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I saw it happen in the videogame Alien:Isolation but not sure how realistic it was. I need help understanding some orbital mechanics for a sci-fi story that I am trying to write.

The scenario I imagine that there is a space-station, orbiting a celestial object.

A crew, with a 2 and a half meters high robot that is able to "leap", and two "astronauts" who would ride this robot would attempt to approach with their spaceship, and jump from the spaceship's airlock to the emergency airlock door of the space station.

Is this possible? Would the spaceship need to go next to the station and go on the same trajectory with the same speed, or would it need to move slightly faster than the space station at the time of the jump?

As a reference here is the scene from the videogame:

This however does not let one see (or I do not see) how the spaceship was behaving relative to the station.

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    $\begingroup$ This is not a good question for this site. Consider asking it on worldbuilding. Space stations orbiting black holes are purely fictional. $\endgroup$
    – Organic Marble
    Jan 23, 2022 at 22:32
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    $\begingroup$ Well but the point of my question has nothing to do with the black hole, but with the jump itself. There is an object orbiting a celestial body. We can switch up the black hole with Earth, if that would help. Is the jump possible then? By aligning speed with the oribiting object, or by being faster than it? $\endgroup$
    – Richard Kutsera
    Jan 23, 2022 at 22:50
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    $\begingroup$ You have an interesting question here and I strongly recommend that you do not accept the first, short, dismissive answer about the black hole. Give it a few days at least to give others a chance to give it some thought, add some comments and hopefully some much more helpful answers. Welcome to Stack Exchange! $\endgroup$
    – uhoh
    Jan 23, 2022 at 22:58
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    $\begingroup$ Yeah, well I am writing a sci-fi that is in the far future where there are technologies like warpdrive and energy-shields, if that helps. Maybe I was just too specific with my question. What I need to know is how a jump from a spaceship to a station in orbit could (if could) happen? Would it require the spaceship to align it's speed with the station, or would the spaceship need to do an approaching maneouver, moving slightly faster than the station? $\endgroup$
    – Richard Kutsera
    Jan 23, 2022 at 23:01
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    $\begingroup$ I now also included a video of the scene from the videogame. $\endgroup$
    – Richard Kutsera
    Jan 23, 2022 at 23:13

2 Answers 2

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It is not mandatory that the two vessels have zero relative velocity, but it would make the operation more controlled (and therefore less exciting). Having vessels in close proximity with significant relative velocity risks collision so would only be likely in uncontrolled or emergency conditions. If your scenario involves relative velocity, the jump transfer is still possible.

There is no theoretical limit to the distance that could be “jumped”, but a long jump would affect the precision (and the chance of successful) arrival.

One big challenge would be rotation during transit, with an uncontrolled attitude on arrival. It would be very difficult to jump without imparting at least a small angular momentum. If you arrive butt-first after a 180* pitch/yaw, you will find yourself disoriented and unable to grab on.

Another issue is that you will all arrive with the same kinetic energy and momentum as when you departed. Just like 3 billiard balls, all heading into a corner cushion. Unless each character is face-forward and latches onto a hand-hold first attempt, someone is going to bounce off into the blackness. Plan to write one character out of the story.

One happy thought is that you can ignore complicated orbital mechanics as it applies to orbital rendezvous: that "back up to catch up" stuff. Because the jump will last only a vey small orbital phase angle, it will not apply.

So, to answer your question, YES. "It is possible. But not recommended" as they said in Red October.

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    $\begingroup$ OP says that 2 are riding on 1, so perhaps all three billiard balls have a string to each other.. so that should save the one bouncing off into to the inky blackness. $\endgroup$
    – blobbymcblobby
    Jan 24, 2022 at 0:18
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    $\begingroup$ @blobbymcblobby ---- A wise strategy to string everyone together. That gives a better chance that at least one will grab on. But I think the line should break and one spin off like Frank Poole. It should be the character that everyone expected to be The Savior. Stephen King always kills The Savior 2/3 of the way through. $\endgroup$
    – Woody
    Jan 24, 2022 at 0:24
  • $\begingroup$ I like it. Can't always have a happy ending! $\endgroup$
    – blobbymcblobby
    Jan 24, 2022 at 0:30
  • $\begingroup$ I can't find the quote here but still "hunting" for it $\endgroup$
    – uhoh
    Jan 24, 2022 at 0:36
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    $\begingroup$ @Oh-oh ---- Sean Connery asks if he can have 110% on reactor power. The Watch Officer says ,"110% possible, but not recommended". $\endgroup$
    – Woody
    Jan 24, 2022 at 0:42
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To me the term jump is defined as a phsyical movement that implies a somewhat impulsive force acting against gravity to move an object and then subsequently the object returns to a datum plane under the return influence of gravity. A lateral velocity component could be included so the return point is at some distance from the starting point. In the strictist sense of this definition "jumping" as defined above from one spacecraft in zero gravity to another cannot be done.

But a body could be propelled using one's own force to an adjacent body in zero gravity. It is advisable to have a restraint cord attached to the other body. It is also advisible to aim precisely. Also, I would not consider this maneuver over a very long distance.

Fun question, tom kosvic

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    $\begingroup$ This is an odd definition of jump. Jumping covers almost any motive push with the legs, and does not require gravity, or that you come back down. By this logic, leaping upward and grabbing a bar overhead isn't a jump, nor is leaping into space from a low-gravity planetoid, nor is pushing off the wall of a rotating space station with your legs. I'd say pretty much any movement with the legs that moves you in the direction of your head is a jump. $\endgroup$
    – Nuclear Hoagie
    Jan 24, 2022 at 21:49
  • $\begingroup$ Per miriam webster definition of jump, 1a: to spring into the air : LEAP especially : to spring free from the ground or other base by the muscular action of feet and legs. That would also imply that gravity returns you to ground, i.e., "what goes up must come down" in common parlance. Enough fun on definition of jump $\endgroup$
    – tckosvic
    Jan 29, 2022 at 16:30

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