Showing papers by "National Security Agency published in 1970"
TL;DR: In this article, the Vinti potential and spheroidal coordinates are used in the solution of the equations of motion of an Earth satellite, permitting computation of the free flight path in closed form.
Abstract: When the Vinti potential and spheroidal coordinates are used in the solution of the equations of motion of an Earth satellite, the Hamilton-Jacobi differential equation is separable, permitting computation of the free flight path in closed form. If the parameters are chosen to include the effect of the Jz and Js terms of the Earth's gravitational potential, the Vinti potential also allows for a major part of the effect of the term in J4. The model can serve as an improved reference orbit in perturbation theory, or it can be used to compute moderately accurate trajectories (extremely accurate over short time intervals) with a considerable saving of machine time over numerical integration. The development in universal variables is valid for orbits of eccentricity greater than unity as well as for periodic orbits. The main purpose of this paper is to generalize the results of Vinti and others to include the nonperiodic cases. Included is a description of a tested method for practical calculation of trajectories and a numerical example for illustration.
9 citations
01 Jan 1970
TL;DR: This paper is concerned with a subject that is generally neglected - computers that cannot be reporgrammed; if you want a computer to do something, you must have a program prepared for the purpose.
Abstract: This paper is concerned with a subject that is generally neglected - computers that cannot be reporgrammed. The title calls attention to an assumption that everybody makes and so no one is conscious of making: If you want a computer to do something, you must have a program prepared for the purpose. To be explicit, someone must conceive an effectively complete procedure for the job, specify it accurately in terms that the computer can accept, and command the computer to carry out the procedure as specified.