Consecutive Rough Soyuz TMA Landings May be Linked
NEW YORK & MOSCOW – Russian space authorities are pledging a thorough investigation in the wake of the second straight incident in which a crew-carrying Soyuz TMA capsule returning from the international space station had a rough landing after re-entering the atmosphere on a steeper-than-normal trajectory.
“They are going to dig deep,” said Alexander Vorobyov, a spokesman for Roskosmos, the Russian space agency. “This is, after all, the second time in a row that this has happened.”
In the latest incident April 19, the Soyuz TMA-11 spacecraft with three passengers on board went into what Roskosmos refers to as a ballistic trajectory during its return from the station. This is a backup landing profile that sends the re-entry capsule back to Earth in an unguided spin at a steep angle that subjects the crew to up to eight times the force of gravity before parachutes deploy. Nominal landings hit peak loads of about six times the force of gravity.
The craft came down some 420 kilometers short of its target landing zone in Kazakhstan.
In October, a Soyuz capsule bringing home the space station’s Expedition 15 crew along with a Malaysian astronaut experienced a similarly steep descent and touched down well outside the designated landing zone. No one was hurt in either incident.
“The fact that we had similar occurrences of something that we thought we understood on two vehicles calls into question some design problems or maybe a manufacturing change,” William Gerstenmaier, NASA associate administrator for space operations, told members of Congress April 24. “Something has changed to the vehicles.”
Vorobyov strongly denied Russian press reports suggesting the crew in the latest incident – space station Expedition 16 crew commander Peggy Whitson, flight engineer Yuri Malenchenko and South Korean astronaut So-yeon Yi – was lucky to make it out alive.
“It is all a black public relations campaign,” Vorobyov said in an interview April 24.
The international space station partners will rely exclusively on the Soyuz to transport crews to and from the orbital outpost after NASA’s space shuttle retires around 2010. NASA hopes to begin negotiations with Russia this summer to procure the necessary Soyuz flights beyond 2011, when the current agreement expires.
More Soyuz spacecraft also will be needed beginning next year, when the space station’s crew size is expected to jump from three to six.
“We’ve been discussing with the Russians their ability to support Soyuz production for next year,” Gerstenmaier said during a media teleconference April 22. “But again we need to watch and understand what the failure mode was.”
Gerstenmaier said it was too early to tell what level of danger the crew aboard the Soyuz TMA-11 was facing. The Russians “are concerned about the event, but the relative danger to the crew – we’ve had no discussion on that at all,” he said.
Malenchenko and Whitson reported being shaken about in their seats early in the landing operation, which suggests that the three-segment Soyuz spacecraft’s disposable propulsion module may not have jettisoned as cleanly as designed, Gerstenmaier said. A similar problem occurred during the October Soyuz landing.
Another potential culprit is an avionics cable that may have shorted out and directed the Soyuz computers to initiate a ballistic descent, he added.
Russian and NASA engineers will have a better handle on the anomaly once the Soyuz crew capsule and its flight recorder are retrieved and the data analyzed.
“It may be a month or so before we start hearing anything definitive back from the commission,” Gerstenmaier said.
The three-segment Soyuz spacecraft long has been Russia’s highly reliable workhorse of manned spaceflight. It consists of a 2,900-kilogram central crew capsule sandwiched between an orbital and docking module on top and a propulsion module – which includes solar arrays and propellant – on the bottom. The three modules separate during re-entry, leaving the bell-shaped crew capsule to return to Earth with the aid of parachutes and retrorockets.
Gerstenmaier said during the teleconference that officials know the following:
Malenchenko and Whitson reported unusual buffeting, jarring and shaking before entering the ballistic descent, suggesting the propulsion module may not have detached properly.
The Soyuz spacecraft lost radio contact with Mission Control during re-entry for an as-yet unexplained reason.
Malenchenko did report some signs of smoke inside the Soyuz spacecraft during re-entry and powered down a display panel at times. Whether the smell came from inside the vehicle or through vents from the exterior is undetermined.
“I don’t see this as a major, major problem, but it is clearly something that should not have occurred,” Gerstenmaier said of the landing incident. “I think there is inherent reliability in this system.”
After last year’s ballistic return of the Expedition 15 crew, Roskosmos replaced the cable on new Soyuz vehicles and double-checked power connections for the explosive bolts governing module separation.
But the Soyuz TMA-11 spacecraft that launched the Expedition 16 crew into space was already docked at the space station by then. The astronauts safeguarded the ballistic system cable using additional insulation, but could not check the module separation system from inside.
The only way to check that system in orbit would be in a spacewalk that would require astronauts to don spacesuits, carefully peel back layers of their Soyuz vehicle’s protective thermal blankets and examine connectors for each of the explosive bolts, Gerstenmaier said.
“We determined, along with the Russians, that that was probably more risky to go out and pull those blankets back,” he said. “We didn’t see any more fixes that didn’t carry more risk associated with them than leaving it as it was.”
Gerstenmaier said he expects NASA and Russian space officials to discuss any new findings from the ongoing investigation prior the planned May maneuver involving the Soyuz TMA-12 spacecraft currently docked at the space station. During that flight, NASA astronaut Garrett Reisman and two Russian cosmonauts will move the craft to a new docking port on the space station.
Testifying before the House Science and Technology space and aeronautics subcommittee during a space station hearing April 24, Gerstenmaier said the Soyuz TMA-11 capsule arrived in Moscow the day before. He said Russia has formed an independent review panel and would inform NASA of its plan for the investigation the week of April 27.
“They are as concerned as we are about this event,” Gerstenmaier said.
He added that NASA will look carefully at safety before using the Soyuz for any activity. “The Russians use the same engineering methodology that we use,” he said. “We’ll learn from this, the Russians will learn from this and we’ll make a better design to push forward.”
Becky Iannotta contributed to this article from Washington. Comments: firstname.lastname@example.org, email@example.com