The cause of a Russian spacecraft鈥檚 fiery descent back to Earth on Saturday is still unknown, but investigators suspect an electrical short circuit or the delayed detachment of a propulsion module might be to blame, NASA鈥檚 space operations director Bill Gerstenmaier said on Tuesday.
On 19 April, the Soyuz TMA-11 automatically switched to a 鈥渂allistic鈥� re-entry mode while returning to Earth. This is a backup mode involving a steeper than normal trajectory; it exposes the crew to up to 10 times the force of gravity on Earth during descent.
On board the spacecraft were South Korea鈥檚 first astronaut, So-yeon Yi, and space veterans Yuri Malenchenko and Peggy Whitson.
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Mission controllers in Moscow lost radio contact with the capsule for about an hour during the descent and as a result were initially unaware that the ballistic re-entry mode had been triggered, or that the capsule had landed some 475 kilometres (295 miles) short of its target.
Saturday鈥檚 ballistic re-entry is the second in a row for the Soyuz spacecraft and the third since 2003.
In a teleconference with reporters on Tuesday, Gerstenmaier downplayed reports of danger to the crew and urged patience as a commission set up by the Russian Federal Space Agency investigated the issue. 鈥淲e don鈥檛 see this as a major problem, but it鈥檚 clearly something that should not have occurred,鈥� Gerstenmaier said. 鈥淲e don鈥檛 like to see things repeat on two flights.鈥�
Electrical short
Russia鈥檚 Interfax news agency quoted an unidentified Russian space official as saying that the Soyuz capsule suffered significant heat damage and that the crew was in serious danger during descent. But Gerstenmaier said he was unaware of any such statements being made. 鈥淭he Russian folks have not told me any of that,鈥� he said. 鈥淭hey鈥檙e concerned about the event, but the relative danger to the crew 鈥� we鈥檝e had no discussion on that at all.鈥�
The initial suspect for the problem is a cable that connects the control panel in the crew capsule to descent hardware on the Soyuz. An electrical short in the cable can automatically trigger the ballistic re-entry mode.
Such a short is suspected to have caused the ballistic re-entry experienced by a Soyuz spacecraft in October 2007.
Wrong orientation
Investigators of the earlier Soyuz TMA-10 mishap also found evidence of a delay in the detachment of a propulsion module from the capsule. If the module does not detach from the crew capsule as planned before hitting the Earth鈥檚 atmosphere, it changes the weight distribution of the spacecraft, potentially causing the crew capsule to descend to Earth in the wrong orientation.
Initial reports from the crew of Soyuz TMA-11 suggests a similar detachment delay occurred during Saturday鈥檚 re-entry. Russian investigators are exploring the possibility that the two events are linked, but Gerstenmaier cautioned against jumping to conclusions.
鈥淭hat鈥檚 not the right leap to make yet,鈥� he said. 鈥淟et the Russians go ahead and get the data, analyse and understand what they鈥檝e got and then we can talk about where we are.鈥�
Critical time
The Soyuz mishaps come at a particularly crucial time for NASA. The agency is preparing to retire its shuttle fleet in 2010 and the replacement Orion Crew Exploration Vehicle (CEV) will not be ready until 2015.
During the five-year gap, the Russian Soyuz will be the primary vehicle for shuttling crew to and from the International Space Station.
Gerstenmaier said it is too early to speculate how the recent accidents will affect NASA鈥檚 future, but hinted that the agency would consider commercial launch options if necessary.
鈥淲e don鈥檛 have the luxury or the funding to go ahead and continue multiple launch systems,鈥� Gerstenmaier said. 鈥淲e鈥檒l work as hard as we can to get our CEV or get a commercial crew transportation capability online as soon as we can.鈥�
