Supersonic spike diffuser noted

A diffuser is the duct that slows a very fast gas stream and turns speed into pressure, and NASA Stennis says its spike-shaped version can do that in much less space. (technology.nasa.gov) In supersonic flow, that slowdown happens through shock waves — abrupt pressure jumps that waste performance if they are too strong or badly placed. NASA’s patent page says the Stennis design cuts both core Mach number and flow deflection, a combination the agency describes as “Pareto-efficient.” (technology.nasa.gov; sciencedirect.com) NASA Stennis says the spike diffuser delivers about double the pumping performance of older second-throat diffusers. The same page says it needs only about 25% of the length of a second-throat design and starts at a pressure ratio about half that of conventional geometries. (technology.nasa.gov; technology.nasa.gov) That matters in places where hardware has to handle high-speed exhaust or intake flow without a long, heavy duct. NASA’s Stennis Space Center, near Bay St. Louis, Mississippi, is the agency’s main rocket propulsion test site, and diffuser performance directly affects how it simulates altitude during engine tests. (nasa.gov; ntrs.nasa.gov) Passive rocket diffusers are built to let the exhaust plume pull surrounding gas with it, creating a low-pressure region like high altitude around the engine nozzle. A NASA technical paper says conventional second-throat designs can demand more driving pressure than an upper-stage engine can provide, which is the limit Stennis engineers were trying to push. (saemobilus.sae.org; ntrs.nasa.gov) NASA publicly highlighted the work in a June 24, 2021 news release on subscale hot-fire testing of advanced diffuser shapes. The agency said the spike diffuser was the first of its kind designed after Stennis engineers invented the technology, and that it showed the best test margin of the concepts evaluated. (nasa.gov) The design is now being pitched through NASA’s Technology Transfer program rather than as a flight-ready product announcement. NASA’s licensing page lists the invention as SSC-TOPS-10, and a separate TechPort entry says Stennis planned validation work on a hot-fire spike diffuser with an experimentally demonstrated performance boost of more than 30% over conventional designs. (technology.nasa.gov; techport.nasa.gov) The social post that resurfaced the diffuser points to a niche but old problem in high-speed propulsion: fitting shock-managing hardware into tighter envelopes without giving up pressure recovery. NASA’s own pitch is simple — more pumping, lower starting pressure, and a much shorter package. (x.com; technology.nasa.gov)