Validation of a X-15 Using a Rapid Aerodynamic Solver Through All Mach Number Regimes

This paper presents a detailed validation study comparing aerodynamic predictions from Altair FlightStream, a surface-vorticity panel-method solver, against NASA wind tunnel test data for the X-15 research aircraft. The X-15’s configuration—featuring a small aspect ratio wing, high sweep, and blunt base regions—provides a rigorous test case for aerodynamic solvers. FlightStream simulations were conducted across four Mach regimes: 0.6 (subsonic), 0.8 (transonic), 1.2 (supersonic), and 6.83 (hypersonic), each aligned with experimental data from NASA Langley wind tunnel tests. At Mach 0.6 and 0.8, solver predictions show good agreement in zero-lift drag (within 5–18%) and lift-curve slope trends, though static margin is notably underpredicted. At Mach 1.2, the Tangent Cone method predicts drag within 2–5% of NASA data but underestimates lift slope by over 20%. At Mach 6.83, FlightStream accurately predicts lift slope (2–4% deviation) and drag (12–15% deviation), with moderate overprediction of static margin. While elevator control trends are consistent, magnitudes are underpredicted across all regimes. These results demonstrate the effectiveness and limitations of FlightStream in capturing complex aerodynamic behavior for low aspect ratio, high-speed vehicles, and validate its use for conceptual & preliminary analysis.