On-orbit operational scenarios, tools and techniques

This paper concentrates on methods and techniques used to develop operational scenarios for orbital missions, including development of models to analyze alternatives, modification of tools and refinement of techniques for future missions. Many of these tools and techniques have been derived from previous tools, techniques and experience from the Orbital Maneuvering Vehicle (OMV) program. Results from use of these tools show the current Cargo Transfer Vehicle nominal mission scenario, with 95 discrete events defined for the CTV mission from the NLS Heavy Lift Launch Vehicle (HLLV) to Space Station Freedom (SSF)

Neuronal Coding of Low Frequency Complex Stimuli at the Cochlear Nucleus and Inferior Colliculus of Cat Brain

Articles have recently appeared by Erickson (1968) and Pfaff (1969) which propose that the study of the activity of a large population of neurons may contribute information about sensory coding which is supplementary to data obtained from single neuron studies. These authors propose that there are not enough neurons in the primary sensory pathways so that every stimulus can be represented by a separate neuron. They maintain that over-all measures of neuronal activity will be more fruitful in the study of sensory coding. The present study used such a measure (multiple unit techniques) to monitor the over-all discharge characteristics of neuronal pools at the cochlear nucleus and inferior colliculus of cat brains to aural stimulation. Measures of spike discharge frequencies were obtained from four adult cats. Stimuli consisted of recorded male and female voices presenting the words one through ten . Data was collected from four sites: left and right cochlear nuclei and left and right inferior colliculi. The dependent variable was the number of neuronal spike discharges counted during each 500 millisecond recording period. The basic hypothesis of the experiment was that the large multiple unit spike bursts to aural stimulation consistently observed at.the sites investigated represented a stimulus coding mechanism. If such a mechanism was operating, it was predicted that analysis of discharge patterns would reveal that the subcortical auditory nuclei discharge differentially to the different stimuli. It was also thought that different voices presenting the same stimuli would evoke very similar patterns of activity both within and between anatomical sites tested. The following effects were investigated: laterality of stimulation; stimuli; voices presenting the stimuli; and anatomical sites both within and between cats. Results clearly indicated that at the level of the cochlear nuclei ipsilateral stimulation evoked a sustained multiple unit spike burst while contralateral stimulation had no observable effect on the on-going neuronal activity. The importance of laterality of stimulation was also clearly confirmed at the inferior colliculi level. Only rarely did ipsilateral stimulation at the inferior collicular level cause any detectable change in the on-going level of neuronal discharge. Contralateral stimulation, however, was consistent in evoking a sustained spike burst. The experiment demonstrated that the multiple unit spike bursts ! observed at the cochlear nucleus and inferior colliculus have a functional significance. Different stimulus words generated discharge patterns which differed from each other. Different voices presenting identical stimuli also generated responses having a moderate to very high similarity to each other. The spike discharge patterns were highly similar at both cochlear nucleus and inferior colliculus in all experimental animals. There was also a very close association between anatomical sites within each cat. The results contributed evidence that the original hypothesis of the existence of a neuronal coding mechanism was confirmed. This phenomenon appeared to be a prominent feature of the neuronal response to low frequency complex stimuli through the level of the inferior colliculus. Low frequency.sounds which are coded at the cochlear nerve by frequency of nerve fiber discharge appear to be encoded in the same way by groups of neurons at the dorsal cochlear nucleus and the inferior colliculus. The fact that the encoding mechanism occurs only below the level of the thalamus suggested that pitch discrimination may be essentially completed before the neuronal discharges arrive at the medial geniculate body of the thalamus

Pentatomidae (Hemiptera: Heteroptera: Pentatomidae) Captured on Purple Prism Traps Deployed for Detection of Emerald Ash Borer (Agrilus planipennis) (Coleoptera: Buprestidae) in Minnesota

The observation of bycatch from insect trapping programs, though often considered bothersome, may hold value for ecological and taxonomic studies. In Minnesota, a large trapping survey consisting of pheromone-baited purple prism traps, has been conducted for early detection of Agrilus planipennis, the emerald ash borer. Stink bugs (Heteroptera: Pentatomidae), which are pests of increasing importance in the North Central U.S., were observed to be captured by these traps. The objective of this study was to use trap bycatch from the A. planipennis traps for further documentation of the abundance and diversity of Pentatomidae in Minnesota. In 2011 and 2012, 4,401 and 5,651 purple prism traps were deployed and checked in Minnesota, respectively. Across both years, a total of 17 species of Pentatomidae were identified from 2 subfamilies, Asopinae and Pentatominae. The most abundant and prevalent species collected were Banasa calva (Say), B. dimidiata (Say), Chinavia hilaris (Say), Euschistus tristigmus luridus Dallas, Menecles insertus (Say), and Podisus maculiventris (Say). The pentatomid community observed on purple prism traps deployed in arboreal habitats differed from pentatomid communities reported in Minnesota crops (i.e., soybean, wheat and corn). Results of this study show that many pentatomid species are captured on purple prism traps and therefore bycatch of these traps could provide valuable information on the pentatomid community. However, purple prism traps should be used in addition to traditional surveillance or scouting methods for pentatomids

Damage Tolerance Assessment Branch

The Damage Tolerance Assessment Branch evaluates the ability of a structure to perform reliably throughout its service life in the presence of a defect, crack, or other form of damage. Such assessment is fundamental to the use of structural materials and requires an integral blend of materials engineering, fracture testing and analysis, and nondestructive evaluation. The vision of the Branch is to increase the safety of manned space flight by improving the fracture control and the associated nondestructive evaluation processes through development and application of standards, guidelines, advanced test and analytical methods. The Branch also strives to assist and solve non-aerospace related NDE and damage tolerance problems, providing consultation, prototyping and inspection services

Study of Acoustic Emissions from Composites

The nondestructive evaluation (NDE) of future propulsion systems utilizing advanced composite structures for the storage of cryogenic fuels, such as liquid hydrogen or oxygen, presents many challenges. Economic justification for these structures requires light weight, reusable components with an infrastructure allowing periodic evaluation of structural integrity after enduring demanding stresses during operation. A major focus has been placed on the use of acoustic emission NDE to detect propagating defects, in service, necessitating an extensive study into characterizing the nature of acoustic signal propagation at very low temperatures and developing the methodology of applying AE sensors to monitor cryogenic components. This work addresses the question of sensor performance in the cryogenic environment. Problems involving sensor mounting, spectral response and durability are addressed. The results of this work provides a common point of measure from which sensor selection can be made when testing composite components at cryogenic temperatures

Detection, Location, and Classification of Space Shuttle Main Engine Nozzle Leaks by Transient Thermographic Inspection

Leak checking and evaluation of pressure vessels by observing the slight temperature changes resulting from structural anomalies has been made possible through developments in high resolution infrared cameras and advanced image processing. These developments have made thermal nondestructive analysis a very practical and efficient method to determine material consistency and structural quality as well as monitor processes. The Space Shuttle Main Engine Nozzle has regions which can not be inspected with standard leak check methods. The Thermographic methods being developed to nondestructively test the Nozzle for leaks in inaccessible regions are reported. Also, a flash heating Thermographic investigation of the braze line bonding the cooling tubes to the outer structural jacket of the nozzle is reported

The Supreme Courte, Judicial Review, and the Public: Leadership Versus Dialogue

Appears in the Correspondence section; response to an article, Dialogue and judicial review, by Barry Friedman (91 Mich. L. Rev. 577 (1993)