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Solar particle events (SPE) are typically dominated by high-energy, low-linear energy transfer (LET) protons. Biological damage to astronauts during an SPE is expected to include a large contribution from high LET target fragments produced in nuclear reactions in tissue. We study the effects of nuclear reactions on integral LET spectra, behind typical levels of spacecraft and body shielding, for the historically largest flares using the high-energy transport code, BRYNTRN in conjunction with several biological damage models. The cellular track model of Katz provides an accurate description of cellular damage from heavy ion exposure. The track model is applied with BRYNTRN to provide an LET decomposition of survival and transformation rates for solar proton events.

An analytical prediction capability for space radiation in Low Earth Orbit (LEO), correlated with the Space Transportation System (STS) Shuttle Tissue Equivalent Proportional Counter (TEPC) measurements is presented. The model takes into consideration the energy loss straggling and chord length distribution of the detector, and is capable of predicting energy deposition fluctuations in a micro-volume by incoming ions through direct events. The charged particle transport calculations correlated with STS 56, 51, 110 and 114 flights are accomplished by using the most recent version (2005) of the Langley Research Center (LaRC) deterministic ionized particle transport code High charge (Z) and Energy TRaNsport (HZETRN) which has been extensively verified with laboratory beam measurements and available space flight data.