​To shield, or not to shield, that is the question.
 
This is part 4 of a 5-blog series on dragon fire vs metal shield. Last time we looked at how much dragon fire would heat up our shield via convection (answer – not much). Today we look at radiation, and we get some much more exciting results.

​How fast does a shield get uncomfortable when you use it to block a gout of dragon’s flame?

This is the third of five posts answering that burning question (pun intended). So far we’ve learned that:

• Dragon flame heats a shield using convection and radiation (and probably some other stuff that we’re ignoring for now) - see Part 1.
• Convection probably dumps about 1,100 Watts of heat into the shield (at least at first) - see Part 2.

In this post we’ll talk about Watts, shields, and microwaves. Let’s get to it!

Our quest – to counsel brave knights on the advisability of bringing a shield to a dragon fight – continues.

This is a pretty hairy problem, as it turns out. There are all kinds of crazy things happening when fire heats metal. I dove pretty deep into several rabbit holes this week – from impinging jets on cooled calorimeters and handbooks for estimating the effects of forest fires on power lines to combustion chemistry and a hitherto-unknown-to-me method of heat transfer involving cool metal changing the molecular structure of half combusted gases.

But let’s ignore all that. We’re already dealing with dragon fire and theoretical shields. Let’s c̶h̶a̶n̶g̶e̶ ̶r̶e̶a̶l̶i̶t̶y̶ ̶s̶o̶ ̶i̶t̶s̶ ̶e̶a̶s̶y̶ ̶t̶o̶ ̶a̶n̶a̶l̶y̶z̶e̶ ̶ stick with our totally reasonable simplifications.

​Remember from last time that we turned something beautiful, like this:

​It’s practically tradition. Brave knights - from Beowulf to Prince Philip - have been casually blocking gouts of flame since before fantasy was a genre. But you’ve been wondering (as I have): 

Making some sweeping assumptions and ignoring things like enchanted shields or flame that melts through stone bridges (see Maleficent, about ten seconds after the scene above), I’ll attempt to answer this question with the powers of engineering.