Atomic Oxygen-Resistant, Low Drag Coatings and Materials

Abstract

Coatings and materials that are atomic oxygen resistant and have an atomically smooth surface that can reduce drag are disclosed. The coatings and materials can be used on at least a portion of a spacecraft intended to operate in harsh environments, such as stable Earth orbits at about 100 km to about 350 km.

What is claimed is: 
     
         1 . A method of reducing drag on a spacecraft orbiting in a gaseous environment comprising the steps of:
 (a) providing a spacecraft;   (b) providing an atomic oxygen resistant material on at least a portion of the spacecraft such that the material provides a surface wherein (E out /E in ) is between 0.5 and 1.0, where E in  is the average incident kinetic energy and E out  is the average exit kinetic energy of atoms or molecules that scatter inelastically from the surface.   
     
     
         2 . The method of  claim 1 , wherein θ out  is greater than θ in /2, where θ in  is the average incident angle and θ out  is the average exit angle of atoms or molecules that scatter inelastically from the surface, the angles being defined relative to a line normal to the surface and θ in  and θ out  are on opposite sides of the line normal to the surface. 
     
     
         3 . The method of  claim 1 , wherein the atomic oxygen resistant material comprises a metal, a metal oxide, a semiconductor oxide, an oxygen resistant compound, or combinations thereof. 
     
     
         4 . The method of  claim 3 , wherein the atomic oxygen resistant material comprises at least one of Al 2 O 3 , SiO 2 , ZnO, TiO 2 , SnO 2 , In 2 O 3 , ZrO 2 , or combinations thereof. 
     
     
         5 . The method of  claim 3 , wherein the atomic oxygen resistant material comprises sapphire. 
     
     
         6 . The method of  claim 1 , wherein the atomic oxygen resistant material comprises an atomic oxygen resistant substrate and an atomic oxygen resistant coating on the substrate. 
     
     
         7 . The method of  claim 6 , wherein the atomic oxygen resistant substrate is a polymeric material comprising a copolymer of at least one polyimide monomer and at least one polyhedral oligomeric silsesquioxane, or a blend of at least one polyimide monomer and at least one polyhedral oligomeric silsesquioxane. 
     
     
         8 . The method of  claim 7 , wherein the polymeric material comprises a silicon oxide content of at least 3.5 wt %, where silicon oxide content refers to the total number of silicon and oxygen atoms present in the material. 
     
     
         9 . The method of  claim 8 , wherein the polymeric material provides an erosion yield of 0.18×10 −24  cm 3  atom −1  or less after exposure to an atomic oxygen fluence of 1.97×10 21  O atoms cm −2 . 
     
     
         10 . The method of  claim 8 , wherein the polymeric material yields an etch depth of less than half an etch depth of Kapton H or Kapton HN after exposure to a given atomic oxygen fluence. 
     
     
         11 . The method of  claim 6 , wherein the atomic oxygen resistant coating is an atomic layer deposition coating. 
     
     
         12 . The method of  claim 1 , wherein the surface provides at least a 10% reduction of drag compared to a surface that diffusely scatters incident atoms or molecules. 
     
     
         13 . The method of  claim 12 , wherein the surface provides approximately less than 50% of drag compared to a surface that diffusely scatters incident atoms or molecules. 
     
     
         14 . The method of  claim 1 , further comprising providing the spacecraft in an Earth orbit at an altitude between 100 km and 350 km. 
     
     
         15 . The method of  claim 1 , wherein the polymeric material comprises a silicon oxide content of up to 7 wt %, where silicon oxide content refers to the total number of silicon and oxygen atoms present in the material. 
     
     
         16 . A spacecraft having at least one portion that reduces drag, comprising:
 an atomic oxygen resistant material, wherein the atomic oxygen resistant material forms the at least one portion of the spacecraft and provides an atomically smooth surface such that θ out  is greater than θ in /2, where θ in  is the average incident angle and θ out  is the average exit angle of atoms or molecules that scatter inelastically from the surface, the angles being defined relative to a line normal to the surface and θ in  and θ out  are on opposite sides of the line normal to the surface.   
     
     
         17 . The spacecraft of  claim 16 , wherein the surface of the at least one portion of the spacecraft is such that (E out /E in ) is between 0.5 and 1.0, where E in  is the average incident kinetic energy and E out  is the average exit kinetic energy of atoms or molecules that scatter inelastically from the surface. 
     
     
         18 . The spacecraft of  claim 16 , wherein the spacecraft orbits the Earth at an altitude between 100 km and 350 km. 
     
     
         19 . The spacecraft of  claim 16 , wherein the surface provides at least a 10% reduction of drag compared to a surface that diffusely scatters incident atoms or molecules. 
     
     
         20 . The spacecraft of  claim 19 , wherein the surface provides approximately less than 50% of drag compared to a surface that diffusely scatters incident atoms or molecules. 
     
     
         21 . The spacecraft of  claim 16 , wherein the atomic oxygen resistant material comprises a layer of metal, metal oxide, semiconductor oxide, or a combination thereof. 
     
     
         22 . The spacecraft of  claim 21 , wherein the layer comprises at least one of Al 2 O 3 , SiO 2 , ZnO, TiO 2 , SnO 2 , In 2 O 3 , ZrO 2 , or combinations thereof. 
     
     
         23 . The spacecraft of  claim 21 , wherein the layer comprises sapphire. 
     
