Space Shuttle Columbia (OV-102) was a Space Shuttle orbiter manufactured by Rockwell International and operated by NASA. Named after the first American ship to circumnavigate the upper North American Pacific coast and the female personification of the United States, Columbia was the first of five Space Shuttle orbiters to fly in space, debuting the Space Shuttle launch vehicle on its maiden flight in April 1981. As only the second full-scale orbiter to be manufactured after the Approach and Landing Test vehicle Enterprise, Columbia retained unique features indicative of its experimental design compared to later orbiters, such as test instrumentation and distinctive black chines. In addition to a heavier fuselage and the retention of an internal airlock throughout its lifetime, these made Columbia the heaviest of the five spacefaring orbiters; around 1,000 kilograms (2,200 pounds) heavier than Challenger and 3,600 kilograms (7,900 pounds) heavier than Endeavour. Columbia also carried ejection seats based on those from the SR-71 during its first six flights until 1983, and from 1986 onwards carried an imaging pod on its vertical stabilizer. The Extended Duration Orbiter pallet was used by the orbiter in thirteen of the pallet's fourteen flights, which aided lengthy stays in orbit for scientific and technological research missions. Columbia was also used to retrieve the Long Duration Exposure Facility and deploy the Chandra observatory, and also carried into space the first female commander of an American spaceflight mission, the first ESA astronaut, the first female astronaut of Indian origin, and the first Israeli astronaut.
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Columbia spent 610 days in the Orbiter Processing Facility (OPF), another 35 days in the Vehicle Assembly Building (VAB), and 105 days on Pad 39A before finally lifting off.[4] It was successfully launched on April 12, 1981, the 20th anniversary of the first human spaceflight (Vostok 1), and returned on April 14, 1981, after orbiting the Earth 36 times, landing on the dry lakebed runway at Edwards Air Force Base in California. It then undertook three further research missions to test its technical characteristics and performance. Its first operational mission, with a four-man crew, was STS-5, which launched on November 11, 1982. At this point Columbia was joined by Challenger, which flew the next three shuttle missions, while Columbia underwent modifications for the first Spacelab mission.
One unique feature that permanently stayed on Columbia from STS-1 to STS-107 was the OEX (Orbiter Experiments) box or MADS (Modular Auxiliary Data System) recorder. On March 19, 2003, this "black box" was found slightly damaged but fully intact by the U.S. Forest Service in San Augustine County in Texas after weeks of search and recovery efforts after the Space Shuttle Columbia disaster. The OEX/MADS was not designed to survive a catastrophic loss like an airplane black box.[16][17]
Columbia was destroyed at about 09:00 EST on February 1, 2003, while re-entering the atmosphere after a 16-day scientific mission. The Columbia Accident Investigation Board determined that a hole was punctured in the leading edge on one of Columbia's wings, which was made of a carbon composite. The hole had formed when a piece of insulating foam from the external fuel tank peeled off during the launch 16 days earlier and struck the shuttle's left wing. During the intense heat of re-entry, hot gases penetrated the interior of the wing, likely compromising the hydraulic system and leading to control failure of the control surfaces. The resulting loss of control exposed minimally protected areas of the orbiter to full-entry heating and dynamic pressures that eventually led to vehicle break up.[19]
The width of a full octave band (its bandwidth) is equal to the upper band limit minus the lower band limit (bandwidth = f2 - f1). For more detailed frequency analysis, the octaves can be divided into one-third octave bands; however, this level of detail is not typically required for evaluation and control of workplace noise.
The U.S. Bureau of Labor Statistics (BLS) publishes annual statistics for occupational injuries and illnesses (including hearing loss) reported by employers as part of required recordkeeping. The BLS data shows, that in private, state government, and local government establishments, hearing loss represented 9.9% of the occupational illnesses reported in 2019, or a total of 16,900 cases (BLS table SNR07.xlsx). For private establishments, hearing loss represented 11.4% of the occupational illnesses during the same year (see Figure 9 below). Between 2014 and 2019, the rate declined from 1.9 to 1.4 cases per 10,000 full-time workers. Although there was a decline in rate during this period, the number of cases is still significant and hearing loss remains as a hazard that must be continuously addressed.
During periodic calibration, the CTC also performs preventive maintenance to ensure that the equipment remains fully functional over its life expectancy. If the calibration team detects a problem, it services the instrument as necessary. When returning equipment to CTC for periodic calibration, be sure to include a note about any problems or concerns with equipment function so they can be evaluated as part of the maintenance process. If equipment is not functioning as expected, CTC requests that the instrument be returned for inspection, even if it is not yet due for calibration.
SLMs provide instantaneous noise measurements for screening purposes (Figure 16). During an initial walkaround, an SLM helps identify areas with elevated noise levels where full-shift noise dosimetry should be performed. In addition, SLMs are useful for:
An effective noise investigation begins before you arrive on site. First, conduct research based on type of industry to determine whether noise hazards are likely. If so, plan to conduct noise measurements and monitoring. Confirm that the instruments' annual calibrations are current (i.e., have not expired), ensure that the batteries are fresh, and calibrate the SLM and noise dosimeters before the opening conference. This will permit you to begin obtaining sound level measurements during your initial walkaround at the site. After these preparations, you will also be ready to start obtaining personal noise dosimetry samples early in the visit, providing an opportunity to collect samples of significant duration. The resulting noise dosimetry might not be full shift, but it will provide valuable information regarding worker noise exposure that first day on site.
Reports of hearing loss by industry are summarized in BLS's "Table SNR08: Incidence Rates of Nonfatal Occupational Illness, by Industry and Category of Illness." This extensive table lists, by industry, the incidence of reported illnesses per 10,000 full-time workers, as shown on OSHA 300 Logs that employers are required to submit. The table includes a column for hearing loss. Comparing the hearing loss reporting rates in various industries will give you an estimate of the impact that noise has on the industry you are inspecting compared with other industries. Note that variations in hearing loss reporting rates can influence the apparent incidence rate.
Request copies of previous noise surveys or evaluations that included sound level measurements. Note noise levels that exceed the AL, along with the associated location, equipment, and activities. Inquire about the duration of exposure and determine which workers might be exposed to the noise by using the equation for calculating the TWA for the percent dose (see Appendix B). Look at noise dosimetry data to determine whether workers were exposed over the AL or the PEL. If the measurements are being used to show compliance, check that the equipment used to make the measurements was at least a Type 2 SLM (or dosimeter) with periodic and daily calibration fully documented.
Sound-absorbing materials are a valuable addition to acoustic enclosures and barriers, which can interrupt a noise path. Acoustic enclosures can be either full or partial and can surround either the noise source or the worker. A personnel enclosure works best if it is lined with sound-absorbing material. An alternative is an enclosure that surrounds a piece of equipment (a noise source), as pictured in Figure 36. Employers and workers should consider the risk of equipment overheating when surrounded by an acoustic enclosure.
Complete enclosures around noise sources are not always possible due to requirements to access maintenance panels and equipment controls, provide ventilation, or keep the process flowing. In these cases, a partial enclosure may still substantially reduce noise. Like full enclosures, partial enclosures should have effective barrier materials on the outside and should be lined with absorptive materials on the inside. Because noise will escape through the opening, the noise path should be treated with sound-absorbing materials if possible. Also, the number of openings should be limited and should be directed away from workers, if possible. Figure 39 shows a partial enclosure that allows access while affording the operator some protection from the noise source.
Noise dosimeter: A type of sound level meter that measures and integrates noise over time providing a value of the average dose. This instrument can calculate the daily noise dose based on a full workshift of measurements, or a dose from a shorter sample. The operator can select different noise dose criteria, exchange rates, and thresholds.
In the shakeout area, full-shift noise levels are 98 dBA to 100 dBA. Four workers are employed here for each of two shifts. Silica exposures for these workers are 3 to 4 times the PEL, given that there is no local exhaust ventilation provided. We propose a total enclosure of the shakeout that will be locally exhausted, mechanically isolated from the shaker table, and lined with some acoustically absorptive material. This control approach, if properly implemented, will reduce the noise exposures to 90 dBA and the silica exposures to one-quarter of the PEL. Given that the daily noise levels do not exceed 100 dBA, is enclosure of the shakeout economically feasible? 2ff7e9595c
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