Description: Arctic Slope Technical Services, Inc. (ASTS) is pleased to propose to continue the development of an additive manufacturing (AM) approach for fabricating bimetallic combustion chambers. Our chamber design, which is applicable to future NASA small launch vehicles, exploits the combined capabilities of selective laser melting (SLM) and magnetic pulse welding (MPW), in order to reduce manufacturing lead time and cost and to improve quality through ease of inspection. The chamber will use a two-piece GRCop-84 liner that is inserted and MP welded into a one-piece Inconel 625 structural jacket. The MPW step will be used to permanently join the two halves of the liner at the throat and the liner itself to the jacket in a structurally sound, watertight manner. Our structural jacket design includes integral propellant manifolds, which eliminates the time and expense associated with machining or casting separate components and welding them in place.The benefits of such a design are substantial. First, it is well understood that for complicated components like a modern combustion chamber, an AM manufacturing approach can drastically reduce cost (by 50% or more) and lead time (weeks instead of months). Second, our particular design overcomes weaknesses of other additive designs by enabling easy inspection of the printed parts that otherwise would have to undergo CT scanning or X-ray inspection, which has proven to be exceptionally difficult for complex internal geometries like regenerative cooling channels and propellant manifolds. Third, our basic material and manufacturing approach is scalable to booster class combustion chambers at a rate controlled solely by scaling of the build volumes available in commercial SLM machines (which is occurring rapidly). In fact, commercial MPW systems are already being used in the automotive industry that can instantaneously weld parts of several meters in length

Benefits: An excellent potential NASA application for this technology is the Exploration Upper Stage Engine (EUSE), a high performance (461-s Isp) LOX/hydrogen upper stage engine that will replace the venerable RL10. Like that predecessor, we fully expect the EUSE to use a closed expander cycle, since it combines exceptional performance with benign turbine environments. Since that cycle is completely reliant upon increasing the enthalpy of the liquid hydrogen to power the turbopump, the main combustion chamber (MCC) lies at the very heart of success for the EUSE.

One truly commercial opportunity has come to our attention, which we are pursuing with vigor. Specifically, Virgin Orbit is a commercial "new space" entrant that is developing a small two-stage launch vehicle that is sure to benefit from our technology. Specifically, their second stage engine is a pump-fed, LOX/RP-1 engine that provides 5,000-lbf of vacuum thrust. To maximize our opportunity to insert this technology, the chamber layout developed under this contract is intended to act as a drop-in replacement for that engine.