A rapid method for optimization of the rocket propulsion system for single-stage-to-orbit vehicles

A rapid analytical method for the optimization of rocket propulsion systems is presented for a vertical take-off, horizontal landing, single-stage-to-orbit launch vehicle. This method utilizes trade-offs between propulsion characteristics affecting flight performance and engine system mass. The performance results from a point-mass trajectory optimization program are combined with a linearized sizing program to establish vehicle sizing trends caused by propulsion system variations. The linearized sizing technique was developed for the class of vehicle systems studied herein. The specific examples treated are the optimization of nozzle expansion ratio and lift-off thrust-to-weight ratio to achieve either minimum gross mass or minimum dry mass. Assumed propulsion system characteristics are high chamber pressure, liquid oxygen and liquid hydrogen propellants, conventional bell nozzles, and the same fixed nozzle expansion ratio for all engines on a vehicle

Mark 4A antenna control system data handling architecture study

A high-level review was conducted to provide an analysis of the existing architecture used to handle data and implement control algorithms for NASA's Deep Space Network (DSN) antennas and to make system-level recommendations for improving this architecture so that the DSN antennas can support the ever-tightening requirements of the next decade and beyond. It was found that the existing system is seriously overloaded, with processor utilization approaching 100 percent. A number of factors contribute to this overloading, including dated hardware, inefficient software, and a message-passing strategy that depends on serial connections between machines. At the same time, the system has shortcomings and idiosyncrasies that require extensive human intervention. A custom operating system kernel and an obscure programming language exacerbate the problems and should be modernized. A new architecture is presented that addresses these and other issues. Key features of the new architecture include a simplified message passing hierarchy that utilizes a high-speed local area network, redesign of particular processing function algorithms, consolidation of functions, and implementation of the architecture in modern hardware and software using mainstream computer languages and operating systems. The system would also allow incremental hardware improvements as better and faster hardware for such systems becomes available, and costs could potentially be low enough that redundancy would be provided economically. Such a system could support DSN requirements for the foreseeable future, though thorough consideration must be given to hard computational requirements, porting existing software functionality to the new system, and issues of fault tolerance and recovery

Capture-ejector satellites

A satellite in the form of a large rotating rim which can be used to boost spacecraft from low-Earth orbit to higher orbits is described. The rim rotates in the plane of its orbit such that the lower portion of the rim is traveling at suborbital velocity, while the upper portion is travelling at greater than orbital velocity. Ascending spacecraft or payloads arrive at the lowest portion of the rim at suborbital velocities, where the payloads are released on a trajectory for higher orbits; descending payloads employ the reverse procedure. Electric thrusters placed on the rim maintain rim rotational speed and altitude. From the standpoint of currently known materials, the capture-ejector concept may be useful for relatively small velocity increments

Laser pulse analysis

Methods are presented for locating threshold points by using laser pulse analysis. It was found that there are errors involved in the determination of each of these quantities, and an attempt was made to separate their effects on the overall range correction. Several series of corrected range measurements for fixed reflectors and satellites were obtained. Residuals were computed by fitting the range measurements to either fixed-reflector distances or short arcs of satellite orbits. Root mean square values of these residuals are presented

MECHANISMS GOVERNING SPECIFICATION OF PHOTORECEPTORS IN THE MAMMALIAN RETINA

Human vision begins with detection of light by photoreceptors (PRs) in the retina, a thin layer of cells at the back of the eye. Cones are the primary daytime and color-detecting PRs that distinguish red, green, or blue light. These cells differentiate into three subtypes through a poorly understood two-step process: first, naïve PRs decide between blue and red/green fates, then between red and green fates. Despite decades of study, we know very little about the molecular mechanisms that generate cones in the human eye. This thesis describes the findings that retinal organoids recapitulate human cone specification in developmental timing, gene expression, and morphology. A temporal switch in PR development was observed where blue cones are specified first, followed by red/green cones. Moreover, this regulation is controlled by thyroid hormone (TH) signaling, which is necessary and sufficient to control cone subtype fates through the nuclear hormone receptor thyroid hormone receptor β (Thrβ). Expression of TH–regulating genes suggests that retina-intrinsic temporal control of TH levels and activity governs cone subtype specification. Interestingly, dysregulation of TH in premature infants is associated with color-vision defects, consistent with these findings. This work establishes human retinal organoids as a model system to study mechanisms of cell fate specification in developing human tissue (Eldred et al., Science, 2018). Despite years of study, the mosaic of cone cell arrangement within the entire human retina has not yet been characterized. To develop the tools necessary to image and analyze this large tissue, in this thesis we quantitatively characterized the distribution of PRs in the mouse retina. We then modeled their generation based on interactions between Thrβ and TH gradients (Eldred et al., under review PLOS Computational Biology). These studies provide a detailed map of cone subtype patterning in the mouse retina, and suggest mechanisms for its development and maintenance. These software and analysis tools will be applied to the human retina to provide the first map of human cones

Multiple Object Fiber Optics Spectrograph Feed For The Hale Telescope

A preliminary design of a fiber-optics feed for the prime-focus spectrograph of the Hale telescope using computer controlled movable fiber has been completed and a test of a proto-type configuration carried out. The complete design will divide a 76mm square field into 10 strips and will place two movable fibers in each strip. The fiber pickups, which are moved by stepper-motor driven lead screws, may be placed anywhere in the strip subject to the limitation that they not pass each other. The prototype consisted of a single strip with two fibers operated with manual input to the stepper motors. In tests performed at the 5 meter Hale telescope in April of 1981 spec-tra of two bright 0 stars (B = 8.5 mag) separated by 5 arc minutes were photographed with a 3 minute exposure using a 1200 line/mm grating and unbaked 103a0 plates. The performance of the prototype configuration was within a factor of two of the unmodified prime-focus spec-trograph indicating a potential for a ten-fold increase in the effective utilization of the telescope for spectrographic survey work when fitted with the 20-fiber feed

Bulletin No. 288 - Draingage and Irrigation, Soil, Economic, and Social Conditions, Delta Area, Utah Division 4: Social Conditions

This study is a part of a more comprehensive one which was organized in 1928 for the purpose of ascertaining what conditions existed in bonded irrigation and drainage districts which were unable to. liquidate obligations incurred. The first such area to be studied was the Delta Area in Millard County. This area was selected for this study because of the pressing need for more detailed and wider information than was available to either the farmers or the bondholders and because available facts based on careful study might aid in achieving fairer settlements. These data might also assist other areas in eliminating wastes which multiply in hastily planned undertakings