The specific TSS-1R mission objectives were: characterize the current-voltage response of the TSS-orbiter system, characterize the satellite's high-voltage sheath structure and current collection process, demonstrate electric power generation, verify tether control laws and basic tether dynamics, demonstrate the effect of neutral gas on the plasma sheath and current collection, characterize the TSS radio frequency and plasma wave emissions and characterize the TSS dynamic-electrodynamic coupling. That current was enough to melt the cable. This plasma diverted to the metal of the shuttle and from there to the ionospheric return circuit. As air bubbled out of the pinholes, the high voltage of the nearby tether, about 3500 volts, converted it into a relatively dense plasma (similar to the ignition of a fluorescent tube), and therefore made the tether a much better conductor of electricity. However, the air trapped in the insulation changed that. That in itself would not have caused a major problem, because the ionosphere around the tether, under normal circumstance, was too rarefied to divert much of the current. Later vacuum-chamber experiments suggested that the unwinding of the reel uncovered pinholes in the insulation. The culprit turned out to be the innermost core, made of a porous material which, during its manufacture, trapped many bubbles of air, at atmospheric pressure. It was encased in teflon-like insulation, with an outer cover of kevlar, inside a nylon (Nomex) sheath. The electric conductor of the tether was a copper braid wound around a nylon (Nomex) string. The satellite remained in orbit for a number of weeks and was easily visible from the ground. Many pieces of floating debris were produced by the plasma discharge and rupture of the tether, and some collided with it. Over 19 kilometers (12 mi) of the tether were deployed (over a period of 5 hours) before the tether broke. STS-75 mission scientists hoped to deploy the tether to a distance of 20.7 kilometers (12.9 mi). The Tether Satellite System circled the Earth at an altitude of 296 kilometers, placing the tether system within the rarefied electrically charged layer of the atmosphere known as the ionosphere. The TSS-1R mission was a reflight of TSS-1 which was flown onboard Space Shuttle Atlantis on STS-46 in July/August 1992. The mission also flew the United States Microgravity Payload (USMP-3) designed to investigate materials science and condensed matter physics. The primary objective of STS-75 was to carry the Tethered Satellite System Reflight (TSS-1R) into orbit and to deploy it spaceward on a conducting tether. Mission objective Tethered Satellite System STS-75 was a 1996 NASA Space Shuttle mission, the 19th mission of the Columbia orbiter.Īllen, Hoffman, Nicollier and Chang-Díaz had previously been members of the STS-46 crew, which had flown the TSS-1 experiment in 1992.
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