Episode 193: STS-102 - Teenage Mutant Ninja Logistics Module (ISS 5A.1: Exp 1/2 Swap)
Table of Contents
On STS-102 it looks like we’re just doing a simple crew swap, but complexity abounds. Get ready for new hardware, two spacewalks, cargo swaps, the first ISS crew swap, and a surprise cameo by the Teenage Mutant Ninja Turtles.
Episode Audio #
Photos #
For more photos, head over to our friends at Wikiarchives.space: https://wikiarchives.space/index.php?/category/877
Videos #
An overview of the payloads in Discovery’s payload bay for STS-102.
NASA animation of how Discovery docked with the ISS.
This is a handy overview of all the major areas of attention for this flight.
This is how PMA-3 was moved from Node 1’s nadir to port CBM. Note how the crew down in the flight deck can’t really see anything. Maybe they could catch a glimpse of it when it’s out to the port side but I don’t think so.
NASA animation of the MPLM installation process.
The undocking and flyaround process. In realtime it takes around an hour.
Post-Flight Presentation #
To see the mission in motion, check out the post-flight presentation!
Click here for full video details.
Lisa Reed Oral History Interviews #
You can read them for yourself here!
Panels and Crew Manual #
If you’d like to look through the Shuttle Crew Operations Manual yourself, take a look here. (If that link doesn’t work, try my local copy here.) Note that this is from a later revision, so there are slight differences between this and the one used by the STS-102 crew. The section on GPC controls is on page 2-6.3, which is PDF page 227.
Transcript #
NOTE: This transcript was made by me just copying and pasting the script that I read to make the podcast. I often tweak the phrasing on the fly and then forget to update the script, so this is not guaranteed to align perfectly with the episode audio, but it should be pretty close. Also, since these are really only intended to be read by myself, I might use some funky punctuation to help remind myself how I want a sentence to flow, so don’t look to these as a grammar reference. If you notice any egregious transcription errors or notes to myself that I neglected to remove, feel free to let me know and I’ll fix it.
Hello, and welcome to The Space Above Us. Episode 193, Space Shuttle flight 103, ISS 5A.1 STS-102: Teenage Mutant Ninja Logistics Module
Last time, we took a break from our usual sequence of fast-paced shuttle missions and settled in for a long stint on the International Space Station with its first long duration crew: Expedition 1. The trio of Bill Shepherd, Yuri Gidzenko, and Sergei Krikalev put in months of strenuous work to transform the growing spacecraft from a place to visit into a place to call home. But after all that effort, they were very much looking forward to passing the torch to the next crew and heading home. So on today’s mission, we’ll go and give them a ride.
On paper, this is an incredibly straightforward mission. We’re going to fly a new crew up, fly the old crew home, deliver some cargo and shuffle things outside around a little bit. But despite that straightforward mission template, there is a surprising amount of detail to dig into. And in fact, we’re not the only ones who will be encountering a surprising amount of stuff to do around this time.
In my research for this episode, I found a fascinating series of oral history interviews with former shuttle crew trainer Lisa Reed, who shed light on the complex process of getting humans ready to leave the planet. Among other things, one topic she touched on was the challenging period that began right here, with this mission, as crews and ground controllers really had to start grappling with the reality that with the Shuttle and Station going at once, there were kind of two separate space programs happening at the same time.
Let’s look at one specific problem to highlight what I mean here. On this mission, we’ll have a crew of seven flying up to the ISS. But of those seven, three were the Expedition 2 crew. This means that their time was primarily taken up by training for their multi-month mission aboard the ISS. So really, on a practical level, STS-102 kind of only had a four person crew. Four people to handle rendezvous burns, take photos, operate the laser rangefinder, manage comms, robot arm support, cargo swaps, and general housekeeping. There was a lot to do. Now of course, the Expedition 2 crew weren’t dead weight, they were able to contribute, and we’ll even see them doing an EVA later in the episode. But they were sort of viewed almost more as passengers than proper members of the crew.
Reed talked about how it was on this mission that the crews and trainers realized they had a resource management problem. They were eventually able to solve this by assigning more of the light duty items to the ISS crews, stuff like photographing the external tank, operating the laser rangefinder during prox ops, and so on, but for a while it was tough. She describes scenarios where crew members were getting out of a four hour training simulation and hustling right over to the Neutral Buoyancy Lab for eight hours of EVA training. Resources and time were stretched thin, and honestly it reminds me of nothing so much as the buildup to Apollo 1. People were just accepting the additional stress and strain so as to not be the one link in the chain that held up the mission. Thankfully, eventually folks did begin to speak up and the situation was rectified, but it was fascinating to see how everyone seemed to be caught off guard by the demands of preparing Shuttle and Station crews at the same time.
So, with that bit of background out of the way, let’s meet our perhaps slightly over-stressed crew for this flight.
Commanding the mission is our old buddy Jim Wetherbee. This marks Wetherbee’s fifth of six missions into space, with his most recent being at the helm of Space Shuttle Atlantis on STS-86, bringing home Mike Foale and delivering Dave Wolf.
