Design and Analysis of Propellant Tanks Support Structure for an Advanced Spacecraft

This paper proposes a new type of configuration to support the propellant tanks in large size spacecrafts. Research in space industry over the last decade is focused on reducing the launch cost of the spacecraft. The main objective of this project work is to develop new concept of propellant tanks support structure for 6 ton class spacecraft. This configuration has four propellant tanks (2 oxygen tanks & 2 fuel tanks) which are mounted in polar form outside the central thrust cylinder and are supported by a flat rigid panel and two struts at fixed end and flat deck at free end. The stiffness requirements of advanced spacecraft are \u3e 8Hz, \u3e27Hz and \u3e30Hz for global lateral mode of the spacecraft, oxygen tanks axial mode and fuel tanks axial mode respectively. For support structure various configurations, were worked out to meet stiffness requirements. The configurations considered are Honeycomb Sandwich panel, Honeycomb Sandwich panel embedded with doublers at tank attachment zone, Honeycomb sandwich panel embedded with rectangle beam at tank attachment zone and Honeycomb sandwich panel with circular struts at tank attachment zone. Design iterations were carried out for above four configurations and suitable configuration was finalized. Static analysis was also carried out for the given load cases to determine strain, Hoffmann failure index, SR and MOS for the composite central thrust cylinder. The geometric modeling of the propellant tanks support structure and main parts of the advanced spacecraft for all the four configurations were modeled by using UNIGRAPHICS-Nx6® and analysis carried out using MSC/PATRAN®, MSC/NASTRAN®

Study of Cost Overrun and Delays of Department of Defense (DoD)\u27s Space Acquisition Program

Defense and Aerospace Systems Acquisition projects, just like any other Large-Scale Complex Engineered Systems (LSCES) experience delays and cost overrun during the acquisition process. Cost overrun and delays in LSCES are due, in part, to high complexity, size of the project, involvement of various stakeholders, organizations, political disruptions, changes in requirements and scope. These uncertainties, due to the exogenous factors, have cost the federal government billions of dollars and delays in completion of the programs. Cost estimation of federal programs is usually based on previous generations of systems produced and almost all the time the costs are underestimated. Underestimation of the cost of the programs is an endogenous factor, which results in cost overrun for any program, the behavior of the cost escalation is pre-forecasted to be normally distributed, but due to the cost overrun, the cost escalation curve may be skewed. In this paper, the authors will be studying the cost escalation and time delays of the Advanced Extremely High Frequency (AEHF), a DoD\u27s space acquisition program. The distribution of the cost and time can aid in understanding the effects of endogenous factors influencing the cost overrun and the effect of change in requirements during the acquisition process. This data will serve as a foundation for further research to create a framework, which will be used, in better forecasting of the cost of the acquisition of the programs

Performance of sanitary sewer collection system odour control devices operating in diverse conditions

Controlling odours from sanitary sewer systems is challenging as a result of the expansive nature of these systems. Addition of oxidizing chemicals is often practiced as a mitigation strategy. One alternative is to remove odorous compounds in the gases vented from manholes using adsorptive media. In this study, odour control devices located at manholes were observed to determine the ability of these systems to reduce hydrogen sulphide from vented gases. The odour control devices incorporated pressure regulation to control gas flow out of manhole covers and adsorptive media to remove hydrogen sulphide in the vented gases prior to release. Pressure regulation was accomplished using a variable volume bladder and two pressure relief valves that permitted gas flow when pressures exceeded 1.3 to 2.5 cm water column. The reduction in gas flow vented from manholes was intended to extend the service life of the adsorptive media, as compared with odour control devices that do not incorporate pressure modulation. Devices were deployed at four locations and three adsorptive media were tested. Although measured collection system hydrogen sulphide concentrations varied from zero to over 1,000 ppm, the removal rates observed using odour control devices were typically above 90%. The lower removal rates observed at one of the sites (50.5 ± 36.1%) appeared related to high gas flow rates being emitted at this location. Activated carbon was used in most of the tests, although use of iron media resulted in the highest removal observed: 97.8 ± 3.6%. The expected service life of the adsorptive media contained within the odour control devices is a function of site-specific hydrogen sulphide concentrations and gas flow rates. The units used in this study were in service for more than 8 to 12 months prior to requiring media replacement

Comparative Study of Skin Color Detection and Segmentation in HSV and YCbCr Color Space

AbstractThis paper presented a comparative study of human skin color detection HSV and YCbCr color space. Skin color detection is the process of separation between skin and non-skin pixels. It is difficult to develop uniform method for the segmentation or detection of human skin detection because the color tone of human skin is drastically varied for people from one region to another. Literature survey shows that there is a variety of color space is applied for the skin color detection. RGB color space is not preferred for color based detection and color analysis because of mixing of color (chrominance) and intensity (luminance) information and its non uniform characteristics. Luminance and Hue based approaches discriminate color and intensity information even under uneven illumination conditions. Experimental result shows the efficiency of YCbCr color space for the segmentation and detection of skin color in color images

IAEA Commissioning Expedition of Linear Accelerator

https://openworks.mdanderson.org/sumexp22/1006/thumbnail.jp