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Advanced Composite Thrust Chambers for In-Space Propulsion

Marshall Space Flight Center, Alabama

Radiation-cooled, bipropellant thrust chambers are being used for in-space propulsion. To increase the performance of radiation-cooled engines, improved chamber materials are needed that will allow higher operating conditions (pressure and temperature), better resistance to oxidation, and reduced mass. During this effort, an innovative composite thrust chamber is being developed that will incorporate advanced hafnium oxide and iridium liner techniques as well as replacing the expensive, high-density rhenium with a low-mass carbon-carbon (C–C) structural wall.

In an effort to increase performance, hafnium oxide thermal barrier coatings and improved iridium liners have been developed, and hot-fire tests of rhenium chambers with these improvements have shown higher operating temperatures are possible. To reduce engine mass, recent efforts have focused on the development of C–C composites with iridium liners.

Preliminary results from tests of iridium-lined C–C chambers have shown considerable promise. Results have demonstrated the potential of combining innovative fabrication techniques such as vacuum plasma spray (VPS), EL-Form®, and tape wrapping and braiding to produce an advanced HfO2-Ir lined C-C thrust chamber. VPS techniques were developed that produced HfO2 gradient and Ir deposits on graphite mandrels.

EL-Form® techniques were successfully used to deposit a dense Ir oxidation protection layer atop the VPS deposits. The ability to produce a C–C jacket on the VPS and EL-Form® coat liner was demonstrated using tape wrapping and braiding techniques. Hot gas testing has shown the ability of the HfO2 coating to reduce the exterior temperature of the C–C jacket, which will enable the use of higher-temperature propellants for improved performance. No damage was observed in the HfO2-Ir liners as a result of hot gas testing.

This work was done by Richard Holmes of Marshall Space Flight Center, and John O’Dell, Alexander Smirnov, and Timothy McKechnie of Plasma Processes, Inc. For more information, contact Sammy Nabors, MSFC Commercialization Assistance Lead, at This email address is being protected from spambots. You need JavaScript enabled to view it..

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:

Timothy McKechnie
Plasma Processes, Inc
4914 Moores Mill Rd.
Huntsville, AL 35811
Phone No.: (256) 851-7653

Refer to MFS-32798-1.