by Terry Virts
In another instance our crew lost a torque wrench, a fairly big tool—probably a foot in length and several pounds of mass. Gone. We all looked for that thing for months. Filters. Nooks and crannies. Misplaced tool containers. Nada—it was gone. Then magically someone found it floating in a module one day. We had no idea where it had been hiding or what adventures it had gone on, but like the prodigal son, it was lost and then it was found.
In yet another instance, a few weeks after arriving at the ISS I was taking some pictures in the Cupola, a seven-windowed observation module that has amazing views of Earth and the universe. I had taken some particularly awesome shots of the aurora borealis and I was really excited to download them and see them. I took the memory card out of the camera to put it in my pocket, and it slipped out of my hand. Off it floated, spinning end-over-end like a quarter flipped at the beginning of a football game. And I watched in slow-motion horror, yelling “Nooooooooooo” as it slipped directly into a crack on the Node 3 wall. It was only a fraction of an inch wide, and that card floated right in there. I waited for it to bounce out and spent weeks checking filters and warned all my crewmates to keep an eye out. Nothing. Someday, decades from now, when the ISS finally drops into the Pacific Ocean, there will be a memory card holding some sweet pics of auroras stuck behind one of the walls. Sigh.
As mentioned before, astronauts experience something we euphemistically call “space brain.” We performed several experiments to quantify this phenomenon, and one in particular was called Cognition. I did this test roughly once per month while in space. I would strap myself down in front of a laptop and do memory, pattern recognition, and reaction tests. The results showed that my brain did slow down a little while in space. This may have been due to floating and its resultant disorientation, or from fluid shift, or neuro-vestibular disorientation, or even elevated levels of carbon dioxide in the atmosphere that impeded brain function. Whatever the scientific explanation, I’m pretty sure that every astronaut would agree—space brain is a thing. You forget easily, don’t notice things that are happening, and can’t think of solutions as well as you could back on Earth, especially in the first few days after arriving in space. I’ve heard women describe the same symptoms while they were pregnant. And though I’d never dream of saying, “I understand what it’s like to be pregnant,” I do think that astronauts get a taste of mild cognitive impairment, aka space brain.
Learning to float and work and live in space was one of the highlights of my career. I loved going through that steep learning curve, until after a few weeks I was a pro—a real spaceman. Able to push off and get to my destination quickly and without spinning around. Able to keep track of tools and equipment and clothes effortlessly. Usually. Except for that memory card.
How to Build a Space Station
A Painstaking, Piece-by-Piece Process
When you see Hollywood space movies like 2001: A Space Odyssey, Interstellar, or The Martian, there is usually some giant spaceship that magically appears and flies off to other planets or galaxies. Which makes for an interesting movie. But in real life, those beasts have to be built; they don’t just appear out of thin air, or out of thin vacuum for that matter (pun intended). This chapter is the story of how the ISS (International Space Station) was built, piece by piece, over several decades, by a multinational partnership.
The idea for an American space station began during the Apollo era in the 1960s. As the Moon landings were drawing to a close, NASA was left with a lot of hardware and talent and wanted to find something productive to do with it. The AAP (Apollo Applications Program) was implemented to develop those ideas, and two missions were eventually flown. I was not even a year old when the AAP office was formed, but it would eventually affect my life in the most profound ways.
The first AAP mission was Skylab, the first American space station in orbit around Earth. Skylab was an outfitted upper stage of the Saturn rocket, and as such required only one flight to launch. Three crews visited Skylab between 1973 and 1974, with the longest stay approaching three months. The second AAP mission was the Apollo-Soyuz Test Program in 1975, in which an American Apollo capsule and a Russian Soyuz capsule docked together in Earth orbit, with the astronauts and cosmonauts performing a very symbolic space handshake in the middle of the Cold War and the aftermath of Vietnam.
While NASA was busy with AAP and developing the space shuttle, the Soviets flew the world’s first space station, Salyut-1, in 1971. Several follow-on Salyut stations were flown until 1986, when the Mir space station was launched. Mir was the first true modular space station to be assembled in space, component by component, eventually comprising six modules. It was abandoned and deorbited into the Pacific in 2001, which coincided with the reason NASA hired me to be an astronaut in 2000—it was time to build the International Space Station.
As the space shuttle program got underway, NASA needed to expand its mission. Launching satellites and performing classified Defense Department missions was great, but not enough for such a high-dollar program. In 1984 President Reagan proposed Space Station Freedom in his State of the Union address, and over the next fifteen years the details of that station would change considerably.
The most important change came with the demise of the Soviet Union. President George Bush (41) directed his vice president, Dan Quayle, to engage the Russians as partners on the fledgling space station. The fear was that the collapse of the Soviet Union would lead to massive turmoil in their aerospace sector, and cooperation on a large-scale space project would provide a productive outlet for the thousands of newly unemployed Russian scientists, engineers, and technicians. It would certainly be better to have them building a space station with us than building nuclear weapons for some unseemly characters on the world stage. A partnership of sixteen nations was formed: Canada, Europe (eleven nations total), Japan, Russia, the United States, and Brazil, which eventually left the ISS partnership for budgetary reasons.
