The Biological Effects of Radiation to Humans on a Manned Mission to Mars By Dan Maierhafer For the Clemson Chapter of the...
Topics of Discussion <ul><li>Mars Facts </li></ul><ul><li>Why go to Mars? </li></ul><ul><li>Types of Mars Missions </li></...
Mars Facts 9.78 m/s^2 3.72 m/s^2 (0.38 x Earth) Gravity 1380 W/m^2 595 W/m^2 Solar Irradiance 23.9 hours 24.6 hours Rotati...
Mars Facts:  Atmospheric Comparison between Mars and Earth N/A 0.03% H 2 O N/A 0.07% CO 20.9% 0.13% O 2 0.93% 1.6% Ar 78% ...
Why go to Mars? <ul><li>All resources required to sustain life and to develop a civilization </li></ul><ul><li>Little liqu...
Types of Mars Trajectories <ul><li>Hohmann Conjunction </li></ul><ul><ul><li>Minimal Delta v </li></ul></ul><ul><ul><li>25...
“Mars Direct” Mission Timeline <ul><li>October 2011:  Unmanned Earth Return Vehicle (ERV) liftsoff from Cape Canaveral, FL...
NCRP Equivalent Dose Limit Guidelines for Astronauts (cSv) 59.25 N/A N/A GOST Annual 100-400 depending on age 400 600 Care...
Natural Sources of Radiation in Space <ul><li>Solar Energetic Particles (SEP) from Solar Flares </li></ul><ul><li>Galactic...
Solar Energetic Particles (SEP) / Proton Flares <ul><li>From explosions near sunspots that release energy of 1 billion meg...
Dose from Ordinary Proton Flares <ul><li>No way to predict </li></ul><ul><li>Happen throughout the day at random intervals...
Dose from Very Large Proton Flares <ul><li>Occur at a time span of every 11 years </li></ul><ul><li>H = 140 to 1400 cSv wi...
Galactic Cosmic Rays <ul><li>Contains charged particles coming from a region 100 AU around our solar system </li></ul><ul>...
Dose from Galactic Cosmic Rays <ul><li>Dose Rate changes with Solar Minima or Maxima </li></ul><ul><li>Solar minima, H = 1...
Protection from Radiation in Space
Are you Asleep?
SP-100 / Stirling Cycle Space Nuclear Power System <ul><li>Designed for manned Mars Rover </li></ul><ul><li>Rated for 500 ...
Nuclear Reactor Shielding 101 <ul><li>Primary Types of Radiation Emitted from a Nuclear Reactor? </li></ul><ul><ul><li>Neu...
SP-100 Shielding <ul><li>Two Layers of Shielding </li></ul><ul><ul><li>182  W layer followed by a LiH layer </li></ul></ul...
Predicted Mission Dose for Astronaut 0.2681 - 0.3026 N/A N/A Total Fatal Cancer Risk 0.0681 - 0.1026 0.05 (1/Sv) 1.3607 - ...
Predicted Risks for Astronaut due to Mission Dose <ul><li>Natural Risk of Cancer is 20% (1 out of 5) </li></ul><ul><li>Sto...
Conclusions <ul><li>Additional Shielding substantially reduces Ordinary Proton Flare Dose </li></ul><ul><li>Very Large Pro...
For more information on Mars <ul><li>The Mars Society </li></ul><ul><ul><li>http://www. marssociety .org/ </li></ul></ul><...
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The Biological Effects of Radiation to Humans on a Manned Mission to Mars

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  • Argon
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  • With proper design, the mission provisions can be used to create an onboard storm shelter to provide protection from solar flares in transit. While capable of delivering a deadly dose of several thousand rems to an unshielded astronaut, solar flares, which are composed of large numbers of protons with energies of about 1 million volts, can be stopped by five inches of water or food material. The ship will have enough provisions on board to provide a small area with more than that amount of shielding. Solar flares occur irregularly, with dangerous events happening for a few hours perhaps once a year. During their year in space (six months in transit each way) the crew will only have to endure one or two brief periods of tight confinement in the storm shelter Cosmic rays, which are made of particles with billions of volts of energy cannot be stopped by such thin shielding. However the magnitude of the dose that will be incurred is only about 50 rem per year. This will cause no immediate hazard. Rather, a statistical risk of cancer will result, comparable to smoking cigarettes for the same period. This may be regarded as an acceptable level of risk. If desired, the hab module can remain connected with a tether to the spent booster upper stages, and then the assembly spun up to create artificial gravity on the way to Mars. Doing this will allow the crew to avoid any ill effects from long-duration zero gravity exposure. Although, in 1996, astronaut Shannon Lucid showed that if a strenuous exercise program were strictly followed, zero gravity for the six month flight time to Mars could be endured without harm.