Joining Wetherbee up at the front of the cockpit is today’s Pilot, and one of our two rookies, Jim Kelly. James Kelly was born on May 14th, 1964, in Burlington, Iowa. He earned a Bachelor’s degree in astronautical engineering from the US Air Force Academy, before becoming an Air Force pilot. He trained on the F-15 and was assigned to Kadena Air Base in Okinawa, Japan, serving as an instructor pilot, evaluator pilot, and mission commander. He also served at Otis Air National Guard Base on Cape Cod, Massachusetts, continuing to fly the F-15 as an instructor and mission commander, before heading out to Edwards to attend Test Pilot School. After graduating, he was assigned to the Air Force Test Center at Nellis Air Force Base in Las Vegas, Nevada. He was serving as a project test pilot and assistant operations officer when he was selected as an astronaut in 1996. This is his first of two flights.
Moving back in the flight deck we find Mission Specialist 1, Andy Thomas. Of course, we know Thomas from a couple flights, but most notably his long duration stint on the Russian space station Mir. Today he’ll be visiting another space station, but this time he won’t be floating around for months. This is his third of four flights.
Sitting behind and between the pilots was Mission Specialist 2, and today’s second rookie, Paul Richards. Paul Richards was born on May 20th, 1964, in Scranton, Pennsylvania. He earned a Bachelor’s degree in mechanical engineering from Drexel University, and a Master’s in the same subject from the University of Maryland. Richards actually got his start at NASA at the Goddard Space Flight Center in Greenbelt, Maryland, where he eventually worked his way up to be lead engineer for the team designing EVA tools for servicing of the Hubble Space Telescope. Among other tools, he designed the Pistol Grip Tool, a standard piece of equipment in any spacewalkers inventory. He did everything from design, fabrication, testing in simulated EVAs, and even financial tracking and documentation. He jumped over to the real thing in 1996 when he was selected as an astronaut. What’s amazing is that since Richards will be performing an EVA on this flight, he’ll be out in space using the very tools that he engineered. This is his first and only flight, but he wasn’t done with NASA. In 2004 he returned to Goddard as the Observatory Manager of the GOES-R series of weather satellites.
Down on the middeck we have three crew members who we’re just going to zip through rapid-fire. That’s because Mission Specialist 3 Yuri Usachov, Mission Specialist 4 Jim Voss, and Mission Specialist 5 Susan Helms are better known as the crew of Expedition 2, the second long duration ISS mission. We most recently saw all three of them on STS-101, the ISS resupply mission last year, where they got a sneak peak at their new orbiting home. This marks Usachov’s 4th flight, Voss’s 5th, and Helms’s 5th, with it also being the final flight for all three of them. Also, I just want to mention that between Wetherbee, Kelly, and Voss, we have three Jameses on this flight, which has gotta be a record.
Space Shuttle Discovery enjoyed a mostly smooth road to the launchpad for this flight. There were some delays due to previous missions being pushed, and a few sources mentioned some RCS thrusters being replaced but I wasn’t able to track that down. Once a proper launch date was set, there were no further issues, and STS-102 sailed through a flawless countdown. This is good, because as with any rendezvous mission, the launch window was tight. The window could be as long as 9 minutes and 58 seconds, but since it was best to shoot for the center of the window, launch controllers just cut that window in half, leaving about five minutes to get Discovery off the pad. On March 8th, 2001, at 6:42 and nine seconds AM Eastern Standard Time, Space Shuttle Discovery lifted off for the 29th time. Or actually, was it 2:42 PM? In a fun little discrepancy, despite listing the correct time in GMT, the official mission report states the mission started at 2:42 PM local time, not 6:42 AM. I’m not entirely sure what happened here, but 2:42 PM happens to have been the time in Moscow, so maybe whoever prepared the document was a little too in sync with our Russian partners in space.
Anyway, just like the countdown, the ascent was uneventful, and Discovery was soon in its initial orbit of around 158 by 234 kilometers. Just as a little side fun fact, if you want to imagine life onboard the Shuttle, the mission report notes that the cabin humidity peaked at around 41%, 5 minutes and 13 seconds into the flight, and the cabin temperature peaked at 27 degrees Celsius, or 81 degrees Fahrenheit, around two and a half hours after lifting off. Sounds a little on the warm side to me but I wouldn’t turn down a seat for that.
This also seems like an appropriate time to include a fun quote from Mission Specialist Andy Thomas. Before the flight, he said: “As a kid in the late ‘60s, I watched Stanley Kubrick’s film “2001: A Space Odyssey,” which is really interesting because that’s a film about a spacecraft called Discovery, which in 2001 is making this mission. And here it is now 2001 and, lo and behold, I’m flying on a spacecraft called Discovery. Now, we’re not going to Jupiter, of course, but it is a bona fide space flight nonetheless.” Bona fide space flight..
Fast forwarding a bit, we find Discovery and its crew making preparations for the final approach to the ISS. This approach is a little different than on previous ISS missions, but if you’ve been listening to this show this whole time it will sound pretty familiar. With Commander Wetherbee at the controls, Discovery will be swooping up to the +V-bar, in front of the ISS, and gently easing back until it makes contact with PMA-2 at the front of the US Lab module. Now, if you’ve been paying unusually close attention, you might protest and say that that’s nothing new, the Shuttle has docked at PMA-2 on the front of the ISS before. And you would be right! But in those cases the station was in a gravity gradient stabilized attitude, so PMA-2 was pointing to zenith, or “up”, instead of forward.
