Anthony Frost writes:

In message
(Henry Spencer) wrote:

In article , Markus Redeker wrote:
That said, ISS isn't in a good orbit to use as a stepping stone,

Which orbit would you prefer?

The best orbit for an orbital assembly base is equatorial,

The big win is launch windows once per orbit instead of once or twice a
day, and there are some lesser issues like lower radiation dose too.

If it's a US project and you're not prepared to build a new launch base
(or operate from floating platforms like Sea Launch), then a 28.5deg orbit
like that originally planned for the space station is best.

Would there be any advantage in using a 23.5 degree orbit, arranged to
be on the ecliptic, if your assembly is for interplanetary trips?

The problem with any such inclined orbital plane is, it won't stay there.
The perturbation exerted by the Earth's equatorial bulge will cause the
plane of any orbit except 0 degrees and 90 degrees to precess. Hence,
your "23.5 degree orbit" will only occasionally be well aligned with the
ecliptic, and can be as far off alignment with the ecliptic as 47 degrees!


I can't work out if being able to not have your assembled craft do a
plane change is actually an advantage, let alone worth the payload and
timing hit for delivering stuff to the assembly station.

Plane changes are only a big deal if you are going from one orbit deep
in a gravity well to another orbit deep in the _SAME_ gravity well.
For translunar or "escape" transfers, the "plane change" can be handled
during one of the mid-course corrections, after one is no longer deep in
Earth's gravity well.


-- Gordon D. Pusch

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