Aerospace, Volume 7, Issue 2 (February 2020) – 10 articles

Nanosatellites are increasingly being used in space-related applications to demonstrate and test scientific capability and engineering ingenuity of space-borne instruments and for educational purposes due to their favourable low manufacturing costs, cheaper launch costs, and short development time. The use of CubeSat to demonstrate earth imaging capability has also grown in the last two decades. In 2017, a South African company known as Space Commercial Services launched a low-orbit nanosatellite named nSight-1. The demonstration nanosatellite has three payloads that include a modular designed SCS Gecko imaging payload, FIPEX atmospheric science instrument developed by the University of Dresden and a Radiation mitigation VHDL coding experiment supplied by Nelson Mandela University. The Gecko imager has a swath width of 64 km and captures 30 m spatial resolution images using the red, green, and blue (RGB) spectral bands. The objective of this study was to assess the interpretability of nSight-1 in the spatial dimension using Landsat 8 as a reference and to recommend potential earth observation applications for the mission. A blind image spatial quality evaluator known as Blind/Referenceless Image Spatial Quality Evaluator (BRISQUE) was used to compute the image quality for nSight-1 and Landsat 8 imagery in the spatial domain and the National Imagery Interpretability Rating Scale (NIIRS) method to quantify the interpretability of the images. A visual interpretation was used to propose some potential applications for the nSight1 images. The results indicate that Landsat 8 OLI images had significantly higher image quality scores and NIIRS results compared to nSight-1. Landsat 8 has a mean of 19.299 for the image quality score while nSight-1 achieved a mean of 25.873. Landsat 8 had NIIRS mean of 2.345 while nSight-1 had a mean of 1.622. The superior image quality and image interpretability of Landsat could be attributed for the mature optical design on the Landsat 8 satellite that is aimed for operational purposes. Landsat 8 has a GDS of 30-m compared to 32-m on nSight-1. The image degradation resulting from the lossy compression implemented on nSight-1 from 12-bit to 8-bit also has a negative impact on image visual quality and interpretability. Whereas it is evident that Landsat 8 has the better visual quality and NIIRS scores, the results also showed that nSight-1 are still very good if one considers that the categorical ratings consider that images to be of good to excellent quality and a NIIRS mean of 1.6 indicates that the images are interpretable. Our interpretation of the imagery shows that the data has considerable potential for use in geo-visualization and cartographic land use and land cover mapping applications. The image analysis also showed the capability of the nSight-1 sensor to capture features related to structural geology, geomorphology and topography quite prominently. Full article

The effect of hot-wet storage aging on the mechanical response of a carbon fiber polyether ether ketone (PEEK)-matrix woven composite has been studied. A wide range of static loads and selected cyclic load tests on the interlaminar fatigue strength were performed. Static tests were conducted in batch mode, including on- and off-axis tension, compression, flexure, interlaminar shear strength (ILSS) and fracture tests in Modes I, II and I/II. Respective mechanical properties have been determined, indicating a degrading effect of aging on strength-related properties. The measured response in general, as well as the variance quantified by batch-mode test execution, indicated the appropriateness of the applied standards on the material under consideration, especially in the case of fracture tests. The material properties presented in the current work may provide a useful basis towards preliminary design with PEEK-based woven thermoplastic composites during service in aerospace applications. Full article

CubeSats usually adopt aluminum alloys for primary structures, and a number of studies exist on Carbon Fiber Reinforced Plastic (CFRP) primary structures. The internal volume of a spacecraft is usually occupied by battery arrays, reducing the volume available to the payload. In this paper, a CFRP structural/battery array configuration has been designed in order to integrate the electrical power system with the spacecraft bus primary structure. The configuration has been designed according to the modular design philosophy introduced in the AraMiS project. The structure fits on an external face of a 1U CubeSat. Its external side houses two solar cells and the opposite side houses power system circuitry. An innovative cellular structure concept has been adopted and a set of commercial LiPo batteries has been embedded between two CFRP panels and spaced out with CFRP ribs. Compatibility with launch mechanical loads and vibrations has been shown with a finite element analysis. The results suggest that, even with a low degree of structural integration applied to a composite structural battery, more volume and mass can be made available for the payload, with respect to traditional, functionally separated structures employing aluminum alloy. The low degree of integration is introduced to allow the use of relatively cheap and commercial-off-the-shelf components. Full article

The decision of a flight crew to undertake a go-around, aborting a landing attempt, is primarily to ensure the safe conduct of a flight. Although go-arounds are rare, they do cause air traffic disruption, especially in busy airspace, due to the need to accommodate an aircraft in an unusual position, and a go-around can also result in knock-on delays due to the time taken for the aircraft to re-position, fit into the landing sequence and execute a successful landing. Therefore, it is important to understand and alleviate the factors that can result in a go-around. In this paper, I present a new method for automatically detecting go-around events in aircraft position data, such as that sent via the ADS-B system, and apply the method to one year of approach data for Chhatrapati Shivaji Maharaj International Airport (VABB) in Mumbai, India. I show that the method is significantly more accurate than other methods, detecting go-arounds with very few false positives or negatives. Finally, I use the new method to reveal that while there is no one cause for go-arounds at this airport, the majority can be attributed to weather and/or an unstable approach. I also show that one runway (14/32) has a significantly higher proportion of go-arounds than the other (09/27). Full article

