ISS astronauts lose 'alarming' amounts of hipbone strength Humanity's conquest of the stars may never arrive by the jaunty strides of a Flash Gordon or Dan Dare. Alas, Earth's future finest will likely hobble out the pod bay door on feeble old-lady hips. My dream of Mae West in space is ruined! Spending extended time in microgravity has long been known to cause a loss in bone …
Time to put a "gravitron", or centrifuge, on the ISS. Arthur C Clarke pointed this out 60 years ago in his novels such as "Islands in the Sky", and depicted space stations that rotated on their axis to simulate artificial gravity. Similar systems were depicted in Clarke's 2001 and 2010, where the Discovery had a centrifuge in its habitat sphere, and the Leonov had two rotating arms housing the crew quarters - a design that was later copied in the Agamemnon and Agrippa spacecraft in Babylon 5. Even more recently, Steven Baxter's "Titan" highlighted the need for the astronauts on the modified Titan-bound space shuttle to use the shuttle's swing arm as a centrifuge to prevent bone deterioration. So why the hell hasn't NASA/ESA implemented a system like this? Since they've known about bone deterioration and centrifugal gravity systems for 50 years there's really no excuse as to why they haven't built a centrifuge onto the ISS!
6+ hours a day eh? That'll be why in all the fictional examples given, the rotating section is also the main living quarters.
Oh and generating electricity from your centrifuge? FYI, the correct icon here for *that* comment is the one with the red triangle containing the words "Joke Alert".........
Wow a series of science fiction writers described a possible answer to a problem - your right why havent NASA/ESA done anything about it?
On the same note, i can think of a lot of authours who tell us using a wormhole will get us to Alpha Centauri really quick. Damn it NASA/ESA why havent you created a way for me to get to Alpha Centauri yet, just read science fiction novels they tell you everything you need to know! *rolleyes*
Correct me if I'm wrong, but wouldn't the centrifuge idea only work so long as friction kept you on the floor?
If you jumped "up" you'd no longer be attached to anything where an acceleration (mock gravity) would apply to your mass, so you'd just end up flying in microgravity again. Or put it another way... light fittings would hang from the "ceiling" of a rotating torus because they're attached to it, and you could stand on the floor, but if you picked up a ball and let it go it wouldn't fall to the floor because it would only have the air acting on it to contribute towards its motion. And since air flows freely, the air itself wouldn't be still relative to a point on the floor, so I think a rotating torus space station would have a constant wind through it and turbulence around objects. Alright if you don't mind living in a space wind tunnel I guess.
Maybe it's not been done because it's a nonsense idea. :-)
NASA already knows they are the answer to bone loss & would simplify a lot of other facilities as well like cooking, hygiene & air conditioning/circulation.
Problem is all the extra mass that needs to be lifted into orbit to build one strong enough to not fly apart the first time something spaks into it costs orders of magnitude more than providing extended medical care for returning astronauts.
Maybe we'll see one if/when mankind visits Mars, round trip length may make it a necessity.
Well- akin to the old women with osteoporosis- perhaps they could come up with a medical solution to the problem...... Hmmmm- mandatory hip replacement surgery prior to placement on the ISS or further afield? Might make people think twice I suppose?
"... really no excuse why they haven't built a centrifuge into the ISS"
Well, except for the complexity, the space requirements, the expense, the fuel requirements to overcome the effects of friction in the bearings and counter-torque while accelerating it to and from speed, the somewhat more pressing needs of carrying out the station's primary mission, the cost of lifting it and installing it on the ISS, etc ...
Steve, do you how dizzy you'd get looking out the window and seeing Earth spin past you 50 times a second ? That and the space tourists would complain they can't get a decent snap out tjhe windo with their P&S because everything is spinning.
You also can't do all those 'fun' activities like putting a drop of water in the middle of the craft and watching it just drift.
Paris - something about dizzy.......
"there's really no excuse as to why they haven't built a centrifuge onto the ISS!"
Off the top of my head, I believe the practical problem is that the optimal balance between size and rotational speed requires a very large centrifuge spinning quite slowly; if the centrifuge is small, the astronauts would have heavy feet and lightweight heads, equals copious amounts of vomit. I assume the optimal solution would be to spin the entire station and perhaps add a couple of "gravity modules" to the far ends of the ISS, but I imagine that this would make it frighteningly tricky to adjust the station's orbit if required.
Most research carried out at the ISS requires microgravity, so making it spin sort of defeats the purpose.
