Check my astrophysics, please!

[Faultline]

I'm writing a science-fiction novel in which, during a couple of chapters, the characters travel for a three-month journey in a starship transport that simulates gravity with centrifugal force.

Check my math, please. I can't seem to find this information in NASA's design study on space colonies. If the ship is designed with the primary living quarters existing within a torus, rotating on a central hub, and that torus is 600 meters in diameter, how often would it need to rotate to simulate Earth gravity?

I assumed (and I may be wrong) that the ring would have to travel at 9.8 meters per second to simulate 1g. Since the circumference would be approximately 1,880 meters, a full rotation would take 3.2 minutes.

That would put it well under the minimum rotational frequency (NASA says 1 rpm is safe) to provide comfort for humans and avoid dizziness from the Coriolis effect in the human ears, right?

Am I right? Also, what would be the line of sight range from within a corridor? At what distance would the curvature of the hallways become apparant?

ph4u171in3
(Faultline)

[Mendel]

I assumed (and I may be wrong) that the ring would have to travel at 9.8 meters per second to simulate 1g. Since the circumference would be approximately 1,880 meters, a full rotation would take 3.2 minutes.

I'm sorry I can't give you the correct numbers since I'm a bit tired but I can give you a hint of how much off you are.

Think about driving with a car along a ring with circumference of 1880 meters. At 9.8 meters per second, that would be close to 36 kilometers per hour. Driving around that ring every 3.2 minutes, do you think you would experience a force of 1g pulling you out of the ring?

[lord bytor]

Ah, SpinCalc to the rescue. For 300 Meter radius I come up with around 1.7 rotations per minute.

[Faultline]

Then I suppose the question should be, "What rotational velocity is needed for a 600 meter ring to produce 1g?"

Faultline

[Matthew]

Then I suppose the question should be, "What rotational velocity is needed for a 600 meter ring to produce 1g?"

Faultline

For an acceleration of 9.8 m/s/s the period of rotation at the outer edge would need to be 49s. This yeilds a rotational velocity of 76.7 m/s.

[Faultline]

Then I suppose the question should be, "What rotational velocity is needed for a 600 meter ring to produce 1g?"

Faultline

For an acceleration of 9.8 m/s/s the period of rotation at the outer edge would need to be 49s. This yeilds a rotational velocity of 76.7 m/s.

Now let me check your math. How do you figure that 1g would be produced if the 600 meter diameter ring rotated every 49 seconds?

That's too fast for comfort. I'd have to build a much larger ring.

Faultline

[Matthew]

Now let me check your math. How do you figure that 1g would be produced if the 600 meter diameter ring rotated every 49 seconds?

That's too fast for comfort. I'd have to build a much larger ring.

Faultline

a=(4 {pi]^2 r)/(T^2)

T=sqr[(4r{pi}^2)/a)
T=sqr[(4x600x9.86)/9.8)]
T=49s

[formulaterp]

The numbers matthewkokai provided assumed a radius of 600 meters. For your proposed station with a diameter of 600 meters, it would have to complete a rotation every 35 seconds (tangential velocity of 54 m/s) to achieve 1g.


In your original post you stated that, per NASA, the minimum rotational frequency (I assume you meant maximum) was 1 rpm and that you needed to simulate 1g. Per those requirements you need a torus about 3 times your proposed size, i.e. radius of 900 meters.

[Faultline]

Thanks for your help so far, that math looks familiar to me even though I slept through most of my algebra in college.

Tell me this. To make a more comfortable rotation rate of 1 rotation per 90 seconds, what size torus do I need to describe in my novel?


Faultline

[TheGalaxyTrio]

Oh, just toss some subwhatsis superstringthingy gravity plates in the floors and be done with it.

I wrote a SF story in college where the characters realize that all their nifty technology was, in fact, impossible, and they come to perceive in the end that they are merely characters in a story, and that their God (that would be me) is too lazy to work out the proper details.

