Eddie
Ah no. The Comet, like the other early pressurised aircraft was designed to what’s called safe life philosophy which means by design there’s no cracks. If there’s no cracks you don’t need know about crack progression rates. It worked for Vickers, Douglas, Boeing and Lockheed and even DH when they finally got it right on Comet 4 /Nimrod.

The cracks progression work feed into the next generation of designs called damage tolerant philosophy which are intended to be safe even if cracked.