A report describes an improved micromachined vaporizing-liquid microthruster (VLM), now under development as a prototype of thrusters for microspacecraft. This thruster is of the resistojet type: the energy for vaporization and expansion of a propellant liquid is provided through electrical-resistance heating. A typical VLM of prior design, fabricated on a chip, was comparatively bulky and was energy-inefficient because much of the energy that should have gone into heating the propellant was wasted in heating the chip.
This work was done by David Bame, Indrani Chakraborty, Juergen Mueller, and Stephen Vargo of Caltech for NASA's Jet Propulsion Laboratory. To obtain a copy of the report, "Micro Machined Vaporizing Liquid Microthruster (VLM) with Superior Thrust Vector Control and Increased Thermal Efficiency," access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Machinery/Automation category.
NPO-21100
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Improved Micromachined Vaporizing-Liquid Microthruster
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Overview
The document presents a technical report on the Improved Micromachined Vaporizing-Liquid Microthruster (VLM), a prototype thruster designed for microspacecraft, developed by a team from Caltech for NASA's Jet Propulsion Laboratory. The VLM is a resistojet type thruster, which means it utilizes electrical-resistance heating to vaporize and expand a propellant liquid for thrust generation.
Previous designs of VLMs were criticized for being bulky and energy-inefficient, primarily because a significant portion of the energy intended for heating the propellant was lost in heating the chip itself. Additionally, the convoluted flow path of the propellant to the exit nozzle in earlier models led to reduced accuracy in thrust-vector control.
The improved VLM addresses these issues through several key enhancements. It is significantly smaller than its predecessors, allowing for more efficient use of space in microspacecraft. Most importantly, the new design features a narrow pipe that is well insulated from the chip, ensuring that the majority of the heating occurs directly in the area where the propellant is vaporized. This design change minimizes energy loss and enhances overall energy efficiency.
Furthermore, the flow path of the propellant has been simplified. In the improved VLM, the section of the flow path downstream of the heater is aligned with the narrow pipe containing the heater, as opposed to the previous designs where the flow path was perpendicular to the heater channel. This alignment is expected to improve thrust-vector control, allowing for more precise maneuvering of microspacecraft.
The report credits the work to a team of inventors: David Bame, Indrani Chakraborty, Juergen Mueller, and Stephen Vargo. It emphasizes that the research was conducted under the auspices of NASA and highlights the potential applications of this technology in future space missions.
Overall, the document outlines significant advancements in microthruster technology, showcasing how the improved VLM could lead to more efficient and effective propulsion systems for small spacecraft, ultimately contributing to the broader goals of space exploration and technology development.
