# Delta-v for landing on the moon

I'm doing a few calculations to understand how to go from the Earth to the Moon. I used an elliptical (Hohmann Transfer) orbit to go from LEO to a circular Moon's orbit performing two $$\Delta v$$ (resulting in $$\Delta v$$ ~ 3.94 km/s). I don't know exactly how to perform the landing process and calculate the required $$\Delta v$$. I few papers in the literature show that it is between 1.5 km/s - 2 km/s. I think I should use an hyperbolic orbit but I'm not sure how. Any clues for a simple calculation? also, does it depend on the altitude above the Moon's surface?

Thank you

• i.imgur.com/AAGJvD1.png Apr 2 '20 at 17:43
• @OrganicMarble That's probably the theoretical value for an ascent to 100km; descent needs a little additional safety margin. Apr 2 '20 at 17:46
• @RussellBorogove You need a safety margin going up, also. So long as your measurement of your location and your landing point is accurate you shouldn't need any more margin going down. (Now, if your measurements are wrong....I've killed too many Kerbals with MechJeb's land anywhere mode.) Apr 3 '20 at 4:00
• @LorenPechtel It’s not symmetrical in practice. For ascent, no rocks to hit in LLO, and you know your surface point is safe. If your endpoint is off by a km or two, you can fix it up at leisure with RCS. Apr 3 '20 at 4:06
• @RussellBorogove Yeah, if there's the slightest question as to your landing you need reserve fuel. Just look at Apollo 11. I'm talking about a situation where it's routine, you know exactly where you're going. Apr 3 '20 at 4:53