Artificial gravity through a rotating system

Will you miss gravity on your way to Mars?

A long mission to Mars currently requires a long journey on-board of a spaceship. Weightlessness imposes some physiological changes on the human body including: bone loss, cardio-vascular perturbations and, muscles deterioration. It also affects the astronaut’s sense of orientation and consequently can generate a lot of stress.

These clinical changes in the human body could affect the astronaut’s health, affect the crew performance and could potentially jeopardize the mission.

How would the centripetal force help humans in space?

Aside of daily exercise for the crew, it may be possible to generate gravity in space with centripetal force, with a rotating system. The Force felt by the astronaut’s body depends on the rotation rate of the system and the distance of the body from the rotation axis. It is possible to generate various gravity levels and therefore the gravity level on different planets or celestial bodies can be simulated. For example, the astronaut could experience the gravity level of the Moon, Mars or Earth.

Centripetal Force - In the scenario , the body feel more gravity on the legs than on the head.

Centripetal Force – In this scenario , the body feels more gravity on legs than on the head.

The artificial gravity generated by rotation has two major disadvantages. Firstly, depending on the configuration of the rotating system, some parts of the astronaut’s body are exposed differently to the gravity. Secondly, the Coriolis Effect disturbs astronaut’s movement by affecting trajectories. For example, similar to being on a carousel, it is very difficult to walk “straight”.

The rotating system design must be the result of trading between physiological needs, rotation rate, radius, and Coriolis Effect. The cost also has a significant impact on the design. Ideally a large rotating system will reduce most disadvantages of the rotation, imagine a giant rotating wheel in space like in a Sci-Fi movie. Unfortunately, the construction of such a spacecraft requires a large amount of money and consequently a large amount of energy.

Giant rotating space wheel - SPL/MIT

Giant rotating space wheel – Crédits SPL/MIT

Otherwise, the crew could be exposed periodically to simulated gravity in a smaller devise. In the movie, 2001: A space Odyssey (1968) by Stanley Kubrick, the crew are placed in a rotating wheel while they are sleeping.

Rotating wheel for astronauts 2001: A space Odyssey (1968) by Stanley Kubrick

Rotating wheel for astronauts
2001: A space Odyssey (1968) by Stanley Kubrick

The human body is perfectly adapted to life on Earth. A long journey in space will transform humans in a new way. Could it be a part of natural evolution?

Because we are all Born For Space!


11 thoughts on “Artificial gravity through a rotating system

  1. I did a brief analysis of the centrifuge in the Discovery spaceship from 2001: A Space Odyssey movie. It seems somewhat disturbing that what should have been a primary science objective for Nasa – testing the effects of different levels of artificial g on model mammalian organisms has not been done. Therefore while we know the problems of micro-g, we have no idea what level of g we need to engineer for to eliminate most of the physiological problems. Artificial gravity would also remove a host of other unknown design issues for space travel, simply to avoid the costs of a centrifuge.

  2. “Artificial gravity”, as in creating gravity without spin?
    If you had that a lot of things would change. Not just gravity plating on the decks, but imagine totally avoiding the gravity of everything in the rearward facing hemisphere, and amplifying the gravity of everything in the forward half. You don’t need rockets, you don’t need other planets, you’re effectively a god.
    Call by ultra-conservative in mission design, but I’d rather stick to hoytethers. Better yet, Sea Dragon SHLV (Not exactly necessary but nice) and external pulse nuclear propulsion & 21 day transits to Mars.

    I have somewhere a news article from the eve of 2001, and an interview with Clarke. The biggest shame is that we have so anemic a space effort that we had zero experience with rotating artificial G (among everything else), he said.

      • Not an orbit. Hyperbolic fast shoot-by trajectory at better than solar escape velocity.
        =~ (SWAG) 50km/sec for Earth orbit departure, while Mars is approaching/at direct opposition (Earth and Mars physically closest in their orbits).
        Another similar ΔV to brake into orbit around Mars.
        We note there is no free-return or return at all if the engines fail to work at braking…

        I expect that any ship loaded for such a jump at such excessive ΔV is a one-way, needing a new complement of propellant of whatever sort is used to get back.
        Realistically, I suspect this might be a stripped-down passenger-only ship. A nuclear pulse upper stage optimized for cargo delivery will still take the minimum energy orbital trajectory, but some 85% of the mass at departure is payload.

  3. The above-mentioned “major problems” with rotating configurations become progressively ameliorated with larger radii. However, in any configuration involving rotation – especially as the radius of rotation is increased to help ease the differential centripetal acceleration as well as excessive coriolis – another major difficulty arises in the management of spacecraft attitude control, which can be a critical parameter for velocity corrections en route and at target rendezvous, orbital insertion and so on, especially as it emerges due to the torque enforced by the mass involved in the rotation. Its not a trivial problem; engineering-wise, additional complexity is inevitable whether attitude control accommodates a constant rotating state or a spin-down for critical velocity change burns. The engineering reality strongly becomes a certain trade-off in complexity between the benefits of supplying gravitational acceleration to the crew versus the challenge of attitude control for velocity changes.

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  6. Another interesting disadvantage of a rotating system is the complexity of maintaining an orbit where the axis of rotation is not orthogonal to the velocity vector. It’s also very difficult to perform trajectory corrections since the rotating system adds a huge amount of angular momentum, which needs to be either dumped by thruster firing or large reaction wheels, or added to the computation of trajectory computation.

    • difficult to perform trajectory corrections since the rotating system adds a huge amount of angular momentum
      It depends on how the rotation is achieved. If it is done by spinning up a counter rotating flywheel, there is no net angular force. There is a weight penalty however. If the rotating system is two tethered components, then it would be more complex to effect trajectory changes.

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