Flight Question Catching up with ISS

AstroBeatle

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Hey everyone, I'm relatively new to orbiter and I'm trying to rendezvous with the ISS on the classic DG. I've already aligned planes and am beginning the rendezvous stage, which begins with catching up with the ISS. I heard that the best method is to warp speed and let a few orbits pass until the ISS catches up with us on the Orbit MFD, however, I could never catch up with the ISS regardless of the number of orbits. It's definitely something to do with being nearly the same orbital velocity as the ISS, how do I fix this?

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PhantomCruiser

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Tex has a video here https://www.orbiter-forum.com/showthread.php?t=2055
It was made for the older versions of Orbiter, but the mechanics are the same. The section you need begins around the 9:15 mark.
You need to sync orbits, which will have your craft and the ISS meet at the same space and time after a few orbits.
 

Ripley

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...however, I could never catch up with the ISS regardless of the number of orbits...
In this case, the fastest way to catch up with your target is to have a more elliptical orbit:
Higher = target will catch you
Lower = you'll catch target

If both your and your target orbits are (nearly) perfectly circular, you'll both have same speeds and youl'll never catch up.
The secret is to change your speed just a tiny bit, by changing your altitude on the opposite side of your planned rendez-vous point.

...It's definitely something to do with being nearly the same orbital velocity as the ISS...
Exactly that.
 
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AstroBeatle

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Yup, I got it figured out, I wonder why I didn't see it earlier, it's fairly obvious.
Higher altitude = lower K.E. and lower velocity. I increased my apoapsis and then matched my periapsis to the ISS's altitude at the same point. Successfully rendezvoused, and completed my very first docking!
35c17eb9332e5208b20b4b7f695485af.jpg


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