This V-bar approach may not sound like that big of a change, but the approach direction in a rendezvous has a large effect on the nature of that rendezvous. Up until now, we’ve been doing R-bar approaches to the ISS, approaching along the imaginary line from the center of the earth, up to the station and beyond. So we’ve been approaching from directly above or below. R-bar approaches are nice because you get that sort of natural braking effect we’ve discussed before. It’s more passively safe. If something goes wrong, typically you can just stop thrusting and the orbiter will drift away in a safe direction. That’s not true on the V-bar. With the V-bar, approaching from in front or behind, the relative orbital motion provides no automatic braking effect. In fact, it’s easy to end up in a relative geometry where the shuttle would have a tendency to drift towards the station. So keeping a close eye on range, range-rate, and maintaining general situational awareness was essential.
So it’s good that Commander Wetherbee is actually doing this for the second time. He was also at the controls for STS-63, the “Near-Mir” flight that rendezvoused with Mir but didn’t actually dock, where he also approached along the V-bar. Practice makes perfect.
And indeed, the rendezvous went smoothly, with Discovery moving up around 183 meters below the ISS before swinging out in front to land on the V-bar 92 meters ahead of it before beginning the final approach. The only twist was that the shuttle crew had to maintain their position on the V-bar for around an hour due to an issue with one of the station’s solar arrays. To prevent stress on the solar panels, they were “feathered”, or turned edge-on to the shuttle, so the orbiter’s powerful thruster plumes wouldn’t blast them. In this case, one of the solar arrays failed to latch in the feathered condition and added a little extra drama to the approach.
In any case, 1 day, 18 hours, 56 minutes, and 17 seconds after lifting off, Space Shuttle Discovery made contact with PMA-2 after a successful rendezvous. And I hope you enjoyed that, because that’s the approach that we’ll be taking from now until the end of the Shuttle program!
After a couple of hours to establish hard dock and equalize the air pressure on either side, the hatches were opened and Commander Wetherbee and Commander Shepherd exchanged handshakes. As the shuttle crew explored the station, one member was overwhelmed by a sensation of deja vu. Well, maybe four members, since Voss, Helms, and Usachov had actually been here before on their previous flight, but specifically I’m talking about Mission Specialist 1, Andy Thomas. Thomas, of course, was the final American to live and work on the Russian space station Mir, which shared the same core construction as the Russian segment of the ISS. In an interview for our buddy Tom Jones’s book Space Shuttle Stories, Thomas said “I was absolutely dumbfounded by the sense of deja vu - how much like Mir they were. Zvezda looked like Mir, was lit up like Mir, and even smelled like Mir. The cosmonauts even displayed pictures of Gagarin and Korolev above the hatch, just as they had on Mir.” I don’t think this case of deja vu was caused by a glitch in the matrix, though. Remember, Zvezda is almost an identical copy of the base block from Mir.
Among the first items on the agenda was the first of three crew swaps. Changing out the crew of the ISS was actually a somewhat delicate process. At any moment there could be an emergency that required an immediate evacuation of the station. This meant that anyone who planned on taking the Soyuz home needed to have their custom seat liner in place. That’s simple enough, but they couldn’t just swap all three members right at the start. The new team needed some time with the old team to be briefed on the realities of running the station. And some members of the new team still has tasks on the Shuttle side, such as Jim Voss and Susan Helms’s upcoming EVA.
With Voss and Helms still needed on the Shuttle side, the first to officially transfer was Yuri Usachov. This makes sense since he was the Expedition 2 commander, and it was essential that he get as much time as possible in this handover. With that in mind, instead of swapping commander for commander, as Usachov headed to the station, Yuri Gidzenko swapped over to the shuttle. This also made sense because you needed to have someone who was a Soyuz pilot on the station at all times. And while I’m sure Krikalev could get it done, Gidzenko had performed all the Soyuz piloting on Expedition 1, and could be safely replaced with Usachov. We’re also swapping a Yuri for a Yuri, so everything is balanced.
On flight day four, it was time for the first of our two EVAs. Perhaps just eager to leave the shuttle as soon as possible, today’s spacewalkers are Jim Voss as EV1, and Susan Helms as EV2. There are a few items on the todo list today, and while I think I have the general series of events right, I want to issue another blanket reminder that there often aren’t super detailed play by play reports of these spacewalks. Combine that with the fact that sometimes the tasks are happening simultaneously and it can be tough to follow. So all this stuff did happen, but please forgive me if they happened in a slightly different order. Anyway, the first item we’ll be discussing is nice and easy. Remember the Early Communications System antenna? This was a basic antenna that was added as sort of an afterthought, as a way for NASA to get telemetry directly from the Unity node before the main communications system came online. It was stuck to the port side of the node, a place we need to be clear in a few hours here, so the EVA crew went ahead and plucked it off the station, returning it to the shuttle payload bay.
