Pre-engineering spaceflight validation of environmental models and the 2005 HZETRN simulation code

Abstract

The HZETRN code has been identified by NASA for engineering design in the next phase of space exploration highlighting a return to the Moon in preparation for a Mars mission. In response, a new series of algorithms beginning with 2005 HZETRN, will be issued by correcting some prior limitations and improving control of propagated errors along with established code verification processes. Code validation processes will use new/improved low Earth orbit (LEO) environmental models with a recently improved International Space Station (ISS) shield model to validate computational models and procedures using measured data aboard ISS. These validated models will provide a basis for flight-testing the designs of future space vehicles and systems of the Constellation program in the LEO environment.

Comparison of the transport codes HZETRN, HETC and FLUKA for galactic cosmic rays

“…HZETRN is a deterministic computer code which has been used for radiation analysis under a variety of shielding conditions in analyzing solar particle event (SPE), galactic cosmic ray (GCR), and low earth orbit (LEO) trapped proton environments. While the code has endured several rounds of verification and validation in these environments (Wilson et al, 1995(Wilson et al, , 2005Nealy et al, 2007), most of the comparisons have focused on integrated quantities, such as dose (D) and individual ion fluences were not examined in detail. Though dose or dose equivalent were generally viewed as sufficient tests for evaluating code accuracy, recent interest in fluence based approaches to radiation risk assessment demand a higher degree of accuracy from the code (Cucinotta et al, 2006).…”

Comparison of the transport codes HZETRN, HETC and FLUKA for a solar particle event

“…While the code has endured several rounds of verification and validation in 0273-1177/$36.00 Published by Elsevier Ltd. on behalf of COSPAR. doi:10.1016/j.asr.2010.11.012 these environments Nealy et al, 2007;Wilson et al, 1995), most of the comparisons focused on integrated quantities, such as dose or dose equivalent, and individual ion fluences were not examined in detail. Though dose or dose equivalent were generally viewed as sufficient tests for evaluating code accuracy, recent interest in fluence based approaches to radiation risk assessment demand a higher degree of accuracy from the code .…”

The Martian surface radiation environment – a comparison of models and MSL/RAD measurements

“…Parts of these discrepancies could be explained by differences in the solar modulation of the GCR. Also, Simonsen et al (1990) and Townsend et al (2011) have used different models for the primary GCR spectra, CREME (Adams et al 1981) and Badhwar-O'Neil 2006(O'Neill 2006, and the transport, BRYNTRN (Wilson et al 1989) and an older version of HZTREN (Nealy et al 2007). Unfortunately, in retrospect it is impossible to disentangle the influences of the different factors from the results and what could have led to the observed discrepancies.…”