Ydoow Posted December 15, 2011 Share Posted December 15, 2011 I read this around the forums, and noticed it in game, something I didn\'t anticipate now that Kerbin and the Mun rotate/revolve.But when I launch a rocket dead-straight up the orbital map shows my orbit leads to the east even though I didn\'t thrust in that direction.I read on the forums that because of the rotation of Kerbin you get 200m/s of velocity to the west though.Could someone just explain what happens here and straighten me out? Link to comment Share on other sites More sharing options...
Hypocee Posted December 15, 2011 Share Posted December 15, 2011 Well, there\'s not much more to it. Newtonian equations only care about velocity relative to the planet\'s center of mass, and the ground (and atmosphere) of a rotating planet are moving relative to the center, fastest at the equator, zero at the poles. That free velocity is a major reason launchpads are as equatorial as their owners can make them. On Kerbin, that\'s about 200 m/s at the equator; on Earth it\'s... 6E6*2pi/24*3600... 450 or so. 'Just remember that you\'re standing on a planet that\'s evolving, revolving at 900 miles an hour...' You\'ll notice a big jump eastward on your NavBall when it switches, or you switch it, from the surface to the orbital REFSMMAT and that horizontal velocity gets integrated.That\'s also the reason weather systems rotate one way in the northern hemisphere and the opposite in the southern. It\'s called 'Coriolis force', and it relates to changing your radius in a rotating system. You\'re actually very gradually adding angular momentum through a tiny 'sideways' force when you move anything toward the equator, and subtracting it as you move toward a pole. On very large scales that force can become significant or overwhelming. Link to comment Share on other sites More sharing options...
Ydoow Posted December 15, 2011 Author Share Posted December 15, 2011 Oh you know what, I see where I was confused.In spaceflights I saw the rotation of kerbin, and it looked like it looked backwards compared to the direction I know the sun travels (east -> west).I didn\'t think of how the earth actually rotates west -> east and that\'s why the sun appears to travel east -> westI assumed Kerbin/Earth rotated the same as the sun, east -> west and that\'s why I was confused why my ship was traveling eastward instead of westward in the Orbital view.So then, to use less fuel, I\'d want to make my ship travel east, right? Link to comment Share on other sites More sharing options...
Hypocee Posted December 15, 2011 Share Posted December 15, 2011 Right. Launch west at the equator and you\'re paying 200 extra m/s. Kerbal? Maybe. Economical? No. Link to comment Share on other sites More sharing options...
Ydoow Posted December 15, 2011 Author Share Posted December 15, 2011 Okay thank you very much.A bit unfortunate though, because I find traveling west makes it easier to intercept the Mun.It\'s like you\'re attacking it, so it\'s harder to miss Link to comment Share on other sites More sharing options...
thorfinn Posted December 15, 2011 Share Posted December 15, 2011 Right. Launch west at the equator and you\'re paying 200 extra m/s. Kerbal? Maybe. Economical? No.It\'s also Israeli, for geographical and military reasons: http://en.wikipedia.org/wiki/Shavit Link to comment Share on other sites More sharing options...
SteevyT Posted December 15, 2011 Share Posted December 15, 2011 It\'s also Israeli, for geographical and military reasons: http://en.wikipedia.org/wiki/ShavitIsrael should resurrect the Sea Dragon so they can do eastward launches. Link to comment Share on other sites More sharing options...
thorfinn Posted December 15, 2011 Share Posted December 15, 2011 Israel should resurrect the Sea Dragon so they can do eastward launches.'Make it big enough that nobody will mistake it for a ballistic missile'?Could be a good strategy... Link to comment Share on other sites More sharing options...
Ydoow Posted December 15, 2011 Author Share Posted December 15, 2011 Good lord...the first stage put it 25 miles up at 1.8km/s...that\'s ridiculous Link to comment Share on other sites More sharing options...
thorfinn Posted December 16, 2011 Share Posted December 16, 2011 Good lord...the first stage put it 25 miles up at 1.8km/s...that\'s ridiculousThat\'s a bit mild for a first stage, actually. Saturns reached 2.3 km/s at first stage cutoff, for example. Tremendous acceleration though, considering the sheer mass carried... I would REALLY like to see that thing fly. But the stability issues of a 36 thousand tons rocket engine.... :o Oh, I also recommend reading this article and this other one, for getting a very good feel of the quantities involved in orbital flight. It\'s rare to see a launch vehicle 'being built' with pieces easily comparable to one another... outside of KSP, that is Link to comment Share on other sites More sharing options...
Ydoow Posted December 16, 2011 Author Share Posted December 16, 2011 That\'s a bit mild for a first stage, actually.Well compared to everything I\'ve built...lol Link to comment Share on other sites More sharing options...
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