Next up is the Lab Cradle Assembly, which of course, we’ll call the LCA. The LCA is an interesting piece of equipment because it will have two highly significant but completely different roles over its lifetime. Today, all Voss and Helms have to do is install it on that big trunnion pin sticking out of the top of the Destiny laboratory module. But on the next flight, the LCA is where the STS-100 crew will attach a piece of equipment carrying the space station’s new robotic arm. As we’ll discuss on that episode, the arm will then walk over to another connector and hand its own deployment platform back to the shuttle arm, freeing up the LCA again. Then, on a later flight, the LCA will connect the lab module to the S0 truss, the central piece of the backbone of the space station. And definitely not something that I confused with the Z1 truss for a long time, definitely not.
Next up was the Rigid Umbilical. This is basically just want it sounded like. Imagine a cable tray, but all covered in white thermal-friendly paint and fabric. Once fully installed, its cables would connect the lab to one of the grapple fixtures for the space station robot arm. Voss and Helms got the Rigid Umbilical in place, but the task of connecting the cables was kicked to the second EVA.
Somewhere during all this, two minor mishaps took place. First, the attachment device for the portable foot restraint came loose from the end of the robot arm and drifted off into space. Not great, but the crew had a spare ready to go. At another time, Helms accidentally dropped a bag filled with stuff to bring back to the airlock. It was only a little out of reach, and moving slowly, but with her feet stuck to the end of the arm all she could do was watch. Thankfully, Pilot Jim Kelly was operating the arm, spotted what happened, and immediately began moving her after the bag, successfully chasing it down! This is especially impressive because at the time, Kelly could not even see Helms out the window, and had to do this all using the view from various video cameras. Andy Thomas said “his feat was one of the most impressive things I’d ever seen done in flight.”
The most important task of the spacewalk was also kind of the simplest. Currently, Pressurized Mating Adapter 3, one of the docking ports, is attached to the underside of the Unity node. We’re going to need that spot later in the mission, so PMA-3 needs to be moved to Unity’s port side, which is now free since we got rid of that antenna. This is actually mostly done with the shuttle robot arm, but first the EV crew needs to disconnect a bunch of cables between PMA-3 and the node. The eight cables mostly went without a fight, but two of them couldn’t be connected to their storage locations, so the crew just tied them off, keeping them out of the way. Since these were spare cables with no planned use, there was no concern about leaving them out in the open.
With their tasks done, Voss and Helms started to head back to the airlock after around six and a half hours outside. But they weren’t quite done yet. A few minutes later, Andy Thomas grappled PMA-3 with the robot arm and began the slow process of moving it over to the port side of the node. This was routine, but also sort of tricky. To see why, or rather, not see, put yourself in the shoes of Andy Thomas. He’s stationed at the aft of the orbiter flight deck, looking out the windows into the payload bay. Right out the window is PMA-2, where Discovery is docked. Rising up out of that is the laboratory module. And eight and a half meters above that is the node. But even if he could see way up there, he’s looking at the zenith side, the top. PMA-3 is on the nadir side, the bottom, completely obscured by the structure of the station. The upshot of all this is that PMA-3 had to be moved with zero direct visibility from the crew member actually operating the arm. He had to rely on a whole bunch of video cameras, and the Space Vision System. And this is why Voss and Helms weren’t quite done. They hung out on standby in case Thomas needed them to head back out and visually guide him in.
But this is a pretty slow process, so it turns out that Voss and Helms would be waiting around in the airlock with nothing to do for over two hours. I was curious what this experience would be like, stuffed into the tiny airlock, still in their bulky EMUs, with nothing to do, so I once again reached out to our buddy Dan Tani. Tani said that hanging out in the airlock like that would be fine. It would be a little boring, but it would also be a nice chance to relax and maybe even take a nap. And since they were inside, they could enjoy a nice stable temperature instead of the wild swings that happen between sunlight and shadow in space. He also pointed out that it was an easy way to add to their total career EVA time, which as we’ll see in a moment, is 100% true. They couldn’t wait around forever, but since they were connected to service umbilicals in the airlock, they were mostly just limited by the longevity of their carbon dioxide scrubbers.
While it took a couple hours to get it into place, the PMA-3 transfer went nice and smoothly, and Voss and Helms were finally free to repressurize the airlock and come back inside. Their extra two hours and fourteen minutes of waiting resulted in an EVA lasting a total of eight hours, fifty-five minutes, and fifty-six seconds. That duration was the all time record until quite recently, having finally been broken by a crew of the Chinese space station Tiangong in 2025. At the time of this recording, it remains the American spacewalk duration record.
On flight day five, the crew again fired up the remote manipulator system and grappled something in the back of the orbiter. Soon, rising from the payload bay was a silvery cylinder about 6.4 meters long and 4.6 meters across. What could it be? A new module for the station? Sort of. It’s time to meet the Multi-Purpose Logistics Module, or MPLM. Or, as the press kit so eloquently puts it, “a space age moving van”.
The MPLM is basically a big ol’ tin can, but with a Common Berthing Mechanism on one end, allowing it to be attached to the station just like any other module. Its 76.4 cubic meter interior volume is almost exactly the same as those standard 40 foot long shipping containers you might see hauled around by trucks on the highway or stacked on cargo ships. Inside, it can carry up to nine metric tons of equipment in a pressurized environment. You can kind of imagine it like Spacelab, but with no tunnel from the middeck. Also, unlike Spacelab, the MPLM is removed from the payload bay and stuck onto the ISS.
