Micro Electric Propulsion Feasibility

Miniature, 50 kg class, strategic satellites intended for extended deployment in space require an on-board propulsion capability to perform needed attitude control adjustments and drag compensation maneuvers. Even on such very small spacecraft, these orbit maintenance functions can be significant and result in a substantial propellant mass requirement. Development of advanced propulsion technology could reduce this propellant mass significantly, and thereby maximize the payload capability of these spacecraft. In addition, spacecraft maneuverability could be enhanced and/or multi-year mission lifetimes realized. These benefits cut spacecraft replacement costs, and reduce services needed to maintain the launch vehicles. For SDIO brilliant pebble spacecraft, a miniaturized hydrazine propulsion system provides both boost and divert thrust control. This type of propulsion system is highly integrated and is capable of delivering large thrust levels for short time periods. However, orbit maintenance functions such as drag make-up require only very small velocity corrections. Using the boost and/or divert thrusters for these small corrections exposes this highly integrated propulsion system to continuous on/off cycling and thereby increases the risk of system failure. Furthermore, since drag compensation velocity corrections would be orders of magnitude less than these thrusters were designed to deliver, their effective specific impulse would be expected to be lower when operated at very short pulse lengths. The net result of these effects would be a significant depletion of the on-board hydrazine propellant supply throughout the mission, and a reduced propulsion system reliability, both of which would degrade the interceptors usefulness. In addition to SDIO brilliant pebble spacecraft, comparably small spacecraft can be anticipated for other future strategic defense applications such as surveillance and communication. For such spacecraft, high capability and reliability, minimal detectability and low cost are requirements. All these miniature spacecraft share a common characteristic: because of their on-board electronic equipment they have, by design, solar order 50-100 W. In a relative sense, such spacecraft are power rich when compared to other larger spacecraft. This power rich situation is offset by very tight mass budgets, which make reductions in propellant mass requirements a key issue in meeting overall spacecraft minimum mass goals. In principle, power rich and propellant poor brilliant pebbles class spacecraft can benefit from using high specific impulse electric propulsion to reduce chemical propellant mass requirements. However, at power levels of order 50 W, arcjets cannot be made to function, ion thrusters are too complex and heavy and resistojets have too low a specific impulse. Recognizing these capability limitations in existing electric propulsion technology, the SDIO/IST sponsored the Phase I SBIR Micro Electric Propulsion (MEP) thruster study described in this report. The objective of this study was to examine the feasibility of developing a very simple, low mass and small volume, electric thruster for operation on hydrazine at less than 100 W of input power. The feasibility of developing such a MEP thruster was successfully demonstrated by EPL by the discovery of a novel plasma acceleration process. The sections in this report summarize the approach, test results and major accomplishments of this proof-of-concept program

“A malignant, seething hatework”: an introduction to U.S. 21st century hardcore horror

The proliferation of U.S. horror films in the 21 st century has engendered an increase in critical and academic response which has almost exclusively focused on the conventions of mainstream horror cinema. That is, films sanctioned by classificatory bodies, released through mid to large production companies and exhibited via selected to wide theatrical releases. While academic work, drawing from film and cultural studies, has provided a much needed engagement with the popularity and themes of contemporary U.S. horror they have tended to exclude marginal or ‘hidden’ hardcore horror film examples. Therefore, this article will provide an introductory account of the films that form part of this horror sub-genre, from Eric Stanze’s Scrapbook (2000) through Fred Vogel’s August Underground trilogy (2001 – 2007) to Stephen Biro’s American Guinea Pig: Bouquet of Guts and Gore (2014). The article will briefly map out the criteria for a definition of hardcore horror before discussing some of its key examples. It is not my intention to simply interpret the films but to look at their ‘archaeology’ to account for the production practices, marketing and distribution strategies, and film reception. The importance of looking at hardcore horror in terms of an archaeology is to reintegrate its marginal status and cultural practices so that a wider examination of the cultural field of U.S. horror in terms of how it is made and experienced can be advanced

Swimming in Histories of Gender Oppression: Grupo XIX de Teatro's Hysteria

Hysteria, first performed in Sao Paulo, Brazil, in 2001, was assembled from oral histories, medical cases, records, and remnants documenting the lives of Brazilian women from the late nineteenth and early twentieth centuries who were incarcerated in Rio de Janeiro's Pedro II Institute. Its UK premiere in 2008, performed by the all-female cast of the Brazilian Grupo XIX de Teatro, included a setting of the show in the old Victoria Baths in Manchester. In this article Elaine Aston identifies ways in which Hysteria keeps open or re-opens the question of feminist liberation. Exploring the show's critique of Western feminism's claims to independence and liberation, her analysis moves towards a mode of interdependent feminist thinking through which liberation might be realized. Elaine Aston is Professor of Contemporary Performance at Lancaster University and editor of Theatre Research International. Her most recent publications include Feminist Views on the English Stage (2003); Feminist Futures: Theatre, Performance, Theory (edited with Geraldine Harris, 2006); Staging International Feminisms (edited with Sue-Ellen Case, 2007); and Performance Practice and Process: Contemporary, (Women) Practitioners (with Geraldine Harris, 2008)

Hollow cathode apparatus

A hollow cathode apparatus is described, which can be rapidly and reliably started. An ignitor positioned upstream from the hollow cathode, generates a puff of plasma that flows with the primary gas to be ionized through the cathode. The plasma puff creates a high voltage breakdown between the downstream end of the cathode and a keeper electrode, to heat the cathode to an electron-emitting temperature

“A malignant, seething hatework”: an introduction to U.S. 21st century hardcore horror

The proliferation of U.S. horror films in the 21 st century has engendered an increase in critical and academic response which has almost exclusively focused on the conventions of mainstream horror cinema. That is, films sanctioned by classificatory bodies, released through mid to large production companies and exhibited via selected to wide theatrical releases. While academic work, drawing from film and cultural studies, has provided a much needed engagement with the popularity and themes of contemporary U.S. horror they have tended to exclude marginal or ‘hidden’ hardcore horror film examples. Therefore, this article will provide an introductory account of the films that form part of this horror sub-genre, from Eric Stanze’s Scrapbook (2000) through Fred Vogel’s August Underground trilogy (2001 – 2007) to Stephen Biro’s American Guinea Pig: Bouquet of Guts and Gore (2014). The article will briefly map out the criteria for a definition of hardcore horror before discussing some of its key examples. It is not my intention to simply interpret the films but to look at their ‘archaeology’ to account for the production practices, marketing and distribution strategies, and film reception. The importance of looking at hardcore horror in terms of an archaeology is to reintegrate its marginal status and cultural practices so that a wider examination of the cultural field of U.S. horror in terms of how it is made and experienced can be advanced

Ion accelerator systems for high power 30 cm thruster operation

Two and three-grid accelerator systems for high power ion thruster operation were investigated. Two-grid translation tests show that over compensation of the 30 cm thruster SHAG grid set spacing the 30 cm thruster radial plasma density variation and by incorporating grid compensation only sufficient to maintain grid hole axial alignment, it is shown that beam current gains as large as 50% can be realized. Three-grid translation tests performed with a simulated 30 cm thruster discharge chamber show that substantial beamlet steering can be reliably affected by decelerator grid translation only, at net-to-total voltage ratios as low as 0.05

DIRC, a New Type of Particle Identification System for BABAR

The DIRC, a new type of Cherenkov imaging device, has been selected as the primary particle identification system for the BABAR detector at the asymmetric B-factory, PEP-II. It is based on total internal reflection and uses long, rectangular bars made from synthetic fused silica as Cherenkov radiators and light guides. In this paper, the principles of the DIRC ring imaging Cherenkov technique are explained and results from the prototype program are presented. The studies of the optical properties and radiation hardness of the quartz radiators are described, followed by a discussion of the detector design.Comment: Invited talk given at the 5th international workshop on B-Physics at hadron machines (Beauty'97), Santa Monica, California, USA, Oct 13-17, 1997. (16pp