Commercial Rockets

THE INTERNATIONAL SPACE STATION / МЕЖДУНАРО́ДНАЯ КОСМИ́ЧЕСКАЯ СТА́НЦИЯ — Russia/USA/EU/Japan, 1998

It’s the most expensive moving vessel ever made. It’s also the most expensive building ever built, and quite probably the most expensive artificial object of any kind in history, unless you count something like the entire interstate highway system as a single construction. It has been occupied continually now for twenty years. And it’s becoming increasingly commercialized. It’s the only one of its kind, but it won’t be for much longer... building another one can now be done far cheaper.

Overall, one end of the station is Russian and the other is American. They were originally going to be two rival stations, Mir 2 and Space Station Freedom, but after the fall of the Soviet Union they decided to stick the two together so they could cooperate. Even now, it may be possible for the two to separate and be independent, and with recent political tensions, the idea has been brought up. (One thing that would make this problematic is that though the Zarya module is Russian built, it’s legally owned by the United States, which paid most of its construction costs. For that matter, some nominally American sections were actually built in Italy.) To spread the cost around, additional help was recruited from Europe and Japan. The Chinese were pointedly not invited. Fresh memories of the Tiananmen Square massacre may have been a factor in the decision. Since then, concerns about sharing our space technology have kept the Chinese excluded even as visitors.

When looking at the station as it is today, it's easy to just see a tangled jumble. But the layout can be understood by starting with the core — the backbone of the structure. This consists (currently) of a stack of five pressurized modules. Each module is sized to make a full load for a shuttle or a Proton or whatever other craft might bring it up, weighing up to twenty tons. It took about two dozen launches to build the station up to its present size.

To navigate the station, it helps if we have a clear sense of direction when moving about. Fortunately, the station mostly keeps a quite consistent orientation relative to the Earth, with one end pointed in the direction of orbital motion and one side faced toward the ground. This allows the people on it to designate certain directions as fore and aft, port and starboard, above and below, like on a traditional ship. (But for the latter, they prefer the terms zenith and nadir.) Or, given its shape, one might be more tempted to compare it to an airplane instead of a ship, with the solar panels and so on taking the role of wings. The five main modules are fairly comparable in size and shape to an airliner’s fuselage... but this analogy breaks down once you start looking at the side modules.

Generally speaking, these modules have a round cross section on the outside and a square one on the inside. Each wall is tall enough for someone to “stand” in front of while working with equipment mounted there, and having it flat instead of concave makes this easier. Cubbies such as sleeping nooks and bathrooms have a flat door and a concave back wall. Installed equipment is designed to fit into standardized slots with round backs and flat fronts, each about the size of a fridge.

Let’s list off the five main modules, going forward from the aft end:

That’s a total of six sleeping spaces. When seven or eight people are up there, someone — often the commander — uses a docked spacecraft as a bedroom, which offers more room than the scant 2.1 cubic meters of a normal cabin, but less privacy. Space is tightest during a crew change, when for as long as a week there might be up to eleven people. At crowded times, schedules for the exercise machines need to be tightly managed. This gear stays busy because in zero gee, it takes like two hours a day of workouts to stay healthy.

So if you think of the station as a small town, these five modules constitute its main street. It’s a continuous tube that allows you to float from one end of the station to the other in a nearly straight line — the main traffic artery. Now let’s look at some of the side streets.

The longest cross street is at the front, branching off of Harmony. Up here you find:

Back in the middle, branching off of Unity, we have the most complicated part:

The Russian modules each have some attachments, most of which are much smaller than the main modules. And unlike the international section, where the side modules protrude to port and starboard, the Russian ones are vertical, sticking out above and below.

The Russians had been planning to expand their end further in the near future, but then decided that the ISS was too old to keep investing in, and that American astronauts have cooties. But they did build another module which could have been ready to attach soon. It is called NEM-1 or the Science Power Module, and does not yet have a friendly name. It would provide additional large solar panels and plenty of other external equipment, along with a good amount of multipurpose habitable space. This would have stuck out from the starboard side of Nauka’s bottom junction. They originally were going to have an NEM-2 as well, presumably on the port side, but the budget got cut.

Zvezda, which is critical for life support, is showing its age, and they’re starting to feel a bit nervous about trusting cosmontauts’ lives to it. It recently sprang a leak, and while that was being fixed, some oxygen equipment broke. (They make oxygen by electrolysing recovered water vapor.) They recently had to repair the toilet as well, and its rear rocket motors may now be unusable due to equipment added next to them. Then they found that the leak they’d patched was just one of two leaks. (Also, Zvezda is an unpleasantly noisy place to live... some cosmonauts bring earplugs.) The new Nauka module has problems too: its main engine wouldn’t fire, and while it was docking a thruster fired for no reason, briefly turning the whole station upside down. And it had a leak of its own. After that mishap, they found cracks in Zarya. Because of issues like these, the whole ISS might be retired within a decade, in favor of new stations... or if those cracks spread, maybe a lot sooner.

