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During the launch and re-entry of space shuttle, what are the measured and estimated temperatures (or distribution) of the shuttle nose cone as a function of altitude? How is the temperature measured (at the cone) and what is the uncertainty or alarm limits?

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The trajectories are quite different between ascent and entry. Launch trajectories are designed so that the aeroheating is very little. Entry trajectories, without the advantage of minutes of powered flight like ascent, cannot avoid significant aeroheating. This aeroheating is several orders of magnitude more than ascent.

The temperature of the heatshield can be estimated by its radius of curvature, the dynamic pressure, and airspeed. Complicated computational fluid dynamics models, anchored by test and flight data, estimate what the temperatures will be at various points across the surface. Monte Carlo simulations provide engineers a distribution of the temperatures, given small changes such as with the vehicle's trajectory, attitude, heatshield surface roughness, and aeroheating model parameters.

It is common that the first several flights of a new vehicle will instrument its heatshield to validate the aeroheating models used for its design. This instrumentation is typically thermocouples. The uncertainty is dependent on how well the instrumentation is built and integrated into the thermal protection system, and how well it is calibrated.

A good summary of the experience in building and using heatshields, written in the early 1990s by NASA, may be found at https://ntrs.nasa.gov/api/citations/19930003261/downloads/19930003261.pdf.

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    $\begingroup$ There was instrumentation on the nose cap of Columbia. The system was called SEADS. Your answer can't really be complete unless you discuss that and its results. $\endgroup$ – Organic Marble Jun 20 at 1:02
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    $\begingroup$ I snuck a peek during the STS-109 reentry (it was dark out). That sucker was white hot... $\endgroup$ – Digger Jul 20 at 14:15
  • $\begingroup$ @OrganicMarble: I've improved the question. It seems that you are able to answer it; would you please consider doing so? $\endgroup$ – DrSheldon Jul 22 at 6:04

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