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# What is the optimal latitude for all three launch pads?

## Question

The ISS is in an orbit that for, among other reasons, helps the relevant launch sites around the globe reach it without becoming very costly (dV wise).

What is the optimal orbit in KSP for a station allowing it to be accessed equally from the KSC, Woomerang and the desert launch pad?

I'm not sure how to work this out, so an explanation might be helpful too  thanks!

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40 minutes ago, bewing said:

Add the latitudes of the 3 launch sites and divide by 3.

Well, by choosing the right time to launch (when your launch site passes below the orbit) you can always launch into an orbit with a larger inclination that your latitude without having to do a plane-change. It is only when you try to launch into an orbit with a lower inclination than the latitude of your launch site (i.e. where you never pass below the orbit) that you have to do a plane change.

So I think the best orbit is one with an inclination of the latitude of the launch site that is furthest from the equator. (And then carefully choosing launch windows and directions.)

P.S. O.K. the above is what they do for the ISS and what I believe is optimal in theory. While playing I would put my station in an equatorial orbit and just pay the costs when launching from Woomerang or the desert launch pad. That way I don't have to worry about launch windows when going to or from the station.

Edited by AHHans

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Inclination = latitude for the most part. And the dV required for a smallish plane change is approximately linear with inclination. Or at least that's going to be your best "first approximation" result. Which means the answer is just an average.

Add the latitudes of the 3 launch sites and divide by 3.

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3 hours ago, AHHans said:

Well, by choosing the right time to launch (when your launch site passes below the orbit) you can always launch into an orbit with a larger inclination that your latitude without having to do a plane-change. It is only when you try to launch into an orbit with a lower inclination than the latitude of your launch site (i.e. where you never pass below the orbit) that you have to do a plane change.

So I think the best orbit is one with an inclination of the latitude of the launch site that is furthest from the equator. (And then carefully choosing launch windows and directions.)

This is correct.  The ISS is in a 53 degree inclined orbit, because that's the latitude of Baikonur Cosmodrome.  NASA can launch into that orbit from Kennedy Space Center, SpaceX will be able to do so when they start launching from Boca Chica, ESA could (if they choose) do so from Kourou (effectively on the equator).  And, of course, Roskosmos can launch to that orbit just by launching east (at the right time).  Everyone except Roskosmos gets two windows a day, one north of east, the other south of east (for logistical reasons, as far as I know, Canaveral launches use only the southward path and Boca Chica will need to do the same for range safety reasons -- can't have even a little chance of a failed launch coming down in Georgia, after all).  Roskosmos gets only one, because they're at the northernmost end of the orbit.

The same is true of launches bound for the Moon, BTW -- it's roughly in the ecliptic, 27-ish degrees from the equator.  Canaveral is just barely south of that latitude, and can launch to the Moon's inclination once a day in a window, as I recall, an hour or so long; launching any other time would require a plane change that's prohibitively expensive.

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An ecuatorial orbit is not good enough?

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An equatorial orbit requires a (costly, in delta-V) plane change, either as a dogleg during launch or after reaching orbit, for any launch site not on the equator.  An orbit at equal or higher inclination to the highest latitude of your launch site choices will allow launching direct from any of the sites.  There is still some dV cost compared to launching due east, but it is less than either an equatorial dogleg or an on-orbit plane change to equatorial from the same latitude.

In other words, if you launch from the equator, and want to make it inconvenient for other programs to reach your station, put it in equatorial orbit.  If you want to make it easy for them, incline it at least as much as their launch site latitude.

Edited by Zeiss Ikon

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Don't forget, the ideal optimal is of course 0, so bearing in mind the highest lattitude launch site, you still want it as close to 0 as possible. I presume that's at least one reason why the ISS isnt polar.

Then again, the closer you are to the pole, the less 0 inclination becomes optimal, or even matters at all, right? Since the launch site isnt travelling east as fast. Hmm... Theres probably some complicated maths involved there.

Edited by surge

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On 1/13/2020 at 6:28 PM, Zeiss Ikon said:

This is correct.  The ISS is in a 53 degree inclined orbit, because that's the latitude of Baikonur Cosmodrome.  NASA can launch into that orbit from Kennedy Space Center, SpaceX will be able to do so when they start launching from Boca Chica, ESA could (if they choose) do so from Kourou (effectively on the equator).  And, of course, Roskosmos can launch to that orbit just by launching east (at the right time).  Everyone except Roskosmos gets two windows a day, one north of east, the other south of east (for logistical reasons, as far as I know, Canaveral launches use only the southward path and Boca Chica will need to do the same for range safety reasons -- can't have even a little chance of a failed launch coming down in Georgia, after all).  Roskosmos gets only one, because they're at the northernmost end of the orbit.

The same is true of launches bound for the Moon, BTW -- it's roughly in the ecliptic, 27-ish degrees from the equator.  Canaveral is just barely south of that latitude, and can launch to the Moon's inclination once a day in a window, as I recall, an hour or so long; launching any other time would require a plane change that's prohibitively expensive.

Minor point of technicality: Baikonur is at 46 degrees inclination. The reason their minimum inclination is 53 degrees is because, in order to not drop rocket stages on China, they have to launch a bit north of east.

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9 hours ago, Starman4308 said:

Minor point of technicality: Baikonur is at 46 degrees inclination. The reason their minimum inclination is 53 degrees is because, in order to not drop rocket stages on China, they have to launch a bit north of east.

After all, only China is allowed to drop rocket stages on China...

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