by Paul Dye
Shuttle-Mir was, for most of the MOD, much more about the Shuttle visits than it was about the long-duration astronauts living on Mir. For those of us planning and flying those Shuttle missions, the long-duration crewmembers were passengers to be delivered and passengers to be picked up. They were our friends, of course, so they were much more than cargo. Since a large part of their science was about how their bodies reacted to long-duration exposure to microgravity and the space environment, it was important to treat them in a way that preserved that science until the doctors had done what they needed to do to them after getting them on the ground. We even developed a supine seating system so that crewmembers would take all the entry loads through their back (referred to as “eyeballs in”) rather than down through their feet (“eyeballs down”) with the standard seating system. We made sure that we had a crewmember on the Mid-deck to watch over them during entry, and we had to plan for emergency egress for what we called a deconditioned crewmember. Deconditioning occurs when the human body spends a long time in free fall, and the muscles and bones weaken because they are not being used. The problem was that the Launch and Entry Suit that all Shuttle crewmembers wore during that time frame, along with the parachute and survival gear, weighed close to 90 pounds, which might as well have been a ton for someone who had been floating in a weightless condition for six months. Emergency egress sort of meant being carried/rolled/pushed over to the hatch by the more able-bodied crewmember, having them hook the individual up to the parachute, and then shoving them out the hatch. We just decided that it would be better if we didn’t get into a situation where a bailout would be necessary.
Of course, in order to transfer crewmembers, their supplies, and their science hardware to the Mir, the first thing we had to do was get docked. The first rendezvous with the Mir, on STS-63, was the product of a great deal of education on both sides. It required a lot of trust building and negotiation. There was a great deal of concern about plume impingement and contamination. Even if we didn’t damage the solar arrays physically by making them flutter, there was still the possibility of molecular contamination, which would cause the arrays to degrade. Everyone is familiar with their car getting a little dusty when it’s been parked outside for a while. You hardly even notice it until you streak it with your finger, and the dust washes right off. But if you let just a little bit of anything get onto an array, it can degrade the performance by a small but measurable amount. And because spacecraft are always optimized for the most performance and the least weight, the arrays must operate at near-design efficiency over the long haul in order to keep the spacecraft viable.
The fact that the Mir was planned to be in orbit for years, and because there was no way to service the arrays, even the tiniest bit of contamination could have long-term effects that could shorten the station’s life. It’s all about the details, just like anything else in spaceflight. So, many, many people studied the dynamics of thruster plume particles, how they moved, and where they went. The plumes from the Shuttle were then analyzed and modeled, and we shared this data with the Russians to get their agreement and buy-in for our plans. Everything was documented, and the engineering and science were agreed to in the rules and plans. But when we ended up having jet problems on that first Shuttle flight to Mir, it all came down to relationships—the trust built up over several years of working together (and probably some good old-fashioned drinking time).
Bill Reeves, a long-time Flight Director, was stationed in Moscow’s MCC (known as TsUP) during that flight. He was there because, out of all of the members of our office, he just had the kind of personality that helped him build a social relationship with the key guys on the other side of the pond. Put another way, he knew how to drink with them, and he knew how to relax with them. Bill spent quite a few years assigned to Aircraft Operations during the Skylab days, and he developed a good Officer’s Club manner. The Russians liked that. They wanted to see you with your hair down, and Bill knew how to do that. So when the jets failed, and we were looking at the loss of the close approach to Mir, he was able to pat his friends on the back and have some heart-to-heart talks that got them to trust our alternate plans. Sometimes you don’t get to trust someone just by holding meetings with them in conference rooms.
Decision-making during the Shuttle-Mir Program always had a bit of-behind-the-scenes drama. The Phase 1 Program Office was developed to run the project after the initial meetings between technical groups. Because the Russians preferred to build trust and friendship via individual-to-individual relationships (rather than by simply having meetings between whomever was in a particular position at the time), discussions on major issues usually occurred on phone calls or in small-scale, face-to-face meetings. The NASA way was to hold large, open board meetings—the Russians rarely worked that way. The net result was that there was a bit more mystery to how and where decisions were being made throughout the program. There was nothing evil about it, and for the most part good, sensible decisions were made. But there was a certain uncertainty about which way things might go on various topics. For those used to working in an open operations environment, it could be a bit unsettling. Decisions got made, and no one knew where they came from. It was just sort of the Russian way.
I always liked to say that flying a space station wasn’t as dangerous as it might seem to those who flew ships up and back from orbit. After all, the only real quick killers were a loss of cabin pressure or a fire… and Mir happened to experience both during the time we flew with them. Less critical, but equally threatening in a programmatic way, was loss of control… and that happened on numerous occasions as well. About the only thing that we didn’t experience together during Shuttle-Mir was a toxic atmosphere. Then again, the fire did a good job of putting the crew’s breathing systems at risk.
