I have a question regarding the structure of the spaceship Vanguard featured in Heinlein's 1941 novel Orphans of the Sky (Wikipedia' synopsys here).

The ship is described as a huge cylinder with many layered decks. The humans live in the lower decks where the gravity level is normal, while the mutants live in the upper decks, where the gravity is weaker and the more weaker as one climbs up. The command center of the Vanguard--long forgotten to the humans-- where the main character Hugh eventually can "see the stars" is in what seems to be the uppermost deck.

It is quite clear that in order to have a gravitational field in a ship travelling inertially in outer space you need to have the ship (or part of it) rotate around an axis, but as you get closer to the axis the gravity gets weaker, e.g. see this famous clip.

So, one would think that going "up" on the Vanguard means moving towards the central axis of the ship and that the geometry of the various decks consists in being concentrical cylinders, all having a common axis. That implies that humans live on the outermost decks (cylinders) while the mutants dwell in the innermost decks (cylinders).

This understanding of the basic geometry of the Vanguard is at odds with some other considerations and events described in the book. For instance:

  • the mutants are described as living nearer to the external hull of the ship. Also the existence of mutants can be explained as an effect of cosmic rays penetrating somehow the hull (shields off due to lack of manteinance?) and this should indeed be felt more near the hull.

  • what would be the purpose of locating the command center in an area of zero or near-zero gravity?

One could think, for instance, of having the innermost decks rotate around the axis at a bigger speed, so to compensate the different gravitational pulls, and to assume that following the mutiny aboard the Vanguard the mechanism regulating the various speeds broke down and got never fixed. This would allow for a command center at normal gravity, but the first objecton above still remains unanswered.

Of course, this being SciFi, we may also assume that the gravity aboard the Vanguard is not due to rotation but to some unexplained technology that produces a virtual gravitational field (something of sort happens, I guess, on Star Trek's Enterprise). Still, I think that it makes sense to assume that this technology would provide for the same gravity everywhere and the difference of gravity at the time of the book events remains mysterious (if the mechanism broke down, the entire ship would be in zero gravity, and not just part of it).

So, I remain clueless. Could anyone help?

Besides, I have a sort of meta-question: generally speaking, how keen was Heinlein about the consistency of his stories with the laws of physics? (I am not an expert of Heinlein)

  • In general Heinlein is pretty good on science. But sometimes.... scifi.stackexchange.com/questions/78925/space-travel-in-waldo Jan 26, 2016 at 20:43
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    Do you have a quote from the book for this: "the mutants are described as living nearer to the external hull of the ship" From my reading of the book, they live in the lower gravity levels nearer the center of rotation. Also, I do not believe there is any textual evidence that the mutation rate was greater in the lower decks. Please prove me wrong by supplying quotes! Jan 26, 2016 at 21:08

3 Answers 3


I have questions about some of your assertions (see the comments) but I can speak to the possible reasons for locating the command center near the center of rotation. The control consoles are located near the center of a large spherical viewscreen (really a spherical planetarium). It would be easier to view all aspects of this viewscreen in a free fall environment. Also, as evidenced by astronauts in the International Space Station, free fall is not a negative environment. Once a short (few day) adaptation period passes, it is reported as being enjoyable. So there is no apparent down-side for locating the bridge in the free fall portion of the ship.

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    You do actually have an interesting point here. With a more technologically savvy eye than that that could have had Heinlein 70 years ago, I was thinking of the control room as a large spherical room where the image of the relevant portion of the Milky Way and the Vanguard itself could be projected as an hologram in the middle. Allowing now navigation officer and captain moving in fee fall around (and maybe in) it, equipped with remote controls looks like a neat idea.
    – AdLibitum
    Jan 26, 2016 at 22:55

Your initial conclusion is right, and I think you are mistaken about some of the contradictions mentioned.

  • The criminal non-crew people living in low gravity are refereed to as "Muties", a slang form of mutineer. While mutants are common among them, and not in the crew, this is explained by the long term program of strict eugenics followed by the crew and not by the Muties.
  • I am unaware of any reference to the Muties living near the hull
  • The Command Center is located in the center of the ship, this makes sense, and is rather important for the plot of the novel. They can only see the stars in one room on this deck, the Captain's Veranda, Which is presumably at the front of this vast cylinder.
  • The decks could not, presumably, rotate at different rates, as that would make travel between them impossible.

The muties do not live near the outer hull; Heinlein clearly states that mutie country occupies the decks with low/zero weight. There is no complex tech providing artifical gravity, nor is weight equalised from hull to centre by differentially rotating decks. This is clear from the description of the gradual increase in weight experienced by Hugh and his friends as they return from their expedition to the upper decks. The only answer which fits is that the Vanguard is a vast cylinder containing concentric layered decks, with weight produced by rotation. The rotation is explicitly mentioned at the climax

when Heinlein describes the guide rails for launching the lifeboat; they are curved to offset the Vanguard's spin.

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    Can you provide a quote where they're described as being in the low/zero weight decks?
    – Edlothiad
    Aug 27, 2017 at 22:18

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