To asteroid, not to asteroid, that is the question

I've been back and forth on this question