If you remember about a year and a half ago, I got called in to work due to decreasing pressure inside the ISS. That turned out to be the famous "drilled hole in the Soyuz" incident. Well, for the last several months, we've been tracking a very slow decrease in pressure. It was very slightly higher than what we'd expect to see (i.e. higher than the specified allowed leak rate), so in mid-August we started doing some troubleshooting including the crew isolating themselves on the Russian segment with all the hatches on the US segment closed. That data was inconclusive due to the very small size of the leak...about 1.5 lb mass of air per day.
On September 7th, the leak rate jumped up to about 3.5 lbm/day, so last weekend the crew again isolated themselves in the Russian segment. This time, the data seemed to indicate the leak somewhere on the Russian segment. The higher leak rate gave us better data on which modules were definitely not leaking.
Last night, saw an e-mail that a co-worker had been called in to Mission Control because the leak rate had increased dramatically...up to ~15 lbm/day. That's a rate that would be unsustainable for very long, and would cause us to decrew ISS (i.e. the astronauts would have to return on their Soyuz and leave the ISS unmanned). As a result Mission Control woke the crew up early and put them to work trying to figure out where exactly on the Russian segment the leak was coming from. They managed to narrow it down to a part of the Service Module (SM). The SM is the arguably the most important part of ISS, since it has all the life support systems on the Russian segment (oxygen generator, CO2 removal, toilet, etc) and the flight computers that control the entire Russian segment, including the thrusters which are used to maintain altitude and attitude control during dynamic operations. Luckily, during the course of their troubleshooting, we saw the leak rate again fall back to the ~ 3.5 lbm/day of air. It's a mystery wrapped in an enigma.
They put the crew to bed early today since we woke them up early, and they'll continue searching for the leak in the SM tomorrow. They also did a repress of the entire ISS using reserve nitrogen on one of the Progress resupply vehicles, but I'm not sure how much more reserve nitrogen or air we have onboard so not sure how much longer we can sustain the current leak rate. I just don't have the data in front of me when I'm here at home. But I did see that that Space-X moved the launch of their next crew Dragon a week later (to Halloween) to give more time for troubleshooting the leak since the crew wouldn't be able to stay onboard for their planned six months. That says to me, we have something less than that 6 months of reserve left. We'll have to manifest more N2 and air on upcoming resupply vehicles. If the leak rate jumps back up to 15 lbm/day, we won't get supplies up fast enough, so it all depends on how fast the leak is and how quickly we can find it and fix it. I'll update this post whenever I get any additional interesting information.
On September 7th, the leak rate jumped up to about 3.5 lbm/day, so last weekend the crew again isolated themselves in the Russian segment. This time, the data seemed to indicate the leak somewhere on the Russian segment. The higher leak rate gave us better data on which modules were definitely not leaking.
Last night, saw an e-mail that a co-worker had been called in to Mission Control because the leak rate had increased dramatically...up to ~15 lbm/day. That's a rate that would be unsustainable for very long, and would cause us to decrew ISS (i.e. the astronauts would have to return on their Soyuz and leave the ISS unmanned). As a result Mission Control woke the crew up early and put them to work trying to figure out where exactly on the Russian segment the leak was coming from. They managed to narrow it down to a part of the Service Module (SM). The SM is the arguably the most important part of ISS, since it has all the life support systems on the Russian segment (oxygen generator, CO2 removal, toilet, etc) and the flight computers that control the entire Russian segment, including the thrusters which are used to maintain altitude and attitude control during dynamic operations. Luckily, during the course of their troubleshooting, we saw the leak rate again fall back to the ~ 3.5 lbm/day of air. It's a mystery wrapped in an enigma.
They put the crew to bed early today since we woke them up early, and they'll continue searching for the leak in the SM tomorrow. They also did a repress of the entire ISS using reserve nitrogen on one of the Progress resupply vehicles, but I'm not sure how much more reserve nitrogen or air we have onboard so not sure how much longer we can sustain the current leak rate. I just don't have the data in front of me when I'm here at home. But I did see that that Space-X moved the launch of their next crew Dragon a week later (to Halloween) to give more time for troubleshooting the leak since the crew wouldn't be able to stay onboard for their planned six months. That says to me, we have something less than that 6 months of reserve left. We'll have to manifest more N2 and air on upcoming resupply vehicles. If the leak rate jumps back up to 15 lbm/day, we won't get supplies up fast enough, so it all depends on how fast the leak is and how quickly we can find it and fix it. I'll update this post whenever I get any additional interesting information.
