At the end of their mission aboard Soyuz 11, cosmonauts Viktor
Patsayev, Georgi Dobrovolsky, and Vladislav Volkov fired the
explosive bolts to separate the re-entry capsule from the
other stage of their spacecraft. The explosion knocked open a
valve. One hundred miles above the Earth, the capsule was
suddenly exposed to the surrounding low pressure of space.
Patsayev tried to close the valve by hand but failed. Air
inside the spacecraft quickly leaked away, causing an abrupt
loss of pressure and the death of all three cosmonauts.
Soyuz 11 crash site: rescuers giving CPR to
cosmonauts.