Space Radiation Superconductive Shield (SR2S) is an EU funded FP7 project which is researching new technology to protect astronauts in space from radiation. On 9th April 2014 in Torino, Italy, SR2S held their first conference to give an update on the project so far. For more information visit: www.sr2s.eu Twitter - @SR2SMars

1. Radiation Environment and
Geant4/GRAS Simulations in SR2S
April 9th, 2014
Martina Giraudo
Marco Vuolo

2. • SR2S introductory VIDEO
• Space radiation Environment
• HZE biological effects
• TAS-I simulation framework
• Simulated Environment
• Geometrical Model
• Simulation Plan & Future Works
Summary

3. SR2S Introductory Video

4. • Cancer risk caused by radiation exposure is
the main obstacle to interplanetary travel
– No simple and effective countermeasures
– Significant uncertainties
• Possible solutions:
– Optimization of space missions length
– MITIGATION MEASURES: SHIELDING and biological
countermeasures
Introduction

5. Space Radiation in Deep-Space
• Space radiation hitting the crew: HZE, primary
protons and secondary protons, neutrons, and
recoil nuclei
• Secondary particles produced as radiation
interacts with matter
• Whole body doses of 1 to 2 mSv/day
accumulated in interplanetary space
Two main components : SPE & GCR

6. Solar particle events (SPEs)
• Mainly energetic protons,
helium nuclei and heavier
nuclei
• Highest intensity at solar
maximum
• Relative short fluxes of
particles
• Energies from 1 to 100 MeV
• Not currently predictable
• Easily shielded by passive
and active shields
Galactic cosmic rays (GCR)
• Continuous source
• Energies ranging from ~10
MeV n-1 to ~ 1012 MeV n-1
• High-LET radiation
• Biological effects poorly
known
• Most significant deep-space
missions radiation hazard
• Modulated by the Sun cycle
• Not easily shielded
Space Radiation in Deep-Space

7. Deep Space Effective Dose Estimations
• When considering passive
shielding option:
– SPE easily shielded
– GCR requires enormous mass to
be shielded because of high
energies and secondary radiation
• Mission at solar maximum
• Thick shielding:
– Mass problems to spacecraft
launch systems
– Bad GCR effective dose reduction
Current shield approach:
NOT a solution
Annual GCR Effective doses or NASA
Effective dose in deep space vs. depth of
shielding for males. Values for solar
minimum and maximum are shown

8. Radiation Biological Risk to the Crew
• Carcinogenesis (morbidity and
mortality risk)
• Acute Radiation Risks – sickness or
death
• Acute and Late Central Nervous System
(CNS) risks
• Chronic & Degenerative Tissue Risks
Differences in biological damage of heavy
nuclei vs x-rays Earth-based data New
knowledge on risks must be obtained
CONTROL
IRON IRRADIATED
OxidativestressisincreasedinMouseHippocampus9
monthsafter2Gyof56Feirradiation

9. HZE effects vs low-LET radiation effects
• HZE produce densely ionizing tracks of
damage
• Complex DNA breaks, “clusters”
containing mixtures of more kinds of
damage
– Poor damage repair
– Cell death more frequent
“Cancer risk from exposure to galactic cosmic rays: implications for space
exploration by human beings” Francis A Cucinotta, Marco Durante

10. • Drugs
– applicable for extended period of time and suitable for high-LET radiation
– no significant side effects, including those on behavior
– stable chemical composition (easy handling and storage)
– better if suitable for oral administration and rapidly absorbed and distributed
throughout the body
• Dietary supports
– Space environmental factors leading to increased oxidative stress
deployment of antioxidant capacity in astronauts
– antioxidant rich diet decreased risk of several diseases, cancer included
– Possible antioxidant radioprotectors: vitamin E and C, melatonin and selenium
• Appropriate crew selection
Biological Countermeasures

11. SR2S Geant4/GRAS simulation
• Simulation framework
• Environment models
• Geometrical model
– Coils & cables
– Mechanical structures
– Habitat
– Detectors
• Simulation plan

12. TAS-I Monte Carlo Simulation Framework
Simulations are simultaneously
run on different processors
Results are saved in ROOT
histogram for post processing
Geant4 Radiation Analysis for
Space
MC toolkit for the simulation of
interaction of particles in matter

13. • GCR
– CRÈME96
– Solar minimum condition
– No Scaling factor: variation from 1 AU to Mars Orbit is negligible for
SR2S scope (see new measurements from MER and MSL missions)
• SPE
– SUPERFLARE fluence
• CREME86 (M11 - M1) representative of period 1955 to 1972 (as envelope
of events of Feb ‘56 and Aug ‘72) composite worst case (hour) flare flux
and mean ions composition;
• OMERE worst hours flare fluxes of: Oct ‘89, Jul ‘00, Oct ’03
– Average flux on 1 year interplanetary mission
• ESP model @ 99% confidence level
• TRAPPED PARTICLES: neglected in SR2S
Modeled Environment

14. • Compromise between accuracy of the
geometrical details and computational time
– Complex geometries simplified to obtain
homogeneous Geant4 materials with average
elemental compositions
– Habitat modeled using average values of thickness
and density
– Mechanical structures simplified
Geometric Model

15. Geometric Model: Mechanical Structures Materials
Solid Hydrogen equivalent mass
Structural Titanium equivalent mass
Fuel Tank
Second Columbus module

16. Geometric Model: Mechanical Structure & SC Cable
Titanium
Bars
Ti equivalent
in mass
Solid
Hydrogen
• In this way computational time is saved and no
significant accuracy is lost
• As soon as the mechanical structure is finalized
the geometry GDML files will be easily updated.

