6.28 where Hhull is the magnitude of the angular momentum vector ghull' Izhull is the moment of inertia about the z-axis, and whull is the angular velocity of the spin, we find: The range of whull is .209 to .314 (2 to 3 RPM). Corresponding to .75g psuedogravity, whull is .2712 radians/sec, leading to an estimate of 8hull' H = 2.87xlo 11 kg-m 2 /sec hull_ 75 g Rotating the spin axis of the hull around the q-axis requires precession. Precessing the hull without changing its rate of spin calls for a torque ~hull applied at right angles to ghull" To preprecess the hull's spin axis in the plane of the ecliptic requires that the torque ~hull be at right angles to the q-axis. This fixes the geometry of the system as shown in Figure 6.15. The vectors ghull and ~hull are in the plane of the ecliptic. The resultant precession vector ghull is in the q-axis direction indicating rotation about that axis. To precess through 2TT radians in one sidereal year (3.1558150 x10 7 sec), the magnitude of ghull must be (2) (3.14159) 3.1558150xl0 7 l.99lxlo7 radian/sec The equation governing the precession is: L =H S1 =I w S1 hull hull hull zhull hull hull Substituting the estimate I and the above value of S1hull' we find: zhull
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