Ballistic missile interceptor guidance by acceleration relative to line-of-sight

1. A method for intercepting a ballistic target vehicle with an interceptor vehicle, said method comprising the steps of:

setting up a line-of-sight between the target vehicle and the interceptor vehicle;

initially accelerating said interceptor vehicle in a direction perpendicular to said line-of-sight whereby the acceleration tends to reduce apparent rotation in space of the line-of-sight as seen from the interceptor vehicle;

at a time at which the rotation rate of said line-of-sight as seen at said interceptor vehicle is zero, accelerating said interceptor along said line-of-sight toward said target vehicle; and

intercepting the target vehicle with the interceptor vehicle.

2. A method according to claim 1 , wherein said initial acceleration includes at least a component lying in a plane including the path of said target.

3. A method according to claim 1 , wherein said step of setting up a line-of-sight between the target and the interceptor vehicle includes the step of setting up an instantaneous line-of-sight between the ballistic target vehicle and the interceptor vehicle.

4. A method for guiding an interceptor vehicle toward a target vehicle, said method comprising the steps of:

at a particular time during the travel of said interceptor vehicle, making a change in the thrust vector of said interceptor vehicle;

prior to said particular time, accelerating said interceptor vehicle in a direction perpendicular to a line-of-sight extending between said interceptor vehicle and said target vehicle; and

following said particular time, accelerating said interceptor vehicle along said line-of-sight toward said target vehicle.

5. A method according to claim 4 , wherein said particular time occurs when the velocity of said interceptor vehicle along said direction perpendicular to said line-of-sight equals the velocity of said target vehicle along said direction perpendicular to said line-of-sight.

6. A method according to claim 4 , wherein said particular time occurs when said line-of-sight as seen from said interceptor vehicle ceases to rotate.

7. A method for guiding an interceptor vehicle toward a target, said method comprising the steps of:

determining at least target position, target velocity, interceptor vehicle position, and interceptor vehicle velocity vectors;

generating, from said target position and interceptor vehicle position vectors, a line-of-sight vector representing the line-of-sight between said interceptor vehicle and said target;

generating, from said target velocity, interceptor vehicle velocity, and line-of-sight vectors, a signal representing the vector difference between the interceptor vehicle velocity and the target velocity, and also generating an orthogonal vector signal representing that component of the vector difference which is orthogonal to said line-of-sight vector;

generating, from said line-of-sight and orthogonal vectors, a desired missile thrust vector; and

controlling the thrust of said interceptor vehicle by applying said desired interceptor vehicle thrust vector; and

intercepting the target with the interceptor vehicle.

8. A method according to claim 7 , wherein said step of determining at least target position, and target velocity vectors is performed extrinsic to said interceptor vehicle, and further comprising the steps of:

associating time tags with said vectors; and

synchronizing said target and interceptor vehicle vectors by the use of said time tags.

9. A method according to claim 7 , wherein said step of generating, from said target position and interceptor vehicle position vectors, a line-of-sight vector, includes the step of generating a line-of-sight unit vector; and

said step of generating an orthogonal vector signal representing that component of the vector difference which is orthogonal to said line-of-sight vector includes the step of generating an orthogonal vector signal representing that component of the vector difference which is orthogonal to said line-of-sight unit vector.

10. A method according to claim 7 , wherein said step of controlling the thrust of said interceptor vehicle includes the step of applying said desired interceptor vehicle thrust vector to an error detector for comparison with actual interceptor vehicle thrust.

11. A method according to claim 7 , wherein said step of generating, from said target position and interceptor vehicle position vectors, a line-of-sight vector, includes the step of generating a line-of-sight unit vector; and

said step of generating an orthogonal vector signal representing that component of the vector difference which is orthogonal to said line-of-sight vector includes the step of generating an orthogonal vector signal representing that component of the velocity vector difference which is orthogonal to said line-of-sight unit vector.

12. A method according to claim 7 , wherein said step of controlling the thrust of said interceptor vehicle involves accelerating the interceptor vehicle in a direction perpendicular to said line-of-sight whereby acceleration tends to reduce apparent rotation in space of the line-of-sight as seen from the interceptor vehicle and puts the interceptor vehicle on an intercept course or trajectory immediately at the completion of nulling the rotation rate of the line-of-sight as seen at the interceptor vehicle.

13. A method for directing an interceptor vehicle toward a ballistic target, said method comprising the steps of:

defining an instantaneous line-of-sight extending between the locations of said target and said interceptor vehicle;

initially accelerating said interceptor vehicle in a direction perpendicular to said instantaneous line-of-sight between said target and said interceptor vehicle, which tends to reduce apparent rotation in space of said instantaneous line-of-sight;

at a time at which said rotation rate of said line-of-sight at said interceptor is zero, accelerating said interceptor vehicle along said line-of-sight toward said target; and

intercepting the target with the interceptor vehicle.

14. A method for guiding an interceptor vehicle toward a target, said method comprising the steps of:

determining at least target position, target velocity, interceptor vehicle position, and interceptor vehicle velocity vectors;

generating, from said target position and interceptor vehicle position vectors, a line-of-sight vector representing the line-of-sight between said interceptor vehicle and said target;

generating, from said target velocity, interceptor vehicle velocity, and line-of-sight vectors, a signal representing the vector difference between the interceptor vehicle velocity and the target velocity, and also generating an orthogonal vector signal representing that component of the velocity vector difference which is orthogonal to said line-of-sight vector;

generating, from said line-of-sight and orthogonal vectors, a desired interceptor vehicle thrust vector; and

controlling the thrust of said interceptor vehicle by applying said desired interceptor vehicle thrust vector; and

intercepting the target with the interceptor vehicle.

15. A method according to claim 14 , wherein said step of determining at least target position, and target velocity vectors is performed extrinsic to said interceptor vehicle, and further comprising the steps of:

associating time tags with said vectors; and

synchronizing said target and interceptor vehicle vectors by the use of said time tags.

16. A method according to claim 14 , wherein said step of generating, from said target position and interceptor vehicle position vectors, a line-of-sight vector, includes the step of generating a line-of-sight unit vector; and

said step of generating an orthogonal vector signal representing that component of the velocity vector difference which is orthogonal to said line-of-sight vector includes the step of generating an orthogonal vector signal representing that component of the velocity vector difference which is orthogonal to said line-of-sight unit vector.

17. A method according to claim 14 , wherein said step of controlling the thrust of said interceptor vehicle includes the step of applying said desired interceptor vehicle thrust vector to an error detector for comparison with actual interceptor vehicle thrust.

18. A method according to claim 14 , wherein said step of controlling the thrust of said interceptor vehicle involves accelerating the interceptor vehicle in a direction perpendicular to said line-of-sight whereby acceleration tends to reduce apparent rotation in space of the line-of-sight as seen from the interceptor vehicle and puts the interceptor vehicle on an intercept course or trajectory immediately at the completion of nulling the rotation rate of the line-of-sight as seen at the interceptor vehicle.