Full report

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NASA/TM--1998-208181 Mirror Material Properties Compiled for Preliminary Design of the Next Generation Space Telescope (30 to 294 Kelvin) P.L. Luz and T. Rice Marshall Space Flight Center, Marshall Space Flight Center, Alabama National Aeronautics and Space Administration Marshall Space Flight Center May 1998

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Available from: NASA Center for AeroSpace Infomtation 800 ElkJ'idge Landing Road Limhicunl Heights. MD 211)9{t-2934 1,301) 6214)391) National Technical Information Service 5285 Port Royal Road Springfield. VA 22161 (703) 487-4650

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TABLE OF CONTENTS I. INTRODUCTION .................................................................................................................... 1 I.I Mirror Material Tasks ........................................................................................................ I .......................................................................................................... I !.2 Scope of this Report 2. MIRROR MATERIAL PROPERTIES THAT ARE CITED ..................................................... 2 .................................................................................................... 2 2.1 Literature Survey Status ........................................................................................................................... 2 2.2 Overview 3. MATERIAL SELECTION COMPARISON FACTORS .......................................................... 5 3.1 Other Considerations ......................................................................................................... 6 4. CONCLUSION ......................................................................................................................... 7 ................................................................................................................................. 8 REFERENCES APPENDIX A--Beryllium 1-70A (Material Properties) APPENDIX B--Beryllium O-50 (Material Properties) ........................................................................ 14 APPENDIX C--Nickel, Pure (Material Properties) Properties) ..................................................... 18 APPENDIX D--Nickel, Electrodeposited (Material Properties) .......................................................... 21 APPENDIX E--CVD Silicon Carbide (Material .................................................................. I! ................................................................... 13 Properties) ............................................................... 25 APPENDIX F--Fused Silica Glass (Material Properties) ............................................................. 28 APPENDIX G--Fused Quartz Glass (Material ........................................................................... 31 APPENDIX H--ULE 7971 (Material Properties) ................................................................................. 34 APPENDIX I--Zerodur (Material Properties) iii

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TECHNICAL MEMORANDUM MIRROR MATERIAL PROPERTIES COMPILED FOR PRELIMINARY DESIGN OF THE NEXT GENERATION SPACE TELESCOPE (30 to 294 KELVIN) 1. INTRODUCTION In February 1996, the Program Development Directorate at NASA Marshall Space Flight Center (MSFC) began studying the feasibility of a Next Generation Space Telescope (NGST) and developed the prephase A program for it. After finishing some initial studies and concepts development work on the NGST, I Program Development handed this work to the Observatory Projects Office at NASA MSFC. NASA Goddard Space Flight Center (GSFC) was later given leadership of the NGST program. 2 NASA GSFC then issued a Cooperative Agreement Notice in April 22, 1996, to solicit proposals from industry to join in feasibility assessments related to the development of an NGST. 3 On August 19-21, 1996, "teams led by Lockheed Martin, TRW, and the GSFC concluded that an NGST was not only feasible and affordable, but that it could be made powerful using recent breakthroughs in space technologies. ''4 1.1 Mirror Material Tasks From April 1996 to June 1997, the Optical Telescope Assembly (OTA) materials team performed a number of tasks for the prephase A (Advanced Studies) design of the NGST, including ( I ) identifying viable mirror material candidates, (2) identifying valid comparison factors, (3) compiling an initial mirror material properties database. (4) trading and comparing the materials, and (5) identifying critical issues and concerns. 1.2 Scope of This Report This NASA technical memorandum reports on the mirror material properties that were compiled from April 1996 to June 1997 for preliminary design of the NGST. This work was performed by the Preliminary Design Office and Materials & Processes Laboratory at NASA MSFC for the NGST OTA team which was led by John T. Humphreys, manager of the AXAF Telescope Office at NASA MSFC, in support of NASA GSFC.

