Life Sciences in the Space Program 



work is progressing on correlating measurements of the electromagnetic emissions 

 and the time course of the initial parts of the event to the eventual absolute 

 magnitude of the event. Finally, efforts to determine accurately all aspects of SPE's 

 are made difficult by the effect of the Earth's magnetic field on the protons and 

 heavier ions emitted. 



Characterization of the galactic cosmic rays shares many of the same problems as 

 the SPE's, namely the effect of the Earth's magnetic field and the need to 

 determine both the spectral distribution and the ion species profile. However, 

 GCR is isotropic and continuous, though the magnitude is affected by the solar 

 cycle. Because HZE particles are not common on Earth, instrumentation adequate 

 to measure them was not developed as early as for the lower LET components of 

 space radiation. 



Shielding 



The interaction of electrons with matter and the production of bremsstrahlung 

 have been well understood as a result of work in the medical field. The transport 

 of protons and HZE particles in matter has been studied only since the 

 development of particle accelerators. Early accelerators produced just protons and 

 helium nuclei at the energies of interest in space research, and it was not until the 

 1970's that an accelerator (the Bevalac at Lawrence Berkeley Laboratory) was devel- 

 oped capable of producing heavier particles at energies similar to those found in 

 GCR. Research in these areas has been led primarily by nuclear and atomic 

 physicists. More recently, NASA's experience in space and the medical applications 

 of charged particle beams have spurred work in charged particle transport. 



The work in this area has proceeded along both theoretical and experimental 

 lines. Measurements at accelerators and reactors, as well as in space, have yielded 

 much information on radiation interactions in matter. Theoretically, research is 

 progressing on combining the measured data with physics theory into models 

 capable of predicting the type, magnitude, and distribution of energy deposition, 

 the nuclear interactions between incoming radiation and target nuclei that produce 

 secondary radiation, and the spatial distribution of both primary and secondary 

 radiation. Radiation transport computer codes are currently used in evaluating 

 mission design parameters and evaluating radiation risks. They reflect, of course, 

 the uncertainties in the measured radiation fields mentioned above, as well as in 

 the theoretical aspects. The transport ot 11/1 particles is particularly uncertain. 

 owing to the relative newness of the field and the lack of data for many ion 

 irs at a range of energies. 



logical Effects 



s of radiation on humans is the research area fraught with the most 

 es. This is the result of a number of factors, such as the difficulty of 

 nts in complex organisms, the fact that humans cannot be used in 



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