Reasons to not implement gravity on ISS ?

[Externet]

That 2001 movie and its turning module to make gravity seemed within reason...

Why has not been pursued ?  No need for it ?  Cost ?

[QuantumT]

The ISS is mainly a place for space research. If they added artificial gravity, they could not do it. It would be pointless.

Artificial gravity would only be beneficial for long term space travel.

[swansont]

Cost and complexity, I would imagine. Also, the ISS probably isn’t large enough to do so in a reasonable fashion.

[Sensei]

22 minutes ago, Externet said:

Reasons to not implement gravity on ISS ?

Because cranks would say they are filming in the studio.. ?

 

Seriously, ISS is too small spaceship.. look what they had in "Elysium".

https://www.imdb.com/title/tt1535108/

The bigger radius of circle, the smaller gradient difference between head and foots.

 

Edited March 15, 2019 by Sensei

[Janus]

Here's a graphic showing how big the ISS is when compared to some other things, including the space station from 2001.

If you look at the ISS, most of its size is due to the solar panels, and only a small part of it is the station proper.  Spinning it while maintaining the proper orientation of the panels would present a problem.

Also keep in mind that the difference in size isn't the only issue.  If you spin the station in order to give it gravity, you also would have to make it strong enough to withstand the stresses, making it bulkier and more massive. 

[Externet]

Thanks.

I meant an 'end?'  module at ISS, not the whole thing...

Perhaps only a 10m diametre attached  'wheel', where personal hygiene, exercising,  and other convenient activities could be conducted better in gravity.  Yes, the whole thing spinning would be counterproductive when so much experiments there are aimed to evaluate the microgravity effects.

The whole thing turning would imply solar panels also turning/tumbling for keeping proper alignment, getting too unreliably complex.

Would gyroscopic effects be a problem ?

[Janus]

1 hour ago, Externet said:

Thanks.

I meant an 'end?'  module at ISS, not the whole thing...

Perhaps only a 10m diametre attached  'wheel', where personal hygiene, exercising,  and other convenient activities could be conducted better in gravity.  Yes, the whole thing spinning would be counterproductive when so much experiments there are aimed to evaluate the microgravity effects.

The whole thing turning would imply solar panels also turning/tumbling for keeping proper alignment, getting too unreliably complex.

Would gyroscopic effects be a problem ?

With a 10 m diameter, your module would have to spin at ~1.4 radians/sec to get 1g at the floor.  However, at head level, it will have dropped to ~2/3g, so you would have a 1/3 g difference between head and feet while standing.   There is also the Coriolis effect to account for.  If you are seated, the center of mass of your body is moving at a certain speed relative to the axis. When you are standing, in order to keep the same rotational rate, it has a smaller  speed.   If you go from a seated to standing position, your center of mass is going to want to keep moving at the same speed.  The result is that you will feel a "force" that is trying to tip you over.  Also, if you drop something, it will fall in a curve.   This, and a changing g value,  Would likely play havoc with your eye-hand coordination, especially if you are going back and forth between the spinning and zero g parts of the station.

 

 

 

[swansont]

Plus it needs to rotate slowly enough so that you can safely access the passageway to get to/from it.

[theHassan]

On 3/16/2019 at 2:47 PM, Externet said:

Thanks.

I meant an 'end?'  module at ISS, not the whole thing...

Perhaps only a 10m diametre attached  'wheel', where personal hygiene, exercising,  and other convenient activities could be conducted better in gravity.  Yes, the whole thing spinning would be counterproductive when so much experiments there are aimed to evaluate the microgravity effects.

The whole thing turning would imply solar panels also turning/tumbling for keeping proper alignment, getting too unreliably complex.

Would gyroscopic effects be a problem ?

Gyro would be one problem, vibration another one. All the vibrations propagating through the whole structure would mess up all the microgravity works on the station.

Power and bearing lifespan comes to mind also.

[Art Man]

Artificial gravity isnt practical because of the amount of space and materials needed to create the artificial gravity, making it expensive and pointlessly inefficient. The ISS isn't big enough and besides it must be steady in order to recieve cargo and complete its missions. If they could and they decided to go ahead and spin the ISS they would need to spin quite fast in order to experience gravity and if it worked the question would be, where would they stand? Have you seen the inside of the ISS? Theres miles of footage. A space station with artificial gravity would need two sections at least, one rotating section and one steady section, thus, the engineering of such a station would be a feat unto itself as nothing like it has been done before.