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1. MIRROR MATERIAL PROPERTIES THAT ARE CITED Refer to appendices A through I for detailed mirror material properties. 2.1 Literature Survey Several sources were consulted for mirror material property data--textbooks; Internet databases; Redstone Scientific Information Center (RSIC) databases, including NASA RECON, DTIC, and CPX WEB; and industrial suppliers of the mirror materials. Information from at least 6 industrial suppliers, ! 6 textbooks, 44 technical papers, and 130 abstracts were reviewed for mirror material property information. 2.2 Overview Requirements from NASA GSFC, the lead center for the NGST study, specify a "scientific requirement for telescope temperatures in the range 40 to 60 K. ''5 Table 1 identifies the lowest temperature at which mirror material properties data was found during our survey of literature, the Intemet, and industrial suppliers. Overall, the expected temperature range of the NGST is approximately 30 to 300 K. Table I. Lowest temperature at which material properties data is cited. Optical Type Material Abbrev. Density Be Spherical Powder Metal Beryllium 1-70A Be 1-70A 10' Beryllium 0-50 Be 0-50 10_ Pure Nickel Ni Room Electrodeposited Nickel EdNi Room Glass Boro Silicate Boro Si Fused Silica Glass SiO 2 (pc) Room Fused Quartz, GE 214 SiO 2 (c) Room ULE 7971 ULE Room Zerodur M Zerodur Room Ceramic CVD Silicon CarbidC M CVD SiCTM 123° Reaction-Bonded SiC RB SiC Composite Carbon/Silicon Carbide C/SiC Room Lowest Temperature (K) at Which Data is Available CTE k Cp E 3oisson's I YTS UTS 10° 0° :0' 10° 0_ R ,om R,lom 5° 10' 20' loom loom 24' 24' 20 _ 20_ Room oom :oom Room 0 ° ;0' :loom oom 78 7_ Room 100° 150' Room :loom Room Room Room Room :loom R om 198' 223° Room 73' 73" 75' :loom :loom 50' loom 133" 123' 123 ° 273" Room 1 ;3° '** R )om R(_om R<_om R( )m Roo'n Unfortunately, low temperature properties for many of the mirror substrate materials were not found in the literature surveyed up to June 1997. The property information cited in literature was typically at room temperature. Refer to the appendices for detailed material properties for the mirror materials in table 1. The text below gives some general information about the mirror materials.

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Beryllium. Beryllium "has flown on sorne of the most ambitious spacecraft programs undertaken, from the Apollo landers to deep space probes like Voyager" and has been used as an optical substrate on many missions, including Voyager, the Relay Mirror Experiment, and AOA. 6 Brush Wellman, the main supplier of beryllium, has the capability to produce near-net-shape beryllium optical substrates by hot isostatic pressing (HIP), cold isostatic pressing (CIP), and cold pressing of beryllium powders. 7 Please refer to appendices A and B for Beryllium 1-70A and Beryllium 0-50 material properties. Pure Nickel. Nickel was recommended for the NGST study by the Optics Lab (EB52) at NASA MSFC. Cold-worked nickel is one of the most ductile materials available. It has an advantage over some other optical materials under consideration, in that it can be machined and joined easily. However, it also has some disadvantages, including thermal deformation parameters that are not favorable a high-mass density, low-specific stiffness, and until the material becomes very cold. There are many factors to consider when choosing a material, and these may influence the selection of a baseline mirror material as the project's life cycle proceeds. Some forms of nickel that are available include, but are not limited to, Nickel 200 (commercially pure-wrought nickel), Nickel 201 (low-carbon grade), and lnco's Duranickel TM alloy (containing 4.4% AI and 0.6% Ti). One may also hear about electroless nickel. Do not confuse this with pure nickel because it is a coating. "Electroless nickel plating is a controlled autocatalytic reduction of nickel ions by a suitable reducing agent, such as sodium hypophosphite, The resulting deposit is not a pure nickel, but essentially used hydrophosphite salt is utilized as a reducing agent)." properties. on a catalytic surface such as iron or aluminum. an alloy of nickel and phosphorus (if the normally 8 Refer to appendix C for pure nickel material Electrodeposited Nickel (EdNi). Beginning in October 1996, MSFC's Optics Lab (EB52) was working on an NGST mirror replication task in which their charter was to "produce high-quality subscale prototype normal incidence mirror elements an aluminum mandrel, deposited a layer of electroless for the NGST". 9 For the replication, they used nickel on it, a layer of gold, and then the final electrolytic nickel mirror surface. They produced the electrolytic nickel in-house using the Barrett process and sulfamate nickel.l° However, since material properties for their nickel have not been determined yet through a material test program, some material property data for EdNi will be quoted as a representative sample. EdNi "is a dense, essentially pure form of nickel. process, intricate contours can be readily and economically Because of the nature of the electrodeposition reproduced or covered with this form of nickel. EdNi can be deposited in thicknesses ranging from thin films to I inch or more. Mechanical properties of annealed EdNi are comparable to those of wrought Nickel 200. In the as-deposited form, the strength and hardness are higher than those of Nickel 200. ''11 Refer to appendix D for EdNi material properties. Chemical Vapor Deposition (CVD) Silicon Carbide TM (SIC). CVD SiC TM is a flee-standing, monolithic single-phase cubic material with high purity, no porosity, superior chemical resistance, thermal conductivity, stiffness, and polishability. It is a result of Morton International's bulk CVD process. 12 Other vendors and forms of SiC--like reaction bonded SiC, hot pressed SiC, and sintered SiC--are available. CVD SiC TM only represents one possible candidate out of many.

