Marshall Space Flight Center Research and Technology Report 2019

Today, our calling to explore is greater than ever before, and here at Marshall Space Flight Centerwe make human deep space exploration possible. A key goal for Artemis is demonstrating and perfecting capabilities on the Moon for technologies needed for humans to get to Mars. This years report features 10 of the Agencys 16 Technology Areas, and I am proud of Marshalls role in creating solutions for so many of these daunting technical challenges. Many of these projects will lead to sustainable in-space architecture for human space exploration that will allow us to travel to the Moon, on to Mars, and beyond. Others are developing new scientific instruments capable of providing an unprecedented glimpse into our universe. NASA has led the charge in space exploration for more than six decades, and through the Artemis program we will help build on our work in low Earth orbit and pave the way to the Moon and Mars. At Marshall, we leverage the skills and interest of the international community to conduct scientific research, develop and demonstrate technology, and train international crews to operate further from Earth for longer periods of time than ever before first at the lunar surface, then on to our next giant leap, human exploration of Mars. While each project in this report seeks to advance new technology and challenge conventions, it is important to recognize the diversity of activities and people supporting our mission. This report not only showcases the Centers capabilities and our partnerships, it also highlights the progress our people have achieved in the past year. These scientists, researchers and innovators are why Marshall and NASA will continue to be a leader in innovation, exploration, and discovery for years to come

Impact of cavitation erosion on nozzle flow characteristics and liquid fuel atomization

Modern Diesel engines with high injection pressures can suffer from cavitation erosion phenomena. Signs of cavitation erosion in automotive components can manifest in high pressure liquid systems components (e.g. injectors, valves and pumps), as well as in the narrow fluid regions next to the cylinder liners on both the water cooling jacket side and the ring assembly side. Special attention must also be given during the design of marine propellers and water turbines, since the performances and the lifespan of these components mainly depends by the appearance of cavitation and, potentially, erosion.Cavitation erosion alters metal devices by changing their geometry from the original design, with consequences on the overall system performances. Since the lifetime of the components can be significantly shortened due to cavitation erosion, numerical and experimental investigations are usually carried out during the design process to evaluate the risk of incurring in cavitation erosion. It is then of crucial importance for the industry to have access to validated numerical models for the prediction of cavitation erosion within the softwares used for the evaluation of new designs. The scope of this work is then to develop a state–of–the–art numerical framework for the prediction of cavitation erosion in a commercially available software. For this reason, liquid compressibility models are implemented in the software with both, analytical formulations and tabular data, commonly used by the industry. The solver capability to correctly resolve pressure wave velocities is proven with simple 1D test cases, comparing the simulation results against analytical solutions. A novel scientific contribution is made by applying the multifluid model to cavitating flows, thus allowing to model slip velocity between the liquid and the vapor phase. The developed numerical framework for the simulation of cavitating flows at erosive conditions is validated against experimental results of simplified geometries and the obtained results about the effect of viscosity variability of commercial diesel showed the importance of fluid properties for the investigation of cavitation erosion. For the first time, pressure peaks related to the collapse of vapor clouds are recorded due to end of injection events and the effect of actual erosion patterns is investigated in terms of internal injector flow and spray. All the developed methods are implemented in a software commercialized by AVL GmbH,therefore of immediate use to engineers for industrial applications

Simulating direct shear tests with the Bullet physics library : a validation study

This study focuses on the possible uses of physics engines, and more specifically the Bullet physics library, to simulate granular systems. Physics engines are employed extensively in the video gaming, animation and movie industries to create physically plausible scenes. They are designed to deliver a fast, stable, and optimal simulation of certain systems such as rigid bodies, soft bodies and fluids. This study focuses exclusively on simulating granular media in the context of rigid body dynamics with the Bullet physics library. The first step was to validate the results of the simulations of direct shear testing on uniform-sized metal beads on the basis of laboratory experiments. The difference in the average angle of mobilized frictions was found to be only 1.0°. In addition, a very close match was found between dilatancy in the laboratory samples and in the simulations. A comprehensive study was then conducted to determine the failure and post-failure mechanism. We conclude with the presentation of a simulation of a direct shear test on real soil which demonstrated that Bullet has all the capabilities needed to be used as software for simulating granular systems

Acceleration of Non-Equidiffusive Flames in Channels: Computational Simulations and Analytical Studies

When a premixed flame front spreads in a narrow pipe, wall friction continuously distorts the flame shape. As a result, the flame front acquires a larger surface area, consumes more fuel per unit time and, thereby, propagates faster. While this mechanism of flame acceleration due to wall friction has widely been studied, especially within the last decade, the analytical and computational studies were mostly devoted to equidiffusive flames, where the Lewis number, defined as the thermal to mass diffusivity ratio, is unity, Le = 1. However, in reality thermal and mass diffusion are typically not balanced, especially in rich and lean mixtures. Hence, the micro-scale, diffusional-thermal effects may appear comparable with macro-scale phenomena such as wall friction. The present work sheds the light on the dynamics and morphology of Le ≠ 1 flames in channels. Specifically, it studies, by means of computational and analytical endeavors, how the interplay of finite flame thickness, stretch effect and the thermal-molecular diffusion influence the overall flame acceleration scenario. It is shown that Le \u3e 1 flames accelerate slower, due to an effective thickening of the flame front. In contrast, Le \u3c 1 flames exhibit faster acceleration due to effective flame channeling and other morphological deformations resembling the diffusional-thermal (DT) instability. The analysis also incorporates the internal transport flame properties into the theory of flame acceleration due to wall friction, by means of the Markstein number, Mk, that characterizes the flame response to curvature and stretch. Being a positive or negative function of thermal-chemical combustion parameters, such as the thermal expansion ratio and the Lewis and Zel\u27dovich numbers, the Markstein number either restrains or promotes the flame acceleration. While Mk may substantially facilitate the flame acceleration in narrow channels, this effects diminishes with the increase in the channel width. The analysis is accompanied by extensive numerical simulations of the Navier-Stokes and combustion equations, which clarify the impact of the Lewis number on the flame acceleration. It is obtained that, for Le lower than a certain critical value, at the initial stage of flame acceleration, globally-convex flame fronts split into two or more fingers , accompanied by a drastic increase in the flame surface area and associated enhancement of the flame acceleration. Later, however, the flame fingers meet, promptly consuming the troughs, which rapidly diminishes the flame surface area and moderates the acceleration. Eventually, this results in a single, globally-convex flame front that keeps accelerating. Overall, the thermal-diffusive effects facilitate the flame acceleration scenario, thereby advancing a potential deflagration-to-detonation transition

A coupled CFD approach for combustor-turbine interaction

The current approach in the industry to numerically investigate the flow in a gas turbine considers each component, such as combustor and turbine, as a stand-alone part, involving no or very minor interactions with other parts, mainly applied through static boundary conditions. Efficient and very specialised CFD codes have been developed in the past to address the different flow characteristic occurring in the different regions of the engine. In order to meet the future requirements in terms of fuel consumption and pollutants emissions, an integrated approach capable of capturing all the possible interactions between different components is necessary. An efficient and accurate way to achieve integrated simulations is to couple already existing specialised codes in a zonal type of coupling. In this Thesis work a methodology to couple an incompressible/low-Mach number pressure-based combustion code with a compressible density-based turbomachinery code for industrial application has been developed. In particular two different couplings have been implemented: the first, based on the exchange of existing boundary conditions through files, comes as a completely separated tools from the original codes, of which no modifications are required, and it is applied to steady state simulations; the second instead, based on the exchange of boundary conditions and body forces through message passing, requires some modifications of the source codes and it is applied to both steady and unsteady cases. A simple analysis shows that not all the primitive variables can be made continuous at the coupling interface between the two codes and a compromise was found that allows minor discontinuity in some of the variables while achieving mass flow conservation and continuity of the temperature profiles. The coupling methodology has been applied to a simplified but realistic industrial case, consisting of a RQL (Rich Burn - Quick quench - Lean burn) combustor coupled with the first stage of the HP turbine. The analysis of the steady case has shown that the combustor field is affected as far as 150% axial chord lengths upstream of the blades leading edge, affecting RTDF and OTDF at the interfaces. In the turbine stage significant differences in both efficiency and degree of reaction were found in the coupled cases with respect to standard standalone simulations using radial inlet profiles. The analysis of the unsteady simulation has instead shown the hot streaks behaviour across the turbine, that are only partially mitigated by the stator blades and, due to segregation effect of hot and cold gases, migrate towards the pressure side of the rotor blades

A New Atomization Paradigm: Smart Wave-Augmented Varicose Explosions

The characterization of viscous, non-Newtonian slurry heating and atomization by means of internal wave excitation is presented for a twin-fluid injector. We detail mechanisms that enhance their disintegration in a novel process called “Wave-Augmented Varicose Explosions” (WAVE). Atomization of such fluids is challenging, especially at low gas-liquid mass ratios. Droplet production is further complicated when slurry viscosity varies widely; if viscosity levels are too high, atomization quality suffers, and an undesirable pressure drop restricts the flow. To mitigate, we introduce and demonstrate “Smart” atomization, a novel implementation of simultaneous proportional integral derivative (PID) control algorithms to accommodate dynamically and extensively changing fluid properties. Unlike a conventional twin-fluid injector, WAVE injects a cold annular slurry flow into a hot core steam flow, encouraging regular slurry waves to form inside the nozzle and producing bulk system pulsation at 1000 Hz. The Kelvin-Helmholtz instability dominates during wave formation, while transonic pressure effects dominate during wave collapse. Numerical simulations reveal three atomization mechanisms that are a direct result of wave formation: 1) wave impact momentum, 2) pressure buildup, and 3) droplet breakaway. The first two are the forces that exploit slurry irregularities to drive rupture. The third occurs as rising waves penetrate the central steam flow and droplets are stripped off. Two effervescent mechanisms are also provided as 1) surface deformation allows steam fingers to force through the wave, and 2) the wave collapses on itself, trapping steam. Both Rayleigh-Taylor and Kelvin-Helmholtz instabilities are self-amplified in a viscosity-shear-temperature instability cycle because the slurry’s viscosity is sensitive to both strain and temperature. Smart atomization is applied to the WAVE framework with two coupled PID controllers to improve atomization robustness. The first controller automates slurry flow based on atomizer pressure drop, while the second compensates for the newly adjusted phase momentum ratio and sets a new steam flow based on droplet size. Three tests with increasingly rigorous models were conducted to capture the response of this coupled controller system to a step increase in viscosity. Though atomization characteristics were drastically altered, for a 100-fold increase in slurry viscosity, the controllers successfully maintained consistent droplet size and slurry flow resistance

Aquatic escape for micro-aerial vehicles

As our world is experiencing climate changes, we are in need of better monitoring technologies. Most of our planet is covered with water and robots will need to move in aquatic environments. A mobile robotic platform that possesses efficient locomotion and is capable of operating in diverse scenarios would give us an advantage in data collection that can validate climate models, emergency relief and experimental biological research. This field of application is the driving vector of this robotics research which aims to understand, produce and demonstrate solutions of aerial-aquatic autonomous vehicles. However, small robots face major challenges in operating both in water and in air, as well as transition between those fluids, mainly due to the difference of density of the media. This thesis presents the developments of new aquatic locomotion strategies at small scales that further enlarge the operational domain of conventional platforms. This comprises flight, shallow water locomotion and the transition in-between. Their operating principles, manufacturing methods and control methods are discussed and evaluated in detail. I present multiple unique aerial-aquatic robots with various water escape mechanisms, spanning over different scales. The five robotic platforms showcased share similarities that are compared. The take-off methods are analysed carefully and the underlying physics principles put into light. While all presented research fulfils a similar locomotion objective - i.e aerial and aquatic motion - their relevance depends on the environmental conditions and supposed mission. As such, the performance of each vehicle is discussed and characterised in real, relevant conditions. A novel water-reactive fuel thruster is developed for impulsive take-off, allowing consecutive and multiple jump-gliding from the water surface in rough conditions. At a smaller scale, the escape of a milligram robotic bee is achieved. In addition, a new robot class is demonstrated, that employs the same wings for flying as for passive surface sailing. This unique capability allows the flexibility of flight to be combined with long-duration surface missions, enabling autonomous prolonged aquatic monitoring.Open Acces

HPCCP/CAS Workshop Proceedings 1998

This publication is a collection of extended abstracts of presentations given at the HPCCP/CAS (High Performance Computing and Communications Program/Computational Aerosciences Project) Workshop held on August 24-26, 1998, at NASA Ames Research Center, Moffett Field, California. The objective of the Workshop was to bring together the aerospace high performance computing community, consisting of airframe and propulsion companies, independent software vendors, university researchers, and government scientists and engineers. The Workshop was sponsored by the HPCCP Office at NASA Ames Research Center. The Workshop consisted of over 40 presentations, including an overview of NASA's High Performance Computing and Communications Program and the Computational Aerosciences Project; ten sessions of papers representative of the high performance computing research conducted within the Program by the aerospace industry, academia, NASA, and other government laboratories; two panel sessions; and a special presentation by Mr. James Bailey

Research and Technology Objectives and Plans Summary (RTOPS)

A compilation of the summary portion of each of the Research and Technology Operating Plans (RTOP) used for management review and control of research currently in progress throughout NASA is presented along with citations and abstracts of the RTOPs. Four indexes are included: (1) subject; (2) technical monitor; (3) responsible NASA organization; and (4) RTOP number

Markov Decision Processes with Embedded Agents

We present Markov Decision Processes with Embedded Agents (MDPEAs), an extension of multi-agent POMDPs that allow for the modeling of environments that can change the actuators, sensors, and learning function of the agent, e.g., a household robot which could gain and lose hardware from its frame, or a sovereign software agent which could encounter viruses on computers that modify its code. We show several toy problems for which standard reinforcement-learning methods fail to converge, and give an algorithm, `just-copy-it`, which learns some of them. Unlike MDPs, MDPEAs are closed systems and hence their evolution over time can be treated as a Markov chain. In future work, we hope MDPEAs can be extended to model even fully embedded agents acting in real digital or physical environments