Description: Aboard crewed spacecraft, such as the ISS or Apollo Command Module, acoustic noise has continuously been a point of concern in regards to communications, , and overall habitability. More specifically, ventilation fans within the Environmental Control and Life Support (ECLS) system have been the main source of acoustic noise on recent crewed missions. Mainstream proposes to develop a toroidal fan to reduce acoustic noise generated by spacecraft ventilation systems. Toroidal fans are manufactured by sweeping the trailing edge of one blade backwards to connect with the leading edge of the following blade. This significantly reduces vortices, turbulence, and flow separation, which account for a large fraction of noise produced by axial fans. In Phase I, Mainstream will leverage our existing CFD and design toolsets to select a toroidal geometry and experimentally demonstrate its viability at reducing acoustic noise while meeting aerodynamic performance metrics. In Phase II, Mainstream will further develop the toroidal fan geometry and integrate the fan into a full-scale ventilation system, ready for drop-in replacement aboard the ISS. The system's full acoustic signature will be determined, as well as additional characterization at sub-ambient conditions, representative of vehicles and habitats of cis-lunar and Mars-transit architecture.

Benefits: NASA applications for the proposed toroidal fan include spacecraft ventilation fans aboard space stations in Earth-orbit, as well as long duration crewed missions where habitability and comfort are essential. Additionally, this technology is applicable in any spacecraft process where forced fluid flow is required, such as oxygen recovery systems, the Carbon Dioxide Removal Assembly (CDRA), and equipment cooling systems.Non-NASA applications are numerous, including any application that requires a low-noise environment. This includes ventilation for both aircraft and submarines, as well as land-based systems that experience issues with volume. With respect to additional manned spacecraft, non-government commercial entities such as Space-X, Blue Origin, Bigelow Aerospace, and others include space tourism as a future goal.