So the Russians are now saying they will build a whole new independent station instead of expanding the old one, though to budget such a thing sounds like it might be very difficult. After the latest round of American diplomatic sanctions, they said they were going to pull out of the ISS at the earliest possible date, after the current term of agreement ends in 2024. After all, they say, “the station’s modules... have mostly worn out their service life.” But a couple weeks later they backed down from this attitude, which probably means they gained some concession or got paid to stay longer. They now say they plan to stay until 2028. When they do leave, they will have to write off Nauka as obsolete despite getting only brief service from it. After all, it is, like Zarya, based on a Salyut design that dates back to the nineteen-seventies. But what about the plans for NEM-1? They’re going to keep it on the ground for now, saving it for the new station. We shall see if they hold to this plan once they get into the process of actually budgeting and constructing the new stuff.

The name would be Russian Orbital Service Station (Российская орбитальная служебная станция), which handily abbreviates as ROSS (РОСС), the root name of the motherland. They want to put it into a sun-synchronous polar orbit so all of Russia would be visible from it, which sounds like it would make relocating Nauka impossible, as the orbital plane change would require something like six km/s of delta-V. It sounds like NEM-1 will be the first module, after some refitting to give it Zvezda-like core functionality. This would be followed by a second similar module which would apparently take over as core, then a node section and a gateway piece. Eventually they’d like three more modules, if they still have the budget to expand.

On the American side, there was talk for a while of adding a big centrifugal wheel up front, so people could sleep in simulated gravity for better health, but it has not been funded.

Where, you may ask, does the big “Canadarm” attach? The answer is, anywhere it wants to. It can swing its free end around, attach it, and detach the former base, switching end for end, and by this means it can inchworm its way all over the station, using any of several attachment points, one of which is a sort of railroad car that allows it to slide to any position along the width of the big external truss. This truss car may be its most used anchorage. Recently an attachment point was added to Zarya. There are two control stations for it, one in the Cupola and one in Destiny. The arm is 17.6 meters long and weighs about 1.6 tons, without the optional “dexterous manipulator” that it can add to the end, which is called Dextre for short, or the Canada Hand. Another add-on that can go on the end is a boom which can add fifteen more meters of reach.  The arm is capable of wrassling objects as big as a space shuttle, as long as it moves them slowly enough. (Moving anything around the outside of the station is always slow... docking and undocking can take a couple of hours, for instance, and the top speed of the truss rail car is one inch per second.)

The ESA is planning to add a smaller arm to Columbus. That would make four arms overall, with those of Kibo and Nauka.

All in all the station is 75 meters long, and the truss has a wingspan of 109 meters. The outer parts of the truss have eight solar panel wings, each with two panels 35 meters long and about 4 wide, which can produce up to 240 combined kilowatts peak power... or could when they were new. Some are now being replaced, with new better cells being rolled out on top of the old ones. The whole station masses well over 400 tons — triple the size of Mir, the next largest object ever put into orbit. There are 932 cubic meters of pressurized volume in it — enough to hold about one ton of air, as they use full sea-level pressure — but only 388 cubic meters in the passageways open to people, which is still the size of a house, though much longer and narrower.

It may yet get a lot bigger — several private companies have plans to attach more modules, and perhaps eventually set them free to become independent stations. The company most serious about this right now is Axiom Space, which already sells ISS tourism flights to multimillionaires. They want to build about eight new modules — a whole second ISS, essentially — onto the front of Harmony, then eventually separate it, perhaps when it’s time for the ISS to retire. Bigelow also had plans, but these are probably kaput. Nanoracks has been making some noises... they suggest an approach with some modules added to the ISS while others share the same orbit without being attached. Sierra Nevada is also working on a large inflatable module, similar to Bigelow’s proposal, but using somewhat different materials. (Sierra likes to note that they actually helped Bigelow build BEAM, specifically the berthing ring and hatch.) It would be roomier than anything rigid that can be packed into a rocket fairing. They call it LIFE, for Large Inflatable Fabric Environment. And they ain’t kidding when they say large: just one might have almost as much habitable space inside as the entire ISS! They say it could be used at the Lunar Gateway, or even on a Mars expedition. But they have not said how much it will weigh... some estimates say over 50 tons, which would make getting it to such locations quite costly.

But though Sierra Nevada is trying to make it sound like it’s a race for who will have the first commercial station, it’s Axiom that has gotten a green light from NASA to send up a module. They will be paid a fixed price up front for the first five years use of it. Bigelow thought the NASA offer was too low, and the consensus is that a purely commercial station isn’t viable without a lot of governmental support. Ideally, this should not be a problem to get as long as it’s significantly less expensive than the ISS.

This first Axiom module is mainly living space — it would add four sleeping quarters, each with a window. The next module, in current plans, would add four more, plus a large cupola. Only after that will they add a lab, though even the first module has some working facilities. Then they’ll add a big solar array on a vertical tower, and some methane-burning thrusters, making it ready to function independently of the ISS. After that, they can keep adding however many more modules there’s demand for. The modules themselves will be built for Axiom by Thales Alenia Space. In 2021, Axiom hired a Dragon to go up to the ISS to do groundwork for starting the construction, along with some tourism for wealthy backers while they’re there. They’ve got three more tourist Dragon flights booked for later. They plan to launch their first module in 2024.

The trend is toward separate stations rather than joint ones. The Russians, as mentioned, want to put up a separate one by 2030, though it would be tough for them to budget such a thing. India also wants to start its own station by 2030. The Chinese should have their own station well established by that time... and the Russians might just see if they can go halfsies on that, or that may be just talk. And there’s increasing speculation that Jeff Bezos’s end goal for the New Glenn is to put up orbital habitats with it. None of these have articles here yet except China’s, as none of the plans are definite enough.