Dangling strap to blame for scary space leak?

“Before departure, the crew performed the hatch seal inspection and cleaning before hatch closure and a visual inspection to ensure the mated surface area was clear of any objects,” the report states. Representatives of the spacecraft manufacturer “believe the crew was more pressed on time and may have been hurried,” and hence overlooked the strap, which could have been sucked into the gap by air flow just as the hatch was being closed and locked.

The crew was more hurried than usual, these experts speculate, due to pressure from specialists back on Earth. “Scientists have become more interested in the biology-type payloads,” the report continues, “which are stored in the ISS freezer until one hour before departure.” But then they must be brought to the landing capsule in insulated packages.

“The more of these payloads you have the more you are rushed at the last minute to complete Soyuz packing and departure preparations,” the experts concluded. The crew was bringing back scientific samples that originally were to have ridden back to Earth aboard a space shuttle mission, but were stranded in orbit when problems on the shuttle flight in July delayed the next flight from September until sometime next spring at the earliest.

As a check on hatch airtightness prior to undocking, air is bled out of the forward (unoccupied) orbital module, and pressure inside the crew cabin in the descent module is monitored. “The hatch leak test results were inconclusive,” the report states, with a “somewhat off-nominal reading, but this did not really indicate a leak.” After a delay of at least six minutes, permission was given to undock, even though Mission Control in Moscow wasn’t sure of the cause of the unusual pressure readings.

But after undocking the pressure drop became more obvious as air from the descent module leaked into the orbital module. This went on for several hours.

However, once the orbital module was jettisoned, the leak — which might then have gotten much worse — instead stopped entirely. The experts interpreted this to mean that the much higher pressure difference across the hatch — now facing the pure vacuum of space — actually compressed the flexible rubber seal and strangled the leak off.

The chance of the alternate possibility — physical rupture of the damaged seal and a considerably increased leak rate leading to total cabin depressurization — remains uncalculated, but in that event the crew’s spacesuits would have saved their lives.

While the experts cited in the report insist that no changes in crew procedures were needed as long as future crews properly perform the hatch seal inspections, the report itself remains preliminary. And the two space professionals aboard the Soyuz that day, Krikalev and Phillips, returned to Houston from Moscow last week without signing off on the version that holds them responsible for the space scare.

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