Sophie Adenot’s mission to the ISS disregards the real challenges facing life in Deep Space
The French media extensively discussed Sophie Adenot on the occasion of her departure for the ISS, as if she were opening the doors of Space to Europe. This was a bit of an exaggeration, considering that, in this mission, Europe provided neither the rocket nor the spacesuit, and that she is only the 300th person (or thereabouts) to go to the ISS. But what irritated me most in all this excitement is that this charming person will be going through an experiment, one of several proposed by CNES and monitored by CADMOS (Center for Assistance in the Development of Activities in Microgravity and Space Operations), called « echo-bones. » The aim is to test a new device for ultrasound exams in order to assess, on account of the weightlessness in which she will be living, the evolution of the structural quality of bone tissue and to quantify the evolution of the blood flow within the bones.
Sophie Adenot arriving in the ISS. Credit: NASA
Humanity has had a space station for over 50 years (Skylab and then the ISS), and for 50 years we’ve known that weightlessness is « bad for your health »—a fact that could logically be deduced without even going into Space. And we’re still studying the effects of this situation: osteoporosis and muscle degeneration since bones and muscles are no longer weight-bearing; cardiac and circulatory problems since the heart continues to pump blood with the same force even though gravity is weaker; increased blood flow to the brain, which has particularly negative effects on the optic nerve’s path to the eyeballs, and so on.
Now that we’ve more than fully grasped that weightlessness has detrimental effects on health, what would be important is to seriously work on designing and building a rotating space station that would avoid weightlessness. But it seems that this doesn’t even cross the minds of our remarkable CNES scientists. Yet, following the initial reflections of Hermann Oberth (1954), these rotating stations have been presented by Stanley Kubrick’s in his magnificent film, 2001: A Space Odyssey (1968), studied by Gerard O’Neill (1976) and by Robert Zubrin’s in 1995 (The Case for Mars), among others. Why this indifference, I would even say why this hostility? Because, no doubt, the scientists at CNES are “serious” people and they’re afraid of being accused of veering into science fiction by discussing such a subject. It’s probably with the same mindset that they also denigrated and mocked the efforts of Elon Musk, an « amateur, » when for several years he was striving to recover his rockets for reuse. The scorn at the time was good fashion and noisy!
Today, therefore, in the field of health, the only thing that should matter is the countermeasures to be taken to address weightlessness within the very structure of space stations (besides, of course, radiation protection, another issue, which is somewhat better addressed), that is to say, considering the construction of one of these rotating stations.
On October 15, 2025, the TASS news agency reported that Energia Space Rocket Corporation (part of Roscosmos) had obtained a patent for a rotating station consisting of a central axis from which four tubes extend at right angles, each carrying at its end a module with a gravity of 0.5g. This gravity is achieved by a rotation of a high 3.35 revolutions per minute because the module is only 40 meters from the axis of rotation. A good idea, but the radius is too short. The consequences of this rapid rotation speed at this distance are an intolerable Coriolis force of 73.5 N and, combined with the short distance to the center, a head-to-toe gravity gradient of 4.5% for a person 180 cm tall, which is too high.
The VAST corp (California), for its part, is considering, in the long term, a 110 m rotating station. They envision it as a « spinning stick, » a straight line of interconnected modules that would be set in rotation. For the same rpm, gravity would naturally vary depending on the distance from the center.
It is to address this problem and to position myself in relation to these projects that I proposed, two weeks ago on this blog, a station that I consider the best compromise in terms of radius (60-meter), number of revolutions per minute (2.73 rpm), and also architecture (torus). Such a station would indeed provide a slightly better gravity (0.5g instead of 4.5) than the Energia station, with a significantly lower Coriolis force (17.5 N) and a lower head-to-toe gravity gradient (3%). Thanks to its torus shape, it would allow for uniform gravity within a large volume, unlike the Vast station, and would not require remaining confined within a very small 0.5g module or constantly passing through the 0g gravity axis to go to another.
Of course, building and, above all, operating a rotating station is not easy. But the necessary technologies exist, and it’s more than time to start getting interested into using them for this purpose.
