Search

Contains research objectives and reports on four research projects., U.S. Air Force (Aeronautical Systems Division) under Contract AF33(616)-7624 with the Aeronautical Accessories Laboratory, Wright-Patterson Air Force Base, Ohio, National Science Foundation under Grant G-24073, National Institutes of Health (Grant HTS-5550)

Contains reports on six research projects., National Science Foundation under Grant G-24073, U. S. Air Force (Aeronautical Systems Division) under Contract AF33(616)-7624 with the Aeronautical Accessories Laboratory, Wright-Patterson Air Force Base, Ohio

Our objective is to develop an engine with high efficiency, and specific impulse which can be varied over more than an order of magnitude to match the requirements of efficient spacecraft propulsion in the constant momentum propulsion regime. Laser ablation propulsion uniquely offers an almost arbitrarily large range of exhaust velocity, since it depends only on incident laser intensity. We have shown that thrust efficiency remains good over the specific impulse range 150 to 3,200 seconds. Considering a laser ablation propulsion device as an electric thruster, use of energetic ablation fuels can give thrust electrical efficiency greater than unity at the bottom of this Isp range. In our laser plasma thrusters (LPT's), we have demonstrated specific impulse which can be varied over a factor-of-15, from 200 to 3000 seconds to match the velocity profile in a mission. The corresponding thrust efficiency varies from 165% to 40%. The micro-LPT product has a 0.1 - 10 mN thrust range. After reviewing the science basis and performance of the existing devices, we describe the unique capabilities predicted for the LPT technology when it is scaled to the 1N thrust level. This scaling permits taking full advantage of the technology's inherent advantages in thrust/power ratio (up to 1.35N/kW), thrust efficiency and thrust density (5,000 to 350,000N/m2). However, the most important capability of the "macro-LPT" design is variable Isp for optimally-efficient, constant-momentum flights. Claims made for the macro-LPT are based on measured performance of our millisecond and nanosecond-pulse LPT devices, and the anticipated performance of a revolutionary liquid ablation fuel., Presented at the JANNAF Propulsion Meeting (54th)/Liquid Propulsion Subcommittee (3rd)/Spacecraft Propulsion Subcommittee (2nd)/Modeling and Simulation Subcommittee (5th) Joint Meeting Denver, CO, 14-17 May 2007. The orginal document contains color images.

Middleton and Elizabeth Reefs are two mid-latitude, annular reefs within the Lord Howe linear chain of volcanic islands and seamounts in the southwestern Pacific Ocean. Drilling, vibrocoring, seismic profiling, and dating indicate that each has a rim of Holocene reef framework, enclosing a lagoon partly filled by prograding sand sheets composed of fragments of coral, coralline algae, foraminifers, and other skeletal debris. The reefs lie close to the latitudinal limits for coral growth and the reef framework is very porous, dominated by branching rather than massive corals. Coralline algae are the principal binding agent in the upper reef framework. Holocene reef growth began on a foundation of Pleistocene reefal limestone encountered at a depth of 8 m in cores on the windward side of Middleton Reef. Holocene corals became established on this foundation around 6,700 radiocarbon yr B.P., implying little if any lag after inundation of the platform by the post-glacial sea-level rise. Windward reef growth tracked sea-level rise ('keep-up' mode), and a prominent reef crest was established on both reefs by 5,000 yr B.P. Leeward margins appear to have been characterized by 'catch-up' growth. Development of cays is limited, and has been restricted by the paucity of coarse coralline debris or cemented conglomerate on which islands could become established. The morphology and development of Middleton and Elizabeth Reefs has been similar to that of tropical atolls, although the rate of subsidence appears to have been relatively slow reflecting their position on the margin of the foundered continental crust of the Lord Howe Rise.

Lord Howe Island and Balls Pyramid are mid-oceanic basaltic islands, 20 km apart, in the Tasman Sea. Subaerial carbonates dating back at least 350 ka and a Holocene fringing reef occur on Lord Howe Island. No reefs or subaerial carbonate deposits occur on Balls Pyramid. Both islands sit near the centre of wide shelves that are on average 40^50 m deep with a distinct break of slope, between 70 and 100 m depth. The Lord Howe shelf is characterised by a discontinuous drowned ridge, which rises to 30 m depth and is located between the mid-shelf and shelf edge. It is composed of limestone and is interpreted as a fossil reef being veneered by Holocene coralline algae. Early to Middle Holocene branching-coral gravel is found in the lee of the fossil reef, indicating limited give-up reef growth during the Postglacial transgression. The surface sediments across the shelf are calcareous, except in close proximity to the island where volcanic content is significant. Coralline algae represent the dominant grain type, with minor amounts of coral. Bryozoans, Halimeda and foraminifera are common; however, they are not volumetrically important. Rhodoliths and molluscs occur near the shelf edge, and appear to have accumulated at times of lower sea level. These subtropical shelves are mid-oceanic examples of the transition between tropical and temperate carbonate sedimentation. They indicate the potential for carbonate production on broad planated shelves outside reef-forming seas.

Aeromedical appraisal of the F4H-1F/SPARROW III weapon system was undertaken to detect any weakness in the human factor as part of the weapon system complex. Results of a questionnaire submitted to pilots and rada operators regarding deficiencies in the Mark IV full pressure suit are discussed. Problems arose in respect to mobility in the pressurized state, visibility, and in mating the g-suit hose with the full pressure suit. Recommendations for solutions to the problems are included. In-flight monitoring of physiologic parameters was accomplished and a discussion of results is included with implications to possible detrimental effects on participants.

Early detection of latent and progressive coronary artery disease in the aviator is patently essential. Presently accepted methods of coronary evaluation appear, however, less than adequate when correlation of arteriosclerotic occlusive episodes and current individual myocardial evaluation is attempted. The presence of ischemic pathology alters the bioelectric signature of the heart in several ways. One variation results from the apparent generation of energies which are lower in amplitude and significantly higher in frequency than the basic clinically accepted electrical waveform. Standard clinical electrocardiograms fail to portray these aberrations. This study describes the development of a precursor electrocardiograph with extended frequency range capability known as WREC I. With this system, data from both normal and pathologic subjects were acquired. Presence of energies higher in frequency than the clinically accepted band were disclosed. The pilot nature of this study exposed several technical specifications or inadequacies of the system including apparent inadequate signal-to-noise ratio, cumbersome nature of contiguous energy spectrums for routine readout, need for environmental noise control, and time consuming characteristics of nonstandard data formats for routine data readout. (Author)