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Really beautiful. Why 0.5G and not 1G though? Aside from the narration that decision doesn't seem to have any impact on the video. I would expect that differen

Really beautiful. Why 0.5G and not 1G though? Aside from the narration that decision doesn't seem to have any impact on the video. I would expect that difference to have a noticeable effect on things like the posture of the plants, the design of the pool, the flight of the butterflies, the posture and gait of the man. Ever accidentally bump a drinking glass, but not enough to knock it over? A wine glass sitting statically on a table will look pretty much the same at 0.5G, but half the downward force means you're probably much more likely to accidentally knock it over. So would we really use the same sort of glasses on a space station like this? Aside from one line about "walk, don't run, don't jump", all of this would be arguably more realistic/accurate if they just called it 1.0G, so I find that decision to be curious.

SideburnsOfDoom 3y ago
> Why 0.5G and not 1G though Then the ring would either have to be larger or faster. Both are harder to build.
- avmich 3y ago
  Then the question is, why not smaller. Actually, why 0.5G is chosen as optimal.
  - m4rtink 3y ago
    Kind middle between Moon (1/6) and Mars (1/3)?
    - avmich 3y ago
      I agree, and disappointed, that we don't really know how different gravity levels affect human body. We could make experiments of that kind on a space station - free-flying if needed - but chose not to up to now. We'll have to wait for something like a private station to test that. Maybe Moon is quite enough. Maybe Mars is not enough. We don't really know, and we'd better find out.
- jrussino 3y ago
  > Both are harder to build. Certainly harder for NASA to build in space, but not any harder for this author to build in a computer :-D Good point though: > Regarding the dimensions, I wanted to make the structure as large as possible, while still getting a clear visual sense of the curvature in the interiors. That is how I ended up with the 450-meter radius and 1 RPM spin rate. So it seems like he wanted to put specific constraints on the size/geometry and worked backwards from there.
  - jrussino 3y ago
    However, you could get ~1G by going to ~1.4 RMP or increasing the radius to ~900m (or finding some sweet spot in between), which doesn't seem like it would greatly impact the "vibe" he's trying to create.
  - SideburnsOfDoom 3y ago
    Right, a part of the film's design was "It should curve enough to look cool". At first I found myself questioning the speed of the rotation, it seemed faster than claimed - 1rpm is not a lot? Then I did the math: A quarter turn is a right angle, floor becomes wall. A quarter minute is every 15 seconds. That's about what's happening in the video. And it's quite disconcerting to watch continuously. I would not want to see faster rotation. So the video is chosen for speed of motion and size of ring, and how they look. 1 G would either be faster motion or less curve, and it seems that the author didn't want those, for valid aesthetic reasons.
- dredmorbius 3y ago
  NB: A centrifugal artificial-gravity environment need not be a ring. It could be a tethered object spinning around a centre of mass, consisting either of two opposed habitable pods or a single pod and a counterweight. A sufficiently large pod would have an arc-of-circle structure, and multiple independent pods might be arranged in a spoke-like pattern. Given tensile strengths of various cables, this should be generally attainable. Dynamic effects within a tensile-cable structure could however be problematic: shimmies, twists, or other movements, particularly if they are somehow amplified with time.
- m4rtink 3y ago
  Stronger/heavier materials needed for higher G, right ? All that added inertia could also make maneuvers & burns harder.
noman-land 3y ago
If the outer ring creates 1G then wouldn't the inner ring have to be lower? Since at the center, gravity will be zero.
- dtgriscom 3y ago
  Acceleration of a point on a disc is as velocity squared, divided by radius. Since velocity of a point on a (rigid) disc is proportional to the radius, this simplifies to acceleration being proportional to the radius. Reduce the radius by half, and the acceleration reduces by half. And, at the center, acceleration is zero. (All this, of course, is assuming the angular rotation rate is constant.)
hiccuphippo 3y ago
It seems to be a vacation ship. Who would go to one in space only to feel the same gravity as down here?
littlestymaar 3y ago
They wanted it to be 450m wide so that the curvature would be clearly visible on camera, and then Two Revolutions per Minute is arguably a worse title than with One ;).
- muxator 3y ago
  Actually it would have been sqrt(2) revolutions per minute :)
  - littlestymaar 3y ago
    Indeed, the force is linear respective to the radius, but quadratic respective to the rotation speed. Thanks for the correction.
dredmorbius 3y ago
Regarding the dimensions, I wanted to make the structure as large as possible, while still getting a clear visual sense of the curvature in the interiors. That is how I ended up with the 450-meter radius and 1 RPM spin rate. From TFA, which consists (apart from the video) of 8 short paragraphs in its entirety.
tomjakubowski 3y ago
Spinning this structure for 1G would only make the problems called out by the author worse. Much worse: > I believe that the perpetually spinning views would be extremely nauseating for most humans, even for short visits. Even worse, I suspect - when it comes to the comfort of the experience - would be the constantly moving light and shadows from the sun.
gnicholas 3y ago
> half the downward force means you're probably much more likely to accidentally knock it over. Yes, but it would also be significantly easier to catch before it hits the floor, right?
lucubratory 3y ago
It was an artistic choice, in order to be able to have large open windows that aren't too disorienting, in a habitat small enough that you can see clear curvature in every room, and still call the project "One Revolution Per Minute". If he had called it "One Point Four Revolutions Per Minute", it could have been 1g and still had the right curvature that he wanted, but then the lights moving past the windows would be a fair bit harder to handle. In general, the major point of artistic license in the project is the windows, which the author acknowledges. A realistic (and still extremely exciting and inspiring) rotating space habitat this size would rotate at 1.4rpm to achieve 1g, and would not have transparent glass windows for safety and nausea reasons (replace them with screens that show a non-rotating view of the outside for a similar effect without the safety and nausea cost). It's also worth noting that the habitat could be made bigger, to have 1rpm cause 1g. It would require a habitat with a radius of 890m, so a total circumference of 5.6km, still well within the tensile strength of steel for suspension under 1g (I personally wouldn't trust a rotating space habitat to be made out of composites or similar materials until we have a much, much better understanding of composite failure modes and a reliable way of testing/repairing such structures - steel is best because we know how to use it, what its limits are, and because it has fatigue resistance without being absurdly expensive like titanium). A habitat like that would not have the rooms visibly curve as much as they do in this video, though.
- rbanffy 3y ago
  > replace them with screens that show a non-rotating view of the outside for a similar effect without the safety and nausea cost What’s the point of travelling without windows?
  - m4rtink 3y ago
    Thats kinda the default when traveling underwater or in space - most of the time there is nothing interesting visible, yet the outside medium can easily kill you and windows help with that. You can have some observation sections, but regular windows everywhere don't make sense in this case.
    - 3y ago