Now, you might be wondering what the big deal here is. We’ve seen plenty of missions with SPACEHAB full of cargo to be transferred over to Mir or the ISS. The difference is that in those cases, the crew would have to move the cargo down the tunnel, turn 90 degrees right before the middeck, go through the PMA, and then into the station. There are some tight turns and narrow passages along the way, which restricted what could be transferred. Since the MPLM used a Common Berthing Mechanism instead of the Pressurized Mating Adapter, the entrance was much wider. This meant the crew could move entire EXPRESS racks, fully assembled, which would be significantly more convenient and reliable. Which is good, because with its impressive volume, the MPLM could move as many as sixteen racks at once.
This is maybe a weird comparison, especially since I have a fair number of international listeners and I don’t know if this company exists overseas, but in the United States we have a company who will drop a big shipping container called a “pod” off at your house. You move all your stuff into it and then they come and pick it up, put it on a truck, move it to your new house and you can unpack at your leisure. I imagine the MPLM to be sort of like that, but if the pod was actually connected to your house as a temporary room. A temporary room with some life support capability, fire detection and suppression, electrical distribution, and cabin pressurization. It’s a pretty cool temporary room.
Three MPLMs were constructed by the Alenia Aerospazio factory in Turin, Italy, starting in 1996. It’s sort of confusing, but I think this is essentially the same company that made the Spacelab and SPACEHAB modules, but after a few more corporate mergers. The three MPLMs were valued at 150 million dollars each, but were provided to NASA by Italy free of charge as their contribution to the ISS project, getting them some orbital research time in return.
Since they’re from Italy, the modules were named Leonardo, Raffaello, and Donatello, after the great Italian artists, with Leonardo joining us today. But of course, if you’re anywhere near my age, those names probably make you think of something else: the Teenage Mutant Ninja Turtles (which also explains the title of today’s episode). Now, before you call me an uncultured buffoon for thinking of the ninja turtles before the artists, I’d like to point out that the MPLM team themselves commissioned an artist to draw one of the teenage mutant ninja turtles in the orange ACES launch and entry suit and used it for their mission patch. You can take a look at the patch on the show notes page for this episode, and if the art looks surprisingly good, there’s a reason. NASA reached out to Mirage Studios, the comic book company that published the Ninja Turtle comics, and got one of the actual TMNT artists, A.C. Farley, do to the artwork. Neat! Or maybe I should say.. cowabunga!
For today’s flight, the MPLM was carrying around 4400 kilograms of cargo. One piece of which, the Human Research Facility, was the first dedicated science rack for the ISS. But this item was actually the lowest priority since there was no rush to start on that research, and it was more important to move the large amount of operational equipment. There were six systems racks, including the ones to run the upcoming ISS robot arm, emergency crew health care equipment, DC to DC converter units which took the raw power from the solar arrays and output something more suitable for interior equipment, avionics to run the Ku-band communications, and a bunch of general supplies.
But critically, the MPLM couldn’t just carry stuff up, it could also carry stuff back down to Earth. If you’ll recall, one of the main reasons why Mir ended up as such a cluttered mess was that there was just no good way to bring equipment back to Earth. There was a limited amount of room in the Progress resupply vehicles if they wanted to dispose of equipment, letting it burn up on reentry. But when it came to bringing things home in one piece, they were pretty much limited to whatever they could carry on their laps in the tiny Soyuz cabin. With an MPLM berthed to the ISS, the crew could easily return a huge amount of cargo, which would then be conveniently delivered to either the Kennedy Space Center or Edwards Air Force Base, just moments away from special support facilities for sensitive cargo. Around 750 kilograms of equipment were transferred back to the MPLM from the ISS on this flight, along with ten spent lithium hydroxide canisters from Discovery, to free up space.
The Multi-Purpose Logistics Module was an incredibly useful piece of equipment and we’ll be seeing plenty of them in the episodes to come.
The MPLM berthing was the major event of flight day five, but it’s also worth noting that we also had our second Expedition member crew swap, with Jim Voss heading over to the station side, and Sergei Krikalev coming over to the shuttle side. The next day, flight day six, it was time for the flight’s second spacewalk, with Andy Thomas as EV1 and Paul Richards as EV2. As mentioned in his introduction, Richards had been working on spacewalk tools for much of his career, so finally having the chance to not only fly in space, but head outside himself was really a dream come true. At one point today he’ll even have an opportunity to use the Pistol Grip Tool he helped design. In a post-flight presentation video he pointed out that he only got to use it on two bolts, joking that he wanted to take more of the station apart with it but they wouldn’t let him.
This spacewalk is kind of a hodgepodge of a few different little tasks. First, they made their way over to the Rigid Umbilical that was installed on the previous spacewalk and completed the work, connecting the cables to the lab module. This, again, will enable control of the space station’s new robot arm on the following flight.
