Possible Soyuz separation problem under scrutiny
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: April 22, 2008;
Updated at 4:25 p.m. with news briefing;
Updated ast 8:40 p.m. with Whitson landing day interview
The Russian Soyuz TMA-11 spacecraft that carried two space station crew members and a South Korean guest cosmonaut back to Earth Saturday may have started its fiery re-entry with a normally discarded propulsion module still attached officials said today, putting the craft in an unusual orientation and subjecting the returning space fliers to higher than normal stresses and buffeting.
"I saw 8.2 Gs on the meter and it was ... pretty dramatic," outgoing space station commander Peggy Whitson, flying as the left-seat Soyuz engineer, told a NASA interviewer shortly after landing. "Gravity's not really my friend right now and 8 Gs was especially not my friend. But it didn't last too long. Chute deploy was nominal and impact ... wasn't quite as bad as I was expecting."
But the separation of the Soyuz modules "was a little more dramatic than I was expecting."
In the meantime, he said the Soyuz TMA-12 spacecraft currently docked to the space station is available for use by the lab's three-man crew if necessary.
"We don't see this as a major problem, but it's clearly something that should not have occurred, we don't like to see things repeat on two flights," he told reporters in an afternoon teleconference. Warning against speculation, he said "it appears, based on what we hear, we may have missed the most probable cause (of the earlier problem). We may have something else going on. ... The important thing is the Russians are taking this extremely serious, they've got the commission started, they're bringing in some independent folks on their side to take a look at this and they'll understand what the problem is."
Using explosive bolts, the Soyuz TMA-11 spacecraft's three modules normally separate just before atmospheric entry and the crew returns in the central descent module, which is equipped with a heat shield. During Saturday's entry, the lower propulsion module apparently failed to immediately separate from the descent module and the spacecraft entered the discernible atmosphere in an unusual orientation. The attached section finally broke away, as planned in such scenarios, allowing the descent module to settle into a normal heat-shield-down attitude.
Gerstenmaier revealed that a similar separation problem occurred during the flight before this one last October, which also ended with a so-called ballistic re-entry. Whether either flight came anywhere close to a catastrophic failure is not known. Gerstenmaier would not speculate, although he generally downplayed the additional risk.
"We're hearing there was a separation problem," he said. "We saw that on the previous Soyuz. That was confirmed by looking at the data on the previous Soyuz that the Russians provided to us. ... In the shuttle world, we get a lot of telemetry and data right away in realtime. In the Soyuz case, we don't get that much information. The attitude wasn't so off nominal that the crew detected it as being off nominal. They felt some motion, some jarring, some bumping around that was higher than they expected. They didn't really have enough data to confirm exactly how the separation occurred. ... The real answer comes when the Russians dump the computer and take a look at the data."
The presumed failure of the lower propulsion module to cleanly separate is believed to have forced the craft into a steeper than normal trajectory and the spacecraft ultimately landed some 295 miles short of its target. The final moments of the descent occurred out of sight and out of contact with Russian recovery forces and mission control near Moscow. Smoke apparently entered the capsule at one point, but it's not clear what might have caused it.
Instead of being met by flight surgeons and engineers, Soyuz commander Yuri Malenchenko, Whitson and guest flier So-Yeon Yi initially were assisted by local residents who were astonished to find the charred spacecraft resting on its side in their fields. Recovery crews eventually arrived and flew the crew back to Star City near Moscow. All three were reported to be in good health, although Malenchenko and Whitson face weeks of physical therapy to help them re-adapt to Earth's gravity after six months in weightlessness.
"It wasn't the search and rescue who got us out of the capsule," Whitson said. "It was just some guys who'd seen it and drove in. Yuri got out by himself before anyone arrived. And then by the time So-Yeon and I were trying to get out, the fellows who came out to meet us helped us out. So it worked out real well and we just waited until the search and rescue team arrived."
Russian space agency officials have not officially confirmed any problems with the separation of the Soyuz spacecraft's three modules, saying only that the spacecraft followed a ballistic, or unguided, trajectory because of an unspecified problem and that the system is designed to safely fly such trajectories without putting the crew in jeopardy.
But this was the second flight in a row to end with a ballistic descent, which can subject the crew to 10 times the normal force of Earth's gravity, and apparently the second flight in a row in which entry began in an unusual orientation, subjecting parts of the capsule to higher heating than normal.
Interviewed shortly after landing, Malenchenko, speaking through an interpreter in footage carried on NASA television, was asked about the experience.
"Well, it was interesting. Interesting is a good description," he said.
"Did it feel like a merry-go-round?" the interviewer asked.
"Well, pretty much so."
He did not say anything about a problem with the module separation system.
Because the Soyuz is a Russian spacecraft, U.S. space officials have adopted a wait-and-see attitude, saying only that Russian engineers have barely started a detailed engineering analysis. With the descent module available for study, Gerstenmaier said he is confident the Russians will eventually figure out what went wrong and do whatever is required to fix it.
"The data recorder on board will provide critical information," he said. "A detailed inspection of the capsule also needs to be done. The Russians are handling this extremely well. This is our second ballistic entry in a row. The Russians immediately set up a commission ... they're going to go out and investigate this, they'll get the capsule back, they'll understand the data and they'll see if there's any impact to future Soyuzes or future missions.
"I have complete confidence in what the Russians are doing. They were very concerned about this when it occurred, they treated it with the same diligence that we would in the United States, they worked this issue extremely hard. They did a lot of work on the previous Soyuz to understand what occurred on it, they fully investigated it. They recognized that at first appearances, it looks like some of the same events occurred on this Soyuz vehicle and because of that potential similarity, they've kind of kicked the gain up on the investigation to make sure they get answers as soon as they can."
