Hybrid rocket performance

A hybrid rocket is a system consisting of a solid fuel grain and a gaseous or liquid oxidizer. Figure 1 shows three popular hybrid propulsion cycles that are under current consideration. NASA MSFC has teamed with industry to test two hybrid propulsion systems that will allow scaling to motors of potential interest for Titan and Atlas systems, as well as encompassing the range of interest for SEI lunar ascent stages and National Launch System Cargo Transfer Vehicle (NLS CTV) and NLS deorbit systems. Hybrid systems also offer advantages as moderate-cost, environmentally acceptable propulsion system. The objective of this work was to recommend a performance prediction methodology for hybrid rocket motors. The scope included completion of: a literature review, a general methodology, and a simplified performance model

Do Bid-Ask Spreads Or Bid and Ask Depths Convey New Information First?

This paper investigates the order in which new information is first reflected in the market – through changes in spreads or through updated depths. We develop an error correction model of spreads and depths and estimate Gonzalo-Granger common factor components using two years of tick-by-tick quote data on all stocks in the Dow Jones Industrial Average. We show that indeed depths rather than spreads are first to impound new information that leads to new quote trends. Specifically, (bid and ask) depths convey information first in virtually every stock in both years, while spreads almost never convey information in 1998, and do so in only 8 out of 30 cases in 1995. Even in those 8 cases, the percentage of new information revealed by spreads ranges from 50 – 59% with the depths accounting for the rest. Our results have important implications for academic research on asymmetric information trading, for security market design, and for public policy.VECM, spreads, depths, information,

Pathophysiology of Asthma and Chronic Obstuctive Pulmonary Disease (COPD)

“Asthma is a disease characterized by an increased responsiveness of the trachea and bronchi to various stimuli and manifested by a widespread narrowing of the airways that changes in severity either spontaneously or in response to therapy.” The airway narrowing is the end result of some combination of bronchial muscle contraction, tissue inflammation, mucosal edema, and luminal occlusion by cellular debris and thickened secretions. During the last decade, basic and applied research has shed light on the physiology of the above changes and has led to breakthroughs in therapy and the more rational use of older and newer therapeutic agents, both separately and together

A Historical Systems Study of Liquid Rocket Engine Throttling Capabilities

This is a comprehensive systems study to examine and evaluate throttling capabilities of liquid rocket engines. The focus of this study is on engine components, and how the interactions of these components are considered for throttling applications. First, an assessment of space mission requirements is performed to determine what applications require engine throttling. A background on liquid rocket engine throttling is provided, along with the basic equations that are used to predict performance. Three engines are discussed that have successfully demonstrated throttling. Next, the engine system is broken down into components to discuss special considerations that need to be made for engine throttling. This study focuses on liquid rocket engines that have demonstrated operational capability on American space launch vehicles, starting with the Apollo vehicle engines and ending with current technology demonstrations. Both deep throttling and shallow throttling engines are discussed. Boost and sustainer engines have demonstrated throttling from 17% to 100% thrust, while upper stage and lunar lander engines have demonstrated throttling in excess of 10% to 100% thrust. The key difficulty in throttling liquid rocket engines is maintaining an adequate pressure drop across the injector, which is necessary to provide propellant atomization and mixing. For the combustion chamber, cooling can be an issue at low thrust levels. For turbomachinery, the primary considerations are to avoid cavitation, stall, surge, and to consider bearing leakage flows, rotordynamics, and structural dynamics. For valves, it is necessary to design valves and actuators that can achieve accurate flow control at all thrust levels. It is also important to assess the amount of nozzle flow separation that can be tolerated at low thrust levels for ground testing

An assessment of the accidental take of sea otters, Enhydra lutris, in gill and trammel nets

The sea otter, Enhydra 1utris, is fully protected in California by both state and federal law. Despite this protection the population has not grown appreciably since at least 1976. Research efforts directed at identifying the reasons for the lack of population growth have concentrated on sources of mortality and their contribution to total mortality. The accidental drowning of sea otters in gill and trammel nets used to take California halibut, Para1ichthys ca1ifornicus, was identified as a source of mortality which has probably increased as the sea otter population expanded into areas of intense fishing. As a result, an existing gill and trammel net fishery observation program in Monterey Bay was expanded to assess the extent and significance of the accidental drownings of sea otters in the areas near Morro Bay and Port San Luis. Three different estimates of the number of sea otters drowned annually in gill and trammel nets were generated using comparable data bases. The average of these estimates was approximately 80 sea otters per year for the level of fishing effort expended during the June 1982 through June 1984 study period. Back calculations of the annual take of sea otters by the gill and trammel net fishery for California halibut were made for each year from 1973 through 1983. These calculations suggest that the level of accidental take of sea otters during the last decade may have been high enough to be a significant factor in the lack of sea otter population growth. (31pp.

