In catalytic flow-through chemical reactors being explored for space vehicle applications, the catalysts would be supported on the surfaces of wires, instead of on particles, as are typically used in traditional packed beds. The original intent of the proposal was to make it possible to build controllable, efficient catalytic hydrazine-decomposition microthrusters for small spacecraft. The basic concept of the proposal should also prove applicable to other flow-through catalytic reactors; for example, reactors that could be used in removing trace contaminants from the environment.
Traditional packed catalytic beds have several disadvantageous characteristics that make control difficult and that pose obstacles to scaling down to the microthruster size range. These characteristics include high back pressures through the beds, attrition due to friability and spalling of catalyst particles, and difficulty of fabrication in small sizes. Usually, as a result, it becomes necessary to make the beds larger than desired, with the further result that propellant is wasted and thermal masses are large (and therefore response times are undesirably long).
The basic concept of the catalyzed-wire reactor allows for adaptation to numerous variations. A reactor of the proposed type could be as simple as a straight tube containing a single catalyst-coated wire suspended on the cylindrical axis. The wire and catalyst could be made of any of a variety of materials; for example, in one application, there might be a need for a tungsten wire with a washcoat (e.g., alumina) supporting a catalyst like platinum. In most cases, multiple catalyst-coated wires would likely be needed. Different wire material could be coated with different catalysts that would be optimized for different reaction temperatures. Catalyst preparation procedures (i.e., washcoat, catalyst, inclusion, etc.) would follow the protocols typically described for metal-supported catalysts. Wires could be made straight or twisted (see figure), wires could be all of the same diameter or of different diameters, and wires could be spaced apart at various distances; the foregoing choices could be made in conjunction with the choice of the shape and inside dimensions of the reactor, all in an effort to optimize the flow or to accommodate a wide range of flow variables in the reactor.
This work was done by Gerald Voecks, J. Morgan Parker, Amy Herr, and Juergen Mueller of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Materials 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
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Refer to NPO-20507, volume and number of this NASA Tech Briefs issue, and the page number.
This Brief includes a Technical Support Package (TSP).
Chemical Reactors Based on Catalyzed Wires
(reference NPO-20507) is currently available for download from the TSP library.
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Overview
The document is a technical support package from NASA, specifically a NASA Tech Brief, detailing innovative advancements in catalyzed wire technology for miniature and micro reactors. This work, conducted by inventors Amy E. Herr, Gerald E. Voecks, J. Morgan Parker, and Juergen Mueller at the Jet Propulsion Laboratory (JPL), addresses significant challenges associated with conventional packed catalyst beds used in spacecraft propulsion systems.
The primary motivation for this research stems from the limitations of traditional packed catalyst beds in space environments. These conventional systems face issues such as high back pressure, attrition due to catalyst particle spalling, and high thermal mass, which can slow ignition response times. Additionally, the inability to scale down these systems to the mini and micro sizes required for future spacecraft leads to inefficiencies, including wasted propellant and constraints on spacecraft design.
The novel approach proposed in this document involves the use of catalyzed wires, which offer a more efficient and flexible solution for creating miniature and micro reactors. This innovation allows for the assembly of various catalyst combinations, making it applicable to a wide range of propulsion needs for small spacecraft. The mini and micro thrusters developed from this technology require significantly smaller volumes of propellant, enabling precise control of thrust and improving overall spacecraft performance.
The document outlines the technical disclosure of this innovation, emphasizing its novelty and the improvements it offers over prior art. By addressing the specific problems associated with conventional systems, the research aims to enhance the capabilities of future spacecraft, making them more efficient and adaptable to the demands of space navigation and control.
In summary, this NASA Tech Brief presents a significant advancement in propulsion technology through the development of catalyzed wire systems for miniature reactors. This innovation not only addresses the limitations of existing technologies but also paves the way for more efficient and effective spacecraft design, ultimately contributing to the future of space exploration and satellite navigation.
