Expanding, And Eventually Replacing, The International Space Station

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Expanding, And Eventually Replacing, The International Space Station

 

 

Aboard the International Space Station (ISS), humanity has managed to maintain an uninterrupted foothold in low Earth orbit for just shy of 20 years. There are people reading these words who have had the ISS orbiting overhead for their entire lives, the first generation born into a truly spacefaring civilization.

But as the saying goes, what goes up must eventually come down. The ISS is at too low of an altitude to remain in orbit indefinitely, and core modules of the structure are already operating years beyond their original design lifetimes. As difficult a decision as it might be for the countries involved, in the not too distant future the $150 billion orbiting outpost will have to be abandoned.

Naturally there’s some debate as to how far off that day is. NASA officially plans to support the Station until at least 2024, and an extension to 2028 or 2030 is considered very likely. Political tensions have made it difficult to get a similar commitment out of the Russian space agency, Roscosmos, but its expected they’ll continue crewing and maintaining their segment as long as NASA does the same. Afterwards, it’s possible Roscosmos will attempt to salvage some of their modules from the ISS so they can be used on a future station.

 

This close to retirement, any new ISS modules would need to be designed and launched on an exceptionally short timescale. With NASA’s efforts and budget currently focused on the Moon and beyond, the agency has recently turned to private industry for proposals on how they can get the most out of the time that’s left. Unfortunately several of the companies that were in the running to develop commercial Station modules have since backed out, but there’s at least one partner that still seems intent on following through: Axiom.

With management made up of former astronauts and space professionals, including NASA’s former ISS Manager Michael Suffredini and Administrator Charles Bolden, the company boasts a better than average understanding of what it takes to succeed in low Earth orbit. About a month ago, this operational experience helped secure Axiom’s selection by NASA to develop a new habitable module for the US side of the Station by 2024.

While the agreement technically only covers a single module, Axiom hasn’t been shy about their plans going forward. Once that first module is installed and operational, they plan on getting NASA approval to launch several new modules branching off of it. Ultimately, they hope that their “wing” of the International Space Station can be detached and become its own independent commercial station by the end of the decade.

 

The First Piece of the Puzzle

The module Axiom will build as part of the recently announced agreement with NASA will be called “Axiom Node One”, or AxN1. It will be a slightly larger version of the design used for the existing Harmony and Tranquility nodes. These cylindrical nodes not only provide living and working environments, but act as vital junctions for expanding the Station. Each one features six Common Berthing Mechanism (CBM) ports that can either be used temporarily for resupply spacecraft such as the SpaceX Dragon or as a permanent mount point for another module. They cannot however be used for crewed spacecraft such as Russia’s Soyuz or the Boeing CST-100 Starliner, as those vehicles use active docking ports that are faster to disconnect in the event of an emergency.

The AxN1 node is also planned to include a so-called “Earth Observatory” module, envisioned as a larger version of the Station’s existing Cupola. Rather than being a simple window, the Observatory will be deep enough to allow crew members to enter and move around in. During flight the Observatory will be attached to the forward CBM port of the AxN1, and after it’s been attached, the Station’s robotic arm will move it to the node’s nadir (Earth-facing) CBM port.

But before it can be installed, things will need to get rearranged slightly. The plan is to berth AxN1 to the front of the Harmony mode, but that’s currently where the second Pressurized Mating Adapter (PMA-2) is installed. This recent video released by Axiom shows how they propose to attach their modules to the ISS, but it starts with PMA-2 already removed and out of sight (the PMA seen on top of Harmony in the video is actually PMA-3).

 

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