In early 2003, the space shuttle Columbia burnt up due to a failed leading edge on the wing from an external tank foam strike. All seven astronauts were killed. Yet, some pages of Ilan Ramon's diary, which were aboard, survived readable. How is it possible that the diary was fine and readable, and yet the shuttle burnt up, and killed everyone?
The shuttle did not "burn(t) up". It broke up. In the chaotic environment following the breakup, aerodynamic heating of individual items varied greatly.
The main body breakup, referred to as the Catastrophic Event (CE) in this document, occurred after Mach 15. It was described as follows
The conclusion was that the forward and midbody orbiter segments separated at the CE. The CE is actually the start of a period of several seconds in which the orbiter underwent a major structural breakup.
The subsequent breakup of the crew module is referred to as the Crew Module Catastrophic Event (CMCE).
The CMCE started with the separation of the forward fuselage from the crew module, exposing the entire crew module to the thermal effects of entry. The main forebody debris field included all recovered crew module pressure vessel structure, almost 90 percent of recovered forward fuselage structure, and around 90 percent of the crew module contents. This indicates that the failures of the forward fuselage and crew module were closely associated. Ballistic analysis confirmed this assessment. .... Forward fuselage debris shows localized thermal damage and very little evidence of debris-debris interaction. Large portions of structure were recovered intact. Material deposition on the interior of the forward fuselage debris was not significant. Reconstruction of the forward fuselage debris supports a structural failure from starboard-to- port and forward-to-aft.
Analysis of thermal vectors on numerous debris items showed multiple independent heat vectors across the structure. For example, many recovered middeck floor panels were nearly pristine with paint still visible, while floor panels from immediately adjacent locations had melted materials deposited on them and other signs of high thermal exposure (figure 1.1-31).
After breakup, individual items experienced their own trajectories and heat exposure. This heat exposure can vary enormously with ballistic number and other effects such as shadowing from other debris items and orientation of the item into the heat vector. The lack of consistent directional heating vectors on crew module debris suggests heating was due to individual item trajectories and random exposure during breakup rather than a major breach resulting in directional heating.
Other fragile material recovered intact:
A roll of unprocessed film containing, among others, this inflight crew photo.