But several U.S. observers privately expressed concern. With U.S. astronaut Michael Fincke scheduled to blast off aboard the next Soyuz in October as commander of space station Expedition 18, NASA managers will be particularly interested in the progress of the Russian probe.
"They've got a good track record with the Soyuz," said one official. But he said this was a "serious" issue that will require conclusive results to restore confidence in the system.
"This has been a remarkably robust system for lots of years," said John Logsdon, a space policy analyst at George Washington University and a member of the Columbia Accident Investigation Board. "What's a little worrisome is apparently there were some similarities with the one before this one. They had a ballistic entry. You don't want that happening on every mission, especially with people coming back from long-duration stays. They're feeling bad enough anyway without going through this.
"Could you compare it to what the CAIB said about the need for laser focus on quality for every mission, every time? Have the people doing Soyuz over and over again lost some of that? I think it's a legitimate concern."
It is a potentially critical issue for both Russia and the United States. NASA plans to retire the space shuttle in 2010 and rely on the Soyuz to ferry U.S. astronauts to and from the space station until a replacement spacecraft debuts in the 2015 timeframe.
After the ballistic entry on the previous flight last year, Gerstenmaier said Russian engineers identified two apparent problems: A suspect cable that might have forced the craft into an automated ballistic entry and a module separation issue involving the circuitry and explosive bolts used to sever structural supports. The cable issue was discussed prior to the TMA-12 launch April 8, but the earlier module separation problem with the Soyuz TMA-10 spacecraft was a surprise to space reporters.
Malenchenko and Whitson were completing a 192-day mission as members of space station Expedition 16 while Yi, who rode into orbit with Expedition 17 commander Sergei Volkov and Oleg Kononenko on April 8, was wrapping up an 11-day voyage.
Volkov, Kononenko and Yi were launched aboard the Soyuz TMA-12 spacecraft, which remains docked at the international space station. It is scheduled to carry Volkov, Kononenko and U.S. space tourist Richard Garriott, son of former Skylab and shuttle astronaut Owen Garriott, back to Earth this fall.
Malenchenko and Whitson rode into orbit last October aboard the same Soyuz TMA-11 spacecraft they returned in Saturday. Undocking from the space station went normally and the Soyuz's braking rockets fired as planned to drop the ship out of orbit for a landing near Arkalyk in Kazakhstan.
The Soyuz TMA spacecraft is made up of a lower propulsion, or service, module equipped with two solar panels, fuel tanks, rocket engines and other systems; a central crew module with the spacecraft's control systems; and an upper orbital module that includes rendezvous equipment and a docking system. Astronauts and cosmonauts ride to and from space strapped into cushioned seats in the central module, the only one of the three equipped with a heat shield. The cramped descent module weighs about 6,400 pounds and has a habitable volume of just 141 cubic feet.
Just before reaching the discernible atmosphere during re-entry, at an altitude of some 400,000 feet, commands are sent to fire explosive bolts to separate the connections holding the spacecraft's three modules together. Only the central descent module is built to withstand the rigors of re-entry. The other two modules burn up in the atmosphere.
In a normal, guided re-entry, the descent module is oriented to modify its lift slightly, permitting a shallower, less severe trajectory. In a ballistic entry, the capsule spins for stability and the descent is steeper, subjecting the crew to more extreme deceleration.
What happened Saturday is not yet clear. Sources say the propulsion module apparently did not immediately separate from the descent module just prior to entry, possibly because an explosive bolt failed to fire. As a result, the crew cabin apparently did not enter the atmosphere in the proper orientation. The attached module broke free at some point, allowing the crew cabin to right itself and continue the descent in the proper orientation.
"What the crew members reported was that they felt some anomalous motion in the spacecraft, they felt a kind of bumping around, movement forward in the seats, movement aft in the seats and movement to the right and movement to the left," Gerstenmaier said. "So they felt a general kind of jostling in their seats that they had not felt before and that was prior to the initiation of the ballistic mode on the spacecraft and after the separation. During that period of time they physically felt some off-nominal motion in the spacecraft."
Descriptions of the Soyuz TMA-11 re-entry brought to mind an early Soyuz entry problem that almost ended in disaster. On Jan. 18, 1969, six months before the Apollo 11 landing on the moon, cosmonaut Boris Volynov faced a particularly dire situation.
"The service module of the Soyuz failed to separate after retrofire," according to Encyclopedia Astronautica, a respected European web site that tracks international space activity. "Once the Soyuz started reaching the tendrils of the atmosphere, the combined spacecraft sought the most aerodynamically stable position - nose forward, with the heavy descent module with its light metal entry hatch at the front, the less dense service module with its flared base to the back. Luckily the struts between the descent and service modules broke off or burned through before the hatch melted through and the descent module righted itself, with the heat shield to the rear, before being consumed. Due to a failure of the soft-landing rockets the landing was harder than usual and Volynov broke his teeth."
Details about the Soyuz entry were not revealed until many years later.
During a news conference in Star City, Russia, Monday, The Associated Press reported that Yi said "during descent I saw some kind of fire outside as we were going through the atmosphere. At first, I was really scared because it looked really, really hot and I thought we could burn."
But she quickly realized the fire was outside the spacecraft. "I looked at the others and I pretended to be OK," she said.
Malenchenko said only that the Soyuz switched to a ballistic trajectory and that "there was no action of the crew that led to this. Time will tell what went wrong."