Low energy method for changing the inclinations of orbiting satellites using weak stability boundaries and a computer process for implementing same

• US 6,097,997 A
• Filed: 05/06/1999
• Issued: 08/01/2000
• Est. Priority Date: 03/25/1997
• Status: Expired due to Fees

• Current Assignee: Galaxy Development LLC
• Original Assignee: Galaxy Development LLC
• Inventors: Belbruno, Edward A.
• Primary Examiner(s): Zanelli, Michael J.
• Assistant Examiner(s): Gibson, Eric M
• Application Number:
  US09/304,265
• Time in Patent Office: 453 Days
• Field of Search: 701/13, 701/226, 244/158 R
• US Class Current: 701/13
• CPC Class Codes: B64G 1/242 Orbits and trajectories
• CPC Class Codes: B64G 1/2427 Transfer orbits
• CPC Class Codes: B64G 1/247 Advanced control concepts for autonomous, robotic spacecraft, e.g. by using artificial intelligence, neural networks or autonomous agents

Abstract

When a satellite is orbiting the earth in an elliptic orbit, it has a certain inclination with respect to the earth'"'"'s equator. The usual way to change the inclination is perform a maneuver by firing the rocket engines at the periapsis of the ellipse. This then forces the satellite into the desired inclination. There is a substantially more fuel efficient way to change the inclination. This is done by an indirect route by first doing a maneuver to bring the satellite to the moon on a BCT (Ballistic Capture Transfer). At the moon, the satellite is in the so called fuzzy boundary or weak stability boundary. A negligibly small maneuver can then bring it back to the earth on a reverse BCT to the desired earth inclination. Another maneuver puts it into the new ellipse at the earth. In the case of satellites launched from Vandenberg AFB into LEO in a circular orbit of an altitude of 700 km with an inclination of 34°, approximately 6 km/s is required to change the inclination to 90°. This yields a savings of approximately 13% in Delta-V as compared to the standard approach which could translate into a significant increase of payload or perhaps a smaller launch vehicle. This may have applications to commercial satellite launches for the Iridium or Teledesic networks and others.

Claims

1. A method of changing an inclination of an object by generating a combination operational ballistic capture transfer (BCT) for the object emanating substantially at earth or earth orbit to arrive at a weak stability boundary (WSB) or WSB orbit at or near the moon or moon orbit and generating an operational ballistic ejection transfer (BET) for the object emanating at the WSB or the WSB orbit to return to the earth or the earth orbit, using a computer implemented process, comprising the steps of:

(a) implementing a forward targeting process by varying velocity magnitude V_E, and flight path angle γ

_E for convergence of first target variables at the WSB or the WSB orbit, the first target variables including radial distance, r_L, and inclination i_L ;

(b) iterating step (a) until sufficient convergence to obtain the operational ballistic capture transfer from the earth or the earth orbit to a weak lunar capture in the WSB or the WSB orbit;

(c) performing an inclination change at the WSB or the WSB orbit;

(d) implementing the forward targeting process by varying velocity magnitude V_L, and flight path angle γ

_L for convergence of second target variables at the earth or the earth orbit from the WSB or the WSB orbit, the second target variables including radial distance, r_E, and inclination i_E including the inclination change performed in step (c); and

(e) iterating step (d) until sufficient convergence to obtain the operational ballistic ejection transfer from the WSB or the WSB orbit to the earth or the earth orbit at the inclination change.

2. A method changing an inclination according to claim 1, wherein the forward targeting process is a second order Newton algorithm.

3. A method according to claim 2, wherein the second order Newton algorithm utilizes two control variables including the velocity magnitude V_E, and the flight path angle γ

_E, and two target variables including the radial distance, r_L, and the inclination i_L.

4. A method according to claim 1, wherein the forward targeting process is a second order Newton algorithm and utilizes two control variables including the velocity magnitude V_E, and the flight path angle γ

_E that are varied to achieve weak stability boundary (WSB) conditions at the moon or the moon orbit using the two target variables including the radial distance, r_L, and the inclination i_L.

5. A method according to claim 1, wherein the velocity magnitude V_E, and the flight path angle γ

_E are decoupled from the moon or the moon orbit in the method of generating operational ballistic capture transfer.

6. A method according to claim 5, wherein the decoupling of the velocity magnitude V_E, and the flight path angle γ

_E provides control of radial distance r_E, inclination i_E, and node Ω

_E at the earth or the earth orbit.

7. A method according to claim 1, wherein the velocity magnitude V_E, and the flight path angle γ

_E are decoupled from angular earth elements including inclination i_E, ascending node relative to earth Ω

_E, and argument of periapsis relative to earth ω

_E, in the method of generating operational ballistic capture transfer.

8. A method according to claim 1, wherein ω

_E is adjusted via at least one of variation of earth injection date (I/D), use of contours, and inclusion of a maneuver.

9. A method according to claim 1, further comprising the steps of:

transforming converged values of V_E, γ

_E into classical elements;

transforming the classical elements to spherical coordinates, wherein the spherical coordinates include the converged values of V_E, γ

_E, and longitude α

_E, latitude δ

_E, flight path azimuth/angle with vertical σ

_E are changed.

10. A method according to claim 1, wherein step (a) comprises the step of entering the parameters including the velocity magnitude V_E, the flight path angle γ

_E using contours to facilitate initial selection of the parameters for said method of generating operational ballistic capture transfer.

11. A method according to claim 1, wherein step (a) comprises the step of entering the parameters using an initial guess in spherical, flightpath coordinates to facilitate initial selection of the parameters for said method of generating operational ballistic capture transfer.

