Babylon 5 had a diameter of 840 meters. If the gravity was 1g, it would have to spin approximately 1.5 times per minute. How fast did it spin or what was the actual "gravity" on board? Are there any technical data available that describe the environment inside the station?

1 Answer 1


There's no technical data that I'm aware of but the show once quoted a rotation of about "60 miles an hour" which was a mistake and would only produce about 0.5g

PBS Space Time did an analysis on this question:

However, I think the PBS Space Time's calculations were a little off and they state that the station had a radius of 500m in radius.

Based on your diameter of 840 meters, a velocity of 60 miles per hour would only generate a centripetal acceleration equivalent to 0.17g and, to get to 1g would need to produce 1.46 rotations per minute and achieve a tangential velocity of 143.64 miles per hour in order to approximate 1g.

Click here to play with your own calculations.

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    If anyone wants to know the equation, if the tangential velocity is v and the radius is r, then the centripetal acceleration is v^2/r...if you want to use units of meters and seconds (where 1 mile per hour is 0.447 meters/second, so for example 60 miles per hour is 60 * 0.447 = 26.82 meter/second), then 1g acceleration would be 9.8 meters/second^2. And your figure of 143.64 miles per hour would be 64.21 meters/second, if you plug that in as v with r=420 meters (half the diameter), acceleration is indeed (64.21^2)/420 = 9.8 meters/second^2.
    – Hypnosifl
    Dec 7, 2015 at 15:58
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    After some googling for the source of the 60 mph statement, I found this synopsis which seems to say Sheridan fell out of transport tube in the interior of the station, and this was seen by people in the "Garden" below. Ivanova said "He's more or less weightless. But the ground is rotating at sixty miles an hour. If we can't catch him, he'll be killed by the impact." Is it possible that the ground beneath him was at a considerably smaller radius than the exterior radius of the station at the point along its axis with the widest cross-section?
    – Hypnosifl
    Dec 7, 2015 at 20:23
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    I found this scan from this section of the official Babylon 5 security manual which shows the "Zen Garden" as being just under the outer radius of that section of the station, and the ambassadorial suites shown as being almost as far out, so it doesn't seem possible the station's radius is around 400 meters while the ground of the Garden is only 73 m as I speculated above.
    – Hypnosifl
    Dec 8, 2015 at 0:27
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    And another diagram roughly confirms the diameter that sm4 mentioned--this page from the same manual says the station is 5 miles long and "the diameter of the largest rotating section" is 0.094 times that, i.e. 0.47 miles = 756 meters (if the length is rounded off, so it could be just under 5.5 miles, then it the diameter could be up to 832 meters; and if 0.094 is rounded off, so it could be up to 0.0945, then it could be up to 836 meters).
    – Hypnosifl
    Dec 8, 2015 at 0:30
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    840m is an interesting choice of diameter. It's very close to the optimal radius that NASA determined when they were looking at potential designs for space habitats (based on their determination that a rotational speed of greater than 1 rotation per minute would be too uncomfortable in the long term). I wonder if somebody got a bit confused between diameter and radius when researching this...?
    – Jules
    Mar 14, 2016 at 21:01

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