wear occurs and component efficiencies deteriorate, thus producing more heat in the system. Based on the energy losses identified, the average efficiency of the studied servo actuator is also evaluated.
With support from the Romanian Nucleu Program, INCAS has taken the initiative to develop a multidisciplinary optimization (MDO) environment capable of generating reusable microlauncher concepts that could be used as the first building blocks in the development and production of a locally based launch vehicle. This paper will present the main work carried out towards the accomplishment of this task, with several mathematical models being proposed to fill in the gaps associated with microlauncher reusability. Towards the end of the paper, a partially reusable microlauncher concept is proposed, which is capable of successfully accomplishing both the main mission, that of inserting a 100 kg satellite into a 400 km altitude, circular polar orbit, and the recovery mission, where the first-stage assembly (including the interstage) is recovered from a secondary location. Preliminary cost estimates are also given for the entire lifespan of the microlauncher, focusing on the economic feasibility of a reusable concept for small launch vehicles.
