Can we counteract muscle degeneration for long transits in space yet?

First of all, I did do a search first, and came up with these two topics, which do not ask what I am asking. I am asking if we are able to build a long transit spacecraft able to produce enough artificial gravity to counteract the muscular atrophy astronauts experience. Skeletal muscles atrophy by 30 percent in eleven minutes, to the point that astronauts have been known to tear muscles when re-adapting to Earth’s gravity. Cite.

I was debating this topic recently with someone, (a very poor debater) who brought up the idea that the solution to the problem is easy. :dubious: “Just spin the spacecraft, duh!” they said. :smack: :rolleyes: When I asked them to provide reliable cites showing that we could spin a spacecraft and provide enough gravity to counteract muscular atrophy, stating that space stations***** didn’t count, they called me lazy for not doing the research myself, then rudely said it was “people like me who are the reason it has taken us so long in the first place” and put me on ignore. :rolleyes: (They refused the idea that the onus was on them to provide the proof for the solution they presented to the problem.)

So, please explain in layman’s terms if we do have the technology needed to accomplish such a thing, and how? Or, why we do not yet have the technology to do such a thing, and why? (I am hoping someone “in the field” can weigh in. It is my understanding that we do not have this ability yet, but I’d like to have a more complete understanding of how and why.)

*****I realize we do not have a space station with artificial gravity yet.

Days, not minutes.

Yes, since Skylab. The last bunch of astronauts to Skylab were in better condition when they came down than when they went up.

:eek::smack: Yep, DAYS! :o My question, and point still stands.

That’s not a long transit craft, (which has microgravity) that’s an orbiting craft. And that was due to better workout equipment, not artificial gravity?

(Copied from your link): Yet despite rigorous workouts, astronauts return to Earth shockingly weaker than when they left. **Only 11 days **in microgravity may atrophy (shrink) muscle fibers as much as 30 percent and cause soreness as damaged muscles tear while readjusting to Earth’s gravity

(my bold)

I thought your figure sounded totally impossible (eleven minutes for 30 percent muscle atrophy). It’s eleven days.

Yes, and if you had read the rest of the topic you would have seen someone else already pointed it out to me, and I admitted the mistake. Do you have anything to add, other than that?

It doesn’t seem hard to imagine current technology being able to spin an entire spacecraft as it travels. Presumably the resistance in space would be small enough that the spinning would require very little energy to maintain. It’s also not hard to imagine this producing enough “gravity” to help prevent atrophy.

I have no cite for this, and it might be I’m wrong, but it seems simple enough.
P.S. I think you meant 11 days, not minutes.

P.P.S. I disagree that the onus is on a person to provide proof for their idea to the extent that you completely disregard it, at least if you want anyone to discuss anything with you ever.

Unfortunately, the Centrifuge Accommodations Module for the ISS was canceled. It’s not big enough to be used as an exercise room like David Bowman in 2001. I imagine it could be scaled up using something like a Bigelow habitat to be used on an interplanetary expedition like the Discovery One.

Of course it isn’t hard to imagine that it is possible, do you think that I didn’t? :confused: But, it seems to me that NASA and the like are focusing on better workout equipment, not creating artificial gravity. Why? Also, I did not disregard it in the debate I spoke of. I provided cites. The person in question leaned towards the Tea Party’s way of thinking though.

I would at least like to be pointed towards reliable sources of information on this subject, that explain it in laymans terms. For the moment, I have this Wikiepdia article, and its cites which I am working through.

Edit: I ask that further replies please give facts/cites, not speculation. Thank you! :slight_smile:

I meant, of course, that the orbiting craft has microgravity! A craft going to another planet would not have that, and would need artificial gravity. Cite.

Microgravity is a misconception to begin with. Astronauts in the Shuttle, Space Station, or anywhere else in orbit are in zero gravity. It’s exactly as easy and as necessary to spin a ship to produce gravity in Earth orbit or on a trip to Mars.

As for how to do it, the simplest way would be to have the crew compartment on one end of a cable, with a counterweight (which could be made up of fuel or equipment they won’t need en route or whatever) on the other end, and spin around the point on the cable that’s the center of gravity. This would be approximately as difficult as making a cable that could suspend the crew compartment from a crane on Earth. Or easier, if you decided that you could make do with less than a full g: It’s not yet known how much gravity you need for health.

Er, no?

Bolding mine. Cite for the bolded part..

Aye, I am reading and processing what information I found now. Does anyone have any more recent data?

Because it’s way, way cheaper. While our engineering abilities are well up to the task of designing and constructing a spinning spaceship to provide centrifugal* pseudo-gravity, lifting the extra weight into space is just plain not worth it. The same amount of energy used to lift more spaceship, more food, water, and air, or more tools and instruments is a much better investment.
*Or centripetal. I don’t remember which, precisely, and I don’t want to argue it. You know what I mean.