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Fabrication: "CVD SiC TM parts up to 60 inches ( 1.5 m) in diameter and 1 inch (25 mm) thick are available. ''13 Engineers in NASA MSFC's cost group are currently checking on the cost of enlarging these facilities for NGST. Refer to appendix E for CVD SiC TM material properties. Silicon Dioxide Glass (Fused Silica & Fused Quartz). Fused silica is the common name for the polycrystalline form of silicon dioxide, a common glass material. Silicon dioxide is also known as quartz, but quartz should not be confused with fused silica because its structure is crystalline and its material properties (thermal conductivity at least) are orthotropic.14 Refer to appendices F and G for fused silica and fused quartz material properties. ULE 7971. ULE TM is Coming Incorporated's Code 7971 Ultra Low Expansion titanium silicate glass. 15 The Hubble Space Telescope's 2.4-m diameter primary mirror blank was made from lightweighted ULE. Fabrication: From a single bottle, solid shapes up to 1.4 m in diameter by 15 cm thick can be fabricated. In addition, Corning's.flowout process can be used to produce sizes up to 2.8 m in diameter; and a hex sealing process can be used to manufacture sizes up to i 0 m in diameter. Hex seal technology was used to produce the 8.3-m ULE mirror blank for the Subaru Telescope which will be located atop Mauna Kea, Hawaii. In 1995, Coming completed the first 8.1-m ULE mirror blank for the Gemini 8-M Telescopes Project which will construct twin telescopes on Mauna Kea and on Cerra Pachon, Chile. 16 Refer to appendix H for ULE 7971 material properties. Zerodur. Zerodur is a glass ceramics material that Schott Glass Technologies, Inc., has developed for optical, 6ptoelectronic, and precision engineering applications. 17 It is an inorganic, nonporous material which has a crystalline phase and a glassy phase. Zerodur mirror substrates have been built for various telescopes, including NASA's Advanced X-Ray Astrophysics Facility (AXAF) telescope, the ESO New Technology Telescope, and several telescopes for the Max-Planck-Institute for Astronomy in Heidelberg. Fabrication of parts up to 8.2 m in diameter is possible. 18 Refer to appendix I for Zerodur material properties.

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1. MATERIAL SELECTION COMPARISON FACTORS Many factors should be considered when trying to determine a suitable material for the mirror substrate of a space-based telescope. An effort was undertaken to identify many of the comparison factors, or figures of merit, which are pertinent to the selection of a telescope's mirror material. Table 2 lists these comparison factors, their definitions, and metric units. The table is loosely divided into seven categorical groupings of comparison factors: (1) structural figures of merit, (2) life cycle factors, (3) material homogeneity and stability, (4) thermal deformations, (5) optical scatter measurements, (6) reflectance, and (7) cost. Table 2. Telescope mirror materials: some factors to consider. Parameter Definition Specific Stiffness E/rho Specific Strength YTS/rho Microyield Strength Stress Producing 1% (Temporal Stability Due to Creep) Creep in 100,000 Hours Fracture Toughness Klc Anisotropy (Property homogeneity) Ratio of Directional Mat'l Properties Hysteresis Due to Thermal Cycling Optical Figure Change Steady State Thermal Distortion CTE/k Transient Thermal Distortion (CTE-rho-Cp)/k Surface Figure A (Deformed- -Peak-to-Valley Deformation Undeformed Shape --.Curvature Tilt Surface Microroughness Departure of Surface From Plane Optical Scatter Scatter From Reflecting Surface Reflectance (Normal Incidence) R=[(n X-l) 2+ Xk2]/ [(n _.+1) 2 + Xk 2] Cost Price/Diameter Units Critieria MJ/kg High is Good kJ/kg High is Good MPa High is Good Dimensionless Near 1 is Good Waves r.ms. Low is Good cm/Megawatt Near 0 is Good u sec/cm 2-K Near 0 is Good mm (Microns) Low is Good Micro-Radians Near 0 is Good Angstroms r.ms. Low is Good Angstroms r.ms Low is Good percent (%) High is Good $/cm Low is Good

