1. straight-surface and isentropic inlet configurationsanalyzed using CFD;Mach1.9design condition.Dataare referenced tothe SFCvalueforthe1808 Biconic inlet.
2. Installed SFCdata are plotted against MFR in Figure 14-A. To generate these results, the SFC cost equation, presented in Eq. 1, was now populated with CFD-based output. As was done for the MOC-based results, the SFC data were converted to percent form relative to the 1808 Biconic's value at near-critical mass flow. Negative values indicate relative performance improvement. Using results from this figure, and including those from the remainder of the down-selected inlet subset analyzed using CFD, the SFC data at near-critical flow are presented by configuration inFigure14-B.
3. The on-design inlet performance characteristics of the partial isentropic design space proved impressive using high fidelity analysis tools, but the off-design characteristics at lower supersonic Mach number remained an open question. To address this, the 1808 Biconic was evaluated against a representative partial isentropic compression inlet, this time 0895 Isentropic. Half-plane global CFD solutions of the intake and diffuser region at near-critical mass flow are compared in Figure 15 between the two configurations at local flow Mach numbers of 1.9,1.7,1.5, and1.3. The reduced strength of the partial isentropic inlet's terminal shock is visually evident at all Mach numbers.
4. Cowl drag coefficient is plotted in Figure 16 as a function of MFR for the two inlet configurations at design speed as well as at the lowerMach numbers. (Results werenotcomputedat Mach 1.3 for the1808 Biconic,although the trend can be inferred from the remaining data.) Note that the partial isentropic configuration maintains an exceptional drag advantage over the straight-surface inlet throughout the Mach range. A modest improvement in offdesign additivedragwasseparatelynotedfor0895 Isentropicrelative to1808 Biconic.
5. area-volume distribution improvements resulting from recent progress in low sonic boom morphing techniques.4-9Avoiding the uncertainty and high development risk associated with largescale laminar flow concepts, the configuration employs variable wing sweep to assure good performance and handling qualities at takeoff, approach, and landing.10The wing itself incorporates a subsonic leading edge and retains excellent internal volume characteristics. The low vehicle nose angle assumes the use of a synthetic-hybrid pilot visionsystem.