International Space StationEarth Preservation and Space Exploration Joseph Bermudez email@example.com December 15, 2009
ISS as the gateway to mankind’s continued exploration in space • Extend ISS support and scientific participation to all nations • Define two main missions: (1) Earth environment - monitoring and analysis (2) Space exploration - flexible mission training, technology development, and equipment testing (Maintain current ISS hardware – replace modular sections when required)
Earth Science Content:Environment Study Emphasis • Define a SPECIFIC scientific mission of the International Space Station as Earth environmental observation • Mission objective would attempt definitive environmental analysis to continually refine conclusions regarding global warming and greenhouse gas fractions
Earth Science Mission RequiresInspiring Worldwide Participation • Develop a global mission strategy tailored for the SOLE manned orbital station * as global, astronaut-tended Earth-monitoring node * focus on global warming problem • astronaut ambassadors further the cause of all mankind and symbolize respect for human diversity
Space Exploration Content: Flexible Mission Systems • International participation • Development of a flexible mission landing vehicle applicable to Moon and Mars mission • Formal training for Mars mission begins with Moon flights
Engineering Challenge:Spacecraft Radiation Shielding • Huge radiation vulnerability exists beyond Earth’s magnetosphere * solar particle events * galactic cosmic radiation • Radiation shielding absolutely required * passive (mass) * active (magnetic field)
Active Radiation Shielding • Huge energy and structural requirements • Large mass penalty • Theoretically possible with high temperature (70 K) superconductors • Effective against charged particles • No generation of secondary radiation • No operational system exists
Passive Radiation Shielding Effective for all radiation types Highly dependent upon material selection and thickness for adequate protection Requires a novel approach due to extreme energies of space radiation (e.g. lead causes secondary radiation)
Passive Radiation Shielding Material Effectiveness dose in Sieverts = dose in Gray × RBE ________________________________ RBE = relative biological effectiveness Shielding Thickness thickness = (mass/area)/(mass/volume) = (mass/area)/density 30 cSv annual dose limit applicable to 3 year mission
Passive Radiation Shielding Material for High Energy Particles DENSE METALS (lead) - allow high energy particles collisions to create secondary radiation (neutrons and nuclear fragments) LIGHT METALS (aluminum) - offer adequate shielding only at prohibitive mass penalty CARBON FIBER (carbon)- provides adequate shielding at less mass penalty than aluminum HIGH HYDROGEN CONTENT MATERIALS(liquid hydrogen, water, polyethylene) - provide optimum protection with minimum secondary radiation and lowest mass penalty
Shielding Materials Comparison Material Density Neutron Absorption gamma (kg/m^3) Cross-section (barns) (MeV) Hydrogen 67.8 0.3326 2.223 Lithium 534 70.5 0.476 Boron 2080 767 0.478 Carbon 2267 0.0035 0.511 Aluminum 2700 0.232 1.809 ( 1 barn = 1e-28 m^2)
Passive Radiation Shielding for Gamma Radiation • Gamma rays may be produced by nuclear interactions when high energy particles hit any spacecraft surface • High density metals (lead, tungsten) provide the most effective shield per unit thickness BUT lighter materials (carbon) may be matched to certain gamma radiation environments
0.5 MeV Gamma Shielding Strategy:Use Structural Material as a Shield Material Density LAC 1000*LAC/Density (kg/m^3) (m^-1) (m^2/kg) Water 1000 9.7 9.699 Carbon 2267 19.6 8.646 Aluminum 2700 22.7 8.407 Lead 11,340 164.0 14.46 (LAC = Linear Attenuation Coefficient, gamma) Carbon fiber structure could serve a dual role as structural material and gamma shield.