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Stress and Deformations. The structural figures of merit, specific stiffness and specific strength, are good indications of how different materials can be compared in terms of stress and deformation due to structural loads. Structural loads which must be considered are quasi-static, random vibration and acoustic loads (from launch), thermal, crew-induced transportation and separation events. loads (if any, on orbit), and shock from Thermal. Thermal loads and their impact on thermal deformations and figure changes have always been an important consideration for space-based telescopes. Thermal loads for mirrors can be characterized as bulk temperature excursions, axial (through the thickness) gradients, and diametrical (across-the-span) gradients. 3.1 Other Considerations Studies must consider many other factors as their telescope projects mature. Two of the most important questions concern material availability (their technology readiness level) and ease of fabrication to the telescope's desired size and precision. These factors have been difficult to quantify for the NGST study. As of June 1997, engineers in the NASA's cost group have been attempting to get quotes from private industry optical firms to estimate handle the NGST optics. the cost of producing facilities large enough to Packaging considerations also lead to some very important questions, such as: will the design fit within a launch vehicle? Will there be any deployment considerations such as budget, mass, and volumetric maintenance. 6 mechanisms? There are also programmatic constraints: service life; and repair and

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1. CONCLUSION This NASA technical memorandum reports on the mirror material properties that were compiled from April 1996 to June 1997, for preliminary design of the NGST. Detailed material properties are included in the appendix. The careful and systematic selection of a mirror material for a space-based telescope is a difficult task because of the many interactions that exist due to structural, thermal, optical, and configuration considerations during the telescope's design. Mirror material selection is very important because it will also affect the selection of materials for the telescope's reaction structure, mirror support, and metering structure. The combination of mirror material and metering structure materials is critical in determining the total system performance. A strain-free and thermally insensitive mirror has little benefit if the metering structure is sensitive to thermal loads. But if the mirrors and metering structure are the same material, or are otherwise athermalized, then temperature soaks can be compensated.

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REFERENCES l° Nein, M.; and Dickerson, T.: "Next Generation Space Telescope: Potential Concepts," NASA Marshall Space Flight Center, Program Development Directorate, March 8, 1996. . Harwood, W.: "NASA Considers Options to Extend, Replace Hubble," Space News April 29-May 5, 1996. . Soliciting Proposals to Join in Feasibility Assessments Related to Development of a Next Generation Space Telescope," NASA Cooperative Agreement Notice (CAN), CAN-52911/361, NASA Goddard Space Flight Center, April 22, 1996. , Stockman, H.S.; and The NGST Study Team: "The Next Generation Space Telescope: Visiting a Time When Galaxies Were Young," The Association of Universities for Research in Astronomy, Inc., p. v, 1997. , Stockman, H.S.; and The NGST Study Team: "The Next Generation Space Telescope: Visiting a Time When Galaxies Were Young," The Association of Universities for Research in Astronomy, Inc., p. 71. 1997. ° Hardesty, R.: and Decker, T.: "The Design and Producibility of Precision Beryllium Structures for Spacecraft Applications," SPIE ,lournal, Vol. 2543, p. 125, 1995. . Brush Wellman: Beryllium/Mining Division, 147 i0 W. Portage River South Rd., EImore, Ohio 43416, Telephone (4 ! 9) 862-4205. . Downloaded on August 2. 1996 from http://www.metalogic.be/: METALogic N.V., a spin-off company of K.U. Leuven Dept. MTM Kapeldreef 60-3001 HEVERLEE-Belgium, telephone +32-16-298.330, lax +32-1 6-298.319, e-mail: webmaster@ METALogic.be. , Redmon, J.: "NGST Mirror Replication Task: One Year Plan," Working Group Chart, NASA/MSFC, October 1996. 10. Engelhaupt, D.: "Working Group Discussion at NASA/MSFC,'" University of Alabama in Huntsville, November 18, 1996. ll. Anonymous: "Material Properties Manual," Rockwell International: Rocketdyne Div., Materials Engineering & Tech., Vol. IIA, 4th Ed., January 31, 1987. 12. Morton Advanced Materials: 185 New Boston Street, Wobum, MA 01801-6203. telephone (617) 933-9243, toll flee sales (800) 552-2283, fax (617) 933-5142, WWW=http://www.mortoncvd.com/

