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Would it ever be possible to make a device that could generate small,short gravitational waves? If so, it would then be possible to use artificial gravitation for space travel. Assuming that gravitational waves would be longitudinal -1st half of wave, slightly compressed space-time, to 2nd half, slightly rarified space-time. Were it possible, then with say 3 such devices focus these waves so that the rarified portions (sic) converge. Were that possible, you would then create a "pseudo-gravity" source. A vehicle could then "lift itself up by its own bootstraps." But could such a thing as a "gravitational wave generator" ever be built?