The project focuses on the development of a new alumina-silicate based cementitious binder (geopolymer) capable of acting as a high performance refractory material with low ablation rate and high early mechanical strength. Such a binder would represent a significant contribution to NASA’s efforts to develop a new generation of refractory ‘hot face’ liners for rocket plume environments created by thrusters powered by either Liquid Oxygen (LOX)/Liquid Natural Gas (LNG) propellants or solid phase rocket fuel. The results of the controlled and full scale tests at NASA SSC E-Complex, a multi-use propulsion test bed, revealed the newly developed geopolymer products exhibited comparable or superior performance compared to commercial refractories currently used by NASA. Erosion rates for the geopolymer samples versus the commercial refractories tested were lower for the majority of the cases, and total erosion was also lower or equal for similar test durations. Geopolymer binders proved to be good candidates for the repair of existing structures due to their excellent adhesion to parent surfaces, as demonstrated by the tests conducted on repaired tested panels. Additionally, the post-test characterization results conducted at Louisiana Tech’s Institute for Micromanufacturing showed an increase in compressive strength following testing, when mullite-based aggregate was used. One sample that was fired more than once, exhibited a 50% increase in compressive strength, suggesting that geopolymer concrete may even improve its properties after repeated firing.
The project involved the development and testing of a new alumina-silicate based multi-purpose, cost-effective, ‘green’ cementitious binder (geopolymer) capable of acting as a high performance refractory material with both a low ablation rate and a high early mechanical strength. This work was built upon previous research undertaken by the research team in the areas of geopolymer binders. Full scale and laboratory controlled tests were performed to compare geopolymer performance to currently available commercial products (e.g. Sentinel, Greencast). Geopolymer’s thermal shock resistance properties were tested on eleven different fly ash stockpiles specimens from around the world. The geopolymer specimens were subjected to ASTM C-1100 (Standard Test Method for Ribbon Thermal Shock Testing of Refractory Materials). Samples were subjected to incremental 5-5-5-15-30 second flame exposure durations and to a 15 or 30 accumulated exposure, depending on the sample performance (e.g., if the plume became detached). Field test durations were limited to prevent excessive erosion of the test panels and subsequent plume detachment. Laboratory testing also demonstrated that geopolymer could withstand thermal shock and exposure to flame. Additionally, a computational model was created to determine the optimal chemical ratios for geopolymer to be exposed to elevated temperatures. Additionally, due to their excellent adhesion to pre-existing surfaces geopolymer binders were proven to be good candidates for use in repair of existing structures upon which they were applied and retrofitted; this was demonstrated and observed via tests conducted on repaired tested panels. Overall, the demonstration testing program revealed that the geopolymer products had equal or superior performance compared to commercial refractories currently used by NASA.More »
Geopolymers will directly benefit NASA funded mission by improving refractory material, and by doing so will potentially enable new engine testing capabilities and increase safety and reliability of existing engine testing infrastructure. The testing program that was part of this project demonstrated that the geopolymer products had equal or superior performance compared to commercial refractories currently used by NASA. Additionally, by utilizing a high strength, corrosion resistant material for the repair of large concrete test and launching stands, like those at SSC and KSC that experienced extensive corrosion related damage and are in need of repair, could significantly reduce general upkeep, maintenance and repair costs.
Benefits to NASA unfunded missions and planned missions include the fact that these new refractory materials could be applied to a wide range of applications and testing equipment that utilize refractory materials across the agency.
Benefits to the commercial space industry would be similar to those that benefit NASA. These new refractory materials could benefit a wide range of assorted commercial space industry applications that require the use of durable cost-effective refractory materials.
Benefits to other government agencies would be similar to those that would benefit NASA. Any other government agencies (i.e. Army, Navy, DoD) that have applications that require the use of refractory materials could similarly benefit from the advantages provided by this improved material.More »
|Organizations Performing Work||Role||Type||Location|
|Stennis Space Center (SSC)||Lead Organization||NASA Center||Stennis Space Center, MS|
|Jacobs Engineering, Inc.||Supporting Organization||Industry|
|Lockheed Martin Space Systems||Supporting Organization||Industry|
|M.L. Smith J. LLC||Supporting Organization||Industry|