Influence of Various Stator Parameters on the Open-Water Performance of Pump-Jet Propulsion

In order to improve the hydrodynamic performance of pump-jet propulsion (PJP) when matching stator with the rotor, the RANS method with SST k-ω turbulence model is employed to study the influence of six kinds of stator parameters, which are classified into three groups, i.e., stator solidity, stator angles and rotor–stator spacing (S). Results show that the stator solidity involves the blade number (Ns) and chord length (L), has an obvious acceleration effect at and after stator, and produces a higher thrust and torque with a slight efficiency change. Further comparing Ns and L results, we find greater distinctions between the two cases when stator solidity is greatly adjusted. Three stator angles, i.e., stagger angle (α), lean angle (γ), and sweep angle (β), are studied. The α has the biggest effect on the thrust, torque, and efficiency; meanwhile, it shifts the advance number that corresponds to maximum efficiency. The effect of γ is similar to α, but its influence is far less than α. However, there is little difference between various β cases except for off-design conditions, where the efficiency drops dramatically as β increases. The S has a slight effect on PJP performance. Even though S decreases 34% relative to the original PJP, the rotor thrust and torque increase by less than 1%. In addition, we compare torque balance locations under various parameters, and each component force is analyzed in detail to explain the reason for performance variation. The present work is conducive to future optimization in PJP design.

Aerothermodynamics and Jet Propulsion

Get up to speed with this robust introduction to the aerothermodynamics principles underpinning jet propulsion, and learn how to apply these principles to jet engine components. Suitable for undergraduate students in aerospace and mechanical engineering, and for professional engineers working in jet propulsion, this textbook includes consistent emphasis on fundamental phenomena and key governing equations, providing students with a solid theoretical grounding on which to build practical understanding; clear derivations from first principles, enabling students to follow the reasoning behind key assumptions and decisions, and successfully apply these approaches to new problems; practical examples grounded in real-world jet propulsion scenarios illustrate new concepts throughout the book, giving students an early introduction to jet and rocket engine considerations; and online materials for course instructors, including solutions, figures, and software resources, to enhance student teaching.

Who Is Attacking Us?

The question “Who is attacking us?” explains cyber threat actors and their motivations for attacking organizations. The chapter begins with a Colonial Pipeline case study that describes the ransomware attack against the U.S. fuel pipeline, a cyberattack on critical U.S. infrastructure. The chapter explains different types of cyberattacks, including social engineering, denial of service, advance persistent threats, brute force attacks, and artificial intelligence attacks. Further, the chapter details the suite of threat actors who launch cyberattacks, including lone hackers, hacktivists, petty criminals, organized criminals, professional criminals, and nation-states. Finally, the chapter describes the importance of sectoral threat intelligence, including Information Sharing and Analysis Centers (ISACs), and types of threats to specific sectors, including finance, healthcare, manufacturing, education, power and utilities, and retail. The chapter concludes with Embedded Endurance strategy lessons from Falco’s experience addressing these issues at NASA’s Jet Propulsion Laboratory.

P-Band InSAR for Geohazard Detection over Forested Terrains: Preliminary Results

Decorrelation of X, C, and L-band InSAR (Interferometric Synthetic Aperture Radar) over densely vegetated regions is a common obstacle for detecting ground deformation beneath forest canopies. Using long-wavelength P-band SAR sensors (wavelength of 69.72 cm), which can penetrate through dense forests and collect relatively consistent signals from ground surface, is one potential solution. Here, we experimented using the NASA JPL (Jet Propulsion Laboratory)’s P-band AirMOSS (Airborne Microwave Observatory of Subcanopy and Subsurface) radar system to collect repeat-pass P-band SAR data over densely vegetated regions in Oregon and California (USA), and generated by far the first P-band InSAR results to test the capability of P-band InSAR for geohazard detection over forested terrains. Our results show that the AirMOSS P-band InSAR could retain coherence two times as high as the L-band satellite ALOS-2 (Advanced Land Observing Satellite-2) data, and was significantly more effective in discovering localized geohazards that were unseen by the ALOS-2 interferograms over densely vegetated areas. Our results suggest that the airborne P-band InSAR could be a revolutionary tool for studying geohazards under dense forest canopies.

Draft Genome Sequences of Heat Shock-Tolerant Microbes Isolated from a Spacecraft Assembly Facility

Heat shock-tolerant microorganisms belonging to the orders Bacillales and Micrococcales were isolated from the Spacecraft Assembly Facility at the Jet Propulsion Laboratory, and 63 draft genome sequences were assembled and identified. Further analyses of these genomes can provide insight into methods for preventing forward contamination.

Estimation of Evapotranspiration and Its Components across China Based on a Modified Priestley–Taylor Algorithm Using Monthly Multi-Layer Soil Moisture Data

Although soil moisture (SM) is an important constraint factor of evapotranspiration (ET), the majority of the satellite-driven ET models do not include SM observations, especially the SM at different depths, since its spatial and temporal distribution is difficult to obtain. Based on monthly three-layer SM data at a 0.25° spatial resolution determined from multi-sources, we updated the original Priestley Taylor–Jet Propulsion Laboratory (PT-JPL) algorithm to the Priestley Taylor–Soil Moisture Evapotranspiration (PT-SM ET) algorithm by incorporating SM control into soil evaporation (Es) and canopy transpiration (T). Both algorithms were evaluated using 17 eddy covariance towers across different biomes of China. The PT-SM ET model shows increased R2, NSE and reduced RMSE, Bias, with more improvements occurring in water-limited regions. SM incorporation into T enhanced ET estimates by increasing R2 and NSE by 4% and 18%, respectively, and RMSE and Bias were respectively reduced by 34% and 7 mm. Moreover, we applied the two ET algorithms to the whole of China and found larger increases in T and Es in the central, northeastern, and southern regions of China when using the PT-SM algorithm compared with the original algorithm. Additionally, the estimated mean annual ET increased from the northwest to the southeast. The SM constraint resulted in higher transpiration estimate and lower evaporation estimate. Es was greatest in the northwest arid region, interception was a large fraction in some rainforests, and T was dominant in most other regions. Further improvements in the estimation of ET components at high spatial and temporal resolution are likely to lead to a better understanding of the water movement through the soil–plant–atmosphere continuum.