posted 02-06-2016 02:06 PM               

What intrigued me about this desk set with an acrylic-encased sample of Avcoat heat shield was what was written on the plaque:

I was in touch with the seller because to my knowledge (and the best of my searches), such an ablator was not part of the space shuttle's thermal protection system.

I asked if perhaps the desk set had been repaired or if the plaque had been added in the time since it was presented, but he said that to his knowledge, it was exactly how his father received it 35 years ago.

I checked the STS-1 Official Flight Kit manifest to see if perhaps a commemorative sample had been flown, but there was no such listing. I suppose it could have been part of Young's or Crippen's PPKs (Young would make some sense, I guess, given his Apollo history), but there is no indication of that, if that was the case.

I did not bid on the auction, but can anyone shed light on how an Avcoat ablator sample ended up on Columbia — if indeed it did?

posted 02-06-2016 06:08 PM            

AVCOAT was used for the heat shield on NASA's Apollo Command Module. In its final form, this material was called AVCOAT 5026-39.

Although AVCOAT was not used for the Space Shuttle orbiters, NASA is using the material for its next generation Orion spacecraft.[6] The Avcoat to be used on Orion is reformulated to meet environmental legislation that has been passed since the end of Apollo.

I can't see any significant linkage between the artifact and the space shuttle. It does look to me to be a cross section of an ablator type heat shield after a re-entry.

The Wiki article had this added info about using Avcoat on Orion.

The biggest challenge with Avcoat has been reviving the technology to manufacture the material such that its performance is similar to what was demonstrated during the Apollo missions," said John Kowal, Orion's thermal protection system manager at Johnson. "Once that had been accomplished, the system evaluations clearly indicated that Avcoat was the preferred system.

posted 02-07-2016 09:56 AM               

Tile From the Apollo Command Module, enclosed in a Perspex cell, mounted on a similar but unused tile, with brass plaques engraved "Allen A. Navarro" and "Avco 5026-39 Ablator Flown on Space Shuttle Flight No. 1, April 1981"...

Developed by AVCO, the tiles were abandoned after the first few flights because the material could not be re-used after the landing. Only three commemorative tiles were reportedly produced, one for the President, one for the chief engineer, and the third for Allen Navarro, the chief contract negotiator between AVCO and NASA.

posted 02-07-2016 10:20 AM               

The second volume of T.A. Heppenheimer's "History of the Space Shuttle" explains:

Late in development, thermal analysis and wind tunnel testing indicated that the areas between the elevons, midway along the span, would reach 3,200 degrees Fahrenheit — far too high for any RSI, even LI-2200. NASA responded by turning to its old standby, the ablative of the Apollo heat shield. Small panels of this ablator, placed at the facing edges of the elevon segments, solved the problem, even though the panels had to be replaced after every flight.

posted 02-07-2016 11:29 AM               

Before the first flight of Columbia and late in the orbiter fabrication cycle, thermal analysis/wind tunnel testing indicated that the areas between the inboard and outboard elevons would encounter temperatures that were too high for tiles to survive even a single mission (~3200° F). Therefore, an ablative material was installed between the split segments of the elevons (outboard end of each inboard elevon and inboard end of each outboard elevon) as shown in figure 8.

The ablative material (AVCOAT 5026-39HC/G) was the same as the Apollo heat shield material. It consisted of an epoxy-novolac resin filled with microballoons and a mixture of silica and E-glass fibers. The resin mixture was injected into a fiberglass, open-faced honeycomb core which was bonded to an aluminum plate.

Since the ablator chars and undergoes surface erosion, it was replaced after each flight. As a result, the ablator system was mechanically attached to the wing structure for easy installation and removal.

The first five flights indicated lower temperatures than initially predicted. All orbiters are now being returned to the original reusable silica tile design in the elevon split area.