ISS Lives On

I figured by now more people would have called or emailed to ask about the whole "ISS Evacuated" headlines that ran rampant yesterday. I guess people don't follow NASA news as much as I hoped...

So just to quell any curiosity, I figured I would make sure to post about the excitement of the past couple of days.

News sites worldwide were freaking out Thursday when the three residents of the International Space Station (of which I am a team member, being part of the training and operations organization, the Mission Operations Directorate) were told to board the Russian Soyuz (their ride home in case of an emergency). The media outlet sure made it seem like ISS was actually abandoned, with headlines like "Astronauts Evacuate Space Station" and the like. I will try to explain what actually happened and the general mood at JSC during the whole event.

Currently, we have 2 NASA Astronauts (Mike Finke and Sandy Magnus) and one cosmonaut (Yuri Lonchakov) living on the International Space Station. Sometime Wednesday night, STRATCOM notified JSC that they were tracking a piece of debris that would potentially violate the "zone of exclusion" (so to speak) at 11:39 am Central time Thursday. Usually, NASA is notified of these conjunctions much earlier, but STRATCOM apparently made some mistakes in their calculations due to the highly elliptical nature of the object's orbit, and only found out about it Wednesday. This was not enough time to conduct a Debris Avoidance Maneuver (DAM), which essentially consists of ISS raising it's orbit to avoid the piece of space junk. For history, since the first pieces of ISS were launched 10 years ago, we have only conducted something like 8 of these maneuvers.

So Thursday morning, as calculations and orbits were updated, Mission Control Center Houston (MCC-H) decided to go to an unmanned config and place crew in the Soyuz, as a precaution. What this consists of is turning off a lot of essential equipment on ISS and things that wouldn't be needed if ISS were unmanned, closing hatches so a debris hit on any one module would not mean we lose all the modules, then going to the Soyuz to ride out the event. If the habitable modules of the space station were to be punctured, atmosphere would leak until station was at vacuum, so by being in the Soyuz crew could just close that hatch and head home safely if there was not enough time to find and patch the hole.

Because of the nature of this particular piece of space junk (both its velocity and size) MCC-H was calculating that it could potentially cause of 2 inch hole in station if it hit. A hole this size would mean crew would have a reserve time (Tres) of about 10 minutes. This is enginerd-speak for "10 minutes until ISS is at vacuum". As some of you don't know, my job at NASA is to conduct training sessions for crew and flight controllers, simulating potential real-life scenarios. Typically, we simulate debris hits or atmosphere leaks with a Tres of about 4-10 hours. This is still an emergency, but it gives an adept crew plenty of time to locate and patch a leak before losing too much atmosphere. A Tres of 10 minutes gives crew just enough time to shut the Soyuz hatch before being in vacuum (IF they are already there in the first place, ready to slam the hatch shut). SOO this was kind of a big deal.

For those of us at JSC who hadn't heard about the conjunction until Thursday morning, this all came as kind of a shock. To find out that in a few hours, a piece of space junk may or may not render your livelihood nonexistent, not to mention potentially threaten the lives of 3 people you have helped train for their important mission. It was a tense few hours as we waited and listened to the Flight Control team coordinate the graceful transition to "unmanned". The crew closed all the US hatches in about 22 minutes (which is a lot faster than we typically budget for this activity), and patiently waited in the Soyuz for the closest approach to pass. It is interesting to note that the crew did not actually shut the Soyuz hatch at this time. I mention this because all the news outlets at the time were reporting that we had evacuated station, when in fact crew was still breathing ISS atmosphere and able to jump out in order to fight a leak if need be.



So there we were, waiting around for about 10 minutes monitoring data, waiting for any sign that ISS had been hit. About the only useful piece of data we had was a display showing us the pressures in each module of the space station. If any of those pressures started to decrease rapidly, we would know there had been a hit.

As is probably old news now, we know the debris did not strike the station, and a few minutes after the calculated time of closest approach passed, crew was told they could exit Soyuz, open hatches and resume their normal duties. And everyone went back to work, a little more sober and a little more in need of a drink.