Two Marshall Space Flight Center (MSFC) engineers are closing in on a December hotfire test of a small thruster that is built from a combination of ceramic and alloy material linings – involving new fabrication processes – which could dramatically extend engine life.
If successful, their research could be directly implemented into aiding engine development from Ares I – onwards.
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Marshall’s Sandy Elam and Robert Hickman, combustion engineer and metallic materials engineer, respectively are heading to a crucial test stage for what is described as new component alloy combinations and innovative ceramic liner technologies, designed to extend engine life.
Their evaluations are initially based on potential viability for use in reaction control system thrusters, although the development process could grow towards larger workhorse engines such as the J-2X – which is currently baselined on the upper stage of the Ares I Crew Launch Vehicle.
‘Similar technology could impact the design of larger engine systems,’ Elam said to MSFC’s Marshall Star. ‘These include innovative liquid oxygen/liquid-methane rockets now in development at Marshall and even the mighty J-2X engines that will power the upper stages of the Ares launch vehicles.’While reusability on the J-2X won’t be a requirement – it could aid reliability, and even reduce the weight of components. Such a technology could also prove to be vital in extending engine life on vehicles that will be tasked with long haul exploration, which NASA is aiming for over the coming decades.
Elam and Hickman noted that sustained heat from engine operation quickly wears out certain components, such as the injector system and the thrust chamber. To mitigate such issues, components are traditionally ‘bulked up’ – increasing both the thickness and mass, which in turn adds weight.
Since 1999, Marshall engineers have been examining new materials and fabrication processes for resolving these issues, in order to deliver lightweight, long-lasting thrust chambers and injectors, designed to withstand higher temperatures and operate for longer periods of time.
In their tests, Elam and Hickman used reaction control system thrusters to test out the two metal combination, currently used on the RCS systems. The first, rhenium, is a ‘refractory’ metal that can withstand sustained high temperatures much more effectively than conventional alloys. The second, iridium, protects against metallic oxidation, a common chemical breakdown process that can speed up engine deterioration over time.
In their findings, the engineers concluded that the current fabrication of thrusters using these two metals produce a ‘less-than-optimum’ strength and durability, noting that over time, the iridium protection diffuses away, exposing the rhenium and reducing the life of the thruster. They also observed that their test article failed to reach the ideal operating temperature margins of 2,500 degrees Celsius.
Aiming for solutions, the two engineers started to test new fabricating options, which began back in August of this year. Two options showed promise, both involving the same metals, but applied using a different fabrication process.
‘In the first, the iridium/rhenium liner is formed using a patented ‘electrodeposition’ process called El-Form, in which a metal solution is introduced via electrical current to a material surface, leaving behind a thin, uniform liner coating – one hopefully more durable than materials bonded via vapor deposition,’ Elam said.
‘The second option is an innovative vacuum plasma spray process that transforms the material elements into ‘functional gradient materials,’ blended composites that smoothly transition at the molecular level from one material at one surface to another material at the opposite surface.’
This change in the way the components are fabricated eliminates the distinct bond joints between the material layers, it is claimed, thus creating an extremely strong and durable component.
‘The next challenge,’ Elam said, ‘was to address the necessary increase in temperature margins.’ The goal was to increase the tolerance margins for the required temperature of 2,500 degrees Celsius – which they noted is required for future vehicle concepts.
This goal involved testing ways to combine the two fabrication processes and add a durable ceramic layer to the interior of the thruster. The iridium layer will still prevent oxidation, but adding the ceramic layer will help reach the heat tolerances required.
‘Achieving this higher temperature limit will provide a safer margin of error and longer life for existing thruster designs,’ Elam added. ‘It also will enable engineers to pursue new thruster designs and consider alternative propellant options, often supporting more powerful engines that can burn hotter and offer higher system performance.’
They will know if their concept works when they carry out the hotfire test next month. The hotfire will be conducted on a small thruster with the ceramic layer, increasing the temperature margin to demonstrate the durability of the new fabrication process and combination of materials.
They will publish their results to fellow propulsion engineers next May in Colorado.
‘We’re hoping to show some dramatic results and make these technologies and techniques available to industry right away,’ Elam said. ‘It’s going to take much more robust, longer-life rocket engines to handle the harsh environments of long-term space exploration.
‘We’re excited to help forge that path.’
Additional credits: Rick Smith – MSFC/Marshall Star. Orion Propulsion, Huntsville, AL.
L2 Resources For Ares I, V and Constellation: Ares I Overview Presentation and risk matrixs (now imfamous on red performance issues). Ares I – T-0 Umbilicals – as per DAC-1C – November. Ares I Paper: FIRST STAGE DESIGN, DEVELOPMENT, TEST, AND EVALUATION – Nov 20. Ares I Paper: STATUS, PLANS, AND INITIAL RESULTS FOR ARES I CLV AERODYNAMICS – Nov 20. Weekly Notes CLV Upper Stage Integrated Test Subsystems – Nov 16. Ares I – T-0 Umbilicals – as per DAC-1C – November.
Ares I-1 Test Flight Plan (full outline) Presentation. Ares I-1 timeline and modification expanded info. Ares I extra solids graphics and info. Ares I troubleshooting latest. Ares I Reference Trajectory. Boeing’s STS to Ares – Lessons Learned Presentation. Latest Ares I and Ares V baseline Configuration image and data. CLV DAC-1C (Changes to CLV Upper Stage).
Ares I-1: Four Seg+Dummy ‘Tuna Can’ stage. Ascent Developmental Flight Test Presentation. CLV Pad 39B Handover Info and Latest. New images of CLV on top of new MLP and LUT. Lockheed Martin CEV/Orion Updates. Constellation news updates. ATK figures on the 5-Seg Booster weight for CLV. 90 Minute Video of Constellation all hands meeting. CLV TIM Meeting Information. CLV/CaLV Infrastructure, Timelines and Information. Escape System Trade Study Presenation.
CEV-CLV Design Analysis Cycle Review (DAC-2) Presentation. Constellation SRR updates. CLV Stick – Troubleshooting/Alternatives/Updates. New CEV Images (include abort mode). Flight Design and Dynamics Division CEV update. CLV Mono-propellant RCS system. CEV pressurisation system review. CLV/CEV Configuration Images. The 2×3 Seg SRB Crew Launch Vehicle Option Presentation…plus more.
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