Unsteady shock-induced separation of the ramp boundary layer was reduced and stabilized more effectively by external perforations than by external or internal slots. At Mach 2.0 peak total-pressure recovery was increased from 0.802 to 0.89 and stable mass-flow range was increased 185 percent over that for the solid ramp. Peak pressure recovery occurred just before instability. The 7 and one-third-diameter duct ahead of the engine reduced large total-pressure distortions but was not as successful for small distortions as obtained with throat bleed. By removing boundary-layer air the bypass nearly recovered the total-pressure loss due to the long duct.

Summary of trafficability studies conducted by the Waterways Experiment Station. It includes information about phase I tests related to "Soil Classification and Trafficability Data" as a sub-project of "Trafficability of Soils as Related to the Mobility of Military Vehicles" (published 1947-1955). It also includes initial results of phase II, "Soils Trafficability Predictions."