I love space and space travel. We should go to Mars, ASAP. One of the common concerns is how to minimize bone loss due to zero gravity- a common solution proposed is to generate artificial gravity by rotating the spacecraft with a counterweight, therefore generating centrifugal force.
But how about the Star Trek VI solution, magnetic boots? Would this work? Has this been tried?
Magnetic boots anchor you to a suitable metallic surface, but you are still in microgravity.
Si
Right, but isn’t the major concern loss of bone in the hips and legs? And if your legs and hips have to work with every step (just like on earth) to counteract the magnetic force of the boots, wouldn’t that go at least some way to helping minimize that bone loss?
It would have to be a magnetic harness that pulled you down from the head onto the surface you were walking on.
Bone loss occurs because the skeleton is not under the usual loads that it experiences due to the weight of the tissues and organs (and itself) that act on it when you’re in normal gravity. Also the loads that you put through it with your muscles.
In the absence of these loads, the body assumes that there’s really no need for all the heavy duty support in the bones, and so it reclaims the materials for use elsewhere. Similarly for muscle - with no need to lift heavy things any more, the muscles weaken due to wastage (the body adjusting to the new environment) unless they are continually exercised.
Magnetic boots would hold you to a surface, but your skeleton would still be weightless with nowhere near the appropriate earth-G loads going through it.
This sort of restructuring happens all the time, even on earth - if you have an artificial hip, the bone around the implant is gradually weakened and reclaimed by the body since the forces running through it are much reduced (the metal shaft takes the load), which eventually causes the bone to weaken so much the implant no longer fits (aseptic loosening), which is why so much research has gone into finding a material with as close-as-possible match to the strength and material properties of the bone it is surrounded by.
In zero G, the entire skeleton is subject to those reshaping processes, since the body no longer needs a strong skeleton to support itself in that environment.
Ok, the harness then. Let’s say it’s like the coveralls (or “poopy suit”) I wore underway while I was in the Navy (so the astronaut wakes up every day and puts it on as his normal work wear). And spread throughout the garment are electromagnets of some sort, and the floor of the spacecraft is ferrous/magnetized/whatever. Would this work? Would the power consumption be totally unworkable? Has anyone tried this?
This is another in the long series of “let’s take an imaginary technology and pair it with another imaginary technology and see what happens.”
Nobody can give a good answer to the effects of imaginary technology.
how about a helmet with elastic cords (with 1 G of resistance) connected to your magnetic boots?
50-80 kg of force passing through your neck probably isn’t a terribly safe way to impart compression force to your long bones.
Gravity acts uniformly on every atom of your body. Simply squashing down from the outside of your soft tissues with an equivalent force, no matter how well-distributed you make it, can’t be very good for the health of said soft tissues and certainly isn’t equivalent to gravity.
ETA…
Spinning a craft, by the way, ain’t too tricky, and once it’s spinning, it’ll keep spinning. Seems like a pretty solid solution.
Actually, it’s a little more complicated than this. The metabolic and biomechanical effects of living in a long term microgravity (weightless) environment are not well understood at the fundamental level, despite being studied for over thirty years. Although some bone demineralization does occur due to a lack of constant use of skeletal muscle to resist gravity during normal walking and sitting (yes, you use your muscles even when sitting, especially if you maintain good posture), there are noted deficiencies in dietary intestinal calcium absorption in weightlessness which exacerbates the problem. Skeletal calcium loss in an otherwise healthy astronaut is around 1% per month, which is way higher (by about an order of magnitude) than compared with an bedridden person of similar health in a terrestrial environment. In addition, the activity of osteoblasts (cells that are constantly building bone tissue) decreases in microgravity for reasons not well understood, while osteoclasts (cells that chew up “old” bone surfaces and return the minerals to the metabolism for reuse) remain active, resulting in bone dedensification (i.e. bones become more porous and brittle, similar to chronic osteoporosis ). As the human body is not evolved to operate in a microgravity environment it is somewhat conceptually erroneous to say that the body is “choosing” to redistribute calcium; rather, the skeletomuscular system is malfunctioning due to an environment that is unnatural for the human body.
