(urth) Cumaean???

[brunians at brunians.org]

Green and Blue are seperate planets? For some reason I thought they were
planet and satellite.

These are the Wolfe books I have reread the fewest times for some reason.



.

>
> On Sun, 16 Dec 2007 11:35:16 +1100 thalassocrat at nym.hush.com wrote:
>>On Sun, 16 Dec 2007 07:55:28 +1100 "Roy C. Lackey"
>><rclackey at stic.net> wrote:
>>>
>>>If the inhumi had to depend on spacecraft to travel between Blue
>>>and Green,
>>>there would be no need to wait for conjunction. Sure, as a matter
>
>>
>>>of physics
>>>it's b.s., but so is astral travel.
>>
>>Maybe the lander only has the delta-vee for the trip when Blue &
>>Green are at or near conjunction? That's when Horn's trip to Green
>
>>
>>on it happens.
>
> I am cluless when it comes to orbital mechanics, but if Wikipedia
> can be trusted I think that lander voyages between Blue and Green
> will only be feasible at around the time of conjunction.
>
> Note that landers don't have some kind of super constant-thrust
> propulsion system - whatever it is, it works like familiar rockets
> in that thrust is applied for limited periods, shutting down in
> between.
>
> It's surely reasonable to assume that some kind of fuel is being
> used and also that a lander has a finite fuel capacity. Even if
> they are much more efficient than current spacecraft, they'll be
> bound by the same considerations.
>
> Presumably this means you need to plan the trip with the same kind
> of Hohmann transfer orbit used for trips in the solar system. And
> that means you need to take into account the same kind of launch
> window restrictions as you do in eg a trip from Earth to Mars.
>
> Launch windows are apparently tied to the synodic period, the time
> for the destination planet to return to the same position in the
> sky as observed from the launch planet. So for Green/Blue trips,
> around the time of conjunction.
>
> Using one of the formulas here
> http://en.wikipedia.org/wiki/Synodic_period you get a synodic
> period of about 6 Blue years for Green as seen from Blue, if you
> assume that the Green year is about 85% of the Blue year.
>
> Obviously, all this subject to correction from anybody who actually
> knows what they're talking about :)
>
> _______________________________________________
> Urth Mailing List
> To post, write urth at urth.net
> Subscription/information: http://www.urth.net
>