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Cannot agree more. If I remembered correctly, there was such an obvious bug in 'Gravity' that in the orbit, if you want to catch up with another object in front

by mrjin 5y ago

Cannot agree more. If I remembered correctly, there was such an obvious bug in 'Gravity' that in the orbit, if you want to catch up with another object in front of you, you cannot simply accelerate, or you will result in getting further from it. In stead you will have to decelerate first and then accelerate again. The result is counter intuitive, I remember that simply because I did not believe it at first and as a result we did such calculation on the blackboard while I was in high school.

silicon2401 5y ago
Is that because you need to decelerate relative to the planet's core to get on an orbit with a smaller radius, so that you can then increase your revolutions per minute at your existing momentum, then accelerate to get back to the orbit the other object's on? I'm trying to visualize the scenario you're describing
- mdorazio 5y ago
  I highly recommend you play Kerbal Space Program if you want to get an intuitive understanding for how it works. But in short, yes, and also if you accelerate towards another orbiting object your own orbit becomes more elliptical such that over sufficient distance you will actually move away from it rather than toward it.
  - silicon2401 5y ago
    Ah I think that's the piece I was missing, makes sense once you said elliptical. Thanks
teraflop 5y ago
Well, it depends. Over short distances and timescales, relative motion behaves pretty much as you would expect for objects in free-fall. It's only over significant fractions of an orbital period that counterintuitive things start happening, with orbital speed and height influencing each other. (You can think of this as a tidal or Coriolis-esque pseudoforce that appears to increase in magnitude as objects get farther from each other.) In general, there are many possible paths you can take to achieve an orbital rendezvous, varying widely in how long they take and how much fuel they consume.

by mrjin 5y ago

silicon2401 5y ago

Is that because you need to decelerate relative to the planet's core to get on an orbit with a smaller radius, so that you can then increase your revolutions per minute at your existing momentum, then accelerate to get back to the orbit the other object's on? I'm trying to visualize the scenario you're describing

mdorazio 5y ago
I highly recommend you play Kerbal Space Program if you want to get an intuitive understanding for how it works. But in short, yes, and also if you accelerate towards another orbiting object your own orbit becomes more elliptical such that over sufficient distance you will actually move away from it rather than toward it.
- silicon2401 5y ago
  Ah I think that's the piece I was missing, makes sense once you said elliptical. Thanks

teraflop 5y ago

Well, it depends. Over short distances and timescales, relative motion behaves pretty much as you would expect for objects in free-fall. It's only over significant fractions of an orbital period that counterintuitive things start happening, with orbital speed and height influencing each other. (You can think of this as a tidal or Coriolis-esque pseudoforce that appears to increase in magnitude as objects get farther from each other.) In general, there are many possible paths you can take to achieve an orbital rendezvous, varying widely in how long they take and how much fuel they consume.