SST Technology Follow-On Program-Phase I. Transonic and Supersonic Test of the SST Prototype Air Intake.

Abstract : The SST prototype intake is an axisymmetric, translating centerbody design incorporating four variable cowl throat doors for transonic airflow matching. An isolated intake test was conducted at the NASA Ames wind tunnel facilities on a 1/3-scale model. Experimental performance simulating controlled operation is presented. Reference schedules were developed that allow closed-loop control of the intake variable geometry and normal shock with negligible degradation from peak performance in the started mode, Mach 1.6 to 2.65. Performance goals were exceeded with boundary layer bleed rates equal to prototype design specifications. It was confirmed that the SST production intake performance goals at cruise can be surpassed with the boundary layer control concept used on the intake. Above Mach 2.1, operational problems were encountered at high angles of yaw, apparently due to bleed deficiencies near the throat door edges. Safe unstarted operation was available at all Mach numbers in the buzz suppression mode, which is normally used from Mach 1.2 to 1.6 and above Mach 1.6 following inadvertent unstarts. Transonic operation was feasible with the fixed-intake-geometry run mode. Performance goals could easily be met in this range, Mach 0.7 to 1.2. A detailed comparison of the prototype intake and the simplified, fixed-cowl production design proposed by NASA Ames is included. A penalty of about 3% airplane range, equivalent to 100 miles, was indicated for the simplified intake resulting from oversizing required for transonic airflow matching and lower operating recovery at cruise. (Author)