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My buddies and I have been arguing about this for a while, speculating about the upcoming Starship test.

STS-27 suffered damage on ascent that knocked off a tile & damaged hundreds more. It only survived because the tile was below a component that served as a sufficient heat sink to prevent thermal failure of the airframe & LOCV.

We all could have sworn that component was a steel bracket of some kind (supported by answers on this site), but looking into it more, it seems like it was aluminum. I also thought it was part of some larger steel structural frame/bracing that together was able to absorb the heat coming from the hole in the heat shield, but that doesn't seem to be the case.

What was the full story?

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A copy of the post-flight mission report is available here.

The relevant portion states

The TPS sustained a significant amount of debris hits from the right-hand chine area aft to the right-hand wing. A tile loss (V070-391015-193) occurred on the lower right-hand side of the fuselage at station Xo -390, Yo60. Structural damage was confined to the cavity over a small antenna access door. The tin plating on the aluminum door was melted with aluminum appearing to be half-way between hardened and annealed. The door also had a small buckle.

(emphasis mine)

The antenna door was over a TACAN lower antenna, found by matching the coordinates given above to a Space Shuttle Systems Handbook drawing.

schematic of shuttle belly

A large, but poorly reproduced black and white picture of the damage can be found in the postflight TPS report.

bad image of the damage

along with this sketch

sketch of the damage

This report is more focused on figuring out where the impacting debris came from, than describing the damage. It calls the antenna an L-band antenna but apparently that band includes TACAN.

A tiny color reproduction of the image appears in Volume 1, Chapter 6 of the CAIB Report. I have rotated it here to match the orientation in the other reports. The link is to a low-res pdf in which the picture is even worse than it appears here.

enter image description here

The recent book Space Shuttle Stories contains the best reproduction of this image I've seen; I scanned this picture from there.

enter image description here

Loss of a single tile, while concerning, was not necessarily catastrophic. As early as STS-001, multiple tiles were lost off the OMS pods.

enter image description here

(NASA photo)

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    $\begingroup$ I'm sorry to be the one to question the wisdom of our local STS expert,but is there any chance you have accidentally marked the wrong side on the first diagram? The report gives Yo of +60, which seems to match the other antenna (TACAN 1). $\endgroup$
    – TooTea
    Commented Apr 16, 2023 at 13:32
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    $\begingroup$ Any chance the drawing in the Handbook is looking down through the orbiter (so that "up" on the diagram is "right"/starboard) instead of facing its belly directly (can't access the Handbook right now to check)? The coordinate system used would then match the definition in Fig 23 of Coordinate systems for the space shuttle program (positive Yo = starboard). $\endgroup$
    – TooTea
    Commented Apr 16, 2023 at 15:07
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    $\begingroup$ @TooTea would that fix the negation of the X coordinate? That's the one that really bugs me. Also, the drawing is labeled "bottom view". $\endgroup$
    – Organic Marble
    Commented Apr 16, 2023 at 15:08
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    $\begingroup$ Oh, missed that completely. Then I guess the axes of the diagram are just mislabeled (or would KSC really use a completely different coordinate system yet still call it Xo/Yo for extra confusion with the JSC definitions)? $\endgroup$
    – TooTea
    Commented Apr 16, 2023 at 15:10
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    $\begingroup$ But then maybe not. I find it extremely unlikely that somebody who probably spent years making technical drawings for the STS would forget Xo=0 was the nose… $\endgroup$
    – TooTea
    Commented Apr 16, 2023 at 15:13

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