THE INTERDEPENDE%NCE OF MANNED SPACECRAFT DESIGN AND RADIATION SHIELDING

The shielding requirements for an orbit 500 km above the earth's surface were determined from data presently available. It is pointed out that shielding a space vehicle for human occupancy depends upon many factors such as orbit and length of time in that orbit. The allowable radiation exposure of the occupants and the weight of the vehicle must receive primary consideration. Available data are reviewed for range-energy relationships of all radiations known to be encountered in space. The shielding properties of various materials are reviewed, and the relative merits of Al and Pb are considered in detail. It is concluded that shielding against protons presents the main problem. Calculations were made of the average radiation path length for high-energy protons or heavy particles through an average man, assuming that the man has the stopping power of water. A value of 50 cm was obtained, and it is shown graphically that all protons of energy equal to or less than 300 Mev will be completely absorbed by the average man. It is concluded that if sufficient shieiding is provided to absorb 52-Mev protons in those regions of a space vehicle where the astronauts will spend most of the time in orbit,more » and provided the radiation flux is no higher than is believed at present, there is no reason why a 4-week flight is not possible from a radiation hazard viewpoint. It is pointed out that solar flares remain the greatest unknown. The need is stressed for a handbook showing the attenuation, degradation, and transmission of the several types of radiation through a variety of structural materials as functions of thickness, and for the breakdown of the number of particles per unit energy interval as a function of energy. ( C.H.)« less