# Does launching to interplanetary space from LEO require the least delta-v?

Based on this chart from wikipedia, (I do not know if I am reading it correctly)

This all assumes LEO-Eq

LEO to C3/0=3.22

LEO to GEO to C3/0=3.9+1.3=5.2

LEO to EML-1 to C3/0=3.77+0.14=3.91

LEO to EML-2 to C3/0=3.43+0.14=3.57

LEO to LLO to C3/0=4.04+1.40=5.44

Does leaving from EML-2 require 10% more delta-v than LEO?

• If LEO is assumed to be the starting point, then yes. But the moon and/or near earth asteroids are possible future propellent sources. In which case LEO would no longer be the default starting point. – HopDavid Dec 30 '18 at 21:42

Your additions from the table are correct, in that they including delta-V used to 'stop' or stabilize each end state orbit. So if all your fuel is being shipped up from earth then you want to minimise the fuel used for anything other than reaching departure velocity from earth, and stablising at GEO or the moon is not doing that.

If you just boosted to GEO altitude but left orbit eccentric and then boosted a second time back at perigee to escape velocity the DV numbers should add up the same as the direct boost in the table, or possibly slightly better if you phased correctly with the moon and/or were using a low thrust system and wanted to maximise gains from the Oberth effect.

Edit based on comment from OP: All of this assumes all your mass is coming from the surface on relatively inefficient but high thrust rockets. You want to stop using these rockets for adding DV as soon as possible, so reaching LEO orbit and building out your low thrust/high efficiency interplanetary stage there is better, and also means you can leave as much fabrication/people/supply mass in LEO as possible.

If you have access to resources already in GEO or moon orbit (say for an emergency asteroid re-direct) than starting an interplanetary mission from there reduces the MISSION cost in DV, but if everything came from earth in the first place that DV cost would need to be accounted for somewhere.

On potential case for non LEO start is if you have a multi use transfer vehicle like the Hermes in 'the Martian'. In this case when you bring it back to earth it is cheaper to park it in a high orbit and shift fresh supplies and crew up to it, rather than consuming DV to bring the entire transfer vehicle mass from escape to LEO and then back out again on the next trip.

Another edge case would involve adding a half stage to your mission where the DV for LEO to just short of escape comes from some form of tug craft which then returns to earth and aerobrakes back to LEO for re-use, but doing this is trading DV cost of getting boosters into orbit (do it once) against the losses of each escape velocity burn (tug is heavier than something expendable due heat shields etc) and still works best starting from LEO.

• The origin of the my question was if there was a transfer station orbiting the Earth, where would it be best located in terms of least amount of fuel used, so including delta-V used to 'stop' or stabilize each end state orbit would be relevant, if I am understanding this all correctly. – Bob516 Dec 31 '18 at 2:20
• The summary of the extensive answer: If everything comes from Earth or is headed for Earth, LEO is best. The more that comes from outer space and returns to outer space (the Hermes part of the answer), the higher the best orbit is. – asdfex Dec 31 '18 at 15:18