OK, I wanted to know more about the advantages (if any) of using lunar ice for rocket fuel for trips to Mars.
Therefore I decided to ask the folks on the New Mars Forums, as (a) they are particularly interested in transport to Mars and (b) some of them seem to know an awful lot about the mechanics of space travel. I posted a question here:
http://www.newmars.com/forums/viewtopic.php?f=5&t=8965which has so far attracted about two pages of very interesting replied and debate.
I'm still trying to get my head around some of the arguments, claims and fuel usage diagrams posted there, but I
think a consensus has emerged that:
a) lunar ice would make good rocket fuel
b) that it would make journeys to Mars cheaper
c) but that this would only be the case if the fuel (oxygen and hydrogen) was uplifted from the lunar surface to one of the Earth-Lunar Lagrangian Points (L1) where there would be a fuel depot. Therefore spacecraft from Earth to Mars would not travel via the Moon to pick up fuel there, but would instead travel from Earth to the fuel depot at Lagrangian point L1 to take on fuel for the journey to Mars.
d) That with cheaper and more plentiful fuel available, it would indeed be possible to take a slightly faster trip to Mars (ie the high cost route) but that - according to one poster anyway - it wouldn't be economic to reduce the Earth-Mars transit time much below 180 days. DLR wrote:
Quote:
The cheapest, slowest way to Mars using conventional chemical rocket engines is a Hohmann orbit, it takes 260 days. You can speed up by expending more propellant, but it is not practical to reduce the trip time to much below 180 days because above that, the propellant requirements simply become too great.
But there is a lot more detail in some of the posts in that thread, and other interesting comments too. And there is an article about Lagrange points on Wikipedia here:
http://en.wikipedia.org/wiki/Lagrange_point