SideburnsOfDoom 3y ago

> Why 0.5G and not 1G though Then the ring would either have to be larger or faster. Both are harder to build.

avmich 3y ago
Then the question is, why not smaller. Actually, why 0.5G is chosen as optimal.
- m4rtink 3y ago
  Kind middle between Moon (1/6) and Mars (1/3)?
  - avmich 3y ago
    I agree, and disappointed, that we don't really know how different gravity levels affect human body. We could make experiments of that kind on a space station - free-flying if needed - but chose not to up to now. We'll have to wait for something like a private station to test that. Maybe Moon is quite enough. Maybe Mars is not enough. We don't really know, and we'd better find out.
jrussino 3y ago
> Both are harder to build. Certainly harder for NASA to build in space, but not any harder for this author to build in a computer :-D Good point though: > Regarding the dimensions, I wanted to make the structure as large as possible, while still getting a clear visual sense of the curvature in the interiors. That is how I ended up with the 450-meter radius and 1 RPM spin rate. So it seems like he wanted to put specific constraints on the size/geometry and worked backwards from there.
- jrussino 3y ago
  However, you could get ~1G by going to ~1.4 RMP or increasing the radius to ~900m (or finding some sweet spot in between), which doesn't seem like it would greatly impact the "vibe" he's trying to create.
- SideburnsOfDoom 3y ago
  Right, a part of the film's design was "It should curve enough to look cool". At first I found myself questioning the speed of the rotation, it seemed faster than claimed - 1rpm is not a lot? Then I did the math: A quarter turn is a right angle, floor becomes wall. A quarter minute is every 15 seconds. That's about what's happening in the video. And it's quite disconcerting to watch continuously. I would not want to see faster rotation. So the video is chosen for speed of motion and size of ring, and how they look. 1 G would either be faster motion or less curve, and it seems that the author didn't want those, for valid aesthetic reasons.
dredmorbius 3y ago
NB: A centrifugal artificial-gravity environment need not be a ring. It could be a tethered object spinning around a centre of mass, consisting either of two opposed habitable pods or a single pod and a counterweight. A sufficiently large pod would have an arc-of-circle structure, and multiple independent pods might be arranged in a spoke-like pattern. Given tensile strengths of various cables, this should be generally attainable. Dynamic effects within a tensile-cable structure could however be problematic: shimmies, twists, or other movements, particularly if they are somehow amplified with time.
m4rtink 3y ago
Stronger/heavier materials needed for higher G, right ? All that added inertia could also make maneuvers & burns harder.

