Background
Soyuz
11 was the first successful visit to the world's first space
station, Salyut 1. However the mission ended in disaster when the crew
capsule depressurised during preparations for re-entry, killing the
three-man crew. This accident resulted in the first and to date only
astronaut deaths to occur in space (not in high atmosphere). The
cosmonauts aboard Soyuz 11 were Vladislav Volkov, Georgi Dobrovolski and
Viktor Patsayev.
The Event
The Space Shuttle Challenger disaster occurred on January 28, 1986, when
Space Shuttle Challenger broke apart 73 seconds into its flight, leading
to the deaths of its seven crew members. The spacecraft disintegrated
over the Atlantic Ocean, off the coast of central Florida, United States
at 11:39 a.m. EST (16:39 UTC).
Disintegration of the entire vehicle began after an O-ring seal in its
right solid rocket booster (SRB) failed at liftoff. The O-ring failure
caused a breach in the SRB joint it sealed, allowing pressurized hot gas
from within the solid rocket motor to reach the outside and impinge upon
the adjacent SRB attachment hardware and external fuel tank. This led to
the separation of the right-hand SRB’s aft attachment and the
structural failure of the external tank. Aerodynamic forces promptly
broke up the orbiter.
The crew compartment and many other vehicle fragments were eventually
recovered from the ocean floor after a lengthy search and recovery
operation. Although the exact timing of the death of the crew is
unknown, several crew members are known to have survived the initial
breakup of the spacecraft. However the shuttle had no escape system and
the astronauts did not survive the impact of the crew compartment with
the ocean surface.
The disaster resulted in a 32-month hiatus in the shuttle program and
the formation of the Rogers Commission, a special commission appointed
by United States President Ronald Reagan to investigate the accident.
The Rogers Commission found that NASA’s organizational culture and
decision-making processes had been a key contributing factor to the
accident. NASA managers had known that contractor Morton Thiokol’s
design of the SRBs contained a potentially catastrophic flaw in the
O-rings since 1977, but they failed to address it properly. They also
disregarded warnings from engineers about the dangers of launching on
such a cold day and had failed to adequately report these technical
concerns to their superiors. The Rogers Commission offered NASA nine
recommendations that were to be implemented before shuttle flights
resumed.
Shortly after Soyuz 11 undocked from Salyut 1 and made an initial retro
fire, communication was lost with the crew far earlier than normal. The
capsule descended and was recovered on June 29, 1971 23:17 GMT. When the
hatch was opened it was discovered that the crew was dead.
Root Cause
After an apparently normal re-entry of the capsule of the Soyuz 11
mission, the recovery team opened the capsule to find the crew dead. It
quickly became apparent that they had suffocated. 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. The two were held together by explosive bolts
designed to fire sequentially, but in fact, they fired simultaneously. The
force of this caused the internal mechanism of the pressure equalization
valve to loosen a seal that was usually discarded later, and normally
allowed automatic adjustment of the cabin pressure. The valve opened in
space, and the gradual loss of pressure was fatal within seconds. The
valve was located beneath the cosmonaut's couches, and was impossible to
locate and block before the air was lost. Flight recorder data from the
single cosmonaut outfitted with biomedical sensors showed death occurred
within 40 seconds of pressure loss. By 935 seconds after the retrofire,
the cabin pressure was zero.
Lessons Learned
The Soyuz spacecraft was extensively redesigned after this incident to
carry only two cosmonauts. The extra room meant that the crew could wear
space suits during launch and landing. A Soyuz capsule would not hold
three cosmonauts again until the Soyuz-T redesign in 1980, which freed
enough space for three cosmonauts in lightweight pressure suits to travel
in the capsule.