S. Guatelli IEEE 2004 – NSS - Rome Dosimetry for Interplanetary Missions: the Geant4 REMSIM application S. Guatelli 1, P. Nieminen 2, M.G. Pia 1 IEEE NSS, October 2004, Rome, Italy Moon habitat 1. INFN Genova, Italy, 2. European Space Agency, ESTEC, The Netherlands Talk by S. Guatelli

S. Guatelli IEEE 2004 – NSS - Rome Vision AURORA human exploration of the Solar System  A project in the European AURORA programme for the robotic and human exploration of the Solar System Mars, the Moon and the asteroids as the most likely targets  The radiation hazard to crew is critical to the feasibility of interplanetary manned missions ● To protect the crew: – shielding must be designed, – the environment must be anticipated and monitored, – a warning system must be put in place Scope of the Geant4 REMSIM simulation First quantitative evaluation of the effects of space radiation environment on astronauts in vehicle concepts for interplanetary missions in vehicle concepts for interplanetary missions in planetary surface habitats in planetary surface habitats

S. Guatelli IEEE 2004 – NSS - Rome Outline  Modeling the interplanetary space radiation  Modeling the vehicle concepts and surface habitats  Modeling the physics interactions  Results  First quantitative dosimetry in vehicle and surface habitats

S. Guatelli IEEE 2004 – NSS - Rome Software process  The adoption of a rigorous software process guarantees reliability Essential for mission critical software application  Iterative and incremental approach First study to evaluate the conceptual possible solution First study to evaluate the conceptual possible solution  The Rational Unified Process (RUP) has been adopted as process framework Sound industrial standard Equivalent to ISO 15504, level 3 at least

S. Guatelli IEEE 2004 – NSS - Rome Strategy  Model of the radiation environment according to current standards  Geant4 based simulation for radiation effects  Dosimetric analysis in a phantom   Simplified geometrical configurations Essential Essential characteristics for dosimetric studies kept Vehicle concepts Surface habitats   Physics processes Electromagnetic physics + hadronic physics

S. Guatelli IEEE 2004 – NSS - Rome Space radiation environment  Selected space radiation components: – Galactic Cosmic rays ● Protons, α particles and heavy ions (C -12, O -16, Si - 28, Fe - 52) – Solar Particle Events ● Protons and α particles Envelope of CREME and CREME solar minimum spectra SPE particles: p and α GCR: p, α, heavy ions Envelope of CREME96 October 1989 and August 1972 spectra At 1 AU Worst case assumption for a conservative evaluation

S. Guatelli IEEE 2004 – NSS - Rome Vehicle concepts  New and alternative  New and alternative vehicle design with respect to hard shell Habitat: inflatable Habitation Module (K.J. Kennedy, NASA JSC, AIAA ) composed by a hard central core and an inflatable exterior shell transportation module to Mars waiting on orbit around Mars transport back to Earth The Geant4 geometry model retains the essential characteristics of the vehicle concept relevant for a dosimetric study Materials and thicknesses of the SIH by: V. Guarnieri, C. Lobascio, P. Parodi, R. Rampini – ALENIA SPAZIO,Torino, Italy SIH (Simplified Inflatable Habitat) is a multilayer consisting of:   MLI: external thermal protection blanket - Betacloth and Mylar   Meteoroid and debris protection - Nextel (bullet proof material) and open cell foam   Structural layer - Kevlar   Rebundant bladder Polyethylene, polyacrylate, EVOH, kevlar, nomex

S. Guatelli IEEE 2004 – NSS - Rome Surface Habitats  Example: surface habitat on the Moon  Cavity in the Moon soil + covering heap Engineering model by V. Guarnieri, C. Lobascio, P. Parodi, R. Rampini – ALENIA SPAZIO,Torino, Italy The Geant4 model retains the essential characteristics of the vehicle concept relevant for a dosimetric study Moon soil

