AXIOM STATION — USA, 2025/2030?

There are several companies hoping to build new commercial space stations to replace the International Space Station after they decommission it around 2030, but most of them will not get separate writeups yet, as there is insufficient evidence that they are building something real. Even the highly publicized Orbital Reef proposal from Blue Origin, despite being taken very seriously and having Bezos billions behind it, still counts as only a paper proposal at the time of this writing. But there is one company whose plan for a new space station is getting actual funding and building actual hardware as I write, and that is the one from Axiom — the company which has been hiring Dragon rides from SpaceX to visit the ISS. Their plan is to first build an extension onto the ISS, and then cut it loose to become independent once it’s fully equipped.

NASA has so far agreed to pay them for one module, essentially leasing a share of it for five years, which is roughly how long it is expected to remain attached. After that, they will presumably pay rent to Axiom like any other tenant whenever they want to send someone there.

The actual construction is being done by Italian contractor Thales Alenia Space, which built many parts of the ISS’s non-Russian half. So there will be a lot of continuity in the basics. The details, however, will have plenty of differences.

So, to look at the basics first: the initial module, known as the Axiom Orbital Segment in its ISS role but as Hab One or AxH1 in its private role, will be a cylinder about 11 meters long and 4.2 in diameter, making it nearly as large as the biggest cylindrical segment of the ISS, Kibō. It has a Common Berthing Mechanism hatch at the back end, four more ringed around the sides, and a docking adapter at the front, where the outline tapers like a plastic bottle. This adapter looks much more compact than the Pressurized Mating Adapter used by the ISS, which sticks out a long way at an offset angle because it was designed to dock to the Shuttle without blocking its cargo bay.

So far this is basically just like other modules that Thales Alenia has made, like Harmony or Tranquility, though stretched in length. But now we get into the differences. First, this Hab One module has its own solar panel, not sticking out on a boom but plated directly onto its upper surface, like the ones on the trunk of a Dragon spacecraft. Second, and more importantly, it has thrusters. I suspect these are mainly inside the tapered section behind the docking ring, meaning that the interior would be a relatively narrow tunnel there. The thrusters are a new design, and will burn cryogenic methane and lox, which is an unusual and questionable choice. Unlike the hypergolic propellants normally used for small thrusters, these liquified gases will be steadily lost as stray heat causes evaporation, which has to be burned or vented to avoid excess pressure. But Axiom has a clever answer: a system to replenish the methane and lox by making it out of the carbon dioxide and water vapor exhaled by the crew! This process would mean that instead of having to send up volatile fuel at regular intervals, they just need an increase to the supply of drinking water, which in the longer term future need not even come from Earth. To me, a complicated untried system like that sounds like it could be trouble prone.

The interior, which is being fitted by Axiom themselves at a facility in Texas, is where the differences from the existing space station modules are most dramatic. Every existing module is packed with useful gear on every available surface, and has a completely utilitarian interior design. Not this one. It’s the first space station interior made to be relaxing... and it has a large space in it with no useful equipment. Instead it’s just an open room, with quilted padding on the walls, mood lighting with colors you can adjust, and good windows. It’s made to be a comfortable hangout for rich tourists.

Elsewhere in the module there are four sleeping cabins, each with a window, and also some areas that do have useful equipment. So despite the non-utilitarian use of space, it’s equipped to be a reasonably complete little space station on its own, though a basic and limited one.

When launched, perhaps on a Falcon Heavy or New Glenn, it will use its own thrusters to rendezvous with the forward end of the ISS, where it will be berthed by the Canadarm onto the forward port of Harmony. (Before it arrives, the docking adapter that’s there now will be relocated elsewhere, perhaps to Harmony’s underside.) It will become an integrated part of the ISS... and Axiom will already be at work on more modules.

Hab Two is planned to be much the same as Hab One, adding sleeping space for four more occupants. It may be a bit lengthened relative to Hab One. It will also come with a new Canadarm. It would stick forward from Hab One, which presumably would have its docking ring put elsewhere. But before that gets added, or maybe shortly after, they have a treat planned for Hab One visitors: an Earth Observatory (AxEO) which is basically a substantially bigger version of the ISS’s Cupola, with windows all around. This would go on the underside for views of Earth.

More modules will come after that. The first module designed for real work might go up around two years after Hab One, in 2027 or so. This will be called the Research and Manufacturing Facility (AxRMF). This would be roughly similar in exterior design to the habs, but shorter, and without any side berthing ports. Evenually they might put several of these around the sides, if demand is there.

