Improved Trajectory Calculations for Helicopter-Launched Missiles.
Abstract
A method has been developed to provide improved trajectory calculations for helicopter-launched missiles based on an earlier U.S. Army trajectory program. In the earlier method the helicopter rotor flow field is simulated but, at a given instant of time, the flow is assumed to be uniform over the whole missile. By incorporating a three-dimensional panel method the forces and moments due to the flow-field nonuniformity are calculated and applied in the form of a perturbation about the uniform flow values. The uniform flow values can be estimated by using experimental results incorporated into the basic trajectory calculation and so in this way the predominant effects of the flow-field separation can be accurately accounted for. A relatively crude model of the flow separation for the perturbation solution is therefore used in which a blowing velocity is imposed over the part of the missile for which the flow would be separated. This method has been applied to the calculation of the trajectory of the 2.75-Inch Rocket launched from a hovering helicopter using two different downwash distributions. It is found that the modification to the trajectory introduced by the calculated effects due to the flow-field nonuniformity is relatively small but it can still be significant as regards accuracy at the target. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1979
- Accession Number
- ADA073263
Entities
People
- J. L. Hess
- R. W. Clark
Organizations
- Douglas