  • The Biological Effects of Radiation to Humans on a Manned Mission to Mars

    1. 1. The Biological Effects of Radiation to Humans on a Manned Mission to Mars By Dan Maierhafer For the Clemson Chapter of the Health Physics Society on February 6, 2001
    2. 2. Topics of Discussion <ul><li>Mars Facts </li></ul><ul><li>Why go to Mars? </li></ul><ul><li>Types of Mars Missions </li></ul><ul><li>Radiation Dose Limits for Astronauts </li></ul><ul><li>Natural Sources of Radiation in Space </li></ul><ul><li>Anthropogenic Sources of Radiation on Mars </li></ul><ul><li>Predicted Mission Dose for Astronaut </li></ul><ul><li>Predicted Risks for Astronaut due to Mission Dose </li></ul>
    3. 3. Mars Facts 9.78 m/s^2 3.72 m/s^2 (0.38 x Earth) Gravity 1380 W/m^2 595 W/m^2 Solar Irradiance 23.9 hours 24.6 hours Rotational Period 365 days 687 days Orbital Period 101,325 Pa (1 atm) 699 - 912 Pa (0.0069 to 0.009 atm) Atmospheric Pressure Earth Mars Parameter
    4. 4. Mars Facts: Atmospheric Comparison between Mars and Earth N/A 0.03% H 2 O N/A 0.07% CO 20.9% 0.13% O 2 0.93% 1.6% Ar 78% 2.6% N 2 0.03% 95.3% CO 2 Earth Mars Atmospheric Composition
    5. 5. Why go to Mars? <ul><li>All resources required to sustain life and to develop a civilization </li></ul><ul><li>Little liquid water, but large frozen water reserves underneath the polar caps </li></ul><ul><li>Deuterium, worth $10000/kg, is five times more common on Mars than it is on Earth </li></ul><ul><li>New technologies will result from Space Exploration </li></ul><ul><li>Expand our sphere of influence </li></ul>
    6. 6. Types of Mars Trajectories <ul><li>Hohmann Conjunction </li></ul><ul><ul><li>Minimal Delta v </li></ul></ul><ul><ul><li>258 days one way </li></ul></ul><ul><li>Opposition </li></ul><ul><ul><li>180 days outbound </li></ul></ul><ul><ul><li>430 days inbound </li></ul></ul><ul><ul><li>Higher H during Venus’ slingshot maneuver </li></ul></ul><ul><ul><li>30 day stay on Mars </li></ul></ul><ul><li>Fast Conjunction </li></ul><ul><ul><li>Burn some extra propellant </li></ul></ul><ul><ul><li>180 days one way </li></ul></ul><ul><ul><li>550 day stay on Mars </li></ul></ul><ul><ul><li>Favored </li></ul></ul>
    7. 7. “Mars Direct” Mission Timeline <ul><li>October 2011: Unmanned Earth Return Vehicle (ERV) liftsoff from Cape Canaveral, FL. </li></ul><ul><li>May 2012: ERV arrives at Mars. Chemical plant starts to make CH 4 and H 2 O from H 2 and CO 2 using Sabatier reaction. </li></ul><ul><li>January 2014: Habitat Module carrying crew of four liftsoff from FL </li></ul><ul><li>June 2014: Habitat Module reaches Mars. Lands near radio beacon on ERV. </li></ul><ul><li>December 2015: Crew of the first Mars mission boards ERV for return to Earth </li></ul><ul><li>June 2016: ERV return capsule enters the Earth's gravitational sphere of influence </li></ul>
    8. 8. NCRP Equivalent Dose Limit Guidelines for Astronauts (cSv) 59.25 N/A N/A GOST Annual 100-400 depending on age 400 600 Career 50 200 300 Annual 25 100 150 30-day BFO Eye Skin Time of Exposure
    9. 9. Natural Sources of Radiation in Space <ul><li>Solar Energetic Particles (SEP) from Solar Flares </li></ul><ul><li>Galactic Cosmic Rays (GCR) </li></ul><ul><li>Trapped Particles in the Van Allen Radiation Belt </li></ul><ul><ul><li>Only in Low Earth Orbit </li></ul></ul>
    10. 10. Solar Energetic Particles (SEP) / Proton Flares <ul><li>From explosions near sunspots that release energy of 1 billion megatons of TNT </li></ul><ul><li>11 year natural cycle with periods of high and low solar flare activity (Solar Maxima and Solar Minima) </li></ul><ul><li>Affects GCR Particle Flux </li></ul>
    11. 11. Dose from Ordinary Proton Flares <ul><li>No way to predict </li></ul><ul><li>Happen throughout the day at random intervals </li></ul><ul><li>H = 0.1 to 140 cSv with no shielding at 1 AU from Sun (Note large slope) </li></ul>
    12. 12. Dose from Very Large Proton Flares <ul><li>Occur at a time span of every 11 years </li></ul><ul><li>H = 140 to 1400 cSv with no shielding at 1 AU from Sun. (Note small slope) </li></ul><ul><li>Wise to avoid these </li></ul>
    13. 13. Galactic Cosmic Rays <ul><li>Contains charged particles coming from a region 100 AU around our solar system </li></ul><ul><li>Majority of Equivalent Dose from H, He, O, C, Ne, Si, and Fe nuclei </li></ul><ul><li>Is moderated by the 11 year cycle of the Sun’s magnetic field </li></ul>
    14. 14. Dose from Galactic Cosmic Rays <ul><li>Dose Rate changes with Solar Minima or Maxima </li></ul><ul><li>Solar minima, H = 113 cSv/yr with no shielding </li></ul><ul><li>Solar maxima, H = 45 cSv/yr (Note low slope) </li></ul>
    15. 15. Protection from Radiation in Space
    16. 16. Are you Asleep?
