34th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 1998
We present the results from a new diagnostic tool for investigating the effects of ignition on th... more We present the results from a new diagnostic tool for investigating the effects of ignition on the discharge symmetry in gas-fed pulsed plasma thrusters (GF-PPTs). Using a fast-framing camera, up to 16 individual pictures of a single GFPPT discharge can be captured at frequencies as high as 20 MHz. This high framing rate capability allows the discharge initiation and current sheet formation to be visualized with a large degree of temporal resolution. Varying the frame rate, number and size of pictures per discharge, as well as the trigger delay sent to the camera allowed multiple discharges at different stages to be visualized. Various configurations of GFPPT electrode geometry and discharge ignition systems were photographed in operation. It is shown that the large surface flash-over ignitors used in early GFPPT designs are unreliable in providing a constant, symmetric discharge initiation. Smaller semi-conductor spark gap ignitors used in later GFPPT designs have demon-
Two flight-qualified clusters of four Colloid Micro-Newton Thruster (CMNT) systems have been deli... more Two flight-qualified clusters of four Colloid Micro-Newton Thruster (CMNT) systems have been delivered to the Jet Propulsion Laboratory (JPL) and subsequently delivered to ESA for spacecraft integration. The clusters will provide precise spacecraft control for the drag-free technology demonstration mission, Space Technology 7 (ST7). The ST7 mission is sponsored by the NASA New Millennium Program and will demonstrate precision formation
The Laser Interferometer Space Antenna (LISA) mission is a space-borne gravitational wave detecto... more The Laser Interferometer Space Antenna (LISA) mission is a space-borne gravitational wave detector consisting of three sciencecraft in heliocentric orbit. Each sciencecraft is delivered to its operational orbit by a propulsion module. Because of the strict thermal and mass balancing requirements of LISA, the baseline mission concept requires that the propulsion module separate from the sciencecraft after delivery. The only
... LISA Missions. [AIP Conference Proceedings 873, 548 (2006)]. John K. Ziemer, Thomas Randolph,... more ... LISA Missions. [AIP Conference Proceedings 873, 548 (2006)]. John K. Ziemer, Thomas Randolph, Vlad Hruby, Douglas Spence, Nathaniel Demmons, Tom Roy, William Connolly, Eric Ehrbar, Jurg Zwahlen, Roy Martin. Abstract. ...
Abstract: Formation flying and microspacecraft constellation missions pose new propulsion require... more Abstract: Formation flying and microspacecraft constellation missions pose new propulsion requirements. Formationflying spacecraft, due to the tight positioning and pointing control requirements, may need thrust control within 1-20 uN to an accuracy of 0.1 uN for LISA ...
34th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 1998
We present the results from a new diagnostic tool for investigating the effects of ignition on th... more We present the results from a new diagnostic tool for investigating the effects of ignition on the discharge symmetry in gas-fed pulsed plasma thrusters (GF-PPTs). Using a fast-framing camera, up to 16 individual pictures of a single GFPPT discharge can be captured at frequencies as high as 20 MHz. This high framing rate capability allows the discharge initiation and current sheet formation to be visualized with a large degree of temporal resolution. Varying the frame rate, number and size of pictures per discharge, as well as the trigger delay sent to the camera allowed multiple discharges at different stages to be visualized. Various configurations of GFPPT electrode geometry and discharge ignition systems were photographed in operation. It is shown that the large surface flash-over ignitors used in early GFPPT designs are unreliable in providing a constant, symmetric discharge initiation. Smaller semi-conductor spark gap ignitors used in later GFPPT designs have demon-
Two flight-qualified clusters of four Colloid Micro-Newton Thruster (CMNT) systems have been deli... more Two flight-qualified clusters of four Colloid Micro-Newton Thruster (CMNT) systems have been delivered to the Jet Propulsion Laboratory (JPL) and subsequently delivered to ESA for spacecraft integration. The clusters will provide precise spacecraft control for the drag-free technology demonstration mission, Space Technology 7 (ST7). The ST7 mission is sponsored by the NASA New Millennium Program and will demonstrate precision formation
The Laser Interferometer Space Antenna (LISA) mission is a space-borne gravitational wave detecto... more The Laser Interferometer Space Antenna (LISA) mission is a space-borne gravitational wave detector consisting of three sciencecraft in heliocentric orbit. Each sciencecraft is delivered to its operational orbit by a propulsion module. Because of the strict thermal and mass balancing requirements of LISA, the baseline mission concept requires that the propulsion module separate from the sciencecraft after delivery. The only
... LISA Missions. [AIP Conference Proceedings 873, 548 (2006)]. John K. Ziemer, Thomas Randolph,... more ... LISA Missions. [AIP Conference Proceedings 873, 548 (2006)]. John K. Ziemer, Thomas Randolph, Vlad Hruby, Douglas Spence, Nathaniel Demmons, Tom Roy, William Connolly, Eric Ehrbar, Jurg Zwahlen, Roy Martin. Abstract. ...
Abstract: Formation flying and microspacecraft constellation missions pose new propulsion require... more Abstract: Formation flying and microspacecraft constellation missions pose new propulsion requirements. Formationflying spacecraft, due to the tight positioning and pointing control requirements, may need thrust control within 1-20 uN to an accuracy of 0.1 uN for LISA ...
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