Extravehicular mobility unit subcritical liquid oxygen storage and supply system

The storage of life support oxygen in the Extravehicular Mobility Unit in the liquid state offers some advantages over the current method of storing the oxygen as a high pressure gas. Storage volume is reduced because of the increased density associated with liquid. The lower storage and operating pressures also reduce the potential for leakage or bursting of the storage tank. The potential for combustion resulting from adiabatic combustion of the gas within lines and components is substantially reduced. Design constraints on components are also relaxed due to the lower system pressures. A design study was performed to determine the requirements for a liquid storage system and prepare a conceptual design. The study involved four tasks. The first was to identify system operating requirements that influence or direct the design of the system. The second was to define candidate storage system concepts that could possibly satisfy the requirements. An evaluation and comparison of the candidate concepts was conducted in the third task. The fourth task was devoted to preparing a conceptual design of the recommended storage system and to evaluate concerns with integration of the concept into the EMU. The results are presented

Reusable rocket engine intelligent control system framework design, phase 2

Elements of an advanced functional framework for reusable rocket engine propulsion system control are presented for the Space Shuttle Main Engine (SSME) demonstration case. Functional elements of the baseline functional framework are defined in detail. The SSME failure modes are evaluated and specific failure modes identified for inclusion in the advanced functional framework diagnostic system. Active control of the SSME start transient is investigated, leading to the identification of a promising approach to mitigating start transient excursions. Key elements of the functional framework are simulated and demonstration cases are provided. Finally, the advanced function framework for control of reusable rocket engines is presented

MIT's interferometer CST testbed

The MIT Space Engineering Research Center (SERC) has developed a controlled structures technology (CST) testbed based on one design for a space-based optical interferometer. The role of the testbed is to provide a versatile platform for experimental investigation and discovery of CST approaches. In particular, it will serve as the focus for experimental verification of CSI methodologies and control strategies at SERC. The testbed program has an emphasis on experimental CST--incorporating a broad suite of actuators and sensors, active struts, system identification, passive damping, active mirror mounts, and precision component characterization. The SERC testbed represents a one-tenth scaled version of an optical interferometer concept based on an inherently rigid tetrahedral configuration with collecting apertures on one face. The testbed consists of six 3.5 meter long truss legs joined at four vertices and is suspended with attachment points at three vertices. Each aluminum leg has a 0.2 m by 0.2 m by 0.25 m triangular cross-section. The structure has a first flexible mode at 31 Hz and has over 50 global modes below 200 Hz. The stiff tetrahedral design differs from similar testbeds (such as the JPL Phase B) in that the structural topology is closed. The tetrahedral design minimizes structural deflections at the vertices (site of optical components for maximum baseline) resulting in reduced stroke requirements for isolation and pointing of optics. Typical total light path length stability goals are on the order of lambda/20, with a wavelength of light, lambda, of roughly 500 nanometers. It is expected that active structural control will be necessary to achieve this goal in the presence of disturbances

INTERNATIONAL LAW-LEGAL CAPACITY OF THE UNITED NATIONS-ASSERTION OF CLAIM IN BEHALF OF ITS AGENTS

In a decision handed down April 11, 1949, the court unanimously answered question I(a) (Can the United Nations sue for damages done to itself?) affirmatively. Question I(b) (Can the United Nations sue for damages done to its agents?) was also answered in the affirmative, but over the dissent of four judges. On question II, the majority of the court asserted that a conflict between the agent\u27s national state and the United Nations would be avoided because the United Nations would be claiming only for breach of the obligation due to it

TAX STATUTES-THE ROLE OF STARE DECISIS IN DETERMINING LEGISLATIVE INTENT

An interesting case history recently unfolded by the Supreme Court reveals a novel application of stare decisis to decisions which interpret an act of Congress. The peregrinations of the Court have caused Congress to intervene on two occasions to settle the questions opened by the Court-although on the second occurrence the Court construed the act precisely as had Congress when it decried the Court\u27s first interpretation. This imbroglio issued from the Revenue Act of 1918 under which Congress provided that transfers intended to take effect in possession or enjoyment at or after his death should be included in the donor\u27s gross estate for purposes of the Federal Estate Tax

Writing for social justice: Journalistic strategies for catalyzing agentic engagement among Latinx middle school students through media education

This study examines the experiences of 15 Latinx sixth-grade students in Los Angeles who participated in a yearlong journalism-based media literacy program embedded in their social studies classes. Students researched, interviewed, wrote, and published articles on the Internet about social justice themes, like immigration, racism, and LGBTQ rights. The intervention uses critical pedagogy and social justice pedagogy. This study seeks to understand how key aspects of these philosophies emerge in students’ reflections of their journalistic learning experiences. Deductive qualitative analysis of focus group data indicates that students experienced transformational, agentic experiential learning that allowed them to explore and question the world. The limited comments about funds of knowledge, local communities, and critical co-investigation suggest that these areas need additional attention during intervention implementation. The journalistic approach illustrates new ways educators can engage in critical and social justice pedagogy in middle school media education

Opportunities for Autism Information Shared Through Professional Conferences

With prevalence most recently reported at 1 in 44 (Maenner et al., 2021) children diagnosed with autism spectrum disorder (ASD) in the United States, school librarians can and should expect to see these children in their schools and in their libraries. However, previous work indicates that school librarians are not being provided with an adequate education about this in their graduate coursework (Layden, Anderson, & Hayden, 2021). This study expands upon previous work to explore the preparation of school librarians about autism by examining the previous five years of state library conference programs