Potential Research Area for Passive Radiation Shielding • Possible application of the macroscopic Whipple micrometeoroid shield effect to the atomic/molecular scale using multi-layered shielding materials * aluminum/borated aluminum * carbon fiber nanotubes (hydrogen added) * polyethylene (boron added) * boron carbide (B4C) • Different material interactions progressively diffuse high energy through a series of nuclear collisions gradually absorbed into polyethylene
Spacecraft Wall (27.1 g/cm^2) Magnesium Whipple Shield (blue) 2 mm thick Carbon Fiber Struts (gray) Vectran Sheet (green) Carbon Fiber Outer Wall (gray) 1 cm thick Borated Polyethylene (red) 7.6 cm thick Carbon Fiber Inner Wall (black) 10.5 cm thick
International Starship Hypothetical spacecraft serving both as a space station and an interplanetary spaceship Demonstration project for application of the passive radiation shielded spacecraft wall 50 m radius rotating at 4 rpm to generate 1g equivalent Nuclear power
International Starship: Physical Description • Circularmanned spacecraft * Perimeter exercise track * Exercise room * Sick bay * Agriculture (hydroponics) • 50 meter radius • Rotating at 4 rpm to create 1g equivalent • 4 center spokes • 4 engines mounted between spokes • Passive radiation shielding with calculated 99% shield efficacy at 3 years due to boron burn-up • Space Station AND Space Exploration Vehicle • Nuclear power
Starship Calculations:Empty Mass WITHOUT Engines ITEM MASS (kg) RATIONALE Whipple Shield Bumper 39,124.4 micrometeoroids Whipple Shield Stuffing 1,067.6 micrometeoroids Whipple Shield Struts 1,000.0 micrometeoroids Carbon Fiber Outer Wall 189,907.0 radiation Borated Polyethylene Shield 751,716.0 radiation Carbon Fiber Inner Wall 1,994,025.0 radiation/structural Titanium Central Spokes 20,000.0 structural ___________ TOTAL 2,996,840.0 kg (compare to ISS completed mass of 471,736 kg)
References • Space Physiology, Jay C. Buckley, jr., (2006), Oxford University Press, p. 54-74. • Space Biology and Medicine, Huntoon, Antipov, Grigoriev, (1996), American Institute of Aeronautics and Astronautics, p. 349-418. • Wilson, Cucinotta, Nealy, Clowdsley, Kim, Deep Space Mission Radiation Shielding Optimization, (2001), Society of Automotive Engineers, Paper Number 01ICES-2326, • Rapp D, Radiation Effects and Shielding Requirements in Human Missions to the Moon and Mars, The International Journal of Mars Science and Exploration, (2006), p. 46-71.
References 5. Levy R, Sargent Janes G, Plasma Radiation Shielding, American Institute of Aeronautics and Astronautics, Vol. 2, No. 10, 1964, p. 1835-1838. 6. Levy R, Radiation Shielding of Space Vehicles by Means of Superconducting Coils, AVCO-Everett Research Laboratory, ARS Journal, (1961), p.1568-1570. 7. Goksel B, Rechenberg I, Surface Charged Smart Skin Technology for Heat Protection, Propulsion, and Radiation Screening, Institute of Bionics and Evolutiontechnique, TU Berlin, (2004), p. 1-7. 8. Shepard S G, Kress B T, Stormer theory applied to magnetic spacecraft shielding, Space Weather, Vol. 5, 2007, S04001, p. 1-9.
References 9. Schimmerling W, Overview of NASA’s Space Radiation Research Program, Gravitational and Space Biology Bulletin,16(2), June 2003, p. 5-10. 10. Radiation Protection: A Guide for Scientists, Regulators, and Physicians, Jacob Shapiro, (2002), Harvard University Press, p. 1-100. 11. Radiation Shielding, J Kenneth Shultis, Richard E Faw, (2000), American Nuclear Society. 12. Atoms, Radiation, and Radiation Protection, James E Turner, (2007),3rd Edition, Wiley VCH.
Credits Image Credits (www.yahoo.com) • Graphs from Yahoo images * slide 7 * slide 9 * slide 10 • Diagram from Yahoo images * slide 8 Graphic Credits (Will Russell) • Spacecraft Wall Section Diagram * slide 18 • Hypothetical Starship * slide 19