6.32 would also have required detailed knowledge of what would cause accelerations, torques, and mass concentrations within the colony.) Qualitatively, however, the ES group anticipated that the spin axis would wander around in unpredictable fashion. VI.5.4: The Shield Around the Hull: As described in Section VI.4.4, the ES group had decided to wrap a form-fitted, despun or slowly spun shield around the spinning hull with a minimum separation distance of 5 meters between the two. The relative (hull to shield) rim velocity was high (between 20.9 and 31.4 meters/sec if the shield were despun). Therefore, uncontrolled contact between hull and shield was unacceptable. Also, as stated in Section VI.4.5, the axis of symmetry of the colony had to point at the Sun. To meet these requirements, the ES group considered two methods, one based on a despun shield, the other on a slowly spun shield. VI.5.5: The Despun Shield Option: If the shield were not spun about its axis of symmetry, it could be set rotating about the q-axis as required by: 1) putting the shield's axis of symmetry in the plane of the ecliptic; 2) applying a torque about the q-axis to the shield until the rotation rate reached l.99lxl07 radian/sec; 3) leaving it alone. The third item above is significant. Once the shield had been set in motion, it would follow the required orbit with the desired once-per-sidereal-year rotation provided no unbalanced forces acted upon it. The ES group noted that if a force was applied to the hull by reacting with the shield,that reaction force, in turn, would require an external force on the shield to balance it or it would_move the shield out of its appointed behavior. It was felt that it would therefore be simpler to apply the external force directly to the hull rather than via the shield. The ES group decided to develop a system with no physical contact between hull and shield and no forces applied to the shield. This was called an "open bearing design".
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