Next, Thomas and Richards retrieved the External Stowage Platform and installed it on a trunion pin on the lab module. This is just a temporary place to stash some spare equipment. Specifically, they retrieved a Flow Control Subassembly, which is a pump for the ammonia used as coolant on the station. There was no problem with the current ammonia pumps, but the system was so critical that it was desired to have a spare on hand ready to go.
It was maybe around this time that Andy Thomas really began to regret a decision he had made at the start of the EVA. I often talk about how in space the smallest little thing will get you. It’s just such a demanding environment that every nuance must be carefully considered. Well, I bet one potential problem that you’ve never considered was a rumpled pressure bladder on a crew member’s foot. As Thomas recalled later, after the airlock depressurized and they were just starting to head outside he started to feel a heavy pressure on the top of his foot. He then realized that he hadn’t properly smoothed the pressure bladder inside the EMU’s boot. He figured that this would just be a nuisance, and didn’t want to make a big fuss and require a repressurization, getting the suit off, smoothing the pressure bladder, getting suited up again, depressurizing again, etc. So he just decided to grit his teeth and ignore it. But as the spacewalk continued, his foot hurt more and more, and by the end he was in a lot of pain. This is problematic because, well, being in pain stinks, but also because it was really distracting as he tried to work. Afterwards Thomas said that he felt that the importance of getting this step right wasn’t really emphasized as much as it should be. But while the words may be a little harsh for this particular mishap, let us not forget: spaceflight will never tolerate carelessness, incapacity, or neglect.
Another big piece of equipment for Thomas and Richards to move was the Early Ammonia Servicer, which was a fancy name for a big 630 kilogram set of ammonia tanks. Again, this was just because the ammonia cooling system was so important that there was a desire to keep a bunch of it around in case of emergency. The trick here was that the tanks needed to go onto a trunnion pin up on the P6 truss, which was too far for the robot arm to reach. So the arm got it as far as it could, and then Thomas and Richards moved it the last little bit, way up above the nose of the shuttle, and manually installed it on the pin.
In one little bonus, Andy Thomas got to head all the way up to the top of the solar array. On the previous flight, three of four latches on the array had been locked into place, and the ground wanted to get that fourth one sorted out. So Thomas got to climb way up to the top of the ISS to close the open latch.
Thomas and Richards headed back inside, and with no PMAs to wait for, the total duration for the spacewalk was 6 hours and 17 minutes.
On flight day 7, an orbit reboost that had been planned for the next day was moved twelve hours earlier in order to put more distance between the ISS and a concerning piece of orbital debris. Four vernier thrusters fired almost continuously for over 47 minutes, imparting 3.6 meters per second of delta-v to the combined structure. Stats like that blow my mind because remember back on Project Gemini when the thrusters would start falling apart after only a few minutes of use? Amazing how things can progress.
There were several other orbit-raising burns over the course of the mission but these are pretty boring now, so I’ll just say that in total, Discovery raised the station’s orbit by about seven and a half kilometers.
Though, it turns out that those boring reboosts would have a not-so-boring consequence. During two of the reboosts, the shuttle-station stack was oriented such that Discovery’s payload bay was pointed out into space. Without radiation from the Earth bouncing back up and heating the payload bay, it got significantly colder than usual. The result was that at a mission elapsed time of 8 days, 21 hours, and 55 minutes, during a flash evaporator system dump, ice began to form at the inlet filter in the shuttle radiators, blocking freon cooling loop 1. The fix to this was relatively simple: get more heat on the radiators. To accomplish this, the attitude of the stack was changed, but the crew was also asked to fire up two of the General Purpose Computers, or GPCs, the main shuttle computers, just to create more heat to dump overboard.
In order to turn on a GPC, let us now turn to page 2.6-3 of the Shuttle Crew Operations Manual and read the section on GPC controls. Here we will see that the switches in question are on panel O6, basically above the commander’s right shoulder. Now, maybe this is obvious, but I believe that since GPCs 2 and 3 had been shut down to save power, the crew would first have to flip the GPC 2 and 3 power switches from OFF to ON. Simple enough, but that just provides power. They also need to have their memory loaded and boot up. To do this, we move to the bottom of the panel, where the MODE switches are. GPC 2 and 3 would be in the “HALT” position. These switches were important, so you couldn’t just flip them. You had to pull the switch out, move to the desired position and then you either pushed it back in or a spring pulled it in, I’m not sure. So to boot up the GPCs, each switch would have to be pulled out and rotated from the bottom “HALT” position to the middle “STBY” position. I’m not sure if it’s necessary to push the switch in and pull it back out again at the STBY setting, but next we flip it to “RUN”. So HALT, STBY, RUN. You’re probably wondering what the problem here is and why I’m getting even deeper into the weeds than usual. The reason is that when starting up a GPC, the procedures called for each GPC to remain in the standby mode for at least 10 seconds before continuing to run mode. But this time.. they were only left in standby for 5-7 seconds. The procedure called for each GPC remaining in standby for at least ten seconds because giving it less time ran the risk of memory corruption in the primary avionics software system, or PASS. Basically, by turning the computers on too fast, they may have scrambled the guidance system. This was.. very bad!
