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Hop's Blog


20 May 2015, 02:40 UTC
(200 words excerpt, click title or image to see full post)

Earth Moon Lagrange 2 or EML2 is one of 5 locations where earth's gravity, moon's gravity and so called centrifugal force all cancel out. It lies beyond the far side of the moon at about 7/6 of a lunar distance from earth.Infrastructure at any of these 5 locations could be kept in place with a small station keeping expense. Other high earth orbits would be destabilized by the influences of the earth, moon or sun.Of these 5 locations, EML2 is the closest to escape. How close?Specific orbital energy is given byv2/2 - GM/rv: velocity with regards to the earthG: gravitational constantM: mass earthr: distance from earth centerHere's specific orbital energies for a few orbits:For earth's surface I'm thinking of someone standing on the equator. The earth's surface at the equator moves about .5 km/s. We're not looking at atmospheric drag or gravity loss.For EML1 and EML2 I'm looking at resulting earth orbits for payloads nudged away from Luna's Hill Sphere.Most the energy is getting from earth's surface to Low Earth Orbit (LEO). Then another huge chunk is getting from LEO to escape.EML2 is right next door to escape (aka C3=0). If the goal line is Trans Mars Injection, EML2 is ...

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