Construction of the ISS began in November 1998, when the Russians launched the FGB, or Zarya storage module, on a massive Proton rocket from the Baikonur Cosmodrome in Kazakhstan. Two weeks later the space shuttle Endeavour added the Node 1 module Unity to the FGB, and the ISS assembly sequence began. Over the next twelve years, the ISS was built, piece by piece, module by module, by a handful of Russian and nearly thirty US space shuttle launches.
There were two challenges to the successful completion of the ISS. The first was technical. Those modules had to be built to common specifications and fit together, built in factories around the world, and then often assembled for the first time in orbit. I used to marvel when, after a module sat collecting dust for years in the processing facility in Florida awaiting its launch, a shuttle would carry it up and attach it to the ISS, and it would work perfectly. This happened time and time again for more than a decade. The technical prowess that went into the space station was extremely impressive.
Second, and even greater than technical, were political and fiscal challenges. Keeping sixteen nations focused on the task of building and operating the ISS for several decades has been the highlight of US foreign policy in the post–WWII period, since the Marshall Plan. Each one of those sixteen nations has an electorate, domestic priorities, competing strategic partners and competitors, fiscal realities, and changing political landscapes. In short, it’s a miracle that the station partnership was able to hold together over such a long period of time. The space station program famously survived the US House of Representatives in 1993 by one vote, 216–215, as well as a US presidency that has swung from Republican to Democrat to Republican to Democrat back to Republican over its thirty-year-plus history. Russia has undergone a traumatic transformation, from the collapse of the Soviet Union in the turbulent 1990s under Boris Yeltsin to Vladimir Putin. Europe, Canada, and Japan have all experienced dramatic shifts in domestic politics. The ISS has survived, even thrived, through it all.
The technical aspects of building a spaceship in orbit are fairly straightforw
ard. Space shuttle payloads were limited to a certain size and weight, so all of the ISS modules had to be built within that constraint—60 feet long, 15 feet in diameter, and no more than 40,000 pounds mass. Had we had a heavy-lift rocket, the ISS could have been built in much less time and at less expense. There was a proposal in the 1990s for a Shuttle-C, or cargo version of the shuttle, that would have replaced the orbiter with a giant cargo module strapped to the side of the orange fuel tank and white boosters. Assuming an unmanned rocket like this had been developed with an 80-ton lift capacity, it would have taken only five or six launches to build a station with roughly the same capability as today’s ISS. And at the end of that hypothetical assembly, we would have had a heavy-lift rocket for flying to the Moon or Mars or beyond. Heck, we could have just restarted the Saturn V program. Alas, we never pursued that strategy and ended up building the entire ISS with a handful of Russian Proton rockets and an awful lot of space shuttle missions—one 15-ton module at a time, each one having its own redundant and inefficient hatches, berthing systems, and extra electrical equipment to allow it to function on its own. Building a lesser number of more massive modules would have really cut down on duplication. But the space shuttle worked, and selfishly, I absolutely loved flying it.
Each assembly flight had a similar profile. The shuttle crew would be highly trained on all of the specifics of that module—how to operate it from inside as well as perform spacewalks outside. The shuttle would launch to an orbit behind and below the partially built ISS, gradually catching up over the course of two days. The commander would dock the shuttle and the crew would immediately go to work, like a NASCAR pit crew when their driver pulls in for a tire change and fuel-up. The module would be pulled out of the shuttle using its robotic arm, handed over to the larger station arm, and then attached, or berthed, to the ISS using a series of mechanical hooks and bolts. Spacewalks would be performed to plug in power and cooling cables—and take a few cool astronaut selfies. Then the shuttle crew would shake hands with and say goodbye to the station crew. They had been happy to see the shuttle guys when they showed up a week before, but they were inevitably even happier to say goodbye, like an in-law visit. Next, the shuttle crew would close the hatch, undock, perform a fly-around (a 360-degree, 400-foot-radius loop around the station), fly away, and return to Earth two days later, after inspecting the shuttle’s heat shield prior to entry.
That sequence was repeated several times a year for more than a decade, assembling the station like a Lego set, until finally, on STS-130, we installed the final two modules in the official assembly sequence—Node 3 (aka Tranquility) and the Cupola. These modules grew the station to a final size of nearly a million pounds of mass and a width of more than 300 feet, bigger than a football field. There have been a few other add-ons to the ISS since that time, notably BEAM, an inflatable module test-bed built by Robert Bigelow, and the PMM, a storage module left behind after STS-133 as a permanent closet for the station. The Russians also have a few new modules on the books, though it’s tough to say if and when they’ll actually make it to ISS.
International Space Station (ISS)
This piece-by-piece, step-by-step technique to build a spaceship may be used for future vehicles. NASA is planning to build a mini-ISS in orbit around the Moon, called Gateway. We will probably eventually use a similar technique to build larger spaceships that will take us to Mars and beyond. Although it is always more efficient to use smaller numbers of larger modules launched by a few heavy-lift rockets than a lot of smaller pieces launched by smaller rockets, I was a fan of the ISS assembly strategy. Selfishly. Because I had the privilege of taking part in one of the most incredible space adventures ever—flying a space shuttle on a mission to finish building the ISS. We’ve never built anything else so magnificent in space, and I doubt we ever will.
