Active Suppression of Pogo on the Space Shuttle

The use of active pogo suppressors on the space shuttle was qualitatively investigated. Suppressor design concepts and the effectiveness of these designs in maintaining the stability of the shuttle vehicle were the primary concerns. Suppressor design concepts were developed by means of a series of parametric stability analyses. These two designs together with two designs provided by NASA were evaluated in detail for control effectiveness, performance relative to a passive suppression device, sensitivity of performance to feedback error, suppressor volume flow requirements, and suppressor development requirements. An active device at the high pressure oxidizer pump inlet was shown to provide a simple and effective design that is insensitive to error in the feedback signal. The sizing of an active suppressor was demonstrated to be dependent upon knowledge of the dynamic characteristics of the system

Analysis of pogo on the space shuttle: Accumulator design guidelines and planar multiengine model development

The design guidelines were generated to support the selection of the baseline accumulator configuration for the space shuttle. They were based upon the elimination of the instabilities that had been predicted for the shuttle system (in the absence of accumulators) using the single-engine model. The multiengine pitch plane stability model was subsequently developed to enable a more refined analysis of the pogo problem. The results obtained with this refined model, in the absence of accumulators, indicated a generally stable system. However, it was found that reasonable adjustment of the axial motion of the feedline aft support on the external tank could induce instability of the system. This instability was eliminated by the addition of high-pressure oxidizer turbopump inlet accumulators to the system. The results obtained with the refined model did not suggest a need to alter the design guidelines that had been obtained previously. The analyses with the multiengine model also treated the question of the use of a phase margin in the system stability requirements

Space shuttle pogo studies

Topics covered include: (1) pogo suppression for main propulsion subsystem operation; (2) application of quarter-scale low pressure oxidizer turbopump transfer functions; (3) pogo stability during orbital maneuvering subsystem operation; and (4) errors in frequency response measurements

Orbophone: a new interface for radiating sound and image

The Orbophone is a new interface that radiates rather than projects sound and image. It provides a cohesive platform for audio and visual presentation in situations where both media are transmitted from the same location and localization in both media is perceptually correlated. This paper discusses the advantages of radiation over conventional sound and image projection for certain kinds of interactive public multimedia exhibits and describes the artistic motivation for its development against a historical backdrop of sound systems used in public spaces. One exhibit using the Orbophone is described in detail together with description and critique of the prototype, discussing aspects of its design and construction. The paper concludes with an outline of the Orbophone version 2

Revealing the intricacies of cancer

A report on the 14th Lorne Cancer Conference, Lorne, Victoria, Australia, 14-17 February 2002

Impact of out-of-class science and engineering activities on physics identity and career intentions

The number of physics bachelor’s degrees that are awarded in the United States annually is small compared to most other science, technology, engineering, and mathematics fields, and only about one-fifth of these degrees are awarded to women. Understanding the influence of students’ science and engineering experiences on career choices is critical in order to improve future efforts to increase the number of physics majors and the participation of women. In this work, we use a physics identity framework to examine the impact of out-of-class science and engineering activities on three identity dimensions and the relationship between these dimensions and physics career choice. Through structural equation modeling of survey data from 5541 college students, we find that out-of-class science and engineering activities have the largest influence on physics performance/competence beliefs, but the association of performance/competence beliefs to overall physics identity and physics career choice is primarily mediated through recognition beliefs and physics interests. Furthermore, out-of-class science and engineering activities have a larger effect on recognition beliefs for men than for women, which is a challenging finding in light of the fact that recognition beliefs are the most influential identity dimension for women. The results of this work begin to highlight the need for out-of-class science and engineering activities that focus on not only enhancing students’ performance/competence beliefs but also students’ interests, particularly those students not previously interested, and women’s recognition beliefs with respect to physics