A convex structure is used with a continuous slope.
A vehicle entering the atmosphere of a planet will do so at hypersonic speeds and will need to decelerate and maneuver through that atmosphere while protecting its payload from excessive heating. As a consequence, the vehicle shape must be designed to provide optimal aerodynamic lift and drag properties, while minimizing convective and radiative heating to the vehicle outer surfaces.
These needs are met by this invention, which provides a convex structure with a continuous slope that can be described by four linear segments and six curvilinear segments joined together to provide a convex shape defined by nine parameters. Viewed parallel to the y-axis in a Cartesian coordinate system, the projected cross-sectional shape includes first and second linear segments, spaced apart from each other and located on opposite sides of an x-axis, with each of the first and second segments being oriented substantially at a selected nonzero angle θc relative to the x-axis, each segment having a first segment end of closest approach to the x-axis with each closest approach segment end being located at substantially the same distance R from the x-axis. The projected shape includes a third linear segment that is oriented substantially perpendicular to the x-axis adjacent to the end of closest approach to the x-axis for each of the first and second linear segments.
The present invention provides an improvement over prior blunt body shapes in that the shape is actually of a class of geometric shapes that is describable by a relatively small number of geometry-shape parameters, and that provides a broad range of geometric shapes with favorable aerodynamic and aerothermal properties. These properties can then be analyzed by optimization methods for desired performance.
Optimization of the vehicle geometry-shape parameters can, for example, minimize heating levels subject to constraints that reduce aerodynamic performance, such as lift/drag, or can minimize weight of a thermal protection system, allowing a greater payload. Other properties can be optimized or established as constraints on a geometric parameter search, such as a requirement that a minimum lift/drag be met or exceeded, while minimizing center of gravity offset from vehicle centerline, to ease packing of a working vehicle while in space operations.
This work was done by James L. Brown, Joseph A. Garcia, and Dinesh K. Prabhu of Ames Research Center.