    17. 17. SP-100 / Stirling Cycle Space Nuclear Power System <ul><li>Designed for manned Mars Rover </li></ul><ul><li>Rated for 500 KW (8,333 - 60W light bulbs) </li></ul>
    18. 18. Nuclear Reactor Shielding 101 <ul><li>Primary Types of Radiation Emitted from a Nuclear Reactor? </li></ul><ul><ul><li>Neutrons and Gamma Rays </li></ul></ul><ul><li>How do you stop a fast neutron ? </li></ul><ul><ul><li>Elastic collision with something of similar mass (the proton in H) </li></ul></ul><ul><ul><li>Absorb with (n,gamma) reaction </li></ul></ul><ul><li>How do you reduce the Intensity of Gamma Rays? </li></ul><ul><ul><li>High Z (atomic number) shield material </li></ul></ul>
    19. 19. SP-100 Shielding <ul><li>Two Layers of Shielding </li></ul><ul><ul><li>182 W layer followed by a LiH layer </li></ul></ul><ul><ul><li>Tungsten (n,gamma) reactions </li></ul></ul><ul><ul><li>LiH decreases number of neutrons reaching second W layer </li></ul></ul>
    20. 20. Predicted Mission Dose for Astronaut 0.2681 - 0.3026 N/A N/A Total Fatal Cancer Risk 0.0681 - 0.1026 0.05 (1/Sv) 1.3607 - 2.0507 (Sv) Totals for Mission 0.015 0.05 (1/Sv) 0.3 (Sv) Max. from Nuclear Rover 0.0166 0.05 (1/Sv) .3313 (Sv) 550 days on Mars Surface 0.0183 - 0.0355 0.05 (1/Sv) 0.3647 - 0.7097 (Sv) Inbound (5g/cm^2 shield) 0.0183 - 0.0355 0.05 (1/Sv) 0.3647 - 0.7097 (Sv) Outbound (5g/cm^2 shield) Cancer Risk Probability of Fatal Cancer Equivalent Dose to BFO Mission Portion
    21. 21. Predicted Risks for Astronaut due to Mission Dose <ul><li>Natural Risk of Cancer is 20% (1 out of 5) </li></ul><ul><li>Stochastic Effects </li></ul><ul><ul><li>Predicted Additional Fatal Cancer Risk using 5 g/cm^2 shielding: 6.8 – 10.3% </li></ul></ul><ul><li>Radiation Dose on Earth is 3-4 mSv/yr </li></ul><ul><li>Ave. Dose from Mars Mission 1.33 Sv/yr </li></ul><ul><li>Deterministic Effects </li></ul><ul><ul><li>At (H>0.4 Sv/yr): Temporary Sterility </li></ul></ul>
    22. 22. Conclusions <ul><li>Additional Shielding substantially reduces Ordinary Proton Flare Dose </li></ul><ul><li>Very Large Proton Flares can be avoided </li></ul><ul><li>GCR Dose is not affected much by additional shielding </li></ul><ul><li>5 g/cm^2 of shielding is too low due to Temporary Sterility effects </li></ul><ul><ul><li>Astronauts could sleep in a smaller 25 g/cm^2 radiation shelter </li></ul></ul><ul><li>Dose Rates are dynamic </li></ul><ul><ul><li>Need a computer model to more accurately simulate doses </li></ul></ul><ul><li>There is a plan to go to Mars now </li></ul>
    23. 23. For more information on Mars <ul><li>The Mars Society </li></ul><ul><ul><li>http://www. marssociety .org/ </li></ul></ul><ul><li>Center for Mars Exploration </li></ul><ul><ul><li>http://cmex-www.arc.nasa.gov/ </li></ul></ul><ul><li>The Whole Mars Catalog </li></ul><ul><ul><li>http://www.spaceref.com/mars/ </li></ul></ul><ul><li>The Planetary Society </li></ul><ul><ul><li>http://www.planetary.org/ </li></ul></ul><ul><li>Current Solar Wind Conditions </li></ul><ul><ul><li>http://space.rice.edu/ISTP/dials.html </li></ul></ul>

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