Spacecraft Requirements Development and Tailoring

Spacecraft design is managed through the use of design requirements. Requirements are flowed from the highest level, the overall spacecraft, to systems, subsystems and ultimately individual components. Through the use of requirements, each part of the spacecraft will perform the functions that are required of it and will interface to the rest of the spacecraft. Functional requirements are used to make sure every component performs as expected and interface requirements ensure that each component works within the larger design environment where it operates. Writing good requirements is difficult and the verification of requirements can be expensive and time consuming. Because of this difficulty and expense, it is important that each requirement truly be required and critical to the overall performance of the vehicle. It is also important that requirements can be changed or eliminated as the system matures to minimize verification cost and schedule. The Capsule Parachute Assembly System (CPAS) Project is developing the parachute system for the NASA Multi-Purpose Crew Vehicle (MPCV) Orion Spacecraft. Throughout the development and qualification cycle for CPAS, requirements have been evaluated, added, eliminated, or more generically, tailored, to ensure that the system performs as required while minimizing the verification cost to the Program. One facet of this tailoring has been to delete requirements that do not add value to the overall spacecraft or are not needed. A second approach to minimize the cost of requirement verification has been to evaluate requirements based on the actual design as it has matured. As the design of the parachute system has become better understood, requirements that are not applicable have been eliminated. This paper will outline the evolution of CPAS requirements over time and will show how careful and considered changes to requirements can benefit the technical solution for the overall system design while allowing a Project to control costs

CEV Seat Attenuation System System Design Tasks

The Apollo crew / couch restraint system was designed to support and restrain three crew members during all phases of the mission from launch to landing. The crew couch used supported the crew for launch, landing and in-flight operations, and was foldable and removable for EVA ingress/egress through side hatch access and for in-flight access under the seat and in other areas of the crew compartment. The couch and the seat attenuation system was designed to control the impact loads imposed on the crew during landing and to remain non-functional during all other flight phases

Evaluation of a Seat Attenuation System for the Orion Crew Module

The function of the crew seat attenuation system for the Orion Crew Module (CM) is to provide the crew with a low injury-risk landing environment under a range of crew configurations and landing conditions. The current design for the seat attenuation system provides the crew with a low risk of injury environment based on the Brinkley criteria for most of the landing conditions considered. Furthermore, the stroking of the seat attenuation system is within limits, and the clearance between the seat support platform and vehicle is not exceeded. For the limited number of landing conditions where a low injury risk is exceeded, the risk is never beyond a moderate level. The results presented in this study are based on a CM structural model that is rigid except for the pallet struts, which attenuate landing loads and reduce the accelerations transferred to the astronauts. The CM simulations include a soft soil landing. Several different crew configurations are evaluated in this study. It is expected that situations where the risk is above low can be eliminated in future design iterations

Book Reviews

Book reviews of: Armies of Deliverance: A New History of the Civil War By Elizabeth R. Varon. College Edition. (New York: Oxford University Press, 2021. Maps, acknowledgments, timeline, notes, suggested readings, glossary, index. Pp. xxv, 531. $29.99 paper. ISBN: 978-0-19-933539-8.) Hurtin’ Words: Debating Family Problems in the Twentieth-Century South. By Ted Ownby. (Chapel Hill: The University of North Carolina Press, 2018. Acknowledgements, illustrations, notes, index. Pp. xiv, 334.$90 cloth, $29.95 paper,$22.99 electronic. ISBN: 978-1-46964-700-5.) Illusions of Emancipation: The Pursuit of Freedom & Equality in the Twilight of Slavery. By Joseph P. Reidy. (Chapel Hill: University of North Carolina Press, 2019. Acknowledgements, illustrations, map, notes, index. Pp. 1, 506. $39.95 Hardcover,$29.99 E-Book. ISBN: 978-1-4696-4836-1.) Civil War Monuments and the Militarization of America. By Thomas J. Brown. (Chapel Hill: University of North Carolina Press, 2019. 384 pp., 6.125 x 9.25, 87 halftones, notes, bibl., index, Paper, $29.97, 978-1-4696-5374-7.) Reconstruction Politics in a Deep South State: Alabama, 1865–1874. By William Warren Rogers, Jr. (Tuscaloosa: University of Alabama Press, 2021. Acknowledgments, illustrations, notes, bibliography. Pp. 1, 439.$54.95 cloth. ISBN: 978-0817320744.) Fugitivism: Escaping Slavery in the Lower Mississippi Valley, 1820–1860. By S. Charles Bolton. (Fayetteville: The University of Arkansas Press, 2019. Acknowledgements, appendix, notes, index. Pp. x, 302. $34.95 cloth. ISBN: 978-1-68226-009-9.) Bernardo de Gálvez: Spanish Hero of the American Revolution. By Gonzalo M. Quintero Saravia. (Chapel Hill: University of North Carolina Press, 2018. Acknowledgements, appendix, notes, bibliography, index. Pp. xi, 602,$38.00 cloth. ISBN: 9781469640792.