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1. Anonymous:"CVD SiliconCarbideTM,''Material specification SC-001, Morton Advanced Materials,Woburn, MA, October 1996. 14. Incropera and DeWitt: Fundamentals o./'Heat and Mass Transl,,r, Third Ed., Appendix A, p. A8, 1990. 15. Coming Incorporated: Advanced Materials Business, HP-CP-08, Coming, NY 14831, telephone (607) 974-7440, WWW=http://www.corning.com. 16. Anonymous: "Zero Expansion Glass ULE TM'' brochure, Corning Incorporated, Coming, NY 1483 I, March 1996. 17. Schott Glass Technologies, Inc.: 400 York Avenue, Duryea, PA 18642, (7 i 7) 457-7485. 18. Anonymous: "Zerodur--Precision From Glass Ceramics," Product brochure 10041, Schott Glass Technologies, Inc., Duryea, PA, October 1991. 19. Anonymous: "Metallic Materials and Elements for Aerospace Vehicle Structures." MIL-HDBK-5F. Department of Defense, pp. I-8 to i-9, November 1990.

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APPENDIX A Beryllium 1-70A Material Properties In October 1997, the authors intended for appendices A and B to contain material properties for Beryllium 1-70 and Beryllium 0-50. However, after a review of our sources for these properties, we realized that the major contributing source was export controlled. After discussions with our management and export control officers, we decided in March 1998 to remove the table of beryllium material properties. Instead, we will list the sources of the properties for your reference. Beryllium sources that are NOT export controlled. Contained CTE vs. temperature data for Beryllium 0-50 Swenson, "HIP beryllium: Thermal expansivity from 4 to 300 K and heat capacity from I to 108 K," Journal of Applied Physics, 70(6), Sept. 1991. Contained Poisson's ratio and Elastic Modulus vs. temperature data for Bery_llium 1-70 J. Focht and D. Caldwell, "Beryllium Materials Characterization Report," Report No. K89-72U(R), Kaman Science Corp., Colorado Springs, CO, Aug. 4, 1989. The major source which DOES contain Export Controlled Information. D.H. Killpatrick, "Report on the Properties of Beryllium," prepared by RDA Logicon for MOD1L, Oak Ridge National Laboratory, Purchase Order 90X-SE860V, May 1990. "WARNING--This document contains technical dam whose export (including transmission to nonresident aliens) is restricted hv the Arms Export Controls Act (22 USC 2751 et seq) or the Export Administration Act of 1979, as amended (50 USC 2401 et seq). Violations of these e,wort laws are subject to criminal penalties. '" A Supplier of Beryllium. Brush Wellman, Beryllium/Mining Division, 14710 W. Portage River S. Rd., Elmore, Ohio 43416, (4191) 862-4205. http://www.brushwellman.com/www/homepage.html II

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APPENDIX B Beryllium 0-50 Material Properties In October 1997, the authors intended for appendices A and B to contain material properties for Beryllium 1-70 and Beryllium 0-50. However, after a review of our sources for these properties, we realized that the major contributing source was export controlled. After discussions with our management and export control officers, we decided in March 1998 to remove the table of beryllium material properties. Instead, we will list the sources of the properties for your reference. Beryllium sources that are NOT export controlled. Contained CTE vs. temperature data for Beryllium 0-50 Swenson, "HIP beryllium: Thermal expansivity from 4 to 300 K and heat capacity from 1 to 108K," Journal of Applied Physics, 70(6), Sept. 1991. Contained Poisson's ratio and Elastic Modulus vs. temperature data for Beryllium 1-70 J. Focht and D. Caldwell, "Beryllium Materials Characterization Report," Report No. K89-72U(R), Kaman Science Corp., Colorado Springs, CO, Aug. 4, 1989. The major source which DOES contain Export Controlled Information. D.H. Killpatrick, "Report on the Properties of Beryllium," prepared by RDA Logicon for MODIL, Oak Ridge National Laboratory, Purchase Order 90X-SE860V. May ! 990. "WARNING--This document contains technical data whose export (including transmission to nonresident aliens) is restricted by the Arms Export Controls Act (22 USC 2751 et seq) or the E.vport Administration Act of1979, as amended (50 USC 2401 et seq). Viol, tions of these export laws are subject to criminal penalties." A Supplier of Beryllium. Brush Wellman, Beryllium/Mining Division, 14710 W. Portage River S. Rd.. Elmore, Ohio 43416, (419) 862-4205. http://www.brushwellman.com/www/homepage.html 13