17. SR2S Toroidal Configuration: Sectoring Analysis
Detector

18. ICRU SPHERE
Used Detectors: ICRU Sphere in
three different positionICRU Sphere structure and composition:
BFO 2 mm
SKIN 2mm150 mm
100 mm
Skin G4_SKIN_ICRP*
Body G4_TISSUE_SOFT_ICRU-4*
BFO G4_TISSUE_SOFT_ICRU-4*
Organs G4_TISSUE_SOFT_ICRU-4*
*http://geant4.web.cern.ch/geant4/UserDocumentation/Use
rsGuides/ForApplicationDeveloper/html/apas08.html

19. Magnetic Field Configuration
120 CoilsBmax= 3.53 T
BL= 7.47 Tm

20. Magnetic field Validation : Analytic model vs. Geant4
Perfect matching between analytical previsions and simulation results

21. Magnetic field Validation : Analytic model vs. Geant4

22. Magnetic field Validation : Analytic model vs. Geant4

23. 1. ICRU sphere in free space
2. Columbus habitat only
SR2S Simulation Plan 1/5

24. 3. Columbus habitat and magnetic field only
4. Columbus habitat, active shielding structures and
magnetic field ON
SR2S Simulation Plan 2/5

25. 5. Columbus habitat with active shielding structures
and NO magnetic field
6. Columbus habitat surrounded by passive shielding
rich in H equivalent in mass to the active one
SR2S Simulation Plan 3/5

26. • Doses have been already calculated for every
considered radiation environment
components for:
– ICRU sphere in deep space
– Example of deep space habitat in deep space
• Results will include data on:
– Doses - Equivalent Doses
– Fluxes - Fluences
SR2S Simulation Plan 4/5
ICRU SPHERE IN FREESPACE

27. • Results will be available by the end of May
and will permit a first evaluation of the active
radiation shielding
• Other evaluations will have to be performed
once the design of the mechanical structure is
finalized
SR2S Simulation Plan 5/5

28. • No actual passive shielding solutions to GCR
• Investigation of magnetic active shielding as a
possible way to overcome the problem
• Necessity to further develop the involved
technology, focusing on:
– Optimization of structures
– Safety and reliability
• Necessity to have biological data for GCR
Conclusions

29. THE END
Thank you for your attention
Questions?

30. BACK UP SLIDES

31. SR2S Environment: Superflare differential flux
1,00E-06
1,00E-05
1,00E-04
1,00E-03
1,00E-02
1,00E-01
1,00E+00
1,00E+01
1,00E+02
1,00E+03
1,00E+04
1,00E+05
1,00E+06
1,00E+07
1,00E-01 1,00E+00 1,00E+01 1,00E+02 1,00E+03 1,00E+04 1,00E+05
protons.MeV-1.cm-2.s-1
MeV
Superflare Differential Flux
CREME86 M11-M1
Oct 89 worst hour
Oct 03 worst hour
Jul 00 worst hour
Aug 72 worst hour

32. SR2S Environment: GCR differential fluxes

33. Mission
Total Mission
Duration
Outbound Stay Return
Total Days in
Deep-Space
Lagrange’s
Points [LEM2]
200 - - - 200
NEA 410 ~170 30 ~210 ~380
MARS TITO
mission
501 228 - 273 501
MARS Short Stay 545 224 30 291 515
MARS Long Stay
(minimum
energy)
919 224 458 237 461
MARS Long Stay
(fast transit)
879 150 619 110 260
Considered Mission Scenarios

34. The Hydrogen GCR flux at 1AU predicted by CREME96 and CREME2009
particle flux models for the solar minimum
CRÈME 96 vs CRÈME2009

35. Differential GCR Protons Fluence for Different Scenarios

36. • Astronauts who are on missions to the ISS, the
moon, or Mars are exposed to ionizing radiation with
effective doses in the range from 50 to 2,000 mSv
• The evidence of cancer risk from ionizing radiation is
extensive for radiation doses that are above about 50
mSv.
Doses in Space

37. HZE
Differences in biological damage of heavy
nuclei with x-rays Earth-based data
New knowledge on risks must be
obtained
Possible acute or late damages to CNS,
caratacts, heart tissues, etc, from low
dose rate (< 50 mGy/h) of HZE
CONTROL
IRON IRRADIATED
OxidativestressinincreasedinMouseHippocampus
9monthsafter2Gyof56Feirradiation

38. • International overview:
– ESA: dose limits based on ICRP recommendations for ground-base
workers with some modifications
– NASA, JAXA: age and gender dependent limits for late effects
• Career Limits based on a 10 years exposure
LEO Exposure Limits – Career Effective Dose Limits

40. Uncertainties in Risk Projection in Radiation Exposure
From Cucinotta and Durante, 2011

41. Magnetic field Validation : Analytic model vs. Geant4