When we get the cover back on the box, Kjell and I separate to work on different tasks for a while. He continues reconfiguring the ammonia lines, and I work on the vent lines on the back side of the space station’s truss. Both are difficult tasks, and we are each absorbed in them completely. This is not the ammonia you might have found under your grandmother’s sink, but something a hundred times stronger and much more lethal. If this ammonia were to get inside the station, we could all be dead within minutes. An ammonia leak is one of the emergencies we prepare for most. So working with the cooling system and the ammonia lines is especially important to get right the first time. We must make sure not to get any of the ammonia onto our suits.
As I had learned on my first spacewalk, I’m finding that the focus required to work outside is absolute. Every time I adjust my tethers, move a tool on my mini-workstation, or even just move, I have to concentrate with every bit of my attention, making sure I’m doing the right thing at the right time in the right way, double-checking that I’m not getting tangled up in my safety tether, floating away from structure, or losing my tools.
After a few hours, I head back toward the CETA cart (CETA stands for crew and equipment translation aid), which is sort of like one of those old manual handcars once used on railways. It’s designed to let us move large equipment up and down the truss. When we were planning this spacewalk, I had raised concerns about whether this task, tying down the brake handle so no one could accidentally lock the brake, really needed to be done. This is much less important than our primary objective of reconfiguring the ammonia system, and it takes me far away from Kjell—too far to help if he runs into any trouble, like in my skydiving dream. The lead flight director insisted that we would be able to do both.
I’m plodding through my task with the brake handle, using reminders written on a checklist on my wrist. I am working mostly on my own, as Megan is concentrating on talking Kjell through his much more complex task. As I continue working, I can hear Kjell struggling with the ammonia connections. These can require all your strength, even for a strong guy like him, and they are technically complex, requiring upward of twenty steps each to mate or demate a connection, all the while remaining alert for ammonia to come shooting out and contaminate your suit. Each time I hear him struggle to complete a step, I again question to myself why I am working on the cart when I should be there to help him.
I finish up and take one last look over my work site, making sure everything looks right, before heading back out to the end of the truss to help Kjell. Hand over hand, it takes me a few minutes to get to him. I look over his suit, inspecting it for yellow spots of ammonia. I see a few places that look suspicious, but when I look closer I can see the threads of the suit material below the discoloration, which rules out ammonia as the cause. I’m glad I decided to wear my glasses, which haven’t slipped or fogged up, or I might not have been able to tell the difference. We’re preparing to vent the ammonia system—Kjell opens a valve and quickly moves clear. High-pressure ammonia streams out the back of the space station like a giant cloud of snow. As we watch, the sun catches the huge plume, its particles glistening against the blackness of space. It’s a moment of unexpected beauty, and we float there for a minute, taking it all in.
When the venting seems to be complete, Megan instructs us to separate—Kjell will stay here and work on cleaning up the ammonia vent tool while I venture back to the solar array joint to remove and stow an ammonia jumper I installed earlier. The solar array joint continually rotates in the same direction to keep the solar arrays pointed at the sun, 360 degrees every ninety minutes, while passing electricity downstream. Megan talks me through the process. I struggle with one of the connections.
“Hey Megan. With the bale all the way aft, the white band should be visible or not?” I ask.
“Yes,” Megan replies, “the forward white band should be visible.”
I work with it for a few more minutes before getting it configured the way it’s supposed to be.
“Okay,” I report. “Forward white band visible.”
“Okay, Scott, I copy the forward white band is visible—check the detent button is up.”
“It’s up.”
When I hear Megan’s voice again, there is a subtly different tone.
“I’m going to ask you to pause right here, and I’m going to tell you guys what we’ve got going on.”
She doesn’t say what this pause is about, but Kjell and I know: Megan has just been given some news within mission control, something the flight directors have to make a quick decision about. It may be something that puts us in danger. She doesn’t leave us hanging for long.
“Okay. Currently, guys, from a momentum management perspective, we’re getting close to a LOAC [loss of attitude control] condition,” she says. She means the control moment gyroscopes, which control the station’s attitude—our orientation in the sky—have become saturated by the venting ammonia. Soon we will lose control of our attitude, and when that happens, we will soon lose communication with the ground. This is a dangerous situation, just as we anticipated.
Megan continues. “So what we need Kjell to do is to pull out of your current activity and head over toward the radiator. We’re going to have you redeploy it.”
If we can’t cinch down this radiator properly, we will have to put it back out in its extended position.
“Copy,” Kjell answers crisply.
“You’ve probably gathered from a timeline perspective where we’re going,” Megan says. “We’re going to have you clean up the vent tool eventually, Kjell. And Scott, you’re going to continue with the jumper, but we are not going after cinching and shrouding the radiator today. It will take too long.”
We both acknowledge her. This situation with the gyroscopes is serious enough to alter our plans. Even under the best of circumstances, when we hear we are close to saturating the gyros, it’s one of those “Oh, shit” moments. The station won’t start spinning out of control like a carnival ride, but losing communication with Megan and all the experts on the ground is never a good thing. And with the two of us outside, a communication blackout would add a new danger to an already risky situation. In all the preparation we’ve done for this spacewalk, we had never discussed the possibility of losing attitude control due to ammonia venting.
Houston is discussing handing over attitude control to the Russian segment. The Russian thrusters can control our attitude, less elegantly, with the use of propellant. The handover process isn’t instantaneous, and we could lose communication with the ground in the meantime anyway. On top of that, the Russian thrusters use hypergolic fuel, which is incredibly toxic and a known carcinogen. If any of the hydrazine or dinitrogen tetroxide got onto our spacesuits, we could bring those chemicals back into the station with us.