A report discusses wind-tunnel tests of a scale model of a con- ceptual two-engine jet airplane designed to carry 10 passengers, have a range of 4,000 miles (≈6,400 km), cruise at a mach number of 2.0, and generate a low sonic boom [char- acterized by a shock overpressure of ≤ 0.5 lb/ft2 (≤24 Pa)]. The model could optionally include either of two differently sized nacelle submodels representing alternative engine designs. In each test, the pressure was measured at intervals along a horizontal line at a specified height below the model. One conclusion drawn from predicted and measured pressure values is that it is more difficult to tailor the geometry of this airplane for low sonic boom than it is to do so for a larger supersonic airplane capable of carrying 300 passengers and for which the allowable shock overpressure is 1.0 lb/ft2 (48 Pa). It was found that decreasing the allowable overpressure intensifies the conflicts between the design choices for reducing sonic boom and those for increasing aerodynamic efficiency. It was also found that due to the nacelles’ aft location, their contribution to the shock overpressures could be expected to be small enough to be unnoticeable by an observer on the ground.
This work was done by Robert J. Mack of Langley Research Center. To obtain a copy of the report, “An Analysis of Measured Sonic-Boom Pressure Signatures From A Langley Wind-Tunnel Model of A Supersonic- Cruise Business Jet Concept,” access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Mechanics category.