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EML2 plane change

30 Dec 2013, 15:13 UTC
EML2 plane change
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Most of my models use circular coplanar orbits. But Jon Goff points out many asteroids have a healthy inclination. Departing for an asteroid from the moon's orbital plane often involves a big plane change. And plane changes can be expensive (see comments in What about Mr. Oberth?)But easy plane changes is a big reason I love EML2. This takes some explaining.Let's look at a 60 degree plane change but no change in speed. I pick 60ยบ because it's easy-- the original and new velocity vector as well as the delta V vector are all sides of an equilateral triangle.If your speed is about 8 km/s (as in low earth orbit), a 60 degree plane change costs about 8 km/s.With higher orbits, plane changes are cheaper. At GEO (about 36,000 km above earth's surface), orbit speed is about 3 km/s and a 60 degree plane change costs 3 km/s.EML2 is about 63,000 kilometers above the moon's surface. It's moving about .17 km/s with regard to the moon. So a 60 degree plane change at EML2 costs .17 km/s:But wait, it gets even better!My favorite route from LEO to EML2 is the one found by Robert Farquhar:The orbit is time reversible. A ...

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