Centrifugal is correct in this context. Good on you for not wanting to argue it, though: There are plenty of folks who do want to argue it, but are wrong.

With regard to the difficulting in spinning a structure for simulated gravity, there are several issues that would need to be resolved, including transporting or erecting a structure with a sufficiently large spin radius, providing sufficient impulse for spin, balancing the structure during spin operations and during spin, and navigating and orienting communication antenna during spin.

The minimum required spin radius is quite large compared to the size of payloads that can be delivered to orbit using conventional launch technology; around 20 m. This is based on both the physiological response (vestibular effects) and the psychomotor response (disorientation from objects behaving differently under gyroscopic motion and centrifugal radial pseudo-acceleration than under gravitational acceleration) that have to be considered. The physiological effects are easier to assess objectively, while psychomotor effects may vary dramatically between people. The effects depend on rotation rate, with <1 RPM giving no significant physiological effects, and >2 RPM considered a general threshold for continuous rotation (though some sources differ). There is relatively little experimental information on these effects in a practical space-like environment, though fairly extensive human testing has been done in a terrestrial environment. According to one source, the minimum rate off rotation and radius for normal human function is 6 RPM with a 14 meter radius, giving 0.58 g acceleration (Thompson A.B., 1965, Physiological design criteria for artificial gravity environments in manned space systems, First Symposium on the Role of the Vestibular Organs in the Exploration of Space, 20-22 January 1965, US Navy School of Aviation Medicine, Pensacola, FL, NASA SP-77, pg 233-241). Assuming a 2 RPM rate, you would need a 220 meter radius of rotation to achieve ~1 g acceleration, which would obviously be very large in comparison to existing spacecraft, though reasonable on the scale of a large permanent space habitat. This scales linearly, so you would get ~0.5 g at a 110 meter radius. If we could tolerate a rotation rate of 5 RPM, we could get 1 g at a radius of about 36 meters, or 0.5 g at 18 meters, which are somewhat more reasonable, though larger than any unitary spacecraft that might be launched from Earth’s surface.

Spinning up such a system would require a substantial impulse (K = 1/2Iw^2) which will be substantial for a large payload, and therefore require additional propellant, both to impart rotation at the beginning of the trip and remove it at the end. One could avoid expending propellant and make it possible to recover energy at the end of the trip by using a counterbalance flywheel, but as this would have to have the same magnitude of angular momentum (with an opposite spin vector) it would be either very large, very heavy, or both. It would also be necessary to provide fine balance control during spin to avoid precession and nutation effects, further complicating the system.

Spinning the craft using a counterbalance mass or having dual craft attached by a tether would be the most simple system. However, this means that there would be no inertial (stationary) portion of the craft at which to mount observation or communication systems. Maintaining communication links and using stellar navigation in a constantly rotating system is very complex. A more complicated system that would have a non-rotating hub and spinning hab modules would be preferable, but substantially more complex.

From an experience standpoint, our most applicable experience was the spin experiment on Gemini XI, where the Gemini spacecraft was tethered to the Agena upper stage and slowly spun to achieve a ~0.02% of Earth gravity. So we have no practical experience with constructing or operating large scale spun spacecraft or habitats. We do frequently spin smaller spacecraft and satellites for stabilization or to ensure even solar heating, but even this is often complicated despite the fact that these structures are essentially rigid (except for liquid propellants) and can be spin-balanced prior to launch. A large habitat-type structure that cannot be spin balanced and may have moving masses within it is several orders of magnitude more complicated and well outside of current experienece in space operations.


You could spin up your craft with an arbitrarily low impulse. Spool out long cables with engines on the ends of them, fire the engines, and then reel the cables back in. It’s pretty much the classic figure-skater problem.

True, but then you have to have very long tethers for the spin motors, and the longer your moment arms are, the less like a rigid structure they behave, and the more non-linearities you have to cope with, especially if the structure isn’t spinning to begin with. Using a “yo-yo despin” mechanism with expendable masses is common to remove rotation on spin-stabilized systems (such as unguided sounding rockets) but you can obviously only do this once.

The point is that which spinning and despinning a spacecraft is certaining mechanically plausible and requires nothing outside of fundamental Newtonian mechanics at the college sophomore level, the actual details of implementing it on a large or inhabited apcecraft are well beyong current engineering experience and are quite complicated.


Would there be an issue with the conservation of angular momentum as well? For example, I’ve hear that on a rotating body, a coin will not spin (I’m still not 100% sure of why) so would there be an issue with flywheels, hard drives or anything else that spins?

Now I’m imagining being stuck on a spaceship for 20 years which Chronos and Stranger keep trying and failing to get to spin at the correct speed, with hundreds of nauseous spacefarers being subjected to contantly varying amounts of gravity and shifts in the rate of spin…