Stepping stone to… what exactly?
We couldn’t even handle a closed source experiment on earth (see biosphere 2), why would one on another celestial body fare any better?
We couldn’t even handle a closed source experiment on earth (see biosphere 2), why would one on another celestial body fare any better?
These kinds of things can be put into cycler orbits around the Moon or Mars[0] which would allow relatively comfortable and cost effective journeys to these locations. As the scale of these kinds of craft expand they could eventually become destinations themselves akin to massive cruise ships in the sky where some people live out their entire lives.
Biosphere 2 was obviously a flawed experiment but it seems that Mir, the ISS, and Tiangong have shown that long term habitation in micro-G is possible, it seems like the extension of that is to try long term habitation of a body with gravity and material to experiment with.
Because (1) the project would be designed seriously and (2) you don't need a completely closed loop. Just one that's mostly closed.
Ok so maybe a multibillionaire. Perhaps Elon musk? Yikes. Or Bezos? Maybe.
The EU is kinda busy increasing their defense spend, preparing to engage in Ukraine so I don’t see them super excited to do this.
China or India perhaps?
Also, why shouldn’t it be completely closed loop? If you’re designing to address the myriad of scenarios that can unfold in space, I’d say you’d want that experience under your belt. Its already easy mode doing this exercise on earth you might as well give yourself a little challenge to capture lessons learned.
NASA.
> why shouldn’t it be completely closed loop?
Because it doesn’t need to be. Engineering an ecological carbon cycle is hard. Putting in long-lived CO2 scrubbers is not.
And then, once you've got it working well here on Earth, then you have a go at doing it on the moon.
This idea that the best place to get started on working out how to do these sorts of things is on the moon makes about as much sense as suggesting that the Space Shuttle program should have had astronauts rushing to work out the kinks of EVA missions in space instead of doing everything they could to test and practice procedures in swimming pools in an effort to learn as much as possible before you blow half a billion dollars on trying it out in orbit.
Agree. A moon base lets us test this out with real-world constraints as opposed to simulants.
We don’t know how to build ecological closed loops. But every failure mode of Biosphere 2’s was almost trivially solvable with expendable components. (The CO2 cascade being the simplest among them.)
> idea that the best place to get started on working out how to do these sorts of things is on the moon
It’s not. It’s the best next step. We’re doing a lot of pre-colonisation lab work already. And we will need to do more before establishing a moon base. The moon base is the interim goal—you don’t put astronauts in swimming pools without a plan for a Shuttle. And Biosphere 2 is a terrible swimming pool for anything we’d do on the Moon or Mars.
So let's say we spend a little more money ($150 million would be approx $335 million today, so maybe $0.5 - 1 billion). That's a lot of money but still a LOT less than establishing a moon base. And by doing it on Earth we can solve for more closed-loop system problems here without also coping at the exact same time with an environment actively trying to kill the participants and a multi-month lead time for any resupplies/"oops"es.
Then we can take those lessons learned and apply them to the much harsher environment of the moon. In other words, it's a lot cheaper and faster to learn some lessons here on Earth first before having to tackle all that plus things like keeping yourself alive.
[0] https://www.npr.org/2025/07/07/nx-s1-5442529/biosphere-2-ear...