[1]

SYMPOSIUM ON SPACE RADIATION HEALTH: INTRODUCTORY REMARKS.  Paul Todd, Space Hardware Optimization Technology, Inc., Greenville, IN

   The field of space radiation health has recently been singled out as one of two major initiatives within the research programs of the U. S. National Aeronautics and Space Administration.  The goals of space radiation health research are to understand qualitatively and quantitatively the ionizing radiations present in the space environment, identify qualitatively and quantitatively the risks associated with these radiations, and discover countermeasures to mitigate these risks.  Speakers in the Symposium will address each of these three components of space radiation health research.   It is helpful to understand some of the quantities and definitions used in this field.  The SI unit of ionizing radiation dose is the Gray (1 Joule of energy loss in 1 kg of matter).  A typical human on earth in a “civilized” culture experiences less than 10^-3 Gy in a year; a cancer patient receives some 60 Gy in a treatment volume during a full course of therapy; and a total-body dose of about 2.5 Gy is the mean lethal dose for humans and many mammals.  Space radiations consist of energetic protons from the sun, protons and electrons from the sun that are trapped in the earth’s magnetic field, and cosmic rays that include energetic nuclei of H, He, C. N. O and Fe atoms..  All of these produce secondary radiations such as neutrons and gamma rays when they interact with matter.  The risks presented to space travelers by these radiations include cancer due to proton a cosmic-ray exposure, immune failure due to high-dose solar proton storms, and possible neurological effects caused by single tracks of cosmic-ray heavy nuclei.  Potential countermeasures include shielding (which increases spacecraft up-mass), medication consisting of radical scavengers (that must be taken immediately before exposure), anti-oxidant consumption (which must be maintained continuously), cytokines (which may ameliorate immune and hematological effects after exposure), and cell transplants (which must be isologous).