The specific mechanisms underlying inadequate total peripheral resistance observed during postflight orthostatic stress should be determined. Current antiorthostatic countermeasures should be reevaluated to refine those that offer protection and eliminate those that do not. Studies should avoid confounding effects of multiple, simultaneous interventions unless data support these combinations. Appropriate methods for referencing intrathoracic vascular pressures to systemic pressures in microgravity should be identified and validated, given the observed changes in cardiac and pulmonary volume and compliance. The biological effects of exposure to radiation in space pose potentially serious health effects for crew members that must be controlled or mitigated before initiation of long-term missions beyond low Earth orbit.
High priority is given to the following.
Determine if exposure to heavy ions at the level that would occur during deep-space missions of long duration poses a risk to the integrity and function of the central nervous system. Determine how the selection and design of the space vehicle affect the radiation environment in which the crew has to exist. Determine whether combined effects of radiation and stress on the immune system in spaceflight could produce additive or synergistic effects on host defenses. The immune system has close interactions with the neuroendocrine system. Results of these studies indicate a close association between alterations in status of the immune system and the state of the neuroendocrine system of the host.