Session
Technical Session IV: Bold New Missions Using Cutting Edge Technology
Abstract
Starting with the Space Shuttle flight 4A (Nov. 30, 2000), the International Space Station (ISS) power system employs large, high voltage, solar arrays with the negative ground tied to chassis. An intense study by a NASA sponsored Tiger Team in the early ‘90s determined that this configuration leads to the structure being at a high negative potential relative to the local plasma (approximately 140v negative without any intervention) and, that at any potential greater than around 70v negative, the anodized aluminum structure and its components will undergo destructive arcing. A set of plasma contactor units (PCUs) was deployed to provide a conductive xenon plasma path for remitting electrons collected by the arrays and thus bring the potential closer to zero and mitigate the arcing danger. In late July 2000, the ISS program office at JSC issued an engineering change notice that directed the development of some means to independently assess the performance of the PCU’s, and to have hardware available for launch on STS-97 (ISS Flight 4A) the very mission scheduled to deliver and install the first set of large Station solar arrays on November 30th. This allowed only a mere 4.5 months to design, build, test, manifest, complete EVA training, and deliver for launch. NASA Glenn, NASA Johnson, and Design_Net Engineering formed a unique team to try to accomplish the directive. The subject of this paper is to describe the Floating Potential Probe (FPP) and the fast-track program approach used to quickly develop this autonomous system for measuring the electrical potential between the ISS and the surrounding space plasma. At the time, most people involved with the Floating Potential Probe (FPP) project believed that there was less than a 10% chance of successfully making it onboard Flight 4A and even less chance that it would work.
The Little Probe That Could! (A Story of Mission Impossible Engineering)
Starting with the Space Shuttle flight 4A (Nov. 30, 2000), the International Space Station (ISS) power system employs large, high voltage, solar arrays with the negative ground tied to chassis. An intense study by a NASA sponsored Tiger Team in the early ‘90s determined that this configuration leads to the structure being at a high negative potential relative to the local plasma (approximately 140v negative without any intervention) and, that at any potential greater than around 70v negative, the anodized aluminum structure and its components will undergo destructive arcing. A set of plasma contactor units (PCUs) was deployed to provide a conductive xenon plasma path for remitting electrons collected by the arrays and thus bring the potential closer to zero and mitigate the arcing danger. In late July 2000, the ISS program office at JSC issued an engineering change notice that directed the development of some means to independently assess the performance of the PCU’s, and to have hardware available for launch on STS-97 (ISS Flight 4A) the very mission scheduled to deliver and install the first set of large Station solar arrays on November 30th. This allowed only a mere 4.5 months to design, build, test, manifest, complete EVA training, and deliver for launch. NASA Glenn, NASA Johnson, and Design_Net Engineering formed a unique team to try to accomplish the directive. The subject of this paper is to describe the Floating Potential Probe (FPP) and the fast-track program approach used to quickly develop this autonomous system for measuring the electrical potential between the ISS and the surrounding space plasma. At the time, most people involved with the Floating Potential Probe (FPP) project believed that there was less than a 10% chance of successfully making it onboard Flight 4A and even less chance that it would work.
