ISS and Hubble have vastly different orbits - different altitudes, different inclinations, requiring a massive delta-V to transfer from one to the other. My question is: has anything ever had to perform such a maneuver (not necessarily between ISS and Hubble specifically)? Or has such a requirement never come up, or just never been feasible?

I'm just asking about precedent for a large inclination change while in orbit.


I am not sure if you want count this one, but the currently ongoing "last mission of Cassini" involves the spacecraft changing its inclination gradually from 35 to 64 degrees when it goes through the gap between Saturn and the innermost part of the rings.

NASA image Cassini

The manoeuvre is not done propulsively as large inclination changes are expensive, and the probe is almost out of fuel. (Just for the record, changing the inclination of a circular orbit by 23.9 degrees is as expensive as reaching escape velocity.) Instead, multiple fly-bys of the moon Titan is used to alter the orbit.

A similar approach was used for the Ulysses spacecraft that used a fly-by of Jupiter to enter a solar orbit with an inclination of 80.2 degrees to perform observations of the polar regions of the Sun.

I can not recall that any purely propulsional large change of inclination has been performed, but there exists a Russian plan to keep the ISS alive a little longer by moving their segment to a higher inclination.

  • $\begingroup$ What do you mean by "Just for the record, changing the inclination of a circular orbit by 41.7 degrees is as expensive as reaching escape velocity." - a plane change of 41.7 degrees should take a burn of about 70% of the current orbital velocity but is not related to escape velocity. $\endgroup$ – asdfex Jul 2 '16 at 10:08
  • $\begingroup$ @asdfex ouch, that angle was in radians. As for escape velocity, it is just for cost comparison. $\endgroup$ – Hohmannfan Jul 2 '16 at 11:17
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    $\begingroup$ Even more severe is the plane change undertaken by the Ulysses spacecraft. It used Jupiter to go into a polar orbit about the Sun. $\endgroup$ – David Hammen Jul 2 '16 at 12:15
  • $\begingroup$ @DavidHammen I forgot about that one. I am going to write it into the answer. $\endgroup$ – Hohmannfan Jul 2 '16 at 12:29
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    $\begingroup$ I was looking for any cases where it would have been done propulsively, like in low Earth orbit where there's nothing to fly by - basically, any cases where the circumstances justified the high cost in propellant. $\endgroup$ – Anthony X Jul 2 '16 at 14:05

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