ieee nss, october 2004, rome, italy

S. GuatelliS. Guatelli IEEE 2004 – NSS - Rome

Dosimetry for Dosimetry for Interplanetary Missions:Interplanetary Missions:the Geant4 REMSIM the Geant4 REMSIM applicationapplication

S. GuatelliS. Guatelli11, P. Nieminen, P. Nieminen22, M.G. , M.G. PiaPia11

IEEE NSS, October 2004, Rome, Italy

Moonhabitat

[email protected]/geant4/space/remsim

1. INFN Genova, Italy, 2. European Space Agency, ESTEC, The Netherlands

Talk by S. Guatelli


Vision A project in the European AURORAAURORA programme for the robotic and

human human exploration of the Solar Systemexploration 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 Scope of the Geant4 REMSIM simulationREMSIM simulation

First quantitative evaluation of the effects of space radiation First quantitative evaluation of the effects of space radiation environment on astronautsenvironment on astronauts

• in vehicle concepts for interplanetary missionsin vehicle concepts for interplanetary missions• in planetary surface habitats in planetary surface habitats


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


Software processSoftware process

The adoption of a rigorous software process guarantees reliability• Essential for mission critical software application

Iterative and incremental approachIterative and incremental approach• First study to evaluate the conceptual possible solutionFirst 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


Strategy

Model of the radiation environment according to Model of the radiation environment according to current standardscurrent standards

Geant4 based simulation for radiation effects Geant4 based simulation for radiation effects

Dosimetric analysis in a phantom Dosimetric analysis in a phantom

Simplified geometrical configurations

EssentialEssential characteristics for dosimetric studies kept

Vehicle concepts

Surface habitats

Physics processesElectromagnetic physics

+ hadronic physics


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 CREME96 1977 and CREME86 1975 solar minimum spectra

SPE particles: p and α

GCR: p, α, heavy ions

Envelope of CREME96 October 1989 and August 1972 spectra

At 1 AUAt 1 AU

Worst case assumption for a Worst case assumption for a conservative evaluationconservative evaluation


Vehicle concepts

New and alternativeNew and alternative vehicle design with respect to hard shell Habitat: inflatable Habitation Module (K.J. Kennedy, NASA JSC, AIAA 2002-6105)

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


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


Physics processes

Proton hadronic inelastic process

Binary Approach Bertini approach

Low Energy rangeBinary 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 ModelQuark 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 dataSee: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


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 Energy deposit (MeV) with respect to the depth in the phantom (cm)in the phantom (cm)

GCR p

• SIH + no shielding

• SIH + 10. 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

ConfigurationsConfigurations

The energy deposit is calculated for all the GCR The energy deposit is calculated for all the GCR components (p, components (p, αα, C - 12, O - 16, Si - 28, Fe - 52 ions), C - 12, O - 16, Si - 28, Fe - 52 ions)

SIH


cm

Preliminary !

e.m. physicse.m. physics

e.m. + hadronic physics – bertini ce.m. + hadronic physics – bertini c..

e.m. + hadronic physics – binary 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) Calculation of the equivalent dose (mSv/day) with respect to the depth in the phantom (cm)with respect to the depth in the phantom (cm) Total equivalent dose in the phantom (mSv/day) Total equivalent dose in the phantom (mSv/day)

with respect to the thickness of the shieldingwith respect to the thickness of the shielding

Fe - 52 Si - 28

O - 16 C - 12 α

pGCR (all ion components)

Preliminary !Preliminary !

SIH + no shielding

2.15 cm Al

4. cm Al

SIH + 5. cm water

SIH + 10. cm water


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 SPEparticles

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.

• 7.41 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


Dosimetry in surface habitats

Add a log on top with variable height x

x

vacuum Moonsoil

GCR and SPE beam

Phantom

Total equivalent dose (mSv/day) in the phantom

with respect to the roof thickness (m)

e.m. physicse.m. physics

e.m. + hadronic physics – bertini ce.m. + hadronic physics – bertini c..

e.m. + hadronic physics – binary 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.m1.5 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


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


Thank you !

ieee nss, october 2004, rome, italy

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