Large lightweight mirror for a large telescope

{
  "publication_number": "US10422933B2",
  "country": "US",
  "kind": "B2",
  "title": "Large lightweight mirror for a large telescope",
  "abstract": "A process for manufacturing a mirror includes preparing a mirror core by successively depositing a plurality of layers of a core material to form a core structure; and bonding, using a bonding material, the mirror core to a front polishable faceplate and a back faceplate. A mirror includes a mirror core including a plurality of layers of a core material; a front polished faceplate; and a back faceplate. The front polished faceplate and the back faceplate are bonded to the mirror core with a bonding material.",
  "claims": [
    "1. A mirror for a ground-based, airborne or outer-space-based telescope, the mirror comprising a mirror core including a plurality of layers of a core material; a front polished faceplate comprising a front faceplate material; and a back faceplate comprising a back faceplate material, wherein the front polished faceplate and the back faceplate are bonded to the mirror core with a bonding material, wherein the bonding material is different from the front faceplate material, the back faceplate material, and the core material.",
    "2. The mirror of claim 1, wherein the mirror core comprises a plurality of core segments bonded together.",
    "3. The mirror of claim 1, wherein one or more of the front faceplate material and the back faceplate material comprise a same material as the core material.",
    "4. The mirror of claim 1, wherein the plurality of layers of the core material are the product of an additive manufacturing process.",
    "5. The mirror of claim 4, where the additive manufacturing process is a 3D printing process.",
    "6. The mirror of claim 1, wherein the front polished faceplate and the back faceplate are bonded to the mirror core via a bond selected from the group consisting of: a low temperature fusion bond, a direct laser bond, a reactive bond, a hydroxide bond, an anodic bond, a low temperature metallic solder bond, a thermal cure adhesive bond and UV cure adhesive bond.",
    "7. The mirror of claim 1 further comprising a multilayer stable reflecting coating on one or both of the front polishable faceplate and the back faceplate.",
    "8. The mirror of claim 1, wherein the core material has one or more properties selected from: a coefficient of thermal expansion in the range from +/−0.03 to 10 ppm/degree Centigrade, a density in the range from 1.8 to 3.5 gm/cc, and a modulus of elasticity in the range of 40 to 500 GPa.",
    "9. The mirror of claim 1, wherein the core material comprises one or more of: a silicon carbide material, a ceramic material, a ceramic-doped polymeric material, a carbon nanotube-filled polymeric material, a glass-ceramic material, a carbon composite material, fused silica, and ultra low expansion glass.",
    "10. The mirror of claim 8, wherein the glass ceramic material has a coefficient of thermal expansion in the range from +/−0.03 to 10 ppm/degree Centigrade.",
    "11. The mirror of claim 1, wherein one or more of the front faceplate material and the back faceplate material comprises a same material as the core material.",
    "12. The mirror of claim 1, wherein the bonding material has one or more properties selected from adhesive strength in the range from 15 MPa to 70 MPa, a coefficient of thermal expansion in the range from 5 to 100 ppm/degree C., and a coefficient of moisture expansion in the range from 1500 to 5000 micro-inches/inch % moisture.",
    "13. The mirror of claim 1, wherein the bonding material has a Young's modulus in the range from 0.5 to 5 GPa.",
    "14. The mirror of claim 1, wherein the bonding material comprises one or more of: a solder alloy, a thermal cure adhesive, a UV-curable adhesive, a ceramic frit, direct laser bonding and low temperature fusion.",
    "15. The mirror of claim 1, wherein one or both of the front polishable faceplate and the back faceplate comprises one or more of an ultra-low expansion glass material, a glass-ceramic material, a fused silica material, a carbon composite material, a beryllium material and silicon carbide material."
  ],
  "description_excerpt": "This invention relates to mirror architectures and additive processes for producing the same.\n\nLarge lightweight mirrors are critical components in ground-based, airborne and outer-space-based imaging applications. Traditional mirrors intended for use in outer space drive the full system schedule requiring high cycle times and costs. While there are opportunities to reduce the cost and schedule in the manufacture of lightweight core, open- and closed-back mirrors, typically only nominal advances have been previously enabled.\n\nPresent methods of manufacturing a mirror for large telescopes involve reducing the weight of mirror by traditional abrasive water jetting (AWJ) or precision machining of a large boule, in which almost 95% material is eventually discarded. Such processing can take up to 2 years from ordering the glass boules to finishing. Due to these long cycle times, completed optical systems can take 3-4 years to manufacture. Corning's ULE® is commonly used for telescope mirrors.\n\nAdvanced ceramics and carbon composite materials have been offered as cost- and schedule-reducing alternatives to Corning ULE®, due to the high stiffness at relatively low mass and thermal expansion of these materials. However, mirrors based on carbon composite have issues with long term stability, and can suffer from deterioration based on thermal and hygro absorption. Fabrication of a composite core also requires precise layering of the carbon fiber prepreg, orientation, autoclaving and significant machining.",
  "cpc": [
    "G02B 5/0816",
    "G02B 7/183"
  ],
  "ipc": [
    "G02B 5/08",
    "G02B 7/183"
  ],
  "assignees": [
    "Harris Corp"
  ],
  "inventors": [
    "James Ted Mooney",
    "Tukaram K. Hatwar"
  ],
  "filing_date": "2018-10-11",
  "publication_date": "2019-09-24",
  "grant_date": "2019-09-24",
  "priority_date": "2016-07-01",
  "application_number": "US-201816157781-A",
  "family_id": "60806176",
  "cited_by_count": 4,
  "citations": [
    "US5316564A",
    "US6206531B1",
    "US20110032629A1",
    "US8602576B1",
    "US20150056415A1"
  ]
}