You could add a spinning section, but this will act as a gyroscope, making manoeuvres more difficult. Even with very low friction between the non-rotating and rotating parts, you would also need power to keep the non-rotating part from slowly gaining rotational speed.
Thirdly, the staff at the ISS use most of their waking time performing experiments in microgravity, and I doubt they would gain much by having gravity in their sleep quarters.
But what you really need is not specifically gravity, but stress and impact on the bones. I'm sure the boffins can think of ways of achieving this without adding gravity.
Keep them in space, let their bodies fully acclimatise.
I suspect that the legs will atrophy, and the arms will become the major means of support and getting around, since legs are unnecessary in 'microgravity' (does micro=0?).
Given a few generations in space I wonder what people will look like?
ttfn
snigger - he said 'Bone'
Er, shurly not?
Centrifugal comes from the latin fugere meaning 'to flee', as opposed to centripetal which comes from petere 'to aim for or strive towards'. If you draw your Newtonian arrows, you'll see that the force is aimed towards the middle, hence centripetal?
It's all an illusion methinks.
Kanhef is correct in that astronauts would have to spend a significant period of time in a centrifuge to gain an effect. But this may not be too much of a difficulty as many routine tasks that the astronauts have to work on would actually be easier to perform under gravity. This would suggest that a workshop facility of some kind could be an effective use of such a centrifuge module.
@anonymous coward: when you let go of the tennis ball, it follows Newton's law - maintaining its straight line velocity in a direction that's tangential to the rotation. As you and your hand describe an arc of the circle , the ball appears to you to be falling - and will eventually hit the floor close to your toe. I haven't done the maths, but I guess the apparent line of fall won't be quite vertical (your hand will describe a slightly larger arc than the ball, so the ball will seem to fall slightly "behind" you (in the sense of rotation). The larger the radius of the space station, the smaller this effect (which I think is associated with the Coriolis effect) will be.
To produce 1g with acceptable low Coriolis effect, the radius of rotation would have to be 224 m (it says here: http://en.wikipedia.org/wiki/Artificial_gravity). And the larger the radius the better for long-term space travellers...
Cheers
As someone pointed out, one can take a look at the B5 design and get some ideas. The B5 station was designed with a non-rotating "spine" running the entire length of the station, from the emergency solarpanels and antenna array, to the cargo loading dock, with the rotating "bottle" beneath it. Such a design is possible to create even in geostationary orbit. It would take some creative thinking, but it can be done. The trick is to create a sufficiently large "army" of remote-operated/autonomous probes to tow back asteroids into orbit around the earth, then use heat from lasers (surface or space-based) to convert the porous asteroid stone into solid pieces of glass-like structure that can be ground into the parts to put together the structure support of the spine and bottle of the station. Onto this, we can the use remote-operated/autonomous launched drones to attach the function modules needed. The real problematic issue here, is to make it completely airtight before we start siphoning atmosphere to move it up there. The other real issue is that to handle such a large body of atmosphere, it would need a hydroponics garden (which would double as a resting place!). Since the spine/bottle design allows for having zero-g laboratories either in the pine, or in modules that are stationary near the center of the rotating bottle, this design doubles up as a laboratory and as a launching station for in-system exploration.
//Svein
"Correct me if I'm wrong, but wouldn't the centrifuge idea only work so long as friction kept you on the floor?"
you're wrong...sort of :)
a bit simplified but:
while in contact with the spinning floor, you have momentum at a tangent to the spin, if you jump, this momentum carries you "sideways" until you meet the floor again. from your point of view, you jump straight up and down (air resistance would probably cause you to land a little to the side of where you jumped from) but to an extranal observer you would jump in an arc.
the only problem comes if you are not in contact with anything when it starts spinning! presuming you don't hit a wall, and can't reach anything, you will never gain the momentum you need to press against the floor and so will just float in place while the station spins around you.
Here is a readable specialist summary from 2004: http://www.radiologytoday.net/archive/rt_080204p10.shtml
It is strange that the new press release does not mention prophylaxis, perhaps a sequel is under way. Pills wouldn't be as heavy to transport as the metal replacements proposed by Shane McKarrick above.
From an external, stationary frame of reference, there is a centripetal force on the person holding them in a circular path. From the person's frame of reference, they are stationary and experience a centrifugal force holding them against the outside wall. Both are real – and are in fact the same thing – but which one you observe depends on your frame of reference.
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