# Space Shuttle type tiles, or something similar: Commercially available?

Related, but vague in conclusion and not really the same: Is the technology behind the Shuttle's heat-shielding tiles used in any product today?

By "Space shuttle tiles", I mean the white rigid material, not carbon-carbon.

Are pieces of high-temperature insulation that are:

1. Made of substantially the same material as the Space Shuttle tiles

2. Meet the specifications for the Space Shuttle tiles, or

3. Substantially similar to the Space Shuttle tiles, including being able to be touched with the hand while visibly glowing red from the interior

commercially available today?

The short answer is probably not. The shuttle tiles were produced by Lockheed in Sunnyvale. Ca, later with tweaks developed at NASA Ames. (Ref 1) /Revised data, see comment below/ The white shuttle tiles had a thermal conductivity at room temperature in air of 0.0485 w/(m K). (Refs 2 & 7) Currently, several vendors make insulating ceramics, including Cotronics' Rescor 310M machinable ceramic, Foundry Services' Fused Silica Foam-50, and Zircar Ceramics' UNIFORM C1. Although all of these have maximum service temperatures greater than 1000 C, their thermal conductivities are greater than shuttle tile by 3.86X, 2.89X, and 2.27X respectively. (Refs 3, 4, and 5) Since the conductivities are given at different temperatures and conditions, the comparisons listed are only approximate.

As far as I know, the only option for thermal insulation that surpasses shuttle tiles would be a silica aerogel. A typical silica aerogel at atmospheric pressure has a thermal conductivity of 0.017 w/(m K). (Ref 6) However, if you lower the pressure to a roughing pump vacuum (< 50 torr), the conductivity is reduced to 0.008 w/(m K). (The lower pressure increases the mean free path of the air so it is large compared to the size of the pores in the aerogel). The only downside, as I know from personal experience, is silica aerogels are very fragile.

Ref 1: Shuttle tile made by Lockheed https://en.wikipedia.org/wiki/LI-900

Ref 2: Shuttle tile data - https://www.nasa.gov/sites/default/files/atoms/files/shuttle_tiles_5_8v2.pdf

Ref 3: Cotronics' Rescor 310M https://www.cotronics.com/vo/cotr/pdf/58%20%20310M%20%20311.pdf

Ref 4: Foundry Services Fused Silica Foam-50 https://www.foundryservice.com/product/fused-silica-foam-50-2500of-low-expansion-50-pcf-insulating-foam-block/

Ref 5: Zircar Ceramics' UNIFORM C1 https://www.zircarceramics.com/product-category/rigid-insulation/rigid-alumina-silica/

Ref 6: Silica aerogel https://pamelanorris.wordpress.com/resources/thermal-properties/

Ref 7: Shuttle tile data http://mae-nas.eng.usu.edu/MAE_5420_Web/section3/appendix3.pdf

• I've used "w/(m * k)" rather than "w/(m*k)" as the system was interpreting the asterisk as a command to switch to italics. – Vince 49 Mar 1 '20 at 16:06
• With aerogel being more conductive I find myself wondering if that figure is an error somehow. – ikrase Mar 1 '20 at 19:26
• +1 w/(m K) works. Since we don't need an explicit multiplication sign between variables (e.g. $E=mc^2$ using MathJax or E=mc^2 in plaintext) we don't need them for units either, a single space between each unit is usually sufficient. But I'm no expert and frequently flummoxed by getting units to look nice in text. – uhoh Mar 2 '20 at 0:34
• @ikrase, I've checked other references and the value listed is reasonable. The issue is, at atmospheric pressure, the mean free path of air (~ 65 nm) is about the same as the average pore size of the silica aerogels (~ 50 nm). To greatly reduce the conduction from the air, the mean free path needs to be large relative to the pore size. Lower the pressure to 50 torr or less does that. – Vince 49 Mar 2 '20 at 2:18
• Wait, are you saying it was comparing LI-900 in thin air to aerogel at sea level? – ikrase Mar 3 '20 at 11:51

One reason they're probably not commercially available is that they are covered under US federal ITAR laws as a result. Specifically from NASA (emphasis mine)

The Space Shuttle is captured under the International Traffic in Arms Regulations (ITAR) categories IV and XV, which include all specifically designed or modified systems or subsystems, components, parts, accessories, attachments, and associated equipment for the Space Shuttle. The Shuttle Thermal Protection System, including the tiles, is controlled for export purposes under the ITAR. A license from the Department of State is required to transfer the tiles to a foreign person either inside or outside the United states. Any tiles transferred to a U.S. person shall be accompanied by a notice indicating to the recipient the export control classification, license requirements to transfer the tiles to a foreign person, and requirement to comply with U.S. export control laws and regulations.

This limits any potential commercial applications

• Interesting. I knew they were giving them away to schools but not all this backstory. – Organic Marble Mar 2 '20 at 21:39
• That has not stopped a tremendous amount of other ITAR-regulated stuff from being fairly readily commercially available, even available as nearly-commodity prosumer electronics. – ikrase Mar 3 '20 at 11:51
• @ikrase Maybe not, but it is a limitation. And the tiles are still in use on the X-37B project, which the Air/Space Force has refused to explain what it's for – Machavity Mar 3 '20 at 13:13