noman-land 3y ago

If the outer ring creates 1G then wouldn't the inner ring have to be lower? Since at the center, gravity will be zero.

dtgriscom 3y ago
Acceleration of a point on a disc is as velocity squared, divided by radius. Since velocity of a point on a (rigid) disc is proportional to the radius, this simplifies to acceleration being proportional to the radius. Reduce the radius by half, and the acceleration reduces by half. And, at the center, acceleration is zero. (All this, of course, is assuming the angular rotation rate is constant.)

hiccuphippo 3y ago

It seems to be a vacation ship. Who would go to one in space only to feel the same gravity as down here?

littlestymaar 3y ago

They wanted it to be 450m wide so that the curvature would be clearly visible on camera, and then Two Revolutions per Minute is arguably a worse title than with One ;).

muxator 3y ago
Actually it would have been sqrt(2) revolutions per minute :)
- littlestymaar 3y ago
  Indeed, the force is linear respective to the radius, but quadratic respective to the rotation speed. Thanks for the correction.

dredmorbius 3y ago

Regarding the dimensions, I wanted to make the structure as large as possible, while still getting a clear visual sense of the curvature in the interiors. That is how I ended up with the 450-meter radius and 1 RPM spin rate. From TFA, which consists (apart from the video) of 8 short paragraphs in its entirety.

tomjakubowski 3y ago

Spinning this structure for 1G would only make the problems called out by the author worse. Much worse: > I believe that the perpetually spinning views would be extremely nauseating for most humans, even for short visits. Even worse, I suspect - when it comes to the comfort of the experience - would be the constantly moving light and shadows from the sun.

gnicholas 3y ago

> half the downward force means you're probably much more likely to accidentally knock it over. Yes, but it would also be significantly easier to catch before it hits the floor, right?

lucubratory 3y ago

It was an artistic choice, in order to be able to have large open windows that aren't too disorienting, in a habitat small enough that you can see clear curvature in every room, and still call the project "One Revolution Per Minute". If he had called it "One Point Four Revolutions Per Minute", it could have been 1g and still had the right curvature that he wanted, but then the lights moving past the windows would be a fair bit harder to handle. In general, the major point of artistic license in the project is the windows, which the author acknowledges. A realistic (and still extremely exciting and inspiring) rotating space habitat this size would rotate at 1.4rpm to achieve 1g, and would not have transparent glass windows for safety and nausea reasons (replace them with screens that show a non-rotating view of the outside for a similar effect without the safety and nausea cost). It's also worth noting that the habitat could be made bigger, to have 1rpm cause 1g. It would require a habitat with a radius of 890m, so a total circumference of 5.6km, still well within the tensile strength of steel for suspension under 1g (I personally wouldn't trust a rotating space habitat to be made out of composites or similar materials until we have a much, much better understanding of composite failure modes and a reliable way of testing/repairing such structures - steel is best because we know how to use it, what its limits are, and because it has fatigue resistance without being absurdly expensive like titanium). A habitat like that would not have the rooms visibly curve as much as they do in this video, though.

rbanffy 3y ago
> replace them with screens that show a non-rotating view of the outside for a similar effect without the safety and nausea cost What’s the point of travelling without windows?
- m4rtink 3y ago
  Thats kinda the default when traveling underwater or in space - most of the time there is nothing interesting visible, yet the outside medium can easily kill you and windows help with that. You can have some observation sections, but regular windows everywhere don't make sense in this case.
  - 3y ago