A sort of surprising number of systems on the Shuttle are like this. Rather than go through the immense time and expense of redesigning and recertifying a component to make an error impossible, they trust in the smart and capable crew and their intensive training to just do it right in the first place. But we can debate the right approach to this sort of thing later. For now, we have a serious problem.
In one of her oral history interviews, shuttle crew trainer Lisa Reed talked about how she and many of her colleagues were looking forward to their first weekend off from training in a long time. She was in the shower, getting ready to head to a St. Patrick’s day party, when her on-call beeper goes off. She calls her boss who says “Guess what I’m doing?” Lisa says “Working.” He says “Yes, guess what you’re doing” to which there was only one reply: “Working.”
Reed and a whole bunch of other people at the Johnson Space Center were trying to answer one simple question: what are the consequences of only waiting 5-7 seconds in standby mode. This is when you really start to feel the age of this multi-decade old program. Because the trouble was.. nobody knew exactly where the ten second rule had come from. Nobody knew who had written it, because all the original people had moved on. Was the number really precisely ten seconds? Or maybe was there some margin in there? Maybe the real answer was seven seconds, and someone just wrote ten to keep things extra safe and make a nice round number. And what exactly would happen if not enough time passed in standby mode?
In the worst case scenario, if the GPCs and PASS were truly toast, Discovery’s crew would have to fall back on a piece of software that had never before been used in flight: the Backup Flight System, or BFS. The BFS is something that I sort of tangentially mentioned in the STS-2 episode but never got a proper introduction. It is essentially a computer program that can handle all of the bare essentials of flying the orbiter. It was stripped down, compared to the primary system, the PASS, and was really just for use in emergencies. The BFS was implemented by a completely different team of software engineers than the PASS, meaning that it was exceedingly unlikely that they would share any common bugs. So if the unthinkable happened and the PASS broke, the BFS would get the crew home.
But the thing about the BFS is that when I say it was stripped down compared to the PASS I mean it. Early versions of the system couldn’t even output to the computer screens, and could only move a few needle displays around. The entire entry and landing would have to be flown manually. I don’t even think the BFS would update the heads up display. And if there was any doubt how serious its use was, the method to engage was the BFS was, I kid you not, a big red button on the hand controllers used by the commander and pilot. Oh, and just as a kicker, it had never actually been used or even tested on a mission. Flying a fully manual entry was, of course, something that Commander Wetherbee and Pilot Kelly had trained for. But after nearly two weeks in space, and with no real world experience, it was not something to be taken lightly.
While trainers, astronauts, and other team members scrambled to determine the consequences of the too-fast-switch and work on a procedure to fix the situation, the decision was made to switch to the BFS. It actually got as far as landing in the crew’s morning briefing printout up on the orbiter. But thankfully, at the last minute, someone thought of a workaround. By doing a full memory dump of some of the GPCs, the integrity of the PASS system could be verified. Once this was done, the software folks were certain that PASS was ok, and the BFS could remain on the shelf. It never would be used in the entire 30 year run of flight operations in the shuttle program.
And since I’m sure you’re dying to know, the folks on the ground did eventually come up with an answer to the initial question. It turned out that the GPCs would be fine.. as long as they were left in standby for at least five seconds. Close call.
Alright, that whole GPC issue was a bit stressful, so let’s take a moment for something more lighthearted. As we’ve seen over the course of the show, just about every space shuttle flight has a number of student experiments riding along in the back of the payload bay. Hosting these experiments was a great service by NASA that encouraged an interest in science and spaceflight in young students who are, of course, the scientists and engineers of the future. So please know that I truly think this was an incredible program with numerous genuine benefits.. but I am about to goof on them a bit. I don’t really mean to mock curious children who are engaging with science, but some of these experiments.. the jokes just write themselves. So here is a selection of some of the experiments flying on board Discovery for STS-102.
The “Microgravity Rainbow” experiment, provided by first and second graders of Beaver Run Elementary in Salisbury, Maryland was actually kind of cool. They mixed 44 vials of Kool-aid, with half of them flying on the shuttle. After the flight, the colors will be compared to the control to see if the flown samples changed at all. I mostly just laughed that it was Kool-aid of all things.
The students of Rostraver Middle School in Belle Vernon, Pennsylvania flew “Operation Cheese Mold” which seems to just be a bunch of cheese. The flown samples will be compared against a control group for mold growth. And I gotta say, considering that these experiments were loaded weeks or months before the flight and were not refrigerated, I’m sure there was plenty of mold to compare. Maybe if you’re bold and take a nibble you can wash it down with some of the Kool-aid experiment.
Continuing with our food theme, students from the Congress Math/Science/Technology Middle School Magnet Team in Boynton Beach, Florida put a bunch of samples of coconuts into vials to see how they’re affected by flying in space. And I’m sure they were very proud of themselves for the experiment’s name: “Coco for Coconauts”.
But the one that made me laugh the hardest came from Virginia Space Academy in Newport News, Virginia, which seems to be something sort of akin to Space Camp. Their experiment, titled “The Ultra Fluffy Outcome” seems to literally just be a bunch of cotton candy. Because why not. Also, “The Ultra Fluffy Outcome” would make a great band name.