The onsite manufacture of propellant oxygen from lunar resources

The Aerojet carbothermal process for the manufacture of oxygen from lunar materials has three essential steps: the reduction of silicate with methane to form carbon monoxide and hydrogen; the reduction of carbon monoxide with hydrogen to form methane and water; and the electrolysis of water to form hydrogen and oxygen. The reactions and the overall process are shown. It is shown with laboratory experimentation that the carbothermal process is feasible. Natural silicates can be reduced with carbon or methane. The important products are carbon monoxide, metal, and slag. The carbon monoxide can be completely reduced to form methane and water. The water can be electrolyzed to produce hydrogen and oxygen. A preliminary engineering study shows that the operation of plants using this process for the manufacture of propellant oxygen has a large economic advantage when the cost of the plant and its operation is compared to the cost of delivering oxygen from Earth

Microgrid Disaster Resiliency Analysis: Reducing Costs in Continuity of Operations (COOP) Planning

The electric grid serves a vital role in the supply chain of nearly all industrial and commercial organizations. A Microgrid infrastructure can provide this service and beneficial non-emergency services including a variety of generation/energy sources. To demonstrate the applicability of microgrids for energy resiliency, we present a microgrid resiliency case study for United Parcel Service’s (UPS) three separate shipping facilities. The goal, to enhance energy security, minimize cost and prevent cascading losses within other related business units. The impacts and consequences of which are quantified in this study using a Mean Failure Cost (MFC) risk assessment measure. MFC accounts for the potential loses to identified stakeholders that may result from a set of identified failures due to a set of identified threats. In this case, our study uses a method we call All Hazards Econometric System (AHES). AHES incorporates the cost of COOP using a strategy that considers the payback period of microgrid installation as compared to other energy delivery strategies

Age and sex differences in long-term outcomes following implantable cardioverter-defibrillator placement in contemporary clinical practice: findings from the Cardiovascular Research Network

BACKGROUND: Patient sex and age may influence rates of death after receiving an implantable cardioverter-defibrillator for primary prevention. Differences in outcomes other than mortality and whether these differences vary by heart failure symptoms, etiology, and left ventricular ejection fraction are not well characterized. METHODS AND RESULTS: We studied 2954 patients with left ventricular ejection fraction \u3c /=0.35 undergoing first-time implantable cardioverter-defibrillator for primary prevention within the Cardiovascular Research Network; 769 patients (26%) were women, and 2827 (62%) were aged \u3e 65 years. In a median follow-up of 2.4 years, outcome rates per 1000 patient-years were 109 for death, 438 for hospitalization, and 111 for heart failure hospitalizations. Procedure-related complications occurred in 8.36%. In multivariable models, women had significantly lower risks of death (hazard ratio 0.67, 95% CI 0.56 to 0.80) and heart failure hospitalization (hazard ratio 0.82, 95% CI 0.68 to 0.98) and higher risks for complications (hazard ratio 1.38, 95% CI 1.01 to 1.90) than men; patients aged \u3e 65 years had higher risks of death (hazard ratio 1.55, 95% CI 1.30 to 1.86) and heart failure hospitalization (hazard ratio 1.25, 95% CI 1.05 to 1.49) than younger patients. Age and sex differences were generally consistent in strata according to symptoms, etiology, and severity of left ventricular systolic dysfunction, except the higher risk of complications in women, which differed by New York Heart Association classification (P=0.03 for sex-New York Heart Association interaction), and the risk of heart failure hospitalization in older patients, which differed by etiology of heart failure (P=0.05 for age-etiology interaction). CONCLUSIONS: The burden of adverse outcomes after receipt of an implantable cardioverter-defibrillator for primary prevention is substantial and varies according to patient age and sex. These differences in outcome generally do not vary according to baseline heart failure characteristics