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APPENDIX C PureNickel Material Properties This appendix contains material properties for pure nickel. Properties. Listed in the following charts are mass density, thermal properties (specific heat, thermal conductivity), and mechanical properties (CTE, modulus of elasticity, Poisson's ratio, and material strength). When available, properties are given over the temperature range of interest for the NGST, from 30 to 294 K. Average CTE values. To assist structural analysts, we calculated average CTE values for the different materials+ where possible, for a temperature drop from room temperature down to the NGST's operating temperature range. We numerically integrated the CTE curve to get thermal strain and then divided by the change in temperature to get an average CTE from 294 to 30 K. If available, these average CTE values are shown below the CTE plots for the various mirror materials. Caution. The listed material strengths are often denoted as being average, typical values. When a telescope project matures, we advise that A-Basis properties be used instead. A-Basis values represent the value at which at least 99 percent of the population of values is expected to equal or exceed the material property allowable, with a statistical confidence of 95 percent. 19 Special notations by the data. If a text notation appears next to a value, talc. indicates that the value was calculated from other data in the table, int. means that the value was linearly interpolated, and assume indicates that the density was assumed to be relatively represent data that was measured in a laboratory. 14 constant versus temperature. All other values

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APPENDIX D Electrodeposited Nickel Material Properties This appendix contains material properties for electrodeposited nickel. Properties, Listed in the following charts are mass density, thermal properties (specific heat, thermal conductivity), and mechanical properties (CTE, modulus of elasticity, Poisson's ratio, and material strength). When available, properties are given over the temperature range of interest for the NGST, from 30 to 294 K. Average CTE values. To assist structural analysts, we calculated average CTE values for the different materials, where possible, for a temperature drop from room temperature down to the NGST's operating temperature range. We numerically integrated the CTE curve to get thermal strain and then divided by the change in temperature to get an average CTE from 294 to 30 K. If available, these average CTE values are shown below the CTE plots for the various mirror materials. Caution. The listed material strengths are often denoted as being average, typical values. When a telescope project matures, we advise that A-Basis properties be used instead. A-Basis values represent the value at which at least 99 percent of the population of values is expected to equal or exceed the material property allowable, with a statistical confidence of 95 percent. 19 Special notations by the data. If a text notation appears next to a value, talc. indicates that the value was calculated from other data in the table, int. means that the value was linearly interpolated, and ass.me indicates that the density was assumed to be relatively represent data that was measured in a labo,'atory. 18 constant versus temperature. All other values

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APPENDIX E CVD Silicon Carbide TM Material Properties This appendix contains material properties for CVD Silicon Carbide TM. Properties. Listed in the following charts are mass density, thermal properties (specific heat, thermal conductivity), and mechanical properties (CTE, modulus of elasticity, Poisson's ratio, and material strength). When available, properties are given over the temperature range of interest for the NGST, from 30 to 294 K. Average CTE values. To assist structural analysts, we calculated average CTE values for the different materials, where possible, for a temperature drop from room temperature down to the NGST's operating temperature range. We numerically integrated the CTE curve to get thermal strain and then divided by the change in temperature to get an average CTE from 294 to 30 K. If available, these average CTE values are shown below the CTE plots for the various mirror materials. Caution. The listed material strengths are often denoted as being average, typical values. When a telescope project matures, we advise that A-Basis properties be used instead. A-Basis values represent the value at which at least 99 percent of the population material property allowable, with a statistical confidence Special notations by the data. If a text notation appears of values is expected to equal or exceed the of 95 percent.19 next to a value, cah'. indicates that the value was calculated from other data in the table, int. means that the value was linearly interpolated, and assume indicates that the density was assumed to be relatively represent data that was measured in a laboratory. constant versus temperature. All other values 21

