A report proposes the development of a microfabricated, integrated colloid thruster as a prototype of devices for propulsion and control of the attitudes of microspacecraft. (In a colloid thruster, a beam of positively charged, microscopic droplets is extracted electrohydrodynamically from a column of liquid and accelerated electrostatically to produce thrust.) Unlike other electrical thrusters, colloid thrusters are amenable to extreme miniaturization. The direction of thrust would be controlled electronically through selective activation of accelerator electrodes, eliminating the need for mechanical gimbals.
This work was done by Mohammed Mojarradi, Juergen Mueller, Jay Polk, and Colleen Marrese-Reading of Caltech for NASA’s Jet Propulsion Laboratory. To obtain a copy of the report, “A Fully Integrated Micro-Colloid Thruster System for Microspacecraft Applications,” access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Machinery/Automation category.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to Intellectual Assets Office JPL Mail Stop 202-233 4800 Oak Grove Drive Pasadena, CA 91109 (818) 354-2240 E-mail:
This Brief includes a Technical Support Package (TSP).
Integrated Colloid Thrusters for Microspacecraft
(reference NPO-20945) is currently available for download from the TSP library.
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Overview
The document presents a report on the development of an integrated colloid thruster designed for microspacecraft, a project undertaken by researchers at Caltech for NASA’s Jet Propulsion Laboratory. This innovative propulsion system utilizes electrohydrodynamic principles to generate thrust by extracting and accelerating positively charged microscopic droplets from a liquid source. The proposed thruster is notable for its extreme miniaturization, with a volume of approximately 1 cm³, excluding the liquid tank.
Key features of the colloid thruster include the use of capillary action to feed the liquid, which eliminates the need for mechanical valves. The system operates at a low supply voltage of 5 V, significantly reducing the complexity and size compared to traditional electric thrusters that typically require several kilovolts. An embedded linear electrostatic accelerator operates in a traveling-wave mode, utilizing shaped DC pulses to create the high electric fields necessary for droplet acceleration. This design allows for the generation of thrust without the high voltages usually associated with electric propulsion systems.
The document highlights the novelty of this work, emphasizing that it represents the first attempt at microfabricating a colloid thruster. The integration of a linear accelerator reduces the need for high voltages and introduces the concept of "electronic gimbling," which allows for electronic control of thrust direction without mechanical gimbals. This advancement addresses the challenges faced by existing electric propulsion systems, such as the re-sputtering issues associated with liquid metal systems and the need for pressurized containers in xenon-based systems.
The report also outlines the motivation behind this development, which stems from the need for high specific impulse miniaturized electric propulsion systems. The liquid colloid propulsion system offers a solution that avoids the drawbacks of current technologies, making it a promising candidate for future space missions.
In conclusion, the integrated colloid thruster represents a significant advancement in micropropulsion technology, with potential applications in the control and propulsion of small spacecraft. The work is attributed to a team of inventors, including Mohammed Mojarradi, Juergen Mueller, Jay Polk, and Colleen Marrese-Reading, and is protected under U.S. patent law, with inquiries for commercial use directed to the JPL Intellectual Assets Office.