S. Guatelli IEEE 2004 – NSS - Rome Physics processes Proton hadronic inelastic process Binary ApproachBertini approach Low Energy range Binary Cascade ( up to 10. GeV ) Bertini Cascade ( up to 3.2 GeV ) Intermediate energy range Low Energy Parameterised ( 8. GeV < E < 25. GeV ) Low Energy Parameterised ( 2.5 GeV < E < 25. GeV ) High energy range ( 20. GeV < E < 100. GeV ) Quark Gluon String Model   E.M. Physics Geant4 Low Energy Package for p, α, ions and their secondaries Geant4 Standard Package for positrons Validation of the Geant4 e.m. physics processes with respect to protocol data See: N42-1 Validation of Geant4 Electromagnetic Physics Versus Protocol Data   Hadronic Physics for protons and α as incident particles For protons two alternative approaches: Bertini and Binary Cascade in the intermediate energy range Precompound and nuclear deexcitation at low energy Quark Gluon String Models at high energy Set of Geant4 hadronic models covering the energy range of interest

S. Guatelli IEEE 2004 – NSS - Rome GCR p 2.15 cm al 4. cm al SIH +10. cm water SIH + 5 cm water SIH +10. cm water / polyethylene SIH + 5. cm water / polyethylene Energy deposit (MeV) with respect to the depth in the phantom (cm) GCR p SIH + no shielding SIH cm water / polyethylene shielding SIH + 5. cm water / polyethylene shielding 2.15 and 4. cm thick aluminum structure (conventional engineering design) Dosimetric analysis of SIH vehicle concept GCR particles vacuum air Phantom: water box Multilayer - SIH shielding Geant4 model Configurations The energy deposit is calculated for all the GCR components (p, α, C - 12, O - 16, Si - 28, Fe - 52 ions) SIH

S. Guatelli IEEE 2004 – NSS - Rome cm Preliminary ! e.m. physics e.m. + hadronic physics – bertini c. e.m. + hadronic physics – binary c. Dosimetric analysis of SIH vehicle concept Thicker layer of shielding limit the exposure of the astronaut to the GCR Water and polyethylene have the equivalent shielding behaviour The hadronic contribution to the dose calculation is relevant Calculation of the equivalent dose (mSv/day) with respect to the depth in the phantom (cm) Total equivalent dose in the phantom (mSv/day) with respect to the thickness of the shielding Fe - 52Si - 28 O - 16 C - 12 α p GCR (all ion components) Preliminary ! SIH + no shielding 2.15 cm Al 4. cm Al SIH + 5. cm water SIH cm water

S. Guatelli IEEE 2004 – NSS - Rome SPE shelter model Geant4 model   When SPE particles are detected by a warning system, the crew moves into the shelter vacuum air Multilayer (28 layers) Phantom Shelter vacuum SIH + 10 cm water GCR and SPE particles Total equivalent dose in the phantom given by GCR: 4.98 mSv/day – e.m. physics 7.83 mSv/day – e.m. + hadronic physics – bertini c mSv/day – e.m. + hadronic physics – binary c. Preliminary ! SPE energy deposit (MeV) in the phantom with respect to the depth (cm) SPE p SPE α SPE energy > 300 MeV Shelter SIH Geant4 model

S. Guatelli IEEE 2004 – NSS - Rome Dosimetry in surface habitats Add a log on top with variable height x x vacuum Moon soil GCR and SPE beam Phantom Total equivalent dose (mSv/day) in the phantom with respect to the roof thickness (m) e.m. physics e.m. + hadronic physics – bertini c. e.m. + hadronic physics – binary c. Energy deposit (MeV) given by SPE with respect to the depth in the phantom (cm) SPE with energy > 300 MeV Worst case (no roof) x = roof thickness - can vary between 0. m and 3. m 0.5 m 1.m 1.5 m 2.m 2.5 m 3. m Preliminary ! SPE p – no roof SPE α– no roof SPE p – 3.m thick roof SPE α – 3 m thick roof

S. Guatelli IEEE 2004 – NSS - Rome Conclusions  A first quantitative study has been performed in a set of vehicle and surface habitats  Simple geometrical configurations representing the essential features of vehicle concepts moon surface habitats  An innovative concept of Inflatable Habitat offers similar radioprotection behaviour as a conventional aluminum structure with significant engineering advantages  Water and polyethylene have equivalent shielding effects  Water shelter is effective in shielding dangerous SPE  A surface habitat built out of local material looks a possible solution thickness to be optimised  Preliminary dosimetric analysis to be further refined

S. Guatelli IEEE 2004 – NSS - Rome Thank you !