As tragic as the Soyuz 11 incident was, it's hardly similar in any of its aspects: "The fault was traced to a breathing ventilation valve, located between the

As tragic as the Soyuz 11 incident was, it's hardly similar in any of its aspects: "The fault was traced to a breathing ventilation valve, located between the orbital module and the descent module, that had been jolted open as the descent module separated from the service module, 12 minutes and 3 seconds after retrofire. The two were held together by explosive bolts designed to fire sequentially; in fact, they had fired simultaneously. The explosive force of the simultaneous bolt firing caused the internal mechanism of the pressure equalization valve to loosen a seal that was usually discarded later and which normally allowed for automatic adjustment of the cabin pressure. The valve opened at an altitude of 168 kilometres, and the resultant loss of pressure was fatal within seconds."