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APPENDIX F Fused Silica Glass Material Properties This appendix contains material properties for fused silica glass. Properties. Listed in the following charts are mass density, thermal properties (specific heat, thermal conductivity), and mechanical properties (CTE, modulus of elasticity, Poisson's ratio, and material strength). When available, properties are given over the temperature range of interest for the NGST, from 30 to 294 K. Average CTE values. To assist structural analysts, we calculated average CTE values for the different materials, where possible, for a temperature drop from room temperature down to the NGST's operating temperature range. We numerically integrated the CTE curve to get thermal strain and then divided by the change in temperature to get an average CTE from 294 to 30 K. If available, these average CTE values are shown below the CTE plots for the various Caution. The listed material strengths are often denoted mirror materials. as being average, typical values. When a telescope project matures, we advise that A-Basis properties be used instead. A-Basis values represent the value at which at least 99 percent of the population material property allowable, with a statistical confidence Special notations by the data. If a text notation appears of values is expected to equal or exceed the of 95 percent. 19 next to a value, talc. indicates that the value was calculated from other data in the table, int. means that the value was linearly interpolated, and assume indicates that the density was assumed to be relatively represent data that was measured in a laboratory. constant versus temperature. All other values 25

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APPENDIX G Fused Quartz Glass Material Properties This appendix contains material properties for fused quartz glass. Properties. Listed in the following charts are mass density, thermal properties (specific heat, thermal conductivity), and mechanical properties (CTE, modulus of elasticity, Poisson's ratio, and material strength). When available, properties are given over the temperature range of interest for the NGST, from 30 to 294 K. Average CTE values. To assist structural analysts, we calculated average CTE values for the different materials, where possible, for a temperature drop from room temperature down to the NGST's operating temperature range. We numerically integrated the CTE curve to get thermal strain and then divided by the change in temperature to get an average CTE from 294 to 30 K. If available, these average CTE values are shown below the CTE plots for the various mirror materials. Caution. The listed material strengths are often denoted as being average, typical values. When a telescope project matures, we advise that A-Basis properties be used instead. A-Basis values represent the value at which at least 99 percent of the population of values is expected to equal or exceed the material property allowable, with a statistical confidence of 95 percent. 19 Special notations by the data. If a text notation appears next to a value, calc. indicates that the value was calculated from other data in the table, int. means that the value was linearly interpolated, and assume indicates that the density was assumed to be relatively represent data that was measured in a laboratory,. 28 constant versus temperature. All other values

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APPENDIX ULE 7971 H Material Properties This appendix contains material properties for ULE 7971. Properties. Listed in the following charts are mass density, thermal properties (specific heat, thermal conductivity), and mechanical properties (CTE, modulus of elasticity, Poisson's ratio, and material strength). When available, properties are given over the temperature range of interest for the NGST, from 30 to 294 K. Average CTE values. To assist structural analysts, we calculated average CTE values for the different materials, where possible, for a temperature drop from room temperature down to the NGST's operating temperature range. We numerically integrated the CTE curve to get thermal strain and then divided by the change in temperature to get an average CTE from 294 to 30 K. If available, these average CTE values are shown below the CTE plots for the various Caution. The listed material strengths are often denoted mirror materials. as being average, typical values. When a telescope project matures, we advise that A-Basis properties be used instead. A-Basis values represent the value at which at least 99 percent of the population material property allowable, with a statistical confidence Special notations by the data. If a text notation appears of values is expected to equal or exceed the of 95 percent. 19 next to a value, talc. indicates that the value was calculated from other data in the table, int. means that the value was linearly interpolated, and assume indicates that the density was assumed to be relatively represent data that was measured in a laboratory. constant versus temperature. All other values 31

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APPENDIX I Zerodur Material Properties This appendix contains material properties for Zerodur. Properties. Listed in the following charts are mass density, thermal properties (specific heat, thermal conductivity), and mechanical properties (CTE, modulus of elasticity, Poisson's ratio, and material strength). When available, properties are given over the temperature range of interest for the NGST, from 30 to 294 K. Average CTE values. To assist structural analysts, we calculated average CTE values for the different materials, where possible, for a temperature drop from room temperature down to the NGST's operating temperature range. We numerically integrated the CTE curve to get thermal strain and then divided by the change in temperature to get an average CTE from 294 to 30 K. If available, these average CTE values are shown below the CTE plots for the various mirror materials. Caution. The listed material strengths are often denoted as being average, typical values. When a telescope project matures, we advise that A-Basis properties be used instead. A-Basis values represent the value at which at least 99 percent of the population of values is expected to equal or exceed the material property allowable, with a statistical confidence of 95 percent, t9 Special notations by the data. If a text notation appears next to a value, cult. indicates that the value was calculated from other data in the table, int. means that the value was linearly interpolated, and assume indicates that the density was assumed to be relatively represent data that was measured in a laboratory. 34 constant versus temperature. All other values