Just to wrap up the apparently never-ending flight day seven, this is when Susan Helms and Bill Shepherd finally swapped places, completing the crew handover. Helms went last because she was helping out with the second EVA, and Shepherd went last because the commander is always the last to leave. The first handover between crews of the International Space Station was complete.
At some point around here, the mission got a little longer. The crew were apparently having difficulty getting the MPLM filled back up with stuff on time, so an extra day was added to the flight. This shouldn’t be too surprising. It’s a new piece of equipment, and we know how much the ground loves to underestimate the challenges of doing stuff in weightlessness. Adding to the complexity was that the center of mass of the MPLM had to be carefully tracked, to ensure that the center of mass of the entire shuttle stayed within a surprisingly narrow window.
On flight day ten, the Node 1 nadir hatch was closed, the RMS was once again used to grapple the MPLM, and Leonardo was placed safely back in the payload bay for its return to Earth.
After 8 days, 21 hours, 33 minutes, and 30 seconds docked to the ISS, the latches of the Orbiter Docking System were retracted, and Space Shuttle Discovery backed away, with pilot Jim Kelly at the controls. I have to imagine that Shepherd, Gidzenko, and Krikalev had their faces glued to the windows to look at the station as they backed away. The last time they had seen it from the outside the ISS had looked very different, with just Zvezda, Zarya, and Unity in place. As they departed, they could now see the Z1 truss, the first set of gigantic solar arrays, and the US laboratory module. The ISS was growing quickly in size and capability, and the Expedition 1 crew had been there to make it happen.
After flying for around an hour, Discovery completed one-and-a-half revolutions around the station at a distance of around 140 meters. Kelly then blipped the thrusters and Discovery flew off into its own orbit. After a day flying on their own, the crew prepared to head back to Earth. For the Expedition 1 crew, this meant taking some special precautions. As we’ve seen on the Shuttle-Mir flights, the long duration crew would go through reentry in seats that had their backs against the floor of the middeck, with the crew’s legs stuck into open middeck lockers. This was to ease the punishing return to gravity, when their cardiovascular systems would suddenly have to make an effort again in order to pump blood up to their brains. Keeping them company would be someone who could relate: Andy Thomas. He went through a similar process after his Shuttle-Mir mission, and would return to Earth on the middeck to help the ISS crew out. This also results in a bit of space shuttle trivia since this marks the first time that a shuttle crew would go through reentry with three people on the flight deck. Obviously on the first four flights we only had the commander and pilot up there, but on every flight after that we had four people. Well, I guess on STS-27 and STS-80 there were were five people on the flight deck, since first Mike Mullane and then Story Musgrave thought would be fun to stand around in the back. But never three people! Maybe making some trivial shuttle history will be a good consolation prize for Andy Thomas missing out on the plasma light show upstairs.
The landing was pushed by one rev due to rain showers and low clouds at the Kennedy Space Center, but after one more trip around the world and an uneventful reentry, Discovery touched down at the Shuttle Landing Facility, concluding a successful mission lasting 12 days, 19 hours, 49 minutes, and 34 seconds.
STS-102 is representative of what is becoming the new normal here on the shuttle program. It’s a deceptively complex mission that saw new hardware, massive cargo transfers, two EVAs, and of course, the first ISS crew swap. It also completed the critical job of fulfilling its link in the chain, clearing the way for the next flight to follow. Even as certain tasks grow closer and closer to something we can call routine, the volume of activity on these flights continues to grow. And all we can do is try to keep up.
In one fun little button to close out this mission, I am pleased to report that after being manifested on 63 previous flights, Development Test Objective 805 was finally completed. This test, which aimed to better characterize the orbiter’s performance when landing in high crosswinds, was first on the docket on STS-39, just shy of ten years ago. Every flight since then has mentioned in the mission report how the crosswinds were insufficient to satisfy the DTO. It’s not like they were going out of their way to check this off the list, they would just do it when it came up naturally, but still. Ten years!
What’s interesting about this is that the crosswinds apparently flared up a bit after they were committed to the entry, and at the time of the landing were actually at 16 knots, a 4 knot violation. That’s just under 30 kilometers an hour for those of you, like myself, who don’t know what the heck a knot is. I’m not sure what speed winds the DTO required, but it sounds like the answer is “too high”, which explains why it’s taken so long to happen.
Just to throw one last twist into the DTO 805 saga, in the post-flight presentation the crew mentions that actually, a couple seconds before touchdown the winds went under the landing limit, and a couple seconds after touchdown they picked up again. And on the next flight DTO 805 is back on the manifest, so maybe the quest continues?
Alright, that closes out STS-102, but to close out this episode, I have to mention something that happens before the next flight. STS-102 ended on March 21st, 2001 after its successful mission to the International Space Station. Just two days later, on March 23rd, 2001, another space station met its fiery demise, as Mir tore through the upper atmosphere, completely missing the Taco Bell target off the coast of Australia. The world was back down to one space station for a while, but one that was getting better and better.
Next time.. well, we’ve just seen the first crew hand-off on the ISS. But what about the first end-effector-off? On STS-100, we’ll do just that, while also wondering how the ISS has a luau and a trampoline.
Ad Astra, catch you on the next pass.