It was always to be remembered that when there was no Shuttle docked to Mir, we Americans were mostly observers. Yes, we had a huge interest in how problems were solved. And yes, we had a majority vote in what our crew did or did not do. But solving problems with the Mir systems, or the overall direction of their program, was the Russians’ right and responsibility. We learned a tremendous amount about how they thought as they worked through the issues, and it was a great learning environment for us as we watched our future partners. They, no doubt, observed us too. Our teams in Russia were usually able to sit in on key troubleshooting sessions because of our interest in the American on board, and we always welcomed the Russians spending time in Houston when we were talking about Shuttle-Mir.
The fire on Mir was caused by a failed oxygen generator. It proved to be a huge threat to the future of the joint program (after we determined that it was not an ongoing threat to our astronaut on board). There was a great deal of discussion at very high levels over the amount of risk we were taking with our astronauts’ lives on board the Mir, mostly because the fire was so dramatic. But as engineers, we sat down, understood the problem—along with the Russian response—and figured a way to justify the risk for the rewards of long-term cooperation with the Russians. Whenever a major failure like this occurred, most of the discussions about determining the cause of the incident and the future of the program went on at a programmatic level. Our operations team meanwhile kept flying on a daily basis. The guiding principle of the folks on the front lines was to continue what they were doing and do it well for as long as they could—until they were turned around. We obviously participated and contributed to the investigations, but it always was remembered that no matter what, if you were in flight, you had to keep flying. It was an old lesson from aviation—no matter what, you first fly the airplane, then you do whatever else you need to do. “Aviate, Navigate, and Communicate—in that order!”
The first docking mission was STS-71, with Robert “Hoot” Gibson in command of the Atlantis. The spacecraft was equipped with the Russian APDS—the Androgynous Peripheral Docking System—that allowed any spacecraft so-equipped to dock with any other that had the same system. It featured no pro
be or drogue—just three docking petals that interlocked with the same type of system on the other vehicle. Capture latches were incorporated into the petals, and the rim included a series of latches that drove from either (or both) sides to bring the sealing rings together for hard dock. The docking systems had to be aligned within about 3 degrees, and within 3 inches of centerline, in order to ensure a good soft dock. Docking velocity depended on the mass of the vehicles being docked—bringing an Orbiter in to dock with the Mir was a slow process because a Shuttle had lots of momentum: its high mass required a low velocity. Docking a Soyuz was a more sporty affair because its mass was low—you needed a higher velocity to get the same momentum. In fact, if you were used to docking a Shuttle, with its stately final approach, and you got into a Soyuz simulator to shoot the same approach, the closure speed was positively terrifying. A Soyuz would move at a good solid foot per second, whereas the Shuttle approached at less than a tenth of that figure. It may not sound fast to you, but with a Soyuz there is not a lot of time to make fine corrections to that narrow cone of acceptable angles and offsets in the last three seconds.
STS-71 was a mission that featured a lot of interesting firsts, including the fact that it landed with more crewmembers than it launched with—and no, there were no babies born on board. The mission featured an actual Mir crew change. The Shuttle brought up two new cosmonauts, and it brought back the two cosmonauts who had spent their mission on board with astronaut Norm Thagard, who also returned on Atlantis. In order to exchange crews, STS-71 had to bring up new seat liners for the Soyuz. Each person who rides up or down in a Soyuz is strapped into a fairly bulky, form-fitted seat insert. This was the first time most of us had been introduced to these liners, but hauling them up and down became a way of life as we changed out crewmembers. Even those scheduled to go up and down on the Shuttle had to bring up a custom-made seat liner, because the Soyuz was their escape craft for their stay on Mir. They had to have a safe couch (and a Sokol suit—the Russian launch and entry garb) in case the worst happened and they had to abandon ship.
Fortunately, nothing that dramatic ever happened during a docked Shuttle mission. The flights did not go by without their excitement, however. The most common failure experienced on the Mir during these years had to be loss of control caused by computer problems. The Mir had an attitude control computer that had three “lanes”—their word for what we would call channels. In reality, it was three computers operating in the same box. Similarly, the Shuttle used four General Purpose Computers operating in sync for ascent and entry. When the Mir lost all three lanes, it lost control. And that meant sooner or later (usually sooner) it would lose its ability to point the solar arrays at the sun. This in turn would mean a power reduction and effectively cause a brownout—or, more commonly, a blackout. When the Shuttle was docked, it could control the attitude of the stack. That is exactly what we did most of the time. But first you had to actually get docked, and you needed Mir to be in control for that.
Several Shuttle missions launched while Mir had known computer lane issues. We worried about additional failures that would leave the station in free drift. Such failures would make docking extremely difficult, if not impossible. Although we developed techniques for doing the maneuver, they wouldn’t work if the Mir was spinning above a certain rate in any or all axes—and when I say spinning, I’m not talking about some Hollywood-like special effect where you can see it doing pirouettes. Anything more than a degree per second is really pretty racy—although it might not look like it to an outside observer. Fortunately, we never had to fly an actual docking with the Mir out of control—but we’d have given it a go if the need had arisen.
