Advancement of Additive Manufacturing for Monopropellant Catalyst Beds

Monolithic catalyst beds potentially have much longer lifetime than packed screen or pebble beds, however they have seen little use in propulsion applications because the limited geometries that could be produced by conventional manufacturing offered poor performance. Advances in additive manufacturing (AM) of ceramics allows for a wide range of geometries, potentially allowing for a catalyst bed with the decomposition performance of a packed bed with the lifetime of a monolith. The greater control over the internal geometry could also allow for precise tailoring of the pressure drop and other characteristics of the bed. Some previous work has been published on additive manufacturing of monopropellant catalyst beds, however this work is limited in many respects. Nearly all work has simply replicated the geometry of conventional extruded monoliths, with the remaining work using simple and relatively low performance geometries, so the full design possibilities allowed by AM remain unexplored. I am working on multiple complex novel catalyst bed geometries that will be tested in an already developed setup for pressure drop and decomposition performance at a variety of bed loadings. While I will be using rocket grade hydrogen peroxide for these tests for simplicity, the additive manufacturing process and the geometric design work could apply to any monopropellant, such as hydrazine and green monopropellants such as LMP-103s or ASCENT (a.k.a. AF-M315E).

Achieving the potential of monolithic beds also requires a consistent, well-adhering washcoating procedure for the additively manufactured supports; one which works well on varied geometry and on support materials that can be readily printed. Washcoat uniformity and adhesion is heavily influenced by the material and surface characteristics of the substrate and much of the existing literature on washcoating for industrial and automotive monolithic catalysts requires modification to work with additively manufactured substrates. I have already made significant progress on improved methods for surface preparation and coating of additively manufactured alumina catalyst supports intended for use with rocket grade hydrogen peroxide or other monopropellants with similar operating temperatures including hydrazine, although higher temperature propellants such as ASCENT would require different materials.

I have also been exploring improvements in the active catalyst for my testing with rocket grade hydrogen peroxide. Many catalyst formulations have been proposed and tested that can have higher performance than traditional silver screens, as well as higher operating temperatures that allow use with 98 wt.% hydrogen peroxide, however most of these have not been compared to each other and their reactivity has not been measured in ways that allow comparison across different testing methods. I am working to rectify this gap in the literature with a comprehensive comparative test program. I also hope to expand to investigation of alternative catalysts for hydrazine in the final year of the project.

Rocket engines capable of deep throttling, defined as being able to operate at less than 25% of their maximum thrust (a dynamic range of 4:1 or better), are extremely valuable for maneuvers that require both substantial delta-V and high precision during different portions of a maneuver. Applications include propulsive entry descent and landing (EDL), especially precision soft landing and ground hazard avoidance. Beyond the 25% of maximum thrust definition, NASA Technology Area Breakdown Structure (TABS) element 9.3.3 gives a target of deep throttling to below 5% of maximum thrust (dynamic range of 20:1) for next generation EDL engines.

This is early/mid-stage (TRL 3) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

None of these are guaranteed paths for this specific project — TechPort itself doesn't have an "apply" button. Reaching out to the contact(s) above with a specific question is usually the fastest way to find out what's actually open.