Piloting Spaceships
Rendezvous, Docking, and Avoiding Space Junk
Flying an airplane is an entirely different proposition than flying a spaceship. I had been a pilot for twenty-five years before I first flew the shuttle in space, so I had a lot of “baggage” to unlearn. The things that make you go faster, slower, up, or down in orbit are entirely different from flying a plane in the atmosphere. So you have to forget how you learned to fly jets if you want to become a good spaceship pilot.
Before we dive into the specifics of flying rockets, here’s a quick primer on flying vehicles on Earth. Every airplane has a throttle and a control stick, or yoke. The throttle is simple enough that even a pilot can’t mess it up. If you move it forward, you go faster. Pull it back and you slow down. The stick or yoke, if you’re unlucky enough to not be in a fighter jet, makes the airplane pitch up (trees get smaller) or pitch down (trees get bigger) and roll left or right. If you want to yaw the plane left or right, you step on the rudder pedals. Pretty simple. You are now ready to begin taking private pilot lessons. However, flying in space can be entirely nonintuitive.
It all starts with orbital mechanics. As a fighter pilot, I used to say, “Isaac Newton is in charge” when describing something that was free-falling without power, a nod to his famous F = m × a equation. That pretty much sums up how objects behave while in space. The first big difference is that you are traveling at a tremendous speed in orbit, which has serious implications for your ability to turn to the left or right even a little bit. Turning requires a tremendous change of velocity, or delta-v, which requires a corresponding amount of rocket fuel, which requires a correspondingly large fuel tank, which ultimately requires a lot of money. A rocket scientist would call moving left or right a plane change, or changing your inclination, which is the heading as you cross the equator. A spaceship continuously flying over the equator has an inclination of zero degrees, but the ISS orbits at an inclination of 51.6 degrees, so it crosses the equator 51.6 degrees north or south of pure east. Your inclination also happens to equal your maximum latitude, so in the case of the ISS it is at 51.6 degrees north or south latitude 22 minutes after passing over the equator. It is back over the equator another 22 minutes after that. Because rockets have a very limited ability to change inclination, they are basically stuck with their launch inclination. So, if you find yourself flying a spaceship in the near future, be sure to launch on the correct heading, because you won’t be able to make significant changes to the left or right.
The next fundamental concept is that satellites move more slowly in higher orbits than in lower orbits. Unlike an airplane, where pushing the throttle forward makes you go faster, accelerating a spaceship first speeds you up, which makes you climb, which then slows you down. Not intuitive, but it’s what happens. In the same way, if you initially slow down, you will sink to a lower orbit, which ultimately makes you move faster. Let’s put this into practice. If you want to close on an orbiting object in front of you, first slow down; then you descend without doing anything else, which then speeds you up and you begin to close on your target. This principle can also be seen in the orbits of the planets. It takes Mercury only 88 days to go around the sun, whereas it takes Pluto (I’m old school and Pluto is a planet!) 248 years, because Pluto is in a much higher orbit, farther from the sun.
A practical application of this principle can be seen with geosynchronous satellites. They are very high up—more than 22,000 miles above the Earth, where it takes them 24 hours to complete one orbit. What’s more, if one of those satellites has an inclination of zero degrees it will orbit directly above the equator. So a satellite 22,000 miles above the equator will stay in that same position over Earth, which is handy for satellite TV coverage—you can point your dish in the same direction and the satellite will always be there.
We had a very unexpected but graphic demonstration of this principle while on Expedition 43. My crewmate Samantha Cristoforetti was doing a personal experiment for a physicist friend of hers, who was investigating the behavior of particles in zero g. He wanted to see how clouds of particles interacted with each other in weightlessness, which could help illustrate
how planets and solar systems were formed. To do this, she built a highly sophisticated device—a clear plastic ball filled with breath mints and M&M’s—to simulate the primordial solar system. She would shake it up and film the small objects as they bounced off each other in random directions. After a few days of this, we noticed that all the candy ended up in a pile on one side of the ball, which made no sense; we had intuitively expected them to continue bouncing around in random motion.
Unbeknownst to us, we were seeing a demonstration of how everything on the ISS was in a slightly different orbit, if only a few millimeters apart. And objects orbiting at different altitudes should move at different speeds. However, because the candy at the top of the ball was in a higher orbit than the ISS center of gravity, if only by a few feet, it should have been moving a little bit slower than the rest of the station. Because it was moving faster than it wanted to, it tried to climb, which caused it to move to the top of the ball, above the center of the station. This was wholly unexpected and fascinated the entire crew. I took that ball and placed it in different modules, and in each case the M&M’s floated away from the station center, stabilizing after just a few minutes. This demonstrated an effect known as gravity gradient, which causes spacecraft during rendezvous to naturally fall away from their target, and also causes elongated objects to naturally float up and down, with their long axis pointed down to Earth. It was an unexpected but fascinating physics lesson, thanks to Sir Isaac Newton!