Lowering the Systematic Error in Measurements of Local Heat Transfer Coefficient by Electric Heating of a Plane Wall

A technique that allows simultaneous heating of the heat-exchange surface and estimation of its local temperature from the corresponding electrical resistance of the heating element is presented. The systematic error in measurements of the local heat transfer coefficient has been analyzed. A relation that takes possible heat loss into account and minimizes the measurement errors has been obtained.     

On similarity criteria in flight mechanics

With the aim of enhancing the simulation of flow processes and dynamics of aircraft motion, the analysis of the appropriate equations and search for new similarity criteria are carried out. New relations are obtained for the equations of aircraft motion allowing for experiments with overweight models under certain conditions.     

Kelvin–Helmholtz Instability: Lessons Learned and Ways Forward

The Kelvin–Helmholtz instability (KHI) is a ubiquitous phenomenon across the Universe, observed from 500 m deep in the oceans on Earth to the Orion molecular cloud. Over the past two decades, several space missions have enabled a leap forward in our understanding of this phenomenon at the Earth’s magnetopause. Key results obtained by these missions are first presented, with a special emphasis on Cluster and THEMIS. In particular, as an ideal instability, the KHI was not expected to produce mass transport. Simulations, later confirmed by spacecraft observations, indicate that plasma transport in Kelvin–Helmholtz (KH) vortices can arise during non-linear stage of its development via secondary process. In addition to plasma transport, spacecraft observations have revealed that KHI can also lead to significant ion heating due to enhanced ion-scale wave activity driven by the KHI. Finally, we describe what are the upcoming observational opportunities in 2018–2020, thanks to a unique constellation of multi-spacecraft missions including: MMS, Cluster, THEMIS, Van Allen Probes and Swarm.     

OSIRIS-REx Flight Dynamics and Navigation Design

OSIRIS-REx is the first NASA mission to return a sample of an asteroid to Earth. Navigation and flight dynamics for the mission to acquire and return a sample of asteroid 101955 Bennu establish many firsts for space exploration. These include relatively small orbital maneuvers that are precise to ～1 mm/s, close-up operations in a captured orbit about an asteroid that is small in size and mass, and planning and orbit phasing to revisit the same spot on Bennu in similar lighting conditions. After preliminary surveys and close approach flyovers of Bennu, the sample site will be scientifically characterized and selected. A robotic shock-absorbing arm with an attached sample collection head mounted on the main spacecraft bus acquires the sample, requiring navigation to Bennu’s surface. A touch-and-go sample acquisition maneuver will result in the retrieval of at least 60 grams of regolith, and up to several kilograms. The flight activity concludes with a return cruise to Earth and delivery of the sample return capsule (SRC) for landing and sample recovery at the Utah Test and Training Range (UTTR).     

Origin of Molecular Oxygen in Comets: Current Knowledge and Perspectives

The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument onboard the Rosetta spacecraft has measured molecular oxygen (O₂) in the coma of comet 67P/Churyumov-Gerasimenko (67P/C-G) in surprisingly high abundances. These measurements mark the first unequivocal detection of O₂ in a cometary environment. The large relative abundance of O₂ in 67P/C-G despite its high reactivity and low interstellar abundance poses a puzzle for its origin in comet 67P/C-G, and potentially other comets. Since its detection, there have been a number of hypotheses put forward to explain the production and origin of O₂ in the comet. These hypotheses cover a wide range of possibilities from various in situ production mechanisms to protosolar nebula and primordial origins. Here, we review the O₂ formation mechanisms from the literature, and provide a comprehensive summary of the current state of knowledge of the sources and origin of cometary O₂.     

3D Investigations of the High Pressure Turbine Vane Platform Convection Cooling and Convection-Film Cooling

3D ANSYS CFX conjugate calculation was carried out to compare cooling effectiveness of the high pressure turbine vane platforms with the film cooling and the convection-film cooling.     

Venus Interior Structure and Dynamics

No two rocky bodies offer a better laboratory for exploring the conditions controlling interior dynamics than Venus and Earth. Their similarities in size, density, distance from the sun, and young surfaces would suggest comparable interior dynamics. Although the two planets exhibit some of the same processes, Venus lacks Earth’s dominant process for losing heat and cycling volatiles between the interior and the surface and atmosphere: plate tectonics. One commonality is the size and number of mantle plume features which are inferred to be active today and arise at the core mantle boundary. Such mantle plumes require heat loss from the core, yet Venus lacks a measurable interior dynamo. There is evidence for plume-induced subduction on Venus, but no apparent mosaic of moving plates. Absent plate tectonics, one essential question for interior dynamics is how did Venus obtain its young resurfacing age? Via catastrophic or equilibrium processes? Related questions are how does it lose heat via past periods of plate tectonics, has it always had a stagnant lid, or might it have an entirely different mode of heat loss? Although there has been no mission dedicated to surface and interior processes since the Magellan mission in 1990, near infrared surface emissivity data that provides information on the iron content of the surface mineralogy was obtained fortuitously from Venus Express. These data imply both the presence of continental-like crust, and thus formation in the presence of water, and recent volcanism at mantle hotspots. In addition, the study of interior dynamics for both Earth and exoplanets has led to new insights on the conditions required to initiate subduction and develop plate tectonics, including the possible role of high temperature lithosphere, and a renewed drive to reveal why Venus and Earth differ. Here we review current data that constrains the interior dynamics of Venus, new insights into its interior dynamics, and the data needed to resolve key questions.     

Numerical Simulation of High-Speed Flows Using the Algebraic Reynolds Stress Model

A turbulence model for high-speed compressible flows is developed. It is based on modeling the rapid and slow parts of pressure-strain correlation depending on gradient Mach number and on the assumption that the velocity fluctuations normal to streamlines play a key role in turbulent mixing process. It is shown that an increase in the flow velocity leads to a slowing of turbulent mixing and an increase in the anisotropy of the flow. Comparison of the calculation results with the available experimental data showed good agreement.     

On increasing the spectral efficiency and transmissivity in the data transmission channel on the spacecraft–ground tracking station line

The algorithms for achieving a practical increase in the rate of data transmission on the space-craft–ground tracking station line has been considered. This increase is achieved by applying spectral-effective modulation techniques, the technology of orthogonal frequency compression of signals using millimeterrange radio waves. The advantages and disadvantages of each of three algorithms have been revealed. A significant advantage of data transmission in the millimeter range has been indicated.     

Superluminous Supernovae

Superluminous supernovae are a new class of supernovae that were recognized about a decade ago. Both observational and theoretical progress has been significant in the last decade. In this review, we first briefly summarize the observational properties of superluminous supernovae. We then introduce the three major suggested luminosity sources to explain the huge luminosities of superluminous supernovae, i.e., the nuclear decay of ⁵⁶Ni, the interaction between supernova ejecta and dense circumstellar media, and the spin down of magnetars. We compare these models and discuss their strengths and weaknesses.