Development of a high power microwave thruster, with a magnetic nozzle, for space applications

This paper describes the current development of a high-power microwave electrothermal thruster (MET) concept at the NASA Lewis Research Center. Such a thruster would be employed in space for applications such as orbit raining, orbit maneuvering, station change, and possibly trans-lunar or trans-planetary propulsion of spacecraft. The MET concept employs low frequency continuous wave (CW) microwave power to create and continuously pump energy into a flowing propellant gas at relative high pressure via a plasma discharge. The propellant is heated to very high bulk temperatures while passing through the plasma discharge region and then is expanded through a throat-nozzle assembly to produce thrust, as in a conventional rocket engine. Apparatus, which is described, is being assembled at NASA Lewis to test the MET concept to CW power levels of 30 kW at a frequency of 915 MHz. The microwave energy is applied in a resonant cavity applicator and is absorbed by a plasma discharge in the flowing propellant. The ignited plasma acts as a lossy load, and with optimal tuning, energy absorption efficiencies over 95 percent (based on the applied microwave power) are expected. Nitrogen, helium, and hydrogen will be tested as propellants in the MET, at discharge chamber pressures to 10 atm

Successful completion of a cyclic ground test of a mercury ion auxiliary propulsion system

An engineering model Ion Auxiliary Propulsion System (IAPS) 8-cm thruster (S/N 905) has completed a life test at NASA Lewis Research Center. The mercury ion thruster successfully completed and exceeded the test goals of 2557 on/off cycles and 7057 hr of operation at full thrust. The final 1200 cycles and 3600 hr of the life test were conducted using an engineering model of the IAPS power electronics unit (PEU) and breadboard digital controller and interface unit (DCIU). This portion of the test is described in this paper with a charted history of thruster operating parameters and off-normal events. Performance and operating characteristics were constant throughout the test with only minor variations. The engineering model power electronics unit operated without malfunction; the flight software in the digital controller and interface unit was exercised and verified. Post-test inspection of the thruster revealed facility enhanced accelerator grid erosion but overall the thruster was in good condition. It was concluded that the thruster performance was not drastically degraded by time or cycles. Additional cyclic testing is currently under consideration

Eighty years of food-web response to interannual variation in discharge recorded in river diatom frustules from an ocean sediment core.

Little is known about the importance of food-web processes as controls of river primary production due to the paucity of both long-term studies and of depositional environments which would allow retrospective fossil analysis. To investigate how freshwater algal production in the Eel River, northern California, varied over eight decades, we quantified siliceous shells (frustules) of freshwater diatoms from a well-dated undisturbed sediment core in a nearshore marine environment. Abundances of freshwater diatom frustules exported to Eel Canyon sediment from 1988 to 2001 were positively correlated with annual biomass of Cladophora surveyed over these years in upper portions of the Eel basin. Over 28 years of contemporary field research, peak algal biomass was generally higher in summers following bankfull, bed-scouring winter floods. Field surveys and experiments suggested that bed-mobilizing floods scour away overwintering grazers, releasing algae from spring and early summer grazing. During wet years, growth conditions for algae could also be enhanced by increased nutrient loading from the watershed, or by sustained summer base flows. Total annual rainfall and frustule densities in laminae over a longer 83-year record were weakly and negatively correlated, however, suggesting that positive effects of floods on annual algal production were primarily mediated by "top-down" (consumer release) rather than "bottom-up" (growth promoting) controls

Contributors to the March Issue/Notes

Notes by Robert A. Oberfell, John Power, John D. O\u27Neill, Arthur M. Diamond, Theodore M. Ryan, C. G. Remmo, and Francis J. Paulson

Applying Software Engineering Techniques to Parser Design: The Development of a C# Parser

In this paper we describe the development of a parser for the C# programming language. We outline the development process used, detail its application to the development of a C# parser and present a number of metrics that describe the parser’s evolution. This paper presents and reinforces an argument for the application of software engineering techniques in the area of parser design. The development of a parser for the C# programming language is in itself important to software engineering, since parsers form the basis for tools such as metrics generators, refactoring tools, pretty-printers and reverse engineering tools

Contributors to the March Issue/Notes

Notes by Robert A. Oberfell, John Power, John D. O\u27Neill, Arthur M. Diamond, Theodore M. Ryan, C. G. Remmo, and Francis J. Paulson

Applying Software Engineering Techniques to Parser Design: The Development of a C# Parser

In this paper we describe the development of a parser for the C# programming language. We outline the development process used, detail its application to the development of a C# parser and present a number of metrics that describe the parser’s evolution. This paper presents and reinforces an argument for the application of software engineering techniques in the area of parser design. The development of a parser for the C# programming language is in itself important to software engineering, since parsers form the basis for tools such as metrics generators, refactoring tools, pretty-printers and reverse engineering tools

The Long haul: the story of the 497th Bomber Group (VH)

From the Foreword, written by Arnold T. Johnson, Col. A.C., Group Commander: This book has been prepared and published in the belief that every member of the 497th Bomb Group will want to have its glorious combat history preserved and that every member will desire to have a copy. It is hoped, as you browse through this book in future years, it will serve to remind you of your many friends and team-mates with whom you served. It is hoped, as you glance through the Roll of Honor , it will keep alive your memory of our brave friends who did not return, and of the great sacrifices a war exacts. Because these gallant men made the supreme sacrifice, we are living to enjoy the Four Freedoms for which this war was fought. As I think back to those days on Saipan, where we lived, worked and fought together, I think of the smoothest functioning team it has ever been my pleasure to serve with. I think of every man performing his duties with loyalty and cooperation and to the best of his ability. Men in the kitchens, on the maintenance line, in the offices, on board the airplanes; each seemed to take pride in making every mission a little better than the last; each knew that his efforts brought the war to a close just a little sooner. Every-man who fought with the 497th Bomb Group deserves the highest praise and commendation. To each of you I extend my sincere appreciation and congratulations for the job you did so well. Preparation of this book did not begin until five months after the group had returned to the States. The group was then stationed at MacDill Field, Tampa, Florida. Very few of the enlisted personnel had returned, many of the officers had returned but there were also many new ones assigned. Many staff positions were filled by personnel who were new to the group. The records of the group, including the squadron records, arrived home in a thoroughly disorganized fashion and a considerable amount of the records were never found. These facts together with the difficulties in obtaining the correct status of missing personnel and present locations of all former personnel have made the task of preparing this book very difficult. It is desired to acknowledge that this book will contain many imperfections and perhaps many errors. The errors are regrettable but everything has been done to avoid them, insofar as has been possible. In spite of this, it is believed that this book is well worth while and will be thoroughly enjoyable to all former personnel of the group.https://digicom.bpl.lib.me.us/ww_reg_his/1109/thumbnail.jp

A Hybrid Sequencing Approach Completes the Genome Sequence of Thermoanaerobacter ethanolicus JW 200

Thermoanaerobacter ethanolicus JW 200 has been identified as a potential sustainable biofuel producer due to its ability to readily ferment carbohydrates to ethanol. A hybrid sequencing approach, combining Oxford Nanopore and Illumina DNA sequence reads, was applied to produce a single contiguous genome sequence of 2,911,280 bp