Finally, the last piece to make the station complete, and ready to separate from the ISS, is the Power and Thermal module (AxPT). This would be more or less equivalent to the external truss on the ISS: an assemblage of solar panels, heat radiators, batteries, gyroscopes, and other infrastructure that doesn’t need to be indoors with the crew. It would mount on top of one of the habs, and unfold to stick up to a considerable height, like 25 meters, so the large panels have lots of room to swing around and follow the sun. And the base would have an EVA airlock. Until this “power tower” is added (maybe three years in), the habs would be well short of self-sufficient on power.

There’s no hard limit to the number of additional hab and lab modules they could stick on, especially after cutting loose from the ISS, which would probably happen around 2030 when the old station is set to be ditched into the Pacific Ocean. They’re hoping to have about eight modules, to make it no smaller inside than the ISS. But that will only happen if they convince people to pay, and there may be competition from other stations.

Other companies have visions of putting up stations that depart much more radically from the ISS’s design legacy. But Axiom is taking the safe route, and producing something which offers maximum continuity with what has been working so far. And for another piece of continuity, they’re planning to add on a module which has been attached to the ISS before: the large former cargo canister dubbed Raffaelo. As mentioned in the ISS article, there were three Multi-Purpose Logistic Modules built by Thales Alenia named Leonardo, Raffaelo, and Donatello. They would ride up and down in the Shuttle carrying supplies (except Donatello, which never flew and ended up being just a spare), but upon Shuttle retirement they made Leonardo a permanent part of the ISS. Now Raffaelo will have a similar destiny on the Axiom station. Like Leonardo it will probably serve no purpose but storage, as it is little but an empty windowless can.

But if you want Axiom to try something wild, they won’t disappoint you: a side project of theirs is AxSEE-1, which they are putting together for another company called Space Entertainment Enterprises. That outfit hopes to actually build an orbiting movie studio! (That same company is also currently backing the attempt to fly Tom Cruise and director Doug Liman up to the ISS to shoot a movie there under pre-Axiom conditions.) This studio would be an inflatable module six meters in diameter, to be attached to Axiom Station. If their funding holds together, this could go up pretty early in the construction, maybe even before Hab Two. Who knows — with the amount they spend on blockbusters nowadays, maybe this idea could actually pay for itself. But I sure won’t be holding my breath on something this starry-eyed ever getting built and launched.

And meanwhile, it may be difficult to complete even the core of the station, because Axiom is running out of cash and starting to do layoffs and pay cuts.

Orbital Reef

So, about that competition. What other stations might be built soon? In terms of money, the most plausible one is probably Blue Origin’s Orbital Reef proposal, which they describe as a “mixed-use business park” in space. It isn’t just them, either; they are teaming up with Sierra Space, makers of the Dream Chaser. Sierra is making an inflatable module called LIFE, for Large Inflatable Fabric Environment. And they ain’t kidding when they say large: just one would have more habitable space inside than either half of the ISS, being at least ten meters in diameter when fully expanded. (What an inflatable module usually lacks is windows — if you want a view, go to one of the smaller hard-walled portions of the station.) 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. So the main use that LIFE modules will probably get is as add-ons to Orbital Reef or other stations. Their artists’ conceptions show the Reef with several LIFE bubbles attached to it and Dream Chasers among the various craft docked to it.

And we have seen Sierra building and testing LIFE components — bursting them open to measure their pressure tolerance, and so on — so we know this is a legit effort. The same can’t be said for Blue Origin’s core part of the station, which consists of a linear stack of traditional cylindrical modules with side ports... except that they are scaled up to New Glenn size, seven meters across. This would mean at least a couple hundred cubic meters of interior space per module. Even the minimal configuration it has when it first opens for business is expected to already have a crew of ten, and as it gains length and adds tenants on the sides, the population might reach triple digits. And with that many people exposed to the dangers of space... I really hope that some of the interior hatches are kept normally closed, so any blowout that might occur would only lose part of the station instead of being instant death for everyone.

Compared to Sierra’s steady progress, Blue Origin has done very little to move this project forward, and a few years after announcing the plan, they admitted that they would be shelving it for the time being. Fortunately the Reef deal allows Sierra to go ahead and put together a LIFE-based space station independently. If they don’t go broke, that is — they’ve had to lay off some workers earlier than Axiom did.

