s. guatelli ieee 2004 – nss - rome dosimetry for interplanetary missions: the geant4 remsim...
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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
S. GuatelliS. Guatelli IEEE 2004 – NSS - Rome
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
S. GuatelliS. 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. GuatelliS. Guatelli IEEE 2004 – NSS - Rome
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
S. GuatelliS. Guatelli IEEE 2004 – NSS - Rome
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
S. GuatelliS. 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 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
S. GuatelliS. Guatelli IEEE 2004 – NSS - Rome
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
S. GuatelliS. 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. GuatelliS. Guatelli IEEE 2004 – NSS - Rome
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
S. GuatelliS. 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 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
S. GuatelliS. Guatelli IEEE 2004 – NSS - Rome
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
S. GuatelliS. 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 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
S. GuatelliS. Guatelli IEEE 2004 – NSS - Rome
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
S. GuatelliS. 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. GuatelliS. Guatelli IEEE 2004 – NSS - Rome
Thank you !