[Airbrush]

I found these plans for AG (artificial gravity) on the ISS.  Centrifuges can be quite small, what they call "on-board centrifuge," and used just for sleeping.  These could be contained within a large ISS module.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150009516.pdf

 

Edited September 2, 2019 by Airbrush

[theHassan]

Still, the main problems remain.

ISS is a microgravity research station (among other things), and the vibrations of the centrifuge would upset it.

Also, do not forget acclimation. Now, an astronaut goes up, gets through "space adaptation syndrome", which is the accepted expression to describe vomiting all around the place, and lives happily ever after. Then they comes down, gets through gravity readaptation, and that is it. With one part of the station having artificial gravity and the rest weightless, one would need to readapt several times a day. And just once forget where you are and drop something. 

It is better this way, I think. Being an astronaut carries a significant occupational health risk. Take it or leave it. 

[Externet]

Nice link,  Airbrush. Thanks.

Interestingly, no mention of vibration or gyroscopic effects; but intermittent operation is considered.

[swansont]

Any internal centrifuge would need a twin rotating in the opposite direction, else the entire craft would begin rotating.

 

Also, 24 RPM in a small chamber, as it is drawn? It seems like that would be disorienting. You'd have a significant variation of acceleration from head to feet — the head looks like it's on the rotation axis..

[Enthalpy]

They want zero gravity.

[mistermack]

Nothing on the ISS is designed to operate at 1g, so they would have to start again, to design a station that could spin safely. 

There's nothing impossible about spinning space stations, I'm sure that they are the way to go in the future, but they are going to cost a lot more if you have to lift all of the materials off the Earth.

One limiting factor, as already mentioned, is the feeling of sickness caused by the Coriolis effect. The minimum diameter for a spinning station producing 1g that doesn't cause sickness in the average person is about 200 metres, so there never was the slightest temptation to spin the ISS. You can compromise, by going for less than 1g, and so spinning a smaller station. But obviously you lose something by compromising. 

It's possible to spin two modules, connected by a 200m tether, rather than a cylindrical station but you might get stability problems with that. With a cylindrical station, you could have the docking point in the centre, so that you would just have to give your approaching craft a very slow spin to make docking no problem. And, you could have the solar array connected to the centre via a cable, so you would just need a mechanism with a bearing to transfer the power to the spinning station. 

In the distant future, it's likely that people will be mining the Moon for raw materials, at a much lower cost than lifting off  from the Earth, and then you could make space stations much bigger and more substantial, so a 200m diameter space station wouldn't be prohibitively expensive.

[zapatos]

16 minutes ago, mistermack said:

Nothing on the ISS is designed to operate at 1g, so they would have to start again, to design a station that could spin safely. 

 

The computers, electronics, etc. won't work if they are subjected to a 1g force?

[Sensei]

22 minutes ago, mistermack said:

Nothing on the ISS is designed to operate at 1g,

During launch of rocket with ISS equipment there used to be much larger g than 1g...

 

[mistermack]

2 minutes ago, Sensei said:

During launch of rocket with ISS equipment there used to be much larger g than 1g...

 

Good point. Maybe equipment is specially packed to survive launching, but even so it would need to be more robust than I was imagining.

[Enthalpy]

The launch and  orbit configurations differ. The deployed solar arrays, the ridiculous trusses that hold them, have no single chance to withstand 1g. All is rolled and folded to a compact sturdy shape during launch.

[mistermack]

Once you leave the Earth's magnetic shield, you would need to provide some all-round shielding for a spinning craft, against the worst solar storms. If it's not spinning, then you could presumably concentrate the protection on one side and turn that towards the Sun till the worst is over.

According to wiki :  "A solar flare on January 20, 2005 released the highest concentration of protons ever directly measured,^[14] giving astronauts as little as 15 minutes to reach shelter." and " Anyone who had been on the Moon's surface during a particularly violent solar eruption in 2005 would have received a lethal dose."  ^[24]

[zapatos]

Why can't you have the shielded side of a spinning ISS face the sun all the time?

[swansont]

35 minutes ago, zapatos said:

Why can't you have the shielded side of a spinning ISS face the sun all the time?

Doesn’t that question answer itself? i.e. it’s spinning? 

[zapatos]

2 minutes ago, swansont said:

Doesn’t that question answer itself? i.e. it’s spinning? 

Imagine a fan spinning in space and blowing toward the sun. The sun facing side of the blades would need shielding while the other side would not.

[swansont]

3 hours ago, zapatos said:

Imagine a fan spinning in space and blowing toward the sun. The sun facing side of the blades would need shielding while the other side would not.

The ISS is not shaped like that