Mar 2 1982
From The Space Library
NASA said that it would change the Shuttle's solid-fuel rocket boosters, reducing weight and increasing payload capability about 6,000 pounds (2,720 kilograms) by replacing 8 of the 11 metal booster motor-case segments with 4 segments made of composite filament. Other components, such as the metal forward and aft domes and the external-tank attachment area of the metal case, would remain. NASA had issued a request for proposals to develop the filament-wound case.
The lightweight case would be needed in high-performance launches from Vandenberg Air Force Base into near-polar orbit, helping to compensate for the loss of lift in west coast launches that could not use Earth's rotation to boost their velocity. The lightweight case could also boost extra-heavy payloads into orbit from KSC. First use of the motor would be in 1985. After plan approval NASA would have Thiokol Corporation make test firings directed by MSFC of solid-fuel rocket motors with filament-wound casings. (NASA Release 82-32; MSFC Release 82-19)
ARC reported changes in the Shuttle's thermal protection system. New materials developed at ARC, stronger, lighter, and costing less than the original ones, would be installed gradually on the four orbiters over the next few years. Some new materials had been installed on Columbia; others were planned for Challenger, which was under construction for delivery this summer, and for Discovery and Atlantis, scheduled for delivery in 1983 and 1984.
Thermal protection of the Shuttle consisted of tiles and other heat-resistant materials applied to the outside to protect its aluminum and epoxy-graphite skin from extreme temperatures ranging from-170°F (-110°C) in space up to 3,000°F (1,648 °C) during reentry. A growing knowledge of reentry problems had brought changes in the system: the original materials had served beyond expectations, but research had provided new answers. Columbia now had a glass-fiber quilt over 20 square feet of its elevon cove, replacing the felt reusable insulation that was inadequate to the 1,500°F (816°C) temperature in that area.
This new material would be used on Challenger, Discovery, and Atlantis. The new orbiters would also use a fibrous refractory composite insulation lighter and stronger than the current tiles that would save about 1,000 pounds on Discovery and Atlantis; the new insulation was developed by ARC and manufactured by Lockheed. (ARC Release 82-05)
ARC noted that Pioneer 10 had been in space 10 years as of March 2. Launched in 1972, the first spacecraft to fly by Jupiter had crossed the asteroid belt, survived the radiation near Jupiter, and operated almost flawlessly on its way out of Earth's solar system. It had traveled 3.27 billion miles, received more than 40 thousand commands, and transmitted more than 125 billion bits of scientific data. Now more than halfway between orbits Uranus and Neptune, 2.5 billion miles from the Sun, Pioneer was currently defining the extent of the solar atmosphere, a bubble in the interstellar medium called the heliosphere.
By June 1983, Pioneer would be at a point outside all of the planets of Earth's system, in their current positions. Its transmissions, traveling at the speed of light, already needed 3 hours and 42 minutes to reach the operations center at ARC, and this time was increasing 1 minute every four days. Nearly all of its systems were still performing well; its magnetometer shut down in 1975, but experimenters could use correlations from five other instruments. Data showed that the heliosphere was far larger than predicted; Pioneer was seeking the boundary between the solar atmosphere and true interstellar space, probably 5 to 10 billion miles from the Sun. Experts at the Deep Space Network hoped to track Pioneer as far out as 5 billion miles.
The solar wind had been expected to slow with distance from the Sun, but this had not happened; almost no motion energy was lost as heat. Turbulence in the heliosphere was caused by solar storms, not solar-wind collisions. As solar storms increased in strength, the heliosphere seemed to alter shape, more oval at the Sun's equator than its roundness at solar minimum. Pioneer 10's sun-sensor could no longer furnish position data because of its great distance from the Sun and the resultant decline in solar brightness. However, mission controllers would use the Pioneer camera (photopolarimeter) to make star maps that would provide the rotation and attitude data needed to define Pioneer's position. (ARC Release 82-04; NASA Release 82-34)
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