Artificial Gravity

Hall, Theodore W. (2016 July). Artificial Gravity in Theory and Practice (ICES-2016-194)

notes from paper

The General Theory of Relativity (GTR) conceives gravity not as a force like the others, but rather as a curvature of space-time. Moreover, it holds that gravity and acceleration are equivalent, differing only as a matter of the frame of reference.

Centripetal acceleration, depicted in Figure 2, is always perpendicular to the velocity. It modifies the direction of the velocity, but not its magnitude. Because the force and velocity have no alignment (the projection of one onto the other is zero), the force does no work and consumes no energy. Once the rotation is brought up to some target value of rotations per minute (rpm), it’s self-sustaining through the conservation of energy and momentum. Rotating structures can also be placed in stable planetary orbits. This makes centripetal acceleration the only viable means of providing weight in space, apart from a planetary surface, for long durations.

Figure 5. Composite comfort chart, based on Hill and Schnitzer [1962], Gilruth [1969], Gordon and Gervais [1969], Stone [1973], and Cramer [1985]. The green central zone depicts conditions that all agreed are comfortable; the red periphery depicts conditions that all agreed are uncomfortable; the hues ranging through yellow and orange depict regions of disagreement.

Habitat designers can and should plan for the phenomenon and its effects, to aid the inhabitants’ adaptation – for example, by orienting tasks to avoid cross-coupling rotations, and by providing visual cues to keep inhabitants oriented to the habitat’s rotation [Hall, 1995; Hall, 2006; Ramsey, 1971].

Engineers have devoted many hours and pages of analysis to the design of artificial-gravity spacecraft, examining mass distributions, moments of inertia, structural stresses, rotating interfaces, and the dynamics of starting, stopping, and steering the rotation. Yet the design of the habitat itself has often been neglected or defaulted to “Earth-normal” gravitational concepts.

The ideal orientation of the module for the artificial-gravity climate would be horizontal, rather than vertical, with its axis parallel to the axis of rotation. Motion parallel to that axis doesn’t involve Coriolis acceleration. There would be straight walls on the east and west sides for workstations, allowing head pitch without cross-coupling with the spacecraft rotation.

Artificial Gravity, Visualization, Empathy and Design

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