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Cosmic Rays and Manned Interplanetary Travel Isaac Shaffer Gary Bowman Keran O’Brien Northern Arizona University. Background. Why do we care? Cosmic rays (like many types of radiation) are potentially hazardous. Largely shielded by Earth’s atmosphere Space craft are at greater risk - PowerPoint PPT PresentationTRANSCRIPT
Cosmic Rays and Manned Interplanetary Travel
Isaac ShafferGary BowmanKeran O’Brien
Northern Arizona University
Background
• Why do we care? • Cosmic rays (like many types of radiation) are potentially hazardous.• Largely shielded by Earth’s atmosphere• Space craft are at greater risk
• NASA has planned manned mission to Mars in 2031– Shielding– Flight time
• How do we measure radiation?– Radiation Absorbed Dose (rad) – Absorbed Radiation– Roentgen Equivalent Man - Effective dose (rem) – Biological Impact of
Absorbed Radiation
The ModelThe computer model we used took into account:
- Impact of the heliosphere on cosmic ray activity- Shape- Strength of Solar wind
- A cylindrical Aluminum space craft hull- Additional polystyrene shielding
The Math:- Parker Transport Equation (for scattering in the heliosphere)- Boltzmann Transport Equation (for scattering in material)- Hybrid of International Commission on Radiation Protection Standards 60 and 103 (dealing with dose and absorption respectively)
The Heliosphere
Calculated Flux Rates vs. Measured Flux Rates
Calculations by distance from the Sun
Toward the Bow shock
0
20
40
60
80
100
120
140
1 11 21 31 41 51 61 71 81
Distance (AU)
Dos
e (r
em/y
r)
Perpendicular to the Bow shock
0
10
20
30
40
50
60
70
80
90
100
1 11 21 31 41 51 61 71 81
Distance (AU)
Do
se (
rem
/yr)
1 g/cm^2
2 g/cm^2
4 g/cm^2
10 g/cm^2
20 g/cm^2
50 g/cm^2
75 g/cm^2
100 g/cm^2
Calculations by Solar wind speed
Effects of Solar Wind
0
20
40
60
80
100
450 600 750 900
Solar Wind (km/s)
Do
se (
rem
/yr) 1 g/cm^2
2 g/cm^2
4 g/cm^2
10 g/cm^2
20 g/cm^2
50 g/cm^2
75 g/cm^2
100 g/cm^2
Results
• Solar activity will be elevated.• NASA’s current mission cap is 100 rem.• 2½ year mission = 40 rem per year limit.
• Shielding equivalent to 20 g/cm^2 is needed.
- Polystyrene would be 19.2 cm (7.8 in) thick.
- A trip to Jupiter (more than 7 years) would require more than 5 times as much shielding.
Conclusion
• Interstellar cosmic rays pose a health risk to a manned mission to Mars.
• Dose rates due to cosmic rays should remain fairly constant within a few AU of the sun.
• Timing missions to coincide with high solar cycles might be beneficial.
Thank you! Questions?