Biologically inspired radiation reflector

Patent metadata

Field	Value
Publication number	US-9908642-B1
Application number	US-201514604553-A
Country	US
Kind code	B1
Filing date	Jan 23, 2015
Priority date	Jan 23, 2014
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

A thermal protection system (TPS) comprising a mixture of silicon carbide and SiO x that has been converted from Si that is present in a collection of diatom frustules and at least one diatom has quasi-periodic pore-to-pore separation distance d(p-p) in a selected range. Where a heat shield comprising the converted SiC/SiO x frustules receives radiation, associated with atmospheric (re)entry, a portion of this radiation is reflected so that radiation loading of the heat shield is reduced.

First claim

What is claimed is:

1. A method for providing a thermal protection component for a space vehicle that enters or re-enters an atmosphere, the method comprising:
(1) providing a plurality of particles, comprising Mg, and a powder bed of frustules of SiO x (x≧1) from diatom shells in a heated fluidized bed reactor (FBR), where at least one diatom shell has average nearest neighbor pore-to-pore spacing d(p-p) that lies in a selected range, D1≦d(p-p)≦D2, with D1≧100 nm and D2≧400 nm;
(2) heating the plurality of particles and the SiO x powder bed to a first temperature no greater than about 800° C., and allowing at least a portion of the particles and the SiO x powder bed to react to form MgO and Si;
(3) leaching MgO to provide a first mixture comprising Si particles and SiO x particles;
(4) providing a hydrocarbon gas, comprising at least one of CH 4 , C 2 H 4 and C 2 H 6 , plus an H 2 gas in the FBR in a temperature range T2=640−800° C.;
(5) allowing the first mixture comprising Si particles and SiO x particles to react with the hydrocarbon gas and with the H 2 gas in the FBR to form a substance comprising SiC and SiO x , whereby at least a portion of the first mixture is converted to a second mixture comprising SiC particles and SiO x particles, wherein a temperature during the reaction of the first mixture with the hydrocarbon gas and with the H 2 gas in the FBR is no higher than 800° C.;
(6) providing a layer of the second mixture, having an initial thickness τ1 at least equal to a selected threshold thickness τ1(thr), on an exposed surface of a heat shield system;
(7) permitting the layer of the second mixture to receive radiation from a source of radiation; and
(8) permitting the layer of the second mixture to serve as an optical reflector to reflect a portion of the radiation received.

2. The method of claim 1 , further comprising choosing said pore-to-pore spacing D1≧200 nm.

3. The method of claim 1 , further comprising choosing said pore-to-pore spacing D2≦300 nm.

4. The method of claim 1 , wherein said hydrocarbon gas contains C 2 H 6 , C 2 H 4 or a combination thereof.

5. The method of claim 1 , further comprising limiting said first temperature to a range, T1=600−640° C.

6. The method of claim 1 , further comprising choosing said threshold thickness τ1(thr) that is sufficient so that, after exposure of said second mixture to said radiation for a selected time interval length Δt, a portion of said second mixture remains on said exposed surface.

7. A method for providing a thermal protection component for a space vehicle that enters or re-enters an atmosphere, the method comprising:
(1) providing a plurality of particles, comprising Mg, and a powder bed of frustules of SiO x (x≧1) from diatom shells in a heated fluidized bed reactor (FBR), where at least one diatom shell has average nearest neighbor pore-to-pore spacing d(p-p) that lies in a selected range, D1≦d(p-p)≦D2, with D1≧100 nm and D2≦400 nm;
(2) heating the plurality of particles and the SiO x powder bed to a first temperature no greater than about 800° C., and allowing at least a portion of the particles and the SiO x powder bed to react to form MgO and Si;
(3) leaching MgO to provide a first mixture comprising Si particles and SiO x particles;
(4) providing a hydrocarbon gas, comprising at least one of CH 4 , C 2 H 4 and C 2 H 6 , plus an H 2 gas in the FBR in a temperature range T2=640−800° C.;
(5) allowing the first mixture comprising Si particles and SiO x particles to react with the hydrocarbon gas and with the H 2 gas in the FBR to form a substance comprising SiC and SiO x , whereby at least a portion of the first mixture is converted to a second mixture comprising SiC particles and SiO x particles, wherein a temperature during the reaction of the first mixture with the hydrocarbon gas and with the H 2 gas in the FBR is no higher than 800° C.;
(6) depositing the second mixture in a plurality of isolated clusters, at least one cluster having an initial thickness τ1 at least equal to a selected threshold thickness τ1(thr), on an exposed surface of a heat shield system;
(7) permitting the deposit of the second mixture to receive radiation from a source of radiation; and
(8) permitting the deposit of the second mixture to serve as an optical reflector to reflect a portion of the radiation received.

8. The method of claim 7 , further comprising choosing said pore-to-pore spacing D1≧200 nm.

9. The method of claim 7 , further comprising choosing said pore-to-pore spacing D2≦300 nm.

10. The method of claim 7 , wherein said hydrocarbon gas contains C 2 H 6 , C 2 H 4 or a combination thereof.

11. The method of claim 7 , further comprising limiting said first temperature to a range, T1=600−640° C.

12. The method of claim 7 , further comprising choosing said threshold thickness τ1(thr) that is sufficient so that, after exposure of said second mixture to said radiation for a selected time interval length Δt, a portion of said second mixture remains on said exposed surface.

Assignees

• The Us Administrator Of The National Aeronautics & Space Administration Nasa
• Nasa

Inventors

• Johnson Sylvia M
• Lawson John W
• Squire Thomas H
• Gusman Michael

Classifications

• C04B35/62685

  characterised by the order of addition of constituents or additives · CPC title

• C04B2235/3418

  Silicon oxide, silicic acids or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint · CPC title

• B64G1/54 Primary

  Protection against radiation · CPC title

• B64G1/58 Primary

  Thermal protection, e.g. heat shields · CPC title

• C04B2235/401

  Alkaline earth metals · CPC title