To address the future needs and requirements of NASA’s Pulsed Plasma Thruster (PPT) research and development program and of Small Business Innovation Research phase I and II contracts, Face Electronics, LC (Norfolk, VA) is addressing the miniaturization and life extension of current PPT circuits by developing a new discharge initiation module in which the heavy, bulky, and electromagnetic-interference-noisy step-up magnetic transformer is replaced by a lower profile, smaller footprint, higher power density piezoelectric transformer.
Latest version of the discharge initiation circuit, the IGNIT-SONER, which uses a piezoelectric transformer to generate high voltage. The prototype measures 2.6 by 2.6 by 0.55 in. (3.70 in.3). IGBT, insulated gate bipolar transistor.
Long description of figure 1.
Taking as a reference the design specifications of the recent PPT developments for the Earth Observing-1 experimental satellite (EO-1) launched in November 2000, Face implemented a novel ultracompact discharge initiation (DI) circuit that reduces the volume of the reference DI circuit used in the EO-1 satellite to one-third. The complete prototype of the system (called IGNIT-SONER) was tested in May 2005 at NASA Glenn Research Center’s facilities. IGNIT-SONER accumulated over 50,000 cycles under full-vacuum conditions (10-6 to 10-7 torr) while operating a PPT model, and it accumulated over 500,000 accumulated cycles under atmospheric lab conditions under maximum firing rates of 5 Hz.
The research program included different levels of technology innovation and technology integration from the development of a novel piezoelectric transformer design to meet the project specifications to the integration of all the associated electronics to completely operate the discharge initiation systems within a PPT unit. Face readapted its basic patented Transoner technology to provide a transformer able to meet the project requirements. The developed transformer is an isolated PPT having over 3-kV input-to-output isolation and able to step up the input voltage to over 2.5 kV. A major feature of the piezoelectric transformer design is the 5-mm profile, which in combination with surface-mounted components, allows a very compact DI circuitry.
Different versions of the Transoner piezoelectric transformers developed for this project by Face.
During phase II project development, Face Electronics successfully addressed several design challenges encountered when operating semiconductor spark plugs. The much lower impedance when using these spark plugs under vacuum conditions in comparison to using air-gap spark plugs demanded the modification of the piezoelectric transformer design and the operation strategy. Face overcame these problems by implementing a novel piezoelectric-to-capacitive-discharge circuit.
Piezoelectric-capacitive discharge concept with a storage capacitor connected across the input voltage source. D1 and D2, discharge initiation circuits; IGBT, insulated gate bipolar transistor.
Long description of figure 3.
In an advanced design being implemented, Face intends to provide a self-adjusted mechanism so that the breakdown voltage of the spark plug can be tuned according to the real requirements of the spark plug. Face expects that this mechanism will extend the life operation of PPT systems by gradually increasing the driving voltage to the spark plug as soon as wear and ignition failure are detected. Currently, PPT life is limited mainly by the spark-plug degradation and the incapability of DI circuits to provide the required increase in voltage to continue the operation.
This promising technology will be useful in a variety of spacecraft applications. The performance achieved promotes consideration of piezoelectric technology not only for piezoelectric igniter applications but also as a replacement for the main transformer in a PPT system. In addition, the technology may be adaptable for other onboard propulsion applications requiring high-voltage generation. Piezoelectric devices are receiving growing interest as replacements for magnetic transformers in a wide range of consumer electronics applications.
Find out more about this research at Face Electronics LC: http://www.transoner.com (external site)
Glenn contact:
Dr. Hani Kamhawi, 216-977-7435, Hani.Kamhawi-1@nasa.gov
Face Electronics contact:
Dr. Alfredo V. Carazo, 757-624-2121, alfredo@faceco.com
Authors:
Dr. Hani Kamhawi and Dr. Alfredo V. Carazo
Headquarters program office:
Aeronautics Research
Programs/Projects:
Electric Propulsion
Last updated: October 16, 2006
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