Spacecraft operable in two alternative flight modes
AssigneeSpace Industries, Inc.
InventorsCaldwell C. Johnson, Maxime A. Faget, David J. Bergeron, III
Life of this patent
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Abstract
A spacecraft is adapted for orbital flight in two alternative modes, referred to as the earth-oriented and quasi sun-oriented modes. The spacecraft comprises a spacecraft body, at least one solar array extendible outwardly from the spacecraft body, passive attitude control means utilizing gravity gradient stabilization means which is extendible and retractable relative to the spacecraft body, and active attitude control means. The gravity gradient stabilization means is effective when extended to stabilize the spacecraft in the earth-oriented mode, and the active attitude control means is effective to stabilize the spacecraft in the quasi sun-oriented mode.
Claims21
A spacecraft adapted for orbital flight in two alternative modes, one of said modes being an earth-oriented mode, and the other of said modes being a quasi sun-oriented mode, said spacecraft comprising:
- a spacecraft body;
- at least one solar array extendible outwardly from the spacecraft body;
- passive attitude control means utilizing gravity gradient stabilization means which is extendible and retractable relative to the spacecraft body;
- and
- active attitude control means comprising means for sensing the spacecraft attitude and means operable in response to outputs from said attitude sensing means for producing attitude control torques;
- said gravity gradient stabilization means when extended being effective to stabilize the spacecraft in the earth-oriented mode, and said active attitude control means being effective to stabilize the spacecraft in the quasi sun-oriented mode.
A spacecraft adapted for orbital flight in two alternative modes, a first of said modes being characterized by unequal moments of inertia about two orthogonal axes of the spacecraft lying in the orbital plane, and a second of said modes being characterized by substantially equal moments of inertia about the same two orthogonal axes of the spacecraft, said spacecraft comprising:
- a spacecraft body having three orthogonal axes x, y, and z;
- at least one solar array extendible outwardly from and rotatable about a point on the spacecraft body which is generally along the y axis;
- gravity gradient stabilization means which is extendible and retractable relative to the spacecraft body generally parallel to the x axis;
- said spacecraft being characterized by moments of inertia I.sub.xx, I.sub.yy, and I.sub.zz about the axes x, y, and z, respectively;
- said gravity gradient stabilization means being extendible or retractable and said solar array being rotatable in said first orbital flight mode to a first position in which I.sub.zz >I.sub.yy >I.sub.xx and to a second position in which I.sub.yy >I.sub.zz >I.sub.xx , and in said second orbital flight mode to a first position in which I.sub.zz >I.sub.yy .congruent.I.sub.xx and to a second position in which I.sub.yy >I.sub.zz .congruent.I.sub.xx.
An attitude control method for controlling the orbital flight of a spacecraft in two alternative flight modes, (1) a first mode being an earth-oriented mode in which the first orthogonal axis of the spacecraft is substantially aligned with the local vertical, the second orthogonal axis is substantially in a direction tangent to the orbital flight path, and the third orthogonal axis is substantially normal to the orbital plane, and (2) a second mode being a quasi sun-oriented mode in which two of the orthogonal axes of the spacecraft lie substantially in the orbital plane, one of these two axes is substantially normal to the direction of solar radiation, and the third orthogonal axis is substantially normal to the orbital plane wherein said spacecraft comprises a spacecraft body;
- at least one solar array extendible outwardly from the spacecraft body;
- passive attitude control means utilizing gravity gradient stabilization means which is extendible and retractable relative to the spacecraft body;
- and active attitude control means;
- said attitude control method comprising:
- stabilizing the spacecraft in an earth-oriented mode during a first period of time by extending or retracting the gravity gradient stabilization means;
- and
- stabilizing the spacecraft in a quasi sun-oriented mode during a second period of time using the active attitude control means.
An attitude control method for controlling the orbital flight of a spacecraft in two alternative flight modes, a first of said modes being characterized by unequal moments of inertia about two orthogonal axes of the spacecraft lying in the orbital plane, and a second of said modes being characterized by substantially equal moments of inertia about the same two orthogonal axes of the spacecraft, wherein said spacecraft comprises a spacecraft body having three orthogonal axes x, y, and z;
- at least one solar array extendible outwardly from and rotatable about a point on the spacecraft body which is generally along the y axis;
- and gravity gradient stabilization means which is extendible and retractable relative to the spacecraft body generally along the x axis;
- said spacecraft being characterized by moments of inertia I.sub.xx, I.sub.yy, and I.sub.zz about the axes x, y, and z, respectively;
- said attitude control method comprising:
- during a first period of time, extending or retracting the gravity gradient stabilization means and rotating the solar array to a first position in which I.sub.zz >I.sub.yy >I.sub.xx or to a second position in which I.sub.yy >I.sub.zz >I.sub.xx to maintain the spacecraft in the first flight mode;
- and
- during a second period of time, extending or retracting the gravity gradient stabilization means and rotating the solar array to a first position in which I.sub.zz >I.sub.yy .congruent.I.sub.xx or to a second position in which I.sub.yy >I.sub.zz .congruent.I.sub.xx to maintain the spacecraft in the second flight mode.
Dependencies are inferred from the claim text.