It should also be noted that while the most obvious role of the skeletal system is to provide a structural framework to which to tie muscles, organs, and other miscellaneous tissues, it also provides a reservoir for calcium and phosphorous, which are critical to metabolic functioning, and a factory/storage system for red and yellow marrow, which provides support for the immune and cardiovascular system. Microgravity also has deleterious effects on the cardiovascular system directly, including impaired function (lack of full pumping capacity) and atrophy of the heart muscle, exacerbation of pre-existing arrhythmia, dehydration, and dilution of blood plasma. The unprotected radiation environment also offers some potential long term hazards not experienced in a normal terrestrial environment including degradation of endothelial cells, which can affect circulatory functioning.
Magnetic boots not only will do nothing to alleviate the above issues, but are also probably impractical for practical purposes. While the magnetic force will hold down an astronaut at the contact points, without gravity to keep the body aligned normal to the “ground”, once one foot is removed from contact the body will tend to flail due to the lack of a usable moment arm by which to control orientation. In comparison, put on a weight belt and try “hopping” across the bottom of a pool on one foot while staying upright; it’s damn near impossible without flailing your arms to maintain orientation, which would be ineffectual in air. In order to control orientation the astronaut would need to use handholds or magnetic walking poles, and would be far more exerting than floating and using handholds, monkey-style.
Fortunately, generating simulated gravity is a fairly straightforward (if not exactly simple) method of using outward inertial forces created by rotating the spacecraft, or a habitable portion of it, just requiring that the radius of rotation is sufficiently large that the Coriolis component of rotation is negligible. Of all the problems involved in long term space habitation and deep space manned missions, this is one of the few that is readily soluble with a modest extrapolation of existing technology.
Stranger
It’s a pity the Stooges are all long dead. This would be genius for slapstick comedy.
Stranger
One of the key signals your body uses to identify how much load your bones are seeing is the impact of your foot against the surface as you walk or run. This is a critical reason why a treadmill on ISS is crucial, and provides a component for astronaut health not covered by alternate exercise (bicycle, “weight” lifting, etc).
There has been at least one astronaut with zero bone density loss for his stay on ISS. Ed Lu. This was stated at the post-flight mission review in Space Center Houston. There may be a cite around somewhere.
It is a complex challenge for the space docs.
It wouldn’t work. Lie on the floor or stand on a chair and you’re still subject to pretty much the same gravitational force - gravity decreases inversely proportional to the square of the distance - at human scales, there is effectively no force gradient.
Not so with magnetic attraction to a steel floor - magnetism falls off with the cube of the distance - so a system of magnets mimicking gravity would have to be very actively controlled - each magnet being increased or decreased in strength according to its position relative to the floor (otherwise, a permanent magnet attached to your head and strong enough to mimic gravity when you’re standing up will smash you violently to the floor if you bend to tie your shoelace).
Not to mention that every ferrous or paramagnetic object would end up sticking to your suit, making you look like an extra to an 'Eightes post-apocalyptic B-movie.
Stranger
Good grief.
This isn’t “imaginary” technology. Nor need it be extremely complicated. You wear a jumpsuit with an appropriate distribution of iron. You place your BFM some decent distance below the floor, rather than right below the floor. Such a system would approximate “gravity” and give you a nice constant load on your skeletal structure and perhaps that would be enough to reduce/eliminate bone loss.
As has been noted by Stranger, there are OTHER issues with zero g that this system would NOT correct for and you still might have bone loss due to those.
Now, even if this did prevent bone loss, thats not to say the magnet might be impractically large and or cause significant problems with other space craft systems or operation.
And, oh yeah…just spin the fracking space ship and be done with it!