High-efficiency REA optimized stationkeeping
AssigneeLockheed Martin Corporation
InventorsNeil Evan Goodzeit, Santosh Ratan, Harald Juergen Weigl
Life of this patent
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Abstract
A velocity change (ΔV) thruster is operated on a spacecraft, which unavoidably causes attitude error. A reaction wheel (RWA) corrects the attitude. At the beginning of the thruster maneuver, the total attitude control momentum required to at least correct for the ΔV thruster attitude errors over the duration of the entire maneuver is determined, and the RWA momentum may also be determined. Attitude control thrusters (REAs) are operated. The REAs are operated to correct at least the net ΔV thruster induced attitude error, and preferably also to reset the RWA to its nominal momentum. The maneuver may be stationkeeping.
Claims8
A spacecraft, comprising:
- at least one ΔV thruster for producing thrust in a particular direction, the thrust of said at least one ΔV thruster being subject to thrust errors which tend to cause disturbance torques:
- at least one reaction wheel for counteracting said disturbance torques;
- at least one control thruster for torquing said spacecraft for thereby imparting momentum to said spacecraft;
- and
- control means coupled to said at least one control thruster and to said at least one reaction wheel, for (a) during a velocity change maneuver, predicting the total momentum change at the end of said velocity change maneuver attributable to said ΔV thruster, and (b) causing said at least one control thruster to operate during said velocity change maneuver to tend to null a momentum error which includes at least the predicted value of said total momentum change at the end of said velocity change maneuver which is attributable to said ΔV thruster.
A method for controlling the attitude and momentum of a spacecraft during a maneuver in which a ΔV thruster is operated, where operation of said ΔV thruster produces disturbance torques;
- operating a reaction wheel to tend to maintain the attitude of said spacecraft, whereby said reaction wheel tends to change momentum during the course of said ΔV maneuver;
- estimating said disturbance torques based on the rate of change of said reaction wheel momentum during some portion of the maneuver, to thereby determine a projected total momentum error attributable to said disturbance torques;
- and
- operating at least one momentum change thruster in response to a momentum error signal including said projected total momentum error attributable to said disturbance torques.
A spacecraft, comprising:
- at least one ΔV thruster for producing thrust in a particular direction, the thrust of said at least one ΔV thruster being subject to thrust errors which tend to cause momentum changes:
- at least one reaction wheel for attitude control of said spacecraft;
- at least one control thruster for torquing said spacecraft for thereby imparting momentum to said spacecraft;
- and
- control means coupled to said at least one control thruster and to said reaction wheel, for (a) during a velocity change maneuver, predicting the total momentum change at the end of said velocity change maneuver attributable to said ΔV thruster, and (b) causing said at least one control thruster to operate during said velocity change maneuver to tend to null a momentum error which includes at least said momentum change at the end of said velocity change maneuver which is attributable to said ΔV thruster.
Dependencies are inferred from the claim text.