Their God kills them in the end to suppress the information, even though it was by His design that they made the discovery in the first place, for I am an arbitrary and angry God.

I got an "A"

[Faultline]

Oh, just toss some subwhatsis superstringthingy gravity plates in the floors and be done with it.

Cute. I had some superscience planned for this novel. There are starships with impossible artificial gravity generators, but they're all the latest thing. None of the older ships (which the young cadet heroes get stuck with) have them and have to rely on rotation to provide gravity for a three month trip.

They would use anti-decalcification and anti-atrophy drugs and just expect them to deal with zero-g, but those were found to be hazzardous to your health.

And people do travel in hyperspace, but its still slow interstellarly speaking. I've decided that the only way to beat the lightspeed barrier is to enter hyperspace, which is, in fact, a dead alternate dimension that has fallen victim to the "expanding universe" problem. It's full of nothing but dark matter and dark energy. "Full" is a bad word for this place, though.

Faultline

[Matthew]

Thanks for your help so far, that math looks familiar to me even though I slept through most of my algebra in college.

Tell me this. To make a more comfortable rotation rate of 1 rotation per 90 seconds, what size torus do I need to describe in my novel?


Faultline

For a ship with an artificial gravity and has a period of 90 seconds you would need a ship with a radius of 2 km.

[Grey]

You can also take a look at this thread, which discussed some of the questions of how things behave under this type of artificial gravity, including a nice link to this site, which goes over some of the numbers in detail, and points out some of the differences from normal gravity that you'd notice. I pointed out here that these effects are larger than you might think, even in a pretty big station.

[eburacum45]

Another thing to consider is- why 1 gee?
Every object in our solar system which has a solid surface suitable for an astronaut to stand on has a lower surface gravity than the Earth

- set your spinning habitat to produce Mars gravity and it can be much smaller.
Set it for Lunar gravity and it can be smaller still.

[W.F. Tomba]

Ah, SpinCalc to the rescue. For 300 Meter radius I come up with around 1.7 rotations per minute.

Since it wasn't made too clear, I'd like to say that this site is specifically set up to calculate artificial gravity produced by spinning, and all you have to do is plug in the numbers.

[Faultline]

Another thing to consider is- why 1 gee?
Every object in our solar system which has a solid surface suitable for an astronaut to stand on has a lower surface gravity than the Earth

- set your spinning habitat to produce Mars gravity and it can be much smaller.
Set it for Lunar gravity and it can be smaller still.

This question is for a sci-fi novel I am writing.

The passengers are from Earth, are very valuable elite trainees bound for an advanced training program, and they don't want to deal with any bone loss, muscle loss, or rehabilitation after arrival.

Unfortunately, an emergency called away their brand-new cruiser which was intended to transport them. The cruiser had super-science artificial gravity generators.

Faultline

[Sock puppet]

Oh, just toss some subwhatsis superstringthingy gravity plates in the floors and be done with it.

I wrote a SF story in college where the characters realize that all their nifty technology was, in fact, impossible, and they come to perceive in the end that they are merely characters in a story, and that their God (that would be me) is too lazy to work out the proper details.

Their God kills them in the end to suppress the information, even though it was by His design that they made the discovery in the first place, for I am an arbitrary and angry God.

I got an "A"

Is there any chance you'd be willing to post that story (probably not on the BABB, not particularly appropriate)? That sounds brilliant.

[TheGalaxyTrio]

Is there any chance you'd be willing to post that story (probably not on the BABB, not particularly appropriate)? That sounds brilliant.

Thanks, but it's long gone. I don't even admit how long ago that was.

The one I really regret losing was from high school. The assignment was to do a fairy tale or fantasy story in the style of our favorite author. I did a 20 page version of The Wizard Of Oz in the style of Dougls Adams. Other HHGTTG fans in the class said I nailed it dead center, and it was as funny as anything in the Hitchhiker's books. But that's gone, too.