Scaling laws and similarity models for the preliminary design of multirotor drones

Multirotor drones modelling and parameter estimation have gained great interest because of their vast application for civil, industrial, military and agricultural purposes. At the preliminary design level the challenge is to develop lightweight models which remain representative of the physical laws and the system interdependencies. Based on the dimensional analysis, this paper presents a variety of modelling approaches for the estimation of the functional parameters and characteristics of the key components of the system. Through this work a solid framework is presented for helping bridge the gaps between optimizing idealized models and selecting existing components from a database. Special interest is given to the models in terms of reliability and error. The results are compared for various existing drone platforms with different requirements and their differences discussed

Simulation and evaluation of sustainable climate trajectories for aviation

In 2019, aviation was responsible for 2.6% of world CO2 emissions as well as additional climate impacts such as contrails. Like all industrial sectors, the aviation sector must implement measures to reduce its climate impact. This paper focuses on the simulation and evaluation of climate scenarios for air transport. For this purpose, a specific tool (CAST for “Climate and Aviation - Sustainable Trajectories”) has been developed at ISAE-SUPAERO. This tool follows a methodology for the assessment of climate impacts adapted to aviation. Firstly, models for the main levers of action, such as air traffic, aircraft energy consumption and energy decarbonization, are provided using trend projections from historical data or assumptions from the literature. Second, the evaluation of scenarios is based on aviation carbon budgets, which are also extended to non-CO2 effects using the concept of GWP*. Several scenario analyses are performed in this paper using CAST allowing different conclusions to be drawn. For instance, the modelling of the scenarios based on the more recent ATAG (Air Transport Action Group) commitments shows that aviation would consume 6.5% of the world carbon budget for +1.5 ◦C. Some illustrative scenarios are also proposed. By allocating 2.6% of the world carbon budget to aviation, it is shown that air transport is compatible with a +2 ◦C trajectory when the annual growth rate of air traffic varies between +1.8% and +2.9%, depending on the technological improvements considered. However, using the same methodology for a +1.5 ◦C trajectory shows that a drastic decrease in air traffic is necessary. Lastly, analyses including non- CO2 effects emphasize the importance of implementing specific strategies for mitigating contrails

Modeling and Design Optimization of an Electric Environmental Control System for Commercial Passenger Aircraft

The aircraft environmental control system (ECS) is the second-highest fuel consumer system, behind the propulsion system. To reduce fuel consumption, one research direction intends to replace conventional aircraft with more electric aircraft. Thus, new electric architectures have to be designed for each system, such as for the ECS. In this paper, an electric ECS is modeled and then sized and optimized for different sizing scenarios with the aim of minimizing fuel consumption at the aircraft level. For the system and for each component, such as air inlets and heat exchangers, parametric models are developed to allow the prediction of relevant characteristics. These models, developed in order to be adapted to aircraft design issues, are of different types, such as scaling laws and surrogate models. They are then assembled to build a preliminary sizing procedure for the ECS by using a multidisciplinary design analysis and optimization (MDAO) formulation. Results show that the ECS design is highly dependent on the sizing scenario considered. An approach to size the ECS globally with respect to all the sizing scenarios leads to an ECS that accounts for around 200 N of drag, 190 kW of electric power, and 1500 kg of mass for the CeRAS aircraft

Hypercapnia increases ACE2 expression and pseudo-SARS-CoV-2 entry in bronchial epithelial cells by augmenting cellular cholesterol

Patients with chronic lung disease, obesity, and other co-morbid conditions are at increased risk of severe illness and death when infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Hypercapnia, the elevation of CO2 in blood and tissue, commonly occurs in patients with severe acute and chronic lung disease, including those with pulmonary infections, and is also associated with high mortality risk. We previously reported that hypercapnia increases viral replication and mortality of influenza A virus infection in mice. We have also shown that culture in elevated CO2 upregulates expression of cholesterol synthesis genes in primary human bronchial epithelial cells. Interestingly, factors that increase the cholesterol content of lipid rafts and lipid droplets, platforms for viral entry and assembly, enhance SARS-CoV-2 infection. In the current study, we investigated the effects of hypercapnia on ACE2 expression and entry of SARS-CoV-2 pseudovirus (p-SARS-CoV-2) into airway epithelial cells. We found that hypercapnia increased ACE2 expression and p-SARS-CoV-2 uptake by airway epithelium in mice, and in cultured VERO and human bronchial epithelial cells. Hypercapnia also increased total cellular and lipid raft-associated cholesterol in epithelial cells. Moreover, reducing cholesterol synthesis with inhibitors of sterol regulatory element binding protein 2 (SREBP2) or statins, and depletion of cellular cholesterol, each blocked the hypercapnia-induced increases in ACE2 expression and p-SARS-CoV-2 entry into epithelial cells. Cigarette smoke extract (CSE) also increased ACE2 expression, p-SARS-CoV-2 entry and cholesterol accumulation in epithelial cells, an effect not additive to that of hypercapnia, but also inhibited by statins. These findings reveal a mechanism that may account, in part, for poor clinical outcomes of SARS-CoV-2 infection in patients with advanced lung disease and hypercapnia, and in those who smoke cigarettes. Further, our results suggest the possibility that cholesterol-lowering therapies may be of particular benefit in patients with hypercapnia when exposed to or infected with SARS-CoV-2

Efficient sizing and optimization of multirotor drones based on scaling laws and similarity models

In contrast to the current overall aircraft design techniques, the design of multirotor vehicles generally consists of skill-based selection procedures or is based on pure empirical approaches. The application of a systemic approach provides better design performance and the possibility to rapidly assess the effect of changes in the requirements. This paper proposes a generic and efficient sizing methodology for electric multirotor vehicles which allows to optimize a configuration for different missions and requirements. Starting from a set of algebraic equations based on scaling laws and similarity models, the optimization problem representing the sizing can be formulated in many manners. The proposed methodology shows a significant reduction in the number of function evaluations in the optimization process due to a thorough suppression of inequality constraints when compared to initial problem formulation. The results are validated by comparison to characteristics of existing multirotors. In addition, performance predictions of these configurations are performed for different flight scenarios and payloads

Aircraft fleet models using a bottom-up approach for simulating aviation technological prospective scenarios

Modeling prospective scenarios for aviation in the context of climate issues is a scientific topic of major interest. For this purpose, the development of models to integrate technological improvements in these scenarios is necessary. This paper focuses on the use of a bottom-up approach to establish aircraft fleet models, in order to integrate them into CAST, an open-source tool for simulating and evaluating prospective scenarios for air transport. These models are based on logistic functions which allow representing the gradual replacement of current aircraft by future aircraft architectures obtained from overall aircraft design. The efficiency improvement of the aircraft fleet can then be assessed. To illustrate the use of the models, some case studies, considering for example turboprop and hydrogen aircraft, are performed for analyzing efficiency scenarios for air transport. Also, the effect of accelerated fleet renewal and earlier introduction of new aircraft architectures is studied

The Qo site of the mitochondrial complex III is required for the transduction of hypoxic signaling via reactive oxygen species production

Mammalian cells increase transcription of genes for adaptation to hypoxia through the stabilization of hypoxia-inducible factor 1α (HIF-1α) protein. How cells transduce hypoxic signals to stabilize the HIF-1α protein remains unresolved. We demonstrate that cells deficient in the complex III subunit cytochrome b, which are respiratory incompetent, increase ROS levels and stabilize the HIF-1α protein during hypoxia. RNA interference of the complex III subunit Rieske iron sulfur protein in the cytochrome b–null cells and treatment of wild-type cells with stigmatellin abolished reactive oxygen species (ROS) generation at the Qo site of complex III. These interventions maintained hydroxylation of HIF-1α protein and prevented stabilization of HIF-1α protein during hypoxia. Antioxidants maintained hydroxylation of HIF-1α protein and prevented stabilization of HIF-1α protein during hypoxia. Exogenous hydrogen peroxide under normoxia prevented hydroxylation of HIF-1α protein and stabilized HIF-1α protein. These results provide genetic and pharmacologic evidence that the Qo site of complex III is required for the transduction of hypoxic signal by releasing ROS to stabilize the HIF-1α protein

Sizing and optimization of a more electric aircraft integrating short-term incremental technologies

In order to reduce the environmental impact of aviation, one of the solutions is to develop more efficient aircraft. These gains can be achieved in different fields such as propulsion, aerodynamics or electrification of systems. This paper focuses on the sizing and optimization of BEITA, a short-medium range aircraft architecture available in the short term by 2025-2030. The aircraft is based on incremental technologies for propulsion, aerostructure and bleedless systems. Light-weight models are proposed for the different improvements, particularly for more electric systems. FAST-OAD, an open source framework for rapid overall aircraft design based on multidisciplinary design analysis and optimization, is used to size the new architecture and a specific life cycle assessment module is used to estimate the environmental impacts. BEITA allows a reduction in fuel consumption of 15% compared to the CeRAS reference aircraft. Optimizations of this architecture are achieved minimizing different cost functions. This study ends with a sizing on a shorter range based on specific payload-range diagrams