MSR Chapter Title 1 Radiator Materials Appendix 1 1 Summary In the course of the radiator design the design team considered a variety of materials for the supports panels and heat pipes The team compiled the important thermo physical properties of materials commonly used for these purposes below 1 2 Structural Materials 1 2 1 Non metals The benefits of non metal structural materials are higher melting points and smaller densities when compared to metal alloys Carbon carbon fiber materials are a new but expanding category of materials that offer tensile strengths similar to metals with very low density in combination with flexibility and chemical resistance The very high melting points of these materials also add structural integrity and a greater margin of safety with respect to overheating transients Table Structural Materials 1 Thermo physical properties of non metallic elements and compounds that are candidates for use in a Martian or Lunar radiator as structural materials Graphite Carbon Carbon Composite Zirconium Carbide Silicon Carbide Solid Specific Thermal Melting Density Heat Conductivity Point Emissivity kg m3 J g K W m K K 2250 0 69 24 3800 0 9 1000 0 3 66 3650 0 9 6730 3200 0 37 0 84 21 50 3805 2200 0 4 1 MSR Chapter Title 1 2 2 Metals The benefits of metallic structural materials include high thermal conductivities and tensile strength however the low melting points pose the problem of long term deformation In addition oxidation effects at high temperatures may alter the thermal or mechanical properties Table Structural Materials 2 Thermo physical properties of metals and metallic compounds that are candidates for use in a Martian or Lunar radiator as structural materials Solid Specific Thermal Melting Density Heat Conductivity Point Emissivity kg m3 J g K W m K K Aluminum 6061 T6 Carbon Steel Stainless Steel Titanium Niobium 2700 0 896 167 855 925 0 1 7872 7850 4500 8570 0 481 0 5145 0 528 0 265 51 9 12 22 17 54 1813 1643 1923 2750 0 9 2 0 63 MSR Chapter Title 1 3 Working Fluids 1 3 1 Non metals The non metallic fluids are generally less reactive less dense and have lower melting points than the metals however their thermal conductivities are also significantly lower The low melting points will make it easier to thaw out the radiator components at startup and decrease the chance of solid blockages occurring Because of the low boiling points of non metallic fluids radiator piping may require extremely high pressures to force fluids to remain liquid as they enter an evaporator section High pressures necessitate ticker walls on radiator piping and increase the chance of major leakage from the system The gases listed are attractive because of their very low masses and reasonable heat capacities However the low density would require high pressures and high flow rates A system of pumps would be required to maintain high flow rates which introduces a major source of failures and significant power consumption The Freon derivatives listed here make up only a partial list of the possible chlorofluorocarbon radiator fluids however environmental regulations may make most of these alternatives impractical Table Working Fluids 3 Thermo physical properties of non metallic elements and compounds that are candidates for use as the working fluid in a Martian or Lunar radiator Liquid Density kg m3 Ammonia 682 CO2 1032 Freon 12 1486 Freon 13 1526 Freon 22 1413 Freon 23 1431 Helium 124 96 Nitrogen 808 6 Gas Specific Thermal Melting Boiling Density Heat Conductivity Point Point kg m3 J g K W m K K K 0 86 1 673 0 0221 195 239 5 2 814 0 657 0 0146 194 5 194 5 6 25 0 54 0 0094 115 243 6 94 0 494 0 0123 84 192 4 706 0 561 116 232 4 57 117 9 191 16 9 5 193 0 1426 0 8 4 4 614 0 742 0 024 63 77 1 3 MSR Chapter Title 1 3 2 Metals The metallic fluids main benefits are high thermal conductivities and boiling points which make them ideal for a low pressure natural flow system However they are also much denser thus heavier and more chemically reactive than other substances under consideration Increased densities may offer an advantage however when considering structural failures since the fissure needed to leak material is much greater than for a light gas such as helium Researchers have done a large amount of research and development with these materials geared towards high temperature heat transfer and space radiators For instance lithium is a common working fluid in terrestrial and space heat pipes because it offers a low density and high specific heat although its melting point may be too high to ensure full melting in the current application Table Working Fluids 4 Thermo physical properties of metals and metallic compounds that are candidates for use as the working fluid in a Martian or Lunar radiator Solid Density kg m3 LeadBismuth Eutectic Lithium Potassium Sodium Liquid Density kg m3 Gas Density kg m3 10500 530 860 970 512 680 927 457 600 711 Specific Heat J g K Thermal Conduct ivity W m K Melting Point K Boiling Point K 0 15 12 397 1943 3 305 0 757 1 225 71 2 99 2 135 453 337 371 1615 1032 1156 4 Heat of Vaporizat ion kJ kg 22730 1985 3874 MSR Chapter Title References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Air Liquide 2004 Gas Data Air Liquide Online http www airliquide com en business products gases gasdata index asp Air Liquide 2004 Material Safety Data Sheets Air Liquide Online http www airliquide com safety msds en index htm Bauccio Michael 1994 ASM Engineered Materials Reference Book 2nd ed ASM International Materials Park OH Boyer H E and Gall T L Eds 1985 Metals Handbook American Society for Metals Materials Park OH Giancoli Douglas C 1989 Physics for Scientists and Engineers with Modern Physics 2nd ed Prentice Hall Publishers Englewood Cliffs NJ Handbook of Chemistry and Physics 84th ed CRC Press LLC 2004 Ho C Y and Holt J M Eds 1996 Structural Alloys Handbook 1996 ed CINDAS Purdue University West Lafayette IN Indium Corporation of America 2004 Table of Specialty Alloys and Solders Indium Corporation of America Online http www indium com products physicalproperties php Metal Handbook Volume 2 Properties and Selection Nonferrous Alloys and Special Purpose Materials 10th ed ASM International 1990 Metals Handbook Desk Edition 1998 Second Edition ASM International ASM Handbooks Online Online http www asmmaterials info Morita K Maschek W Flad M Tobita Y Yamano H 2004 Thermophysical Properties of Lead Bismuth Eutectic Alloy for Use in Reactor Safety Analysis Meeting of NEA