Author Topic: Spaceport maximum and minimum inclination?  (Read 3139 times)

Offline xpell

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Spaceport maximum and minimum inclination?
« on: 02/29/2012 02:10 PM »
Hi, I'm new here and have a question.  ;D (Please relocate if it isn't in the appropiate subforum)

I've recently learnt that spaceports have a maximum and minimum launch inclination, and that minimum inclination corresponds to the spaceport geographical latitude. But I'm not really grasping the concept, and after I've searched a lot in the Internet and wherever, I haven't found any explanation. So I'm asking it here.

a) Why do spaceports have a maximum or minimum inclination?
b) I assume that certain launchs' target orbit is way lower than the minimum inclination (for example, equatorial launches from Baikonur). How do they do this? Extra thrust or what?
c) If so, could you launch a spacecraft from Baikonur, another one from Plesetsk (let's say both at 62º), rendezvous them in orbit, then move them to a low-inclination interplanetary injection orbit?

And how is this calculated? :-P

Thank you in advance! (I know I'm asking a lot of questions here, but I'd love to know how this works!)

Offline JayP

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Re: Spaceport maximum and minimum inclination?
« Reply #1 on: 02/29/2012 03:03 PM »
Hi, I'm new here and have a question.  ;D (Please relocate if it isn't in the appropiate subforum)

I've recently learnt that spaceports have a maximum and minimum launch inclination, and that minimum inclination corresponds to the spaceport geographical latitude. But I'm not really grasping the concept, and after I've searched a lot in the Internet and wherever, I haven't found any explanation. So I'm asking it here.

a) Why do spaceports have a maximum or minimum inclination?
b) I assume that certain launchs' target orbit is way lower than the minimum inclination (for example, equatorial launches from Baikonur). How do they do this? Extra thrust or what?
c) If so, could you launch a spacecraft from Baikonur, another one from Plesetsk (let's say both at 62º), rendezvous them in orbit, then move them to a low-inclination interplanetary injection orbit?

And how is this calculated? :-P

Thank you in advance! (I know I'm asking a lot of questions here, but I'd love to know how this works!)

A.The minimum inclination is because the (first) orbit has to pass above the launch site. Think of an orbit as a circle that is drawn on an imaginary plane where the plane is at some angle to the equator and touches a point at the very center of the earth. If that plane also touches a specific point on the surface of the earth (your launch site), the angle to the plane of the equator can never be less than the latitude of the second point. Theoretically, any launch site can launch to any inclination up to the inverse of its latitude (measured from due east) and there is no “Maximum” inclination, but in reality, range considerations come into play to limit inclination to some value.

B. They do it by changing the inclination of the plane once they are in orbit (or by doing a dog leg maneuver during launch, but that is impractical for getting to a equatorial orbit from most of the current launch sites) Avoiding the problem altogether is most of the rationale behind things like SeaLaunch and the San Marco platform.

C. Yes they could, but orbital rendezvous and plane change are 2 separate problems and would be handled as such.
« Last Edit: 02/29/2012 03:24 PM by JayP »