12. A method according to claim 1, further comprising the steps of:

transforming converged values of V_L, γ

_L into classical elements;

transforming the classical elements to spherical coordinates, wherein the spherical coordinates include the converged values of V_L, γ

_L, and longitude α

_L, latitude δ

_L, flight path azimuth/angle with vertical σ

_L are changed.

13. A method according to claim 1, wherein the velocity magnitude V_L, and the flight path angle γ

_L are decoupled from angular earth elements including inclination i_L, ascending node relative to earth Ω

_L, and argument of periapsis relative to earth ω

_L, in the method of generating operational ballistic capture transfer.

14. A method of changing at least one of an inclination and an altitude of an object including at least one of a space vehicle, satellite and rocket by generating a combination operational ballistic capture transfer (BCT) for the object emanating substantially at earth or earth orbit to arrive at a weak stability boundary (WSB) or WSB orbit at or near the moon or moon orbit and generating an operational ballistic ejection transfer (BET) for the object emanating at the WSB or the WSB orbit to return to the earth or the earth orbit, using a computer implemented process, comprising the sequential or non-sequential steps of:

(a) generating the BCT using a forward targeting process by varying velocity magnitude V_E, and flight path angle γ

_E for convergence of first target variables at the WSB or the WSB orbit, the first target variables including radial distance, r_L, and inclination i_L ;

(b) traveling from the earth or the earth orbit to a weak lunar capture in the WSB or the WSB orbit using the operational ballistic capture transfer;

(c) optionally performing an inclination change at the WSB or the WSB orbit;

(d) generating the BET using the forward targeting process by varying velocity magnitude V_L, and flight path angle γ

_L for convergence of second target variables at the earth or the earth orbit from the WSB or the WSB orbit, the second target variables including radial distance, r_E, and inclination i_E optionally including the inclination change performed in step (c); and

(e) traveling from the WSB or the WSB orbit to the earth or the earth orbit at a predetermined arbitrary altitude using the operational ballistic ejection transfer.

15. A method according to claim 14, wherein at least one of the operational ballistic capture transfer and the operational ballistic ejection transfer are dynamically generated in the at least one of the space vehicle, the satellite, and the rocket.

16. A method according to claim 14, wherein at least one of the operational ballistic capture transfer and the operational ballistic ejection transfer are dynamically generated in a central controller remote from the space vehicle or the rocket.

17. A navigational system for changing at least one of an inclination and an altitude of an object including at least one of a space vehicle, satellite and rocket by generating a combination operational ballistic capture transfer (BCT) for the object emanating substantially at earth or earth orbit to arrive at a weak stability boundary (WSB) or WSB orbit at or near the moon or moon orbit and generating an operational ballistic ejection transfer (BET) for the object emanating at the WSB or the WSB orbit to return to the earth or the earth orbit, using a computer, wherein the computer implements the sequential or non-sequential functions of:

(a) generating the BCT using a forward targeting process by varying velocity magnitude V_E, and flight path angle γ

_E for convergence of first target variables at the WSB or the WSB orbit;

(b) generating the BET using the forward targeting process by varying velocity magnitude V_L, and flight path angle γ

_L for convergence of second target variables at the earth or the earth orbit from the WSB or the WSB orbit; and

(c) navigating the object from the earth or the earth orbit to a weak lunar capture in the WSB or the WSB orbit using the operational ballistic capture transfer, and navigating the object from the WSB or the WSB orbit to the earth or the earth orbit at a predetermined arbitrary altitude using the operational ballistic ejection transfer.

18. A computer program memory, storing computer instructions to generate an operational ballistic capture transfer for an object emanating substantially at earth or earth orbit to arrive at the moon or moon orbit using a computer, the computer instructions including:

(a) generating a forward targeting process by varying velocity magnitude V_E, and flight path angle γ

_E for convergence of first target variables at a weak stability boundary WSB or a WSB orbit, the first target variables including radial distance, r_L, and inclination i_L ;

(b) iterating step (a) until sufficient convergence to obtain the operational ballistic capture transfer from the earth or the earth orbit to a weak lunar capture in the WSB or the WSB orbit;

(c) generating the forward targeting process by varying velocity magnitude V_L, and flight path angle γ

_L for convergence of second target variables at the earth or the earth orbit from the WSB or the WSB orbit, the second target variables including radial distance, r_E, and inclination i_E ; and

(e) iterating step (d) until sufficient convergence to obtain the operational ballistic ejection transfer from the WSB or the WSB orbit to the earth or the earth orbit at the inclination change.

19. A method of changing at least one of an inclination and an altitude of an object including at least one of a space vehicle, satellite and rocket, using a computer implemented process, comprising the sequential or non-sequential steps of:

(a) generating a ballistic capture transfer (BCT) using a forward targeting process by varying velocity magnitude V_E, and flight path angle γ

_E, for convergence of first target variables at a weak stability boundary WSB or the WSB orbit;

(b) traveling from the earth or the earth orbit to a weak lunar capture in the WSB or the WSB orbit using the operational ballistic capture transfer;

(c) optionally performing an inclination change at the WSB or the WSB orbit;

(d) generating a ballistic ejection transfer (BET) using the forward targeting process by varying velocity magnitude V_L, and flight path angle γ

_L for convergence of second target variables at the earth or the earth orbit from the WSB or the WSB orbit; and

(e) traveling from the WSB or the WSB orbit to the earth or the earth orbit at a predetermined arbitrary altitude using the operational ballistic ejection transfer.