Both the Mir and the Shuttle used essentially a 14.7 psi nitrogen and oxygen atmosphere, which made it easy to keep the hatches open all the time they were docked together. This open hatch policy was good because the primary goal of any of these missions was cargo transfer. It was our job to bring up as many supplies and science experiments as we could, and it was during this period of time that the job of tracking transfer items became a solid part of the Payload Officer’s job description. There was always a huge list of things that had to go from the Shuttle to the Mir, and another equally long list of things that had to come back. The Russians, up until the Shuttle visited, were very limited in their return capability—the unmanned Progress supply ships burned up on reentry, so they couldn’t bring anything home. The Soyuz could only bring back about as much as a person could carry in their lap, as there was very little return stowage space available in the tiny capsule that made it to the ground. But the Shuttle was roomy, and it was designed for reentry with comparatively huge cargos. Anything brought back from inside the Mir had to be stowed in the Orbiter’s crew cabin, but this work provided practice and spurred the development of cargo techniques that were used all the way through the ISS construction and servicing missions at the end of the Shuttle program.
One of the big cargo elements on almost every flight were Russian black boxes from the KOURS automated docking system. The KOURS consisted of a number of computers and sensor boxes that were mounted in the Progress or Soyuz, and the KOURS controlled the rendezvous and docking of these vehicles. Russians generally used automated docking, with hand-flying as a backup option if the computers were to fail. The KOURS system was developed in the days of the old Soviet Union, and the factory that designed and built them was in Ukraine—a former Soviet state, but now an independent nation. That meant the KOURS had to be obtained from “outside the country,” so to speak. Because relations were sometimes strained between Russia and Ukraine, there were times when KOURS devices were simply not available to the Russian space program. Therefore, the cosmonauts busily removed the black boxes from every Progress vehicle that arrived and stored them for return on the Shuttle—sort of like recycling old soda bottles. (As I recall, we never did see our five cents per box, though.)
The Shuttle, by contrast, was always flown manually for docking. Well, manually with computer assistance, of course—it was all fly-by-wire. Many fans of science fiction movies expect that the pilot of a docking vehicle is flying in what we call “all six axes,” not only translating in/out, up/down, and left/right… but also pitching, rolling, and yawing the vehicle. While you can do that if you want, it does keep you pretty busy. And when you are docking something as big as the Shuttle to something that has as many things sticking out as the Mir, it is nice not to have to worry about, say, bumping the tall tail of the Shuttle into the tip of a solar array because you pitched a little too far. So we used the computers to maintain attitudes, while the astronauts flew the translations.
Letting the computer (autopilot) fly the attitude (orientation) of the Shuttle was actually quite elegant. It knows how it is pointed because the Inertial Measurement Units (IMUs) have been aligned. We assume that we know where the Mir is pointed, because they have a similar system, and we told them how to point. So if you assume a perfect knowledge of both vehicles’ attitudes, you can bring them together with perfect orientation. Of course, nothing is perfect, so we developed the technique of slowing to a stop just about 30 feet out and using a special alignment target to see if there was any error in the relative attitudes between the two vehicles. The target was designed so that you could actually read the misalignment in roll and pitch. But you didn’t use the joystick to line things back up. Instead, you typed the correction into the pointing display, the Shuttle made the minor correction, and in you went—aligned by eyeball. A TV camera was mounted in the center of the docking port hatch so that you could look straight up the centerline as you approached. We had alternate alignment techniques in the event of a camera failure, but they took a little more interpretation than looking straight up the central axis of where you were moving.
One of the things that the joint teams recognized right off the bat when we started to talk about docking Shuttle to Mir was that the docking ports on the existing station were a little too close for comfort—the Shuttle really ha
d to get in close to the central node, the solar arrays from various modules, and the KRYSTAL (one of the experiment modules radiating from the Mir’s central node). The solution was a special docking module. It was really not much more than an extension tunnel added to the end of the KRYSTAL that put a little more distance between the Shuttle and the stack. This was designed and built by the Russians, shipped to Florida, and launched on STS-74, the second docking mission. It used an APDS on each end, of course. In order to attach it, the RMS (Remote Manipulator System) was used to lift it out of the payload bay and stack it onto the docking port on the Shuttle. The Shuttle then flew in to dock to Mir. When we departed, we left it latched on the Mir end and detached from the Shuttle end.
A certain amount of momentum was required to get the APDS capture latches to soft dock the module to the docking port on the Shuttle. The RMS really wasn’t designed to generate that kind of force, so it couldn’t just slam the docking module onto the Orbiter after it was pulled out of the bay. Once again, physics was our friend. It really doesn’t make any difference if the docking system is slammed onto the Orbiter, or vice versa. So the RMS was used to align the docking module and hold it just a couple of feet above the Orbiter. Then the arm was commanded to go limp, and the Shuttle jets were fired to ram the Shuttle into the module. Momentum did the rest of the work: the latches captured, and we had a snout sticking up out of the payload bay. The Shuttle docking with Mir went on, and when STS-74 departed, the docking module stayed behind. It served as the docking port for all future Shuttle-Mir missions.