DGIdb 5.0: Rebuilding the Drug-Gene Interaction Database for precision medicine and drug discovery platforms

The Drug-Gene Interaction Database (DGIdb, https://dgidb.org) is a publicly accessible resource that aggregates genes or gene products, drugs and drug-gene interaction records to drive hypothesis generation and discovery for clinicians and researchers. DGIdb 5.0 is the latest release and includes substantial architectural and functional updates to support integration into clinical and drug discovery pipelines. The DGIdb service architecture has been split into separate client and server applications, enabling consistent data access for users of both the application programming interface (API) and web interface. The new interface was developed in ReactJS, and includes dynamic visualizations and consistency in the display of user interface elements. A GraphQL API has been added to support customizable queries for all drugs, genes, annotations and associated data. Updated documentation provides users with example queries and detailed usage instructions for these new features. In addition, six sources have been added and many existing sources have been updated. Newly added sources include ChemIDplus, HemOnc, NCIt (National Cancer Institute Thesaurus), Drugs@FDA, HGNC (HUGO Gene Nomenclature Committee) and RxNorm. These new sources have been incorporated into DGIdb to provide additional records and enhance annotations of regulatory approval status for therapeutics. Methods for grouping drugs and genes have been expanded upon and developed as independent modular normalizers during import. The updates to these sources and grouping methods have resulted in an improvement in FAIR (findability, accessibility, interoperability and reusability) data representation in DGIdb

P20-19 LB. Extensive HLA-driven viral diversity following a single-source HIV-1 outbreak in rural China

Background: High rates of mutation in HIV infected individual allow the virus to adapt rapidly in vivo to selective forces such as anti-retroviral therapy (ART) and host immune pressure. This provides an opportunity to determine the relative contribution of different components of the immune response to HIV-1 infection in driving viral diversity, which may also facilitate assessment of their role in controlling viral replication. It is accepted that HIV-1-specific cytotoxic T-lymphocytes (CTL) may drive the selection of viral variants that can escape T-cell recognition but the extent of this selective pressure has been controversial. Methods: Two digit HLA typing; ELISPOT assay; HIV-1 sequence analysis; HIV sequence clustering and phylogenetic analysis of HLA associations using the neighbour-joining method, S-Plus 8.0, “Partitioning around medoids” (PAM) method and Stratification analysis by Mantel-Haenszel tests Results: Here we describe the consequences of HLA-associated selection on viral diversity in the main targets of T-cell recognition following an outbreak of HIV-1 in a cohort of 258 former plasma donors in rural China. The surprising finding that all the donors appear to have been infected with the same strain of clade B HIV-1 ensured that the analysis was not confounded by “founder effect”. At least 32.63% (232/711) of the mutations in the gag, pol and nef genes leading to amino acid substitutions were associated with class I HLA molecules: of these, 27.16% (63/232) were found within or close to known CD8+ T-cell epitopes. Conclusion: Taken together our data confirm that CD8+ T-cell pressure has a major impact on HIV-1 viral diversity and represent an important element of viral control in the infected host

DGIdb 2.0: Mining clinically relevant drug-gene interactions

The Drug–Gene Interaction Database (DGIdb, www. dgidb.org) is a web resource that consolidates dis-parate data sources describing drug–gene interac-tions and gene druggability. It provides an intuitive graphical user interface and a documented applica-tion programming interface (API) for querying these data. DGIdb was assembled through an extensive manual curation effort, reflecting the combined in-formation of twenty-seven sources. For DGIdb 2.0, substantial updates have been made to increase content and improve its usefulness as a resource for mining clinically actionable drug targets. Specif-ically, nine new sources of drug–gene interactions have been added, including seven resources specifi-cally focused on interactions linked to clinical trials. These additions have more than doubled the over-all count of drug–gene interactions. The total num-ber of druggable gene claims has also increased by 30%. Importantly, a majority of the unrestricted, publicly-accessible sources used in DGIdb are now automatically updated on a weekly basis, providing the most current information for these sources. Fi-nally, a new web view and API have been developed to allow searching for interactions by drug identifiers to complement existing gene-based search function-ality. With these updates, DGIdb represents a com-prehensive and user friendly tool for mining the druggable genome for precision medicine hypothe-sis generation

Explanatory pluralism in the medical sciences: theory and practice

Explanatory pluralism is the view that the best form and level of explanation depends on the kind of question one seeks to answer by the explanation, and that in order to answer all questions in the best way possible, we need more than one form and level of explanation. In the first part of this article, we argue that explanatory pluralism holds for the medical sciences, at least in theory. However, in the second part of the article we show that medical research and practice is actually not fully and truly explanatory pluralist yet. Although the literature demonstrates a slowly growing interest in non-reductive explanations in medicine, the dominant approach in medicine is still methodologically reductionist. This implies that non-reductive explanations often do not get the attention they deserve. We argue that the field of medicine could benefit greatly by reconsidering its reductive tendencies and becoming fully and truly explanatory pluralist. Nonetheless, trying to achieve the right balance in the search for and application of reductive and non-reductive explanations will in any case be a difficult exercise

Mind the (yield) gap(s)

This paper explores the origin of the notion of “yield gap” and its use as a framing device for agricultural policy in sub-Saharan Africa. The argument is that while the yield gap of policy discourse provides a simple and powerful framing device, it is most often used without the discipline or caveats associated with the best examples of its use in crop production ecology and microeconomics. This argument is developed by examining how yield gap is used in a selection of recent and influential agricultural policy documents. The message for policy makers and others is clear: “mind the (yield) gap(s)”, for they are seldom what they appear