The rotation axis, made up of different modules, presents no unexplored problems. It’s simply a matter of recreating a new ISS (110 meters at its longest dimension). This is not beyond our reach, especially since in my project, this axis is stationary and the technologies have progressed since the construction and assembly of the ISS modules. In the case of Vast, the complication arises from the fact that the spinning stick would rotate on its own axis. But this rotation has already been tested in numerous probes, for thermal control purposes, with rotation being initiated and potentially corrected using small lateral thrusters. The difference here would be the length of the stick, which obviously assumes that the modules are securely attached to each other, since a greater length implies stronger gravity the further one moves from the rotation axis. Corrections would have to be very gentle.
The station, composed of a torus rotating around a stationary axis, presents entirely different challenges than a simple stick, but meeting these challenges is nowadays feasible.
Construction:
The torus, as well as the radial tubes connecting it to the axis, will be made of modules of a length to be determined (10 to 12 meters each in order to allow transportation on a Starship). They will need to be assembled in space, meaning they will be fitted together and welded after being bolted. This initial phase, carried out with the station non yet rotating, requires that the tubes be formerly precisely marked on the ground to facilitate the on-site assembly. The main complication will arise from the fact that the torus modules must have a very slight longitudinal curvature corresponding to the overall circumference of the torus. Their mass will also be a factor.
The entire torus and the ends of the tubes, along with the thermal insulation, radiation shielding, and life support equipment, will constitute a very large mass (some 4,000 tons out of 5275 t). Since this mass will be rotating, it will have inertia and weight. This will create a pull-away tension from the axis and also inertial effects in the event of station movement or displacement of significant masses (from some 500 kilograms) within the torus. The tension will be relatively low, given the chosen gravity of 0.5g, but it will still justify making the modules as light and strong as possible, therefore using aluminum (aluminum alloys: 7075-T6 – with zinc, or Al-Li 2195 – with lithium, commonly used in space, are proposed).
The connecting modules to the radial tubes, and especially the central sphere where the four radial tubes converge, must be particularly robust (see diagram in the title illustration). Frequent altitude and attitude corrections will affect the overall stability of the structure, and these must be anticipated. This can be achieved first by performing maneuvers slowly and progressively, and second by ensuring that all components are held firmly together, beyond the support provided by the radial tubes. The best solution for this is to install a system of guy wires or stays connecting the radial tubes to each other and to the torus, and also connecting the radial tubes to the axis (or more precisely, sleeves extending a few meters up the axis on either side of the sphere and fixed to it). These sleeves, which rotate with the sphere, will be equipped with bearings for connection to the fixed section. The axis itself will be controlled along its entire length by longitudinal stays to counteract inertia during attitude changes. The connection between the radial tubes and the sphere will be reinforced by bases.
Functioning:
Once the station is assembled, its rotation will be initiated very gradually by four lateral thrusters outside the torus, which will use electricity (solar panels) to eject a gas. The main challenge then becomes determining the quantity of gas required and therefore its onboard storage. In effect, it is essential to maintain the station on its halo orbit, keep the station’s axis pointed towards the Sun, and correct any imbalances that might result from docking or internal activity. As I discussed in my previous articles (Christophe de Reyff’s commentary), the use of xenon posed a problem due to the quantities of gas required, now estimated at 4.6 tons per year, and the price ($4,000/kg). The alternative would be to use argon, which is much cheaper ($5/kg). Note: The entire gas stockpile (two years’ supply, or about ten tons) could be stored in a volume of 8.6 m³ in one of the modules on the central axis.
The inertia effects will inevitably mean limiting the movement of mass inside the torus (the artificial intelligence claude.ai, estimates it at 500 kg for this station). Therefore, gathering all the passengers in a single room held by the torus, is excluded (it was not considered anyway) but all 30 residents (maximum capacity) can be accommodated in the « storm shelter » located on the stationary central axis, when needed. Apart from real storm, this will make an excellent meeting room for brain storming!
That said, the availability of such a station would be extremely important for all the reasons explained in my previous blog posts, and also to prepare for building spacecrafts with rotating tori destined to travel towards distant worlds. Europe would do well to start considering this topic and perhaps, one can dream, begin experiments on controlling rotating tori in space (or limiting the effects of HZE radiation). This would be more useful than continuing to conduct bone densitometry tests, however innovative the equipment used might be.
copyright Pierre Brisson
Title illustration: image of the core of my rotating station, generated by claude.ai
Links:
https://cnes.fr/projets/mission-epsilon/experiences-francaises
