ROBERT SIEGEL, host: I'm Robert Siegel.
MELISSA BLOCK: I'm Melissa Block, and this is ALL THINGS CONSIDERED from NPR News.
SIEGEL: For nearly 11 years, we humans have had an uninterrupted presence on the International Space Station and that streak could be coming to an end. Last week, an unmanned Russian rocket loaded with supplies for the Space Station came crashing back to Earth. And Russia has now delayed future launches, pending an investigation of what went wrong.
And since this summer's retirement of NASA's shuttle program, the Space Station has been dependent on Russian Soyuz rockets to transport astronauts. Well, yesterday, NASA said if Russian rockets are not flying by mid-November, the Space Station could be left temporarily empty.
To ponder that idea, we're joined by Dr. Leroy Chiao. He is a retired NASA astronaut with his own experience of working on the Space Station.
Welcome back to the program.
Dr. LEROY CHIAO: Oh, great to be back.
SIEGEL: First, there are now six astronauts currently at the Space Station. And NASA says that none are in danger. How and when would they get back to Earth?
CHIAO: Well, that's correct. None are in danger because they have their own spacecraft up there. There are two Soyuz spacecraft docked to the station. And each one can accommodate three crew members - the three that went up and down. And so if there were an emergency, if there were the need, all six crew members could safely come back to Earth.
SIEGEL: Very few of us, of course, can imagine what it's like to be up there in the Space Station, but you were there. And I believe your last mission was 193 days long. If you - did you know what to do in case of emergency? What were the instructions to do if you had to bail out?
CHIAO: Oh, absolutely. We went through extensive emergency training. Of course, there are very few things that can kill you rapidly or quickly in space. One would be fire, one would be depressurization and one would be a toxic release of some kind.
And in any case, the procedure is very similar. It's to try to find the problem, isolate it, and work your way backwards towards your rescue vehicle, towards your escape vehicle. So we simulate this many times on the ground, emergency training, to go through and run these procedures.
SIEGEL: Well, first, let's imagine for a second now that it was decided that all six of the people up there should leave. Is that NASA's call, by the way? Is it entirely NASA's call?
CHIAO: Well, NASA's the lead center, but - lead control center, that is, and the lead partner in the International Space Station program. But, of course, Russia's the other major partner. If it came down to it, ultimately it would be NASA's call. But most decisions like that would be pretty clearly, you know, unanimous one way or the other.
SIEGEL: Well, the ISS, the Space Station, is massive. I gather it's about the length and width of a football field. And it's full of stuff. I mean, there are things being done there. If there were no people onboard, what would its effectiveness be to do whatever scientific work it's doing?
CHIAO: Well, of course, the science would stop. I mean, there would be some automatic science experiments onboard that may continue running.
However, the biggest problem with de-crewing the station is one that you may not be able to get back aboard. There are a number of small - relatively small failures that can happen that can cause the station to lose attitude control. And if that were to happen, then the station would start to tumble, you know, a slow tumble, and would basically be out of control.
And so basically what could happen is you could have - we could lose the entire station. It would eventually - the orbit would decay and it would reenter the Earth's atmosphere and break apart in many large pieces, would survive the reentry and pose a hazard to, you know, to land masses on the ground.
SIEGEL: Was NASA mistaken to bank so entirely on the Soyuz rockets at this stage?
CHIAO: Well, you know, I was one of the - well, we were all concerned, but I was especially concerned, as an astronaut, as an operator, in this gap that we were going to have after the shuttle was retired and before any commercial operations might succeed or we had the next follow-on government vehicle. And we knew that the gap was gong to be longer than advertised. We knew it would probably be at least five, maybe seven or more years before we would have that capability in the United States again. And so there was risk involved in putting all our eggs in one basket, if you will. And now that problem has appeared.
And so I personally - and my colleagues - you know, we know how long it takes to investigate a launch or failure and put a fix in place. And, boy, November is cutting it very close. We may really have to de-crew the station. And in that case we will run a much higher risk of potentially losing the station.
SIEGEL: Dr. Chiao, thank you very much for talking with us once again.
CHIAO: My pleasure.
SIEGEL: That's Leroy Chiao, he's now, among other things, an executive vice president and director of Excalibur Almaz, a private manned spaceflight company. Transcript provided by NPR, Copyright NPR.