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Solar thermal propulsion is an innovative concept that will double the efficiency of currently used LH2 - L02 chemical upper stages. Solar thermal propulsion uses the sun's energy to heat a low molecular weight working fluid such as hydrogen to very high temperatures (3,000 K). The stored thermal energy is then converted to kinetic energy as the working fluid exits a diverging nozzle. This document will report on the completed Phase I Integrated High Payoff Rocket Propulsion Technology (IHPRPT) Solar Thermal Propulsion Demonstration, The Air Force Research Lab (AFRL) has sponsored the team of Thiokol Propulsion and SRS Technologies to demonstrate the technological readiness and performance of an inflatable solar thermal propulsion system. The program culminates in a full-up integrated proof-of-concept ground test of a direct gain solar thermal propulsion system. These tests will demonstrate that the technology is ready for development of flight hardware for Solar Orbital Transfer Vehicles.

Electrical power is a major driver for nearly all classes of space missions and, consequently, the maximization of available power is an on-going challenge. Advanced missions within the Air Force are investigating the use of flexible PV array systems. The rapidly-evolving technology of flexible thin film PV cells lends itself particularly well to a flexible array concept. A parallel incentive for development of flexible PV arrays are the possibilities of synergistic advantages for certain types of spacecraft, in particular the Solar Thermal Propulsion (STP) Vehicle. The large sun-tracking solar concentrators of an STP vehicle present a highly-efficient support and pointing system for a large flexible PV array mounted on the deployed support torus, or the concentrator. The work performed focused on advancing the technologies that will improve and extend the application of solar arrays in a variety of space and aerospace environments. SRS Technologies performed analyses and demonstrated the feasibility of combining thin film PV array technology with methods to manufacture deployable membrane concentrators for solar thermal propulsion. Significant issues addressed were: the interconnection of the newly developed cells, proper thermal control, and electrostatic charge control of the complete system in the space environment. SRS demonstrated a self- metallizing polyimide concept for electrical interconnection of the backplane, and printing PV array interconnect circuitry directly on the thin film prior to lamination to the array. The actions accomplished indicated the feasibility and desirability of a flexible, high specific power, PV array concept and have established a firm foundation and roadmap for development of an operational concept.

Spacecraft powered by solar thermal propulsion engines will be able to provide the velocity change required to economically maneuver large payloads from one orbit to another or to perform interplanetary missions. This innovative concept, when applied, will double the efficiency of currently used LH2 - L02 chemical upper stages. Solar thermal propulsion uses the sun's energy to heat a low molecular weight working fluid such as hydrogen to very high temperatures (3,000K). The stored thermal energy is then converted to kinetic energy as the working fluid exits a diverging nozzle. Under Integrated High Payoff Rocket Propulsion Technology (IHPRPT) funding, the Air Force Research Lab (AFRL) has sponsored the team of Thiokol Propulsion and SRS - Technologies to demonstrate the technological readiness and performance of an inflatable solar thermal propulsion system. This paper will address the results of this program, which includes the fabrication and thermal vacuum testing of a 4 X 6 meter inflatable flight quality solar concentrator. The program culminates in a full-up integrated proof- of-concept ground test of a direct gain solar thermal propulsion system. The results of this test will be reported. These tests will demonstrate that the technology is ready for development of flight hardware for Solar Orbital Transfer Vehicles.

This study evaluated the relative fit of both Finn's (1989) Participation-Identification and Wehlage, Rutter, Smith, Lesko and Fernandez's (1989) School Membership models of high school completion to a sample of 4,597 eighth graders taken from the National Educational Longitudinal Study of 1988, (NELS:88), utilizing structural equation modeling techniques. This study found support for the importance of educational engagement as a factor in understanding academic achievement. The Participation-Identification model was particularly well fitting when applied to the sample of high school completers, dropouts (both overall and White dropouts) and African-American students. This study also confirmed the contribution of school environmental factors (i.e., size, diversity of economic and ethnic status among students) and family resources (i.e., availability of learning resources in the home and parent educational level) to students' educational engagement. Based on these findings, school social workers will need to be more attentive to utilizing macro-level interventions (i.e., community organization, interagency coordination) to achieve the organizational restructuring needed to address future challenges. The support found for the Participation-Identification model supports a shift in school social workers' attention from reactive attempts to improve the affective-interpersonal lives of students to proactive attention to their academic lives. The model concentrates school social work practices on the central mission of schools, which is educational engagement. School social workers guided by this model would be encouraged to seek changes in school policies and organization that would facilitate educational engagement.