     
         24 . The spacecraft of  claim 16 , wherein the atomic oxygen resistant material comprises an atomic oxygen resistant substrate and an atomic oxygen resistant coating on the substrate. 
     
     
         25 . The spacecraft of  claim 24 , wherein the atomic oxygen resistant substrate comprises a polymeric material comprising at least one polyimide monomer and at least one polyhedral oligomeric silsesquioxane, or a blend of at least one polyimide monomer and at least one polyhedral oligomeric silsesquioxane. 
     
     
         26 . The spacecraft of  claim 25 , wherein the polymeric material comprises at least 3.5 wt % silicon oxide, where silicon oxide content refers to the total number of silicon and oxygen atoms present in the material. 
     
     
         27 . The spacecraft of  claim 25 , wherein the polymeric material comprises a silicon oxide content of up to 7 wt %, where silicon oxide content refers to the total number of silicon and oxygen atoms present in the material. 
     
     
         28 . The spacecraft of  claim 25 , wherein the polymeric material provides an erosion yield of atomic oxygen resistant coating is ×10 −24  cm 3  atom −1  or less after exposure to an atomic oxygen fluence of 1.97×10 21  O atoms cm −2 . 
     
     
         29 . The spacecraft of  claim 25 , wherein the polymeric material yields an etch depth of less than half an etch depth of Kapton H or Kapton HN after exposure to an atomic oxygen flux for a given duration. 
     
     
         30 . The spacecraft of  claim 24 , wherein the atomic oxygen resistant coating is an atomic layer deposition coating. 
     
     
         31 . The spacecraft of  claim 24 , wherein the atomic oxygen resistant coating comprises a metal, a metal oxide, a semiconductor oxide, an atomic oxygen resistant compound, or combinations thereof. 
     
     
         32 . The spacecraft of  claim 24 , wherein the atomic oxygen resistant coating comprises at least one of Al 2 O 3 , SiO 2 , ZnO, TiO 2 , SnO 2 , In 2 O 3 , ZrO 2 , or combinations thereof. 
     
     
         33 . The spacecraft of  claim 24 , wherein the atomic oxygen resistant coating comprises at least one of Al 2 O 3  or SiO 2 , or other atomic oxygen resistant compound. 
     
     
         34 . The spacecraft of  claim 24 , wherein the substrate comprises a metal, a metal oxide, a semiconductor oxide, an atomic oxygen resistant compound, or combinations thereof. 
     
     
         35 . An atomic oxygen resistant material comprising:
 a surface such that (E out /E in ) is between 0.5 and 1.0, where E in  is the average incident kinetic energy and E out  is the average exit kinetic energy of atoms or molecules that scatter inelastically from the surface, and θ out  is greater than θ in /2, where θ in  is the average incident angle and θ out  is the average exit angle of atoms or molecules that scatter inelastically from the surface, the angles being defined relative to a line normal to the surface and θ in  and θ out  are on opposite sides of the line normal to the surface.   
     
     
         36 . The atomic oxygen resistant material of  claim 35  comprising a metal, a metal oxide, a semiconductor oxide, or combinations thereof. 
     
     
         37 . The atomic oxygen resistant material of  claim 36 , wherein the material comprises an atomic oxygen resistant coating with at least one layer of Al 2 O 3 . 
     
     
         38 . The atomic oxygen resistant material of  claim 37 , wherein the atomic oxygen resistant coating is on an atomic oxygen resistant substrate. 
     
     
         39 . The atomic oxygen resistant material of  claim 38 , wherein the atomic oxygen resistant substrate comprises a polymeric material comprising a copolymer of at least one polyimide monomer and at least one polyhedral oligomeric silsesquioxane, or a blend of at least one polyimide monomer and at least one polyhedral oligomeric silsesquioxane. 
     
     
         40 . The atomic oxygen resistant material of  claim 39 , wherein the polymeric material comprises at least 3.5 wt % silicon oxide, where silicon oxide content refers to the total number of silicon and oxygen atoms present in the material. 
     
     
         41 . The atomic oxygen resistant material of  claim 39 , wherein the polymeric material provides an erosion yield of atomic oxygen resistant coating is ×10 −24  cm 3  atom −1  or less after exposure to an atomic oxygen fluence of 1.97×10 21  O atoms cm −2 . 
     
     
         42 . The atomic oxygen resistant material of  claim 39 , wherein the polymeric material yields an etch depth of less than half an etch depth of Kapton H or Kapton HN after exposure to a given atomic oxygen fluence. 
     
     
         43 . The atomic oxygen resistant material of  claim 39 , wherein the atomic oxygen resistant coating is an atomic layer deposition coating. 
     
     
         44 . The atomic oxygen resistant material of  claim 38 , wherein the atomic oxygen resistant coating comprises a metal, a metal oxide, a semiconductor oxide, an atomic oxygen resistant compound, or combinations thereof. 
     
     
         45 . The atomic oxygen resistant material of  claim 44 , wherein the atomic oxygen resistant coating comprises at least one of Al 2 O 3 , SiO 2 , ZnO, TiO 2 , SnO 2 , In 2 O 3 , ZrO 2 , or combinations thereof. 
     
     
         46 . The atomic oxygen resistant material of  claim 45 , wherein the atomic oxygen resistant coating comprises at least one of Al 2 O 3 , or SiO 2 .