For the future, Sierra is planning a LIFE 2 module which is even bigger and has several windows. It would launch in a seven meter fairing like that of Blue Origin’s New Glenn, whereas the original will use a five meter fairing, which is the size offered by most of today’s larger rockets, such as the Vulcan. And then LIFE 3 was originally going to be the same diameter as the 2 but elongated, but now they’re taking it further than that. The original five meter fairing model is now designed to expand to over six hundred cubic meters, and the Life 2 for seven meter fairing version is now going to be over four times as roomy. The Life 3 is now planned to require an eight meter fairing, and redouble the volume of the Life 2. This would contain a staggering 5400 cubic meters — the capacity of a medium sized office building — with a nineteen meter inflated diameter, and lots of windows for the dozens of inhabitants. Sounds like it might be too much for a New Glenn to lift, and the only possible launch vehicle for it would be a Starship.

Starlab

A less ambitious plan to use a LIFE-sized inflatable module came from a partnership of Nanoracks with Lockheed, who call it Starlab. Their idea was to make something big enough to support many people — 340 cubic meters — which can be put up with just one launch, which would make it a lot less expensive than any design with many separate pieces. Lockheed would physically build the inflatable part, but Nanoracks would own it.

But wait — Lockheed’s inflatable module is now out. In its place, a new module from Airbus is in. And it won’t be inflatable, it’ll be a traditional metal can, but it will still be nice and big — eight meters around, with the interior divided into three decks. One deck even has a centrifuge to provide a bit of gravity! That’s a first. They call it LOOP, without explaining if that’s an acronym or whatever. It would have to be lifted to orbit by a Starship. Lockheed will still build some of the smaller components. Like Starship, its hull will be made of stainless steel, and by aerospace standards is apparently going to be quite sturdy and heavy, just because they know Starship can lift it. This should make it safer to live in, hopefully.

Since it’s Airbus, the European Space Agency is getting a deal that ensures their ongoing access to this station. And they are starting programs to pay commercial companies in Europe to make crew and cargo capsules to support them in this or any other space station they end up inhabiting.

Bigelow Aerospace also had inflatable module plans, but they are now kaput. I think their plans, like Axiom’s, may have been based on starting with ISS expansions. Nanoracks also talked up such an approach, including both some modules attached to ISS and others floating nearby in a parallel orbit, before they switched to the Starlab plan.

Northrop

NASA is doing its best to make sure that America has a solid amount of space habitat available after the ISS is retired, and has granted some starting funds to support the development of the Starlab and Orbital Reef proposals. They also gave a grant to Northrop Grumman. Their design looks quite basic compared to some others — for starters, just a couple of cylinders with ports, one being somewhat fatter than the other. They say it will have room for four at first and eight later. It sounds like their goal is to provide a replacement for the capabilities of the ISS, and no more than that, to keep the price down. Their renderings make it look none too roomy even if the crew is just four. It doesn’t have a name yet other than Commercial Space Station... and it looks likely that it never will, as Northrop is now dropping this proposal, and instead will just play supporting roles on other stations, such as this one:

Voyager

Other proposals are emerging from companies not yet blessed by NASA. An outfit called Voyager Space has announced grandiose plans to build a huge 2001-style wheel in orbit, with the rotation providing gravity equivalent to that of the moon for up to four hundred people. They gave an absurd date of 2026 for when this could start construction. They also wanted to make a smaller nonrotating station called Pioneer with room for 28. But now they are backing Starlab, as they own the majority of Nanoracks.

Vast Haven

Another odd proposal comes from a company called Vast. They recently bought Launcher, a small rocket company which had not advanced far enough yet to get its own page. They are making a rocket smaller than Electron with a staged-combustion engine. But Vast seems to be more interested in their satellite platform / space tug, which they call Orbiter. Anyway, Vast also wants to make space stations, including ones that spin for gravity. They’re making noises about cylindrical modules tethered to spin around a common center, which makes it sound like it would be difficult to reach a free-fall area to do some work. But before that, they want to start with the most basic and rudimentary space station possible: a single can with a dock at one end and a viewing dome at the other. This would in no way support permanent habitation; it would just be a place that you visit for a few weeks in a Dragon or similar craft, which can extend the duration of the vehicle’s life support. They call it Haven One. The goal of this bare-minimum space station is simple: get it into orbit before anyone else’s. It sounds like they’ve already started building it, so if they follow through Vast could be the next project to get its own page. But apparently this company’s money comes from some kind of cryptocurrency hustle, so don’t be surprised if it ends up going the way of all Ponzi schemes.

Finally, I will mention what might end up eventually becoming the cheapest option: anyone who wants a thousand cubic meters of habitable space in orbit can just buy a Starship. The idea is that they will be affordable because they are mass-produced, so the inefficiency of having big unused fuel tanks and engines attached to your habitat won’t matter economically. Plans are being kicked around for linking them up in pairs or stacks or rings, but I don’t think any company is putting money into these ideas yet.