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APPROVAL MIRROR MATERIAL PROPERTIES COMPILED FOR PRELIMINARY DESIGN OF THE NEXT GENERATION TELESCOPE (30TO 294 KELVIN) P.L. Luz and T. Rice The information in this report has been reviewed for technical content. Review of any information concerning Department of Defense or nuclear energy activities or programs has been made by the MSFC Security Classification Officer.This report, in its entirety, has been determined to be unclassified.

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Form Approved REPORT DOCUMENTATION PAGE I OMB No. 0704-0188 I Publc reponlng burden lor thus collectonof lnlormatlon IS esbmatedto average 1 hour psi response.lncludngthe tlme for reviewinginstructions searchtng exlsbngdata sources gatherngand matntainlngthe data needed and compietngand reviewing the collection at nlotmalonSend comments regardingthis burden esbmateor any othw aspect of lhls collectonof nformationrncludmgsuggesbons for reducing thsburden, to WashngtonHeadquartersServlces Orrecforate for InbrmatonOperation and Reports 1215 Jeflerson DavfsHghwaySulte 1204 ArlngmnVA 22202 4302 and m the Onlceol Management and Budget Papemark Reducbon Project (0704 0188) WashngtonDC 20503 1. AGENCY USE ONLY (Leave Blank) 2. REPORT DATE May 1998 I 4. TITLE AND SUBTITLE 3. REPORT TYPE AND DATES COVERED Technical Memorandum L 5. FUNDING NUMBERS Mirror Material Properties Compiled for Preliminary Design of the Next Generation Space Telescope (30 to 294 Kelvin) 6. AUTHORS P.L. Luz and T. Rice 7. PERFORMING ORGANIZATIONNAMES(S) AND ADDRESS(ES) George C. Marshall Space Flight Center Marshall Space Flight Center, Alabama 358 12 9. SPONSORINGIMONITORINGAGENCY NAME(S)AND ADDRESS(ES) National Aeronautics and Space Administration Washington, DC 20.546-000 l - - 8. PERFORMING ORGANIZATION REPORT NUMBER M-869 10. SPONSORINGlMONITORING AGENCY REPORT NUMBER NASARM- 1998-208 18 1 Prepared by Preliminary Design Office, Program Development Directorate 12a. DISTRIBUTIONIAVAILABlLlTY STATEMENT Unclassified-Unlimited Subject category 23 Nonstandard Distribution 13. ABSTRACT (Maxrmum200 words) 12b. DISTRIBUTIONCODE I This technical memorandum reports on the mirror material properties that were compiled by NASA Marshall Space Flisht Center (MSFC) froni April 1996 to June 1997 for preliminary desien of the Next Generation Space Telescope (NGST) study. The NGST study began in February 1996, when the Program Development Directorate at NASA MSFC studied the feasibility of the NGST and developed the prephase A program for it. After finishing some initial studies and concepts development work on the NGST, MFSC's Program Development Directorate handed this work to the Observatory Projects Office at MSFC and then to NASA Goddard Space Flight Center (GSFC). This technical memorandum was written by MSFC'< Preliminary Desisn Office and Materials and Processes Laboratory for the NGST Optical I Telescope Assembly (OTA)team, in support of NASA GSFC. It contains material properties for , 9 mirror substrate materials, using information from at least 6 industrial suppliers, 16 textbooks, I 44 technical papers, and 130 technical abstracts. 14. SUBJECT TERMS (15. NUMBER OF PAGES substrates. mirror material selection, 44 mirror materials, optical ~naterials.lnirror structural design. thermal design. telescopes, optics. Il6. PRICE COD;,^ I . 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATIONOF ABSTRAC OF REPORT OF THIS PAGE Unclassified Unclassified SN 7540-01-280-5500 OF ABSTRACT Unclassified Unlimited StandardprescribedbyFormANS 298slo235(Revl i 2-89) 298 102