Current Air Traffic Controller working positions (CWPs) are reaching their capacity owing to increasing levels of air traffic. The multimodal CWP prototype TriControl combines automatic speech recognition, multitouch gestures, and eye-tracking, aiming for more natural and improved human interaction with air traffic control systems. However, the prototype has not yet undergone systematic evaluation with respect to feasibility. This paper evaluates the operational feasibility, focusing on the system usability of the approach CWP TriControl and its fulfillment of operational requirements. Fourteen controllers took part in a simulation study to evaluate the TriControl concept. The active approach controllers among the group of participants served as the main core target subgroup. The ratings of all controllers in the TriControl assessment were, on average, generally in slight agreement, with just a few showing statistical significance. However, the active approach controllers performed better and rated the system much more positively. The active approach controllers were strongly positive regarding the system usability and acceptance of this early-stage prototype. Particularly, ease of use, user-friendliness, and learnability were perceived very positively. Overall, they were also satisfied with the command input procedure, and would use it for their daily work. Thus, the participating controllers encourage further enhancements to be made to TriControl. Full article

Nowadays, technologies have a massive impact on the design of avionic systems, even for the conservative space industry. In this paper, the single event effect (SEE) characterization of a highly integrated and radio frequency (RF) agile transceiver is being presented which is an outstanding candidate for future radio systems in NewSpace applications and space avionics. The device being investigated allows programmable re-configuration of RF specifications, where classical software-defined radios (SDR) only define an on-demand re-configuration of the signal processing. RF related configurations are untouched for common SDR and developed discretely by the specific application requirements. Due to the high integrity and complexity of the device under test (DUT), state-of-the-art radiation test procedures are not applicable and customized testing procedures need to be developed. The DUT shows a very robust response to linear energy transfer (LET) values up to 62.5 MeV.cm²/mg, without any destructives events and a moderate soft error rate. Full article

Further investigation on the impact of the so called Peukert effect on optimal control of a battery-electrically driven airplane is presented. To analyse the impact of the Peukert effect, an ideal model without this battery concerning effect and a realistic model containing different Peukert exponents are built up. For the different models, optimal trajectories are generated and altitude dependency of a maximum range horizontal flight criterion is investigated. On the one hand, it can be shown that the Peukert effect causes a special form of optimal trajectories. On the other hand, it turns out that range optimal horizontal flight is more efficient in lower altitudes, if the Peukert effect is taken into account. The particular efficiency properties of battery electrical propulsion can be explained with its consumption characteristic, which appear in form of a power function with real exponent. Full article

Due to the intrinsic masking effects of combinational circuits in digital designs, Single-Event Transient (SET) effects were considered irrelevant compared to the data rupture caused by Single-Event Upset (SEU) effects. However, the importance of considering SET in Very-Large-System-Integration (VLSI) circuits increases given the reduction of the transistor dimensions and the logic data path depth in advanced technology nodes. Accordingly, the threat of SET in electronics systems for space applications must be carefully addressed along with the SEU characterization. In this work, a systematic prediction methodology to assess and improve the SET immunity of digital circuits is presented. Further, the applicability to full-custom and cell-based design methodologies are discussed, and an analysis based on signal probability and pin assignment is proposed to achieve a more application-efficient SET-aware optimization of synthesized circuits. For instance, a SET-aware pin assignment can provide a reduction of 37% and 16% on the SET rate of a NOR gate for a Geostationary Orbit (GEO) and the International Space Station (ISS) orbit, respectively. Full article

We have developed a remote and precise feedback control system using optical measurement technology to alter the angle of a flap, which is part of a wind tunnel test model, automatically and to earn the aerodynamic data efficiently. To rectify the wasteful circumstance that Japan Aerospace Exploration Agency (JAXA)’s low-turbulence wind tunnel stops ventilation every time to switch model configurations, we repaired hardware for remote operation and generated software for feedback control. As a result, we have accomplished a system that dramatically advances the efficiency of wind tunnel tests. Moreover, the system was able to consider the deformation of the model through optical measurement; the system controlled flap angles with errors less than the minimum resolution of optical measurement equipment. Consequently, we successfully grasped the nonlinearity of three aerodynamic coefficients $C_L$ , $C_D$ , and $C_{Mp}$ that was impossible so far. Full article

Iodine is considered as a feasible alternative to xenon as a propellant for electric propulsion systems, thanks to its good propulsive performance, high availability, and high storage density. However, as iodine is stored in solid state at ambient temperature, current state-of-the-art propellant management systems are not suitable to be used with it. Moreover, due to its high reactivity, iodine imposes requirements on material-compatibility, hindering the use of mass flow measurement and control systems typically used with other propellants. The architecture of a controlled iodine feeding system for low power (200 W class) ion and Hall effect thrusters is presented and the resulting prototype is described. It consists of a sublimation assembly whose temperature is used to control the tank pressure, a normally-closed ON-OFF valve, and a thermal throttle to perform the fine control of the mass flow rate. A 1D thermal-fluid model concerning the vapor generation in the tank, and its evolution along the different components is detailed. The thermal throttle model has been experimentally verified using air as a working fluid. The model results agree with the measurements of the verification tests in the hypothesis of the presence of an extended region at the entrance of the pipe where the laminar flow velocity and temperature profiles are not fully developed (known as entry flow region). Finally, the system is experimentally characterized and the model of the full system is calibrated using experimental measurements. The calibration shows that the thermal throttle flow presents an entry flow region, that the viscosity is correctly modeled, and that there is a difference between the measured tank temperature and the effective sublimation temperature. Full article