Abstract: To study the effects of curved earth’s surface on the ranges of projectiles and rockets, a modified rigid body trajectory model is built based on Kane method in which the curved earth’s surface and the changes in both the size and direction of the gravity acceleration are considered. The concept of geodesic line is introduced to the range calculation of projectiles or rockets. Four calculation methods for the range under the condition of curved earth’s surface are discussed, such as inverse solution of geodetic problem and so on. The range errors calculated with the modified rigid body trajectory model and the ordinary rigid body trajectory model are compared. The result shows that the spheroidal distance algorithm has a high calculation precision in the range of 300 km, and can be used to calculate the range on the curves earth’s surface. The modified rigid body trajectory model is more accurate than the ordinary rigid body trajectory model in the consideration of the curved earth’s surface.

Key words: ordnance science and technology, curved earth’s surface, trajectory model, range