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Space Shuttle Columbia gets TLC
X-Press Editor Columbia (Orbiter OV-102) completed its 18-month stay at the Human Space Flight and Exploration Facility in March. A skilled workforce at the Air Force Plant 42 facility in Palmdale enhanced the vehicle's performance and safety with 80 major maintenance tasks. QuickTime movie of Columbia Departure Another 244 maintenance items were completed, as well as a structural inspection that included 379 separate requirements. Palmdale workers also checked off 206 deferred tasks – items that do not affect crew safety or full mission capability and await orbiter down time. One of the biggest tasks of this overhaul was an extensive investigation of 236 miles of wire throughout the Space Shuttle. To put that in perspective, imagine a wire extending from Palmdale to Big Sur. Mandatory trips to the factory are required about every three years, where workers scrutinize every nook and cranny of the orbiter and install the most up-to-date equipment that will assist astronauts in completing their tasks in space safely. Aside from the rivet-by-rivet look at Columbia, NASA wanted the nation's first Space Shuttle to receive an even more intensive wire inspection. In addition to the usual extensive analysis of the wires, technicians had a closer look inside wire harnesses and applied protection to areas where wires could potentially come into contact with a screw, rivet, or other protruding metal edge. Selected wire harnesses and bundles of wires that were enclosed in convoluted tubing were removed, disassembled, evaluated, reassembled and reinstalled to validate NASA inspection criteria used for Discovery and Endeavour. Extensive tests also sought to confirm the wiring's resistance to damage, vibration, electrical shorting and age-related degradation. Columbia has always been the heftiest of the orbiters because it was heavily instrumented for the early flights of the Space Shuttle Program. The extra instrumentation enabled the gathering of a wealth of information on the orbiter's performance. Much of that wiring was left intact when the research equipment was removed in order to avoid the extra time and cost required to remove those wires, said Allen M. Hoffman, director of Boeing's Assembly, Integration and Test operations for the Human Space Flight and Exploration Facility. Because of the extensiveness of this modification and maintenance job, much of that experimental equipment and wiring unique to Columbia was removed. This part of the overall weight loss program helped the orbiter shed about 950 pounds. During this refurbishment, Columbia also joined Atlantis in having a fully digital cockpit, which was installed to replace cathode-ray tube screen, dials and gauges that were state-of-the-art when the orbiter first flew on April 12-14, 1981. The Multifunctional Electronic Display Subsystem (MEDS) consists of 11 flat, color displays that make up what is referred to as a "glass cockpit" that features the latest technology. For example, the screens provide easy access to vital information through two-and three-dimensional color graphic and video capabilities of its onboard information management system. Nine of the display units are across the forward instrument panel, another at the right hand mission station console, and the eleventh is at the aft flight deck on orbit station, Hoffman said. The newly installed digital screens allow astronauts – including a payload specialist working at the console behind the pilot and co-pilot – to immediately select from menu options on the screen the information they needed to complete their tasks. MEDS was primarily built in Palmdale, with the screens fabricated by Honeywell Space Systems, Phoenix, Ariz. The system provides the most advanced cockpit controls currently available and are a space-qualified version of the display technologies used in Boeing's 777. Also included in the major overhaul is the inspection of the orbiter's thermal protection system. As more and more information is available on the temperatures endured by the Space Shuttles and where the heat is focused, different materials are developed to lighten the orbiter while providing the maximum protection and safety for Space Shuttle crews. For example, research showed that areas of the orbiter sporting heavy quartz fabric to withstand temperatures of 1,400 degrees Fahrenheit required less than half that level of protection. Therefore, the heavy quartz fabric was replaced with a Nomex felt blanket that protects the orbiter up to 750 degrees. Each of the orbiters has 24,000 unique tiles that cover its underbelly and areas that become hot, but not as hot as the nose and leading edges that are made of a reinforced carbon-carbon material that can stand temperatures of up to 3,600 degrees. The black silica tiles on the bottom of the Space Shuttle are sensitive to moisture, but are sufficient to protect that area of the orbiter with an upper protection range of 1,600 degrees. Each silica tile is specially designed and manufactured on order using information that is stored in a computer. A strain isolator pad is a felt-like material that covers the hull of the Space Shuttle and is a layer between the hull and the light-weight black silica tiles. The tiles would pop off the orbiter if they were affixed directly onto it because of the flexing that occurs as a result of the heat created by acceleration and re-entry pressures. Because the Space Shuttles "flex" in flight, the space that a tile occupies can change and require modifications during the maintenance and modification cycle. In fact, looking up close at a tile, numbers representing its precise position on the orbiter and its unique part number are clearly visible. Tiles range in thickness from a quarter-inch to four and a half inches depending on the heat that a given area of the Shuttle experiences. A closer look at a Space Shuttle tile also reveals a little hole in the middle. A waterproofing solution is reinjected into each tile following every mission. It impregnates the silica material and acts as an inhibitor for that silica from absorbing any type of moisture. It dissipates, or burns out, during the re-entry process, so the tiles are reserviced or processed during each post-flight inspection and processing period, Hoffman said. Prior to Columbia's departure on March 1, Palmdale crews also performed some preflight vehicle checkouts, which reduced the time required to process the orbiter for its next mission at Kennedy Space Center in Florida. Columbia first rolled out of the Boeing facility (then Rockwell International Space Systems) on March 8, 1979 and is a veteran of 26 space flights. |
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Responsible NASA Official: John Childress For questions, contact: Dryden Web Group Page Curator:WD-Team Modified: March 26, 2001 |
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