CertifyingSoyuz, Wayne Hale
"So as new human certification ratings are proposed, they rely heavily on new standards and specifications, requirements for analysis, engineering calculation, computer simulation, piece-part testing and just a little bit on flight demonstration. Of course, the Shuttle and the Soyuz don't comply with those standards; they were built in different times with more primitive standards. But they demonstrate a level of reliability or safety that is apparently acceptable. If someone were to build their own spacecraft and/or launch vehicle; fly it successfully many times, demonstrate its capabilities in actual flight; then I suspect the new human rating requirements would be tossed aside in favor of demonstrated actual flight performance."