Soyuz flights are mostly around 51.8° inclination, and the Soyuz manual gives this as a reference value. Why is 51.8° the standard inclination? That's not the latitude of Baikonur, and I couldn't find any explanation on Google.


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As Baikonur is at 45.965° north latitude, it would make sense if 45.965° was the standard inclination for Soyuz (and for the ISS). That would be a launch due east, thereby taking the greatest advantage of the Earth's rotation. The reason the standard inclination is 51.8° is that a failed due east launch might rain debris on China. Avoiding passing over China during launch while still taking as much advantage of the Earth's rotation as possible requires launching a bit north of due east and results in an inclination of at least 51.65° (the inclination of the ISS).

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    $\begingroup$ This explains most "weird" trajectories. Why does Israel launch retrograde? Why does the Polar Corridor from the Cape involve a dogleg? And so on. The answer is always to avoid overflying inhabited territory, either enemy (Israel), friendly/neutral (Cape) or your own (Vandenberg). $\endgroup$ Commented Jan 16, 2023 at 10:31
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    $\begingroup$ @JörgWMittag Israel is a particularly interesting case. They launch due west to avoid raining down debris on their own territory or on potential enemy territory, thereby incurring a 30% penalty on mass to orbit compared to launching due east. Many Israeli satellites have been launched by other countries' launch vehicles. However, national pride dictates that Israel must have its own launch capability despite that 30% penalty. $\endgroup$ Commented Jan 16, 2023 at 11:05
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    $\begingroup$ @JörgWMittag The strange orbit of Ofeq 11 - how does it (actually) do this? and Why use a retrograde orbit? $\endgroup$
    – uhoh
    Commented Jan 16, 2023 at 11:30
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    $\begingroup$ @DavidHammen: They also launch military satellites. I'm not sure they could have hired that out until very recently. $\endgroup$
    – Joshua
    Commented Jan 16, 2023 at 16:58
  • $\begingroup$ @DavidHammen National pride AND ensuring that they have the capability when needs must. Israel cannot afford to be wholly beholden to any other country for 'mission critical' functions. You know that :-) $\endgroup$ Commented Jan 18, 2023 at 12:50

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