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For satellites in Very Low Earth Orbit (VLEO) or the upper atmosphere, Air-Breathing Electric Propulsion (ABEP) can be used to counteract the drag effects of the atmosphere or provide attitude control without the need for onboard propellant storage. The Dense Plasma Focus (DPF) inspired the design of an ABEP Pulsed Plasma Thruster (TAMU PPT) which takes advantage of the simplicity, scalability, and high energy density of the DPF. This work details the design and testing of a PPT for use on satellites in the upper atmosphere. Testing was conducted at a variety of pressures and pulsing energies to determine which conditions provide maximum thrust and thrust to power ratios (TPR). It was found through single pulse experiments that a pressure of 6.3 hPa (corresponding to an altitude of about 35 km) and an energy per pulse of 9 J yield a TPR of 21 mN/kW. High frequency operation at 20 Hz in similar conditions showed a TPR of up to 28 mN/kW with a corresponding thrust of 4.8 mN. High speed imaging of the plasma plume found plasma velocities in excess of 2 km/s and identified metal ejecta with velocities up to 350 m/s. The pinching phenomenon associated with a DPF was also observed and a plasma jet velocity up to 50 km/s was recorded. The TPR of the TAMU PPT demonstrated in this work is comparable to that of other ABEP thrusters, however the TAMU PPT has an advantage when comparing thrust density. The TAMU PPT has a thrust density between 4.8 and 19 mN/cm2 while other ABEP thrusters have thrust densities between 0.019 and 0.36 mN/cm2. [ABSTRACT FROM AUTHOR]

The Air-Breathing Ion Engine (ABIE) is an electric propulsion system capable of compensating for drag at low altitudes by ingesting the surrounding atmospheric particles to be utilized as propellant. The current state of the art of the ABIE performance is evaluated via Direct Simulation Monte Carlo (DSMC), due to the rarefied nature of the atmosphere in Very-Low Earth Orbit (VLEO). Nevertheless, the scarce availability of relevant simulation methodologies in the literature limits the repeatability of such numerical studies. Therefore, this paper proposes an independent methodology applicable to the modelling and simulation of Atmosphere-Breathing Electric Propulsion (ABEP) intakes that aims to validate the ABIE DSMC results retrieved from the literature. This is achieved by investigating the ABIE intake collection efficiency and compression ratio through the open-source solver dsmcFoam+ and by assessing the results against the available RARAC-3D DSMC data. First, the variation of grid transparency is discussed and compared between both solvers, yielding a mean percentage error of 2.97 % for the compression ratio and 2.06 % for the collection efficiency. Second, the absence of intermolecular collisions is verified for which errors of 1.61 % for collection efficiency and 3.49 % for compression ratio are observed. Then, the variation of flow incidence angle is simulated between 0 ∘ and 15 ∘ , yielding differences lower than 1.80 % . Consecutively, the intake aspect ratio is varied between 10 and 40, for which a maximum discrepancy of 1.83 % is measured and, finally, the drag coefficient of the intake is obtained in dsmcFoam+ to define the power density requirements. [ABSTRACT FROM AUTHOR]

Osteoglossomorpha is a significant taxon for studies of evolution and various aspects of fish biology as an evolutionarily old group of fish. The taxon exhibits anatomical, morphological and physiological diversity and various adaptations such as air breathing or electroreception as well as modifications visible in sight and olfactory organs. A peculiarity of this group is the presence of four types of spermatozoa, namely complex introsperm and uni-, bi-, and aflagellate aquasperm. Given the unique morphology and large dimensions of some species, osteoglossomorphs are popular in aquaristics as ornamental fish, and in fisheries because they are an important source of food in many countries. The aim of this paper is to focus on some aspects of the biology and unique features as well as the importance for humans of this unusual group of fish. [ABSTRACT FROM AUTHOR]

The air-breathing ion engine (ABIE), a concept for atmosphere-breathing electric propulsion for atmospheric drag compensation for satellites in very low earth orbit, is expected to be realized. The ABIE employs electron cyclotron resonance (ECR) ion engine technology and consists of an intake, an ECR plasma generator, ion optics, and a neutralizer. In the present study, a plasma generator with ion optics was designed and fabricated, and its performance was evaluated. In the ABIE, rarefied air in a vacuum chamber enters a discharge chamber, and it is then ionized by an ECR discharge. Finally, the generated ions are extracted by the ion optics. By measuring the current, we investigated the location of the specific source of ions extracted from the plasma generator. It was found that ions leak from the discharge chamber through apertures for air inflow on the yokes and side shielding panels of the plasma generator. The function of the side panels around the plasma generator is not only to prevent electron inflow but also to prevent ion outflow. We modified the side surface of the plasma generator to a three-layer structure, which suppressed the ion leakage successfully. [ABSTRACT FROM AUTHOR]

In air-breathing proton exchange membrane fuel cells (Air PEM FCs), a high rate of water evaporation from the cathode might influence the resistance of the membrane electrode assembly (MEA), which is highly dependent on the water content of the Nafion membrane. We propose a dead-end hydrogen anode as a means of intermediate storage of water/humidity for self-humidification of the membrane. Such an inflatable bag integrated with a single lightweight MEA FC has the potential in blimp applications for anode self-humidification. A dynamic numerical water balance model, validated by experimental measurements, is derived to predict the effect of MEA configuration, and the membrane's hydration state and water transfer rate at the anode on MEA resistance and performance. The experimental setup included humidity measurements, and polarization and electrochemical impedance spectroscopy tests to quantify the effect of membrane hydration on its resistance in a lightweight MEA (12 g) integrated with an inflatable dead-end hydrogen storage bag. Varying current densities (5, 10, and 15 mA/cm 2 ) and cathode humidity levels (20, 50, and 80%) were examined and compared with the numerical results. The validated model predicts that the hydration state of the membrane and water transfer rate at the anode can be increased by using a thin membrane and thicker gas diffusion layer.

Pure oxygen is vital in medical treatment, first aid, and chemical synthesis. Hypoxia can cause severe damage to the organ systems such as respiratory, digestive, and nervous systems and even directly cause death. Notably, the severe Coronavirus disease 2019 (COVID-19) pandemic has exacerbated the shortage of medical oxygen in the world. Hence, a safe, economical, and portable oxygen supply device is urgently needed. Here, we have successfully prepared a device with air-breathing electrochemical extraction of pure oxygen (ABEEPO) with light weight and high energy efficiency. By renovating the structure of the electrolytic cell, the components bipolar plate and end plate are replaced with a plastic membrane, and the component current collector is replaced with a highly conductive graphene composite membrane electrode. Due to the use of the plastic membrane and graphene composite membrane electrode, the weight of the electrolytic cell is reduced from 1319.4 to 1.6 g, and the flexibility of the electrolytic cell is successfully realized. Through optimizing anode catalysts, working area, and operating voltage, a high flow rate per mass (234 mL h -1 g -1 ) was achieved at a voltage of 1.2 V. The device exhibits high stability in 2 h. The new portable oxygen production device would be effective for hypoxia treatment.