Tripropellant combustion process

The addition of small amounts of hydrogen to the combustion of LOX/hydrocarbon propellants in large rocket booster engines has the potential to enhance the system stability. Programs being conducted to evaluate the effects of hydrogen on the combustion of LOX/hydrocarbon propellants at supercritical pressures are described. Combustion instability has been a problem during the development of large hydrocarbon fueled rocket engines. At the higher combustion chamber pressures expected for the next generation of booster engines, the effect of unstable combustion could be even more destructive. The tripropellant engine cycle takes advantage of the superior cooling characteristics of hydrogen to cool the combustion chamber and a small amount of the hydrogen coolant can be used in the combustion process to enhance the system stability. Three aspects of work that will be accomplished to evaluate tripropellant combustion are described. The first is laboratory demonstration of the benefits through the evaluation of drop size, ignition delay and burning rate. The second is analytical modeling of the combustion process using the empirical relationship determined in the laboratory. The third is a subscale demonstration in which the system stability will be evaluated. The approach for each aspect is described and the analytical models that will be used are presented

Low heat transfer oxidizer heat exchanger design and analysis

The RL10-IIB engine, a derivative of the RLIO, is capable of multi-mode thrust operation. This engine operates at two low thrust levels: tank head idle (THI), which is approximately 1 to 2 percent of full thrust, and pumped idle (PI), which is 10 percent of full thrust. Operation at THI provides vehicle propellant settling thrust and efficient engine thermal conditioning; PI operation provides vehicle tank pre-pressurization and maneuver thrust for log-g deployment. Stable combustion of the RL10-IIB engine at THI and PI thrust levels can be accomplished by providing gaseous oxygen at the propellant injector. Using gaseous hydrogen from the thrust chamber jacket as an energy source, a heat exchanger can be used to vaporize liquid oxygen without creating flow instability. This report summarizes the design and analysis of a United Aircraft Products (UAP) low-rate heat transfer heat exchanger concept for the RL10-IIB rocket engine. The design represents a second iteration of the RL10-IIB heat exchanger investigation program. The design and analysis of the first heat exchanger effort is presented in more detail in NASA CR-174857. Testing of the previous design is detailed in NASA CR-179487

Design and analysis report for the RL10-2B breadboard low thrust engine

The breadboard low thrust RL10-2B engine is described. A summary of the analysis and design effort to define the multimode thrust concept applicable to the requirements for the upper stage vehicles is provided. Baseline requirements were established for operation of the RL10-2B engine under the following conditions: (1) tank head idle at low propellant tank pressures without vehicle propellant conditioning or settling thrust; (2) pumped idle at a ten percent thrust level for low G deployment and/or vehicle tank pressurization; and (3) full thrust (15,000 lb.). Several variations of the engine configuration were investigated and results of the analyses are included

Characterization of controlled gamblers and pathological gamblers using the social representation theory

Introduction In industrialized countries, gambling disorder tends to become a major issue. The use of the social representation theory provides clues for a better understanding of pathological gamblers. Objective This paper investigates the representation of risk in a gambling context among lay people (Study 1) and among controlled gamblers and probable pathological gamblers (Study 2). Method In the first study, 1106 people answered a free association task based on the target expression ‘risk in a gambling context’. In the second study, a small sample of gamblers, half of them being probable pathological gamblers (based on their score at the SOGS), participated in a semi-structured interview about risk in a gambling context. Interview guidelines were constructed based on the results obtained from Study 1. Results In Study 1, results indicate that the overall representation of risk in a gambling context differs from the one in a general context. The results are interpreted through the prospect theory and the decision-making dual-process model. Results from Study 2 show that, contrarily to those being probable pathological gamblers, controlled gamblers orient their discourse around the notion of pleasure and do not perceive gambling as a threat for their ego. Conclusion Controlled gamblers fear to lose money, while probable pathological gamblers fear to lose the game

Surface Wave Multipath Signals in Near-Field Microwave Imaging

Microwave imaging techniques are prone to signal corruption from unwanted multipath signals. Near-field systems are especially vulnerable because signals can scatter and reflect from structural objects within or on the boundary of the imaging zone. These issues are further exacerbated when surface waves are generated with the potential of propagating along the transmitting and receiving antenna feed lines and other low-loss paths. In this paper, we analyze the contributions of multi-path signals arising from surface wave effects. Specifically, experiments were conducted with a near-field microwave imaging array positioned at variable heights from the floor of a coupling fluid tank. Antenna arrays with different feed line lengths in the fluid were also evaluated. The results show that surface waves corrupt the received signals over the longest transmission distances across the measurement array. However, the surface wave effects can be eliminated provided the feed line lengths are sufficiently long independently of the distance of the transmitting/receiving antenna tips from the imaging tank floor. Theoretical predictions confirm the experimental observations

Dynamics in sub-monolayer Fe-films

Abstract The properties of thin films are directly connected with the atomic structure. At elevated temperatures this structure is determined by atomic dynamics. Pronounced effects are expected for thin films of low coverage. We have investigated electronic and dynamical properties of a submonolayer Fe film on a W(1 1 0) substrate with nuclear resonance scattering (NRS) in grazing-incidence geometry. This atomistic technique is best suited for such investigations due to its element (isotopic) and submonolayer sensitivity as demonstrated in the model system of Fe/W(1 1 0). A simple relaxation model was used to explain the temperature dependence of the NRS spectra. The relaxation rates and diffusion coefficients have been calculated

EQIP\u27s First Year: A Step Closer to Higher Quality in Surgical Education.

OBJECTIVE: To describe the first year of the Educational Quality Improvement Program (EQIP) DESIGN: The Educational Quality Improvement Program (EQIP) was formed by the Association of Program Directors in Surgery (APDS) in 2018 as a continuous educational quality improvement program. Over 18 months, thirteen discrete goals for the establishment of EQIP were refined and executed through a collaborative effort involving leaders in surgical education. Alpha and beta pilots were conducted to refine the data queries and collection processes. A highly-secure, doubly-deidentified database was created for the ingestion of resident and program data. SETTING & PARTICIPANTS: 36 surgical training programs with 1264 trainees and 1500 faculty members were included in the dataset. 51,516 ERAS applications to programs were also included. Uni- and multi-variable analysis was then conducted. RESULTS: EQIP was successfully deployed within the timeline described in 2020. Data from the ACGME, ABS, and ERAS were merged with manually entered data by programs and successfully ingested into the EQIP database. Interactive dashboards have been constructed for use by programs to compare to the national cohort. Risk-adjusted multivariable analysis suggests that increased time in a technical skills lab was associated with increased success on the ABS\u27s Qualifying Examination, alone. Increased time in a technical skills lab and the presence of a formal teaching curriculum were associated with increased success on both the ABS\u27s Qualifying and Certifying Examination. Program type may be of some consequence in predicting success on the Qualifying Examination. CONCLUSIONS: The APDS has proved the concept that a highly secure database for the purpose of continuous risk-adjusted quality improvement in surgical education can be successfully deployed. EQIP will continue to improve and hopes to include an increasing number of programs as the barriers to participation are overcome