Neutral buoyancy is not identical to weightlessness. SpaceShipTwo's planned trajectory would achieve a suborbital journey with a short period of weightlessness. Graveline authored ten professional publications and reports on biological deconditioning and weightlessness countermeasures. WK2 will provide preview flights offering several seconds of weightlessness before the suborbital event. Some conditions, such as weightlessness and cosmic radiation, could not be simulated. Parabolic flights are sometimes used to examine the effects of weightlessness on a living organism. The interplay of acceleration due to the trampoline and weightlessness becomes apparent. It is related to motion sickness, and arises as the vestibular system adapts to weightlessness. He planned to conduct experiments regarding the effects of weightlessness on fluids. Sex in space is human sexual activity in the weightlessness of outer space. Even Galileo had accepted the weightlessness of air as a simple truth. The Space Age created new human factors issues such as weightlessness and extreme g-forces. A major effect of long-term weightlessness involves the loss of bone and muscle mass. Leonov had spent eighteen months undergoing weightlessness training for the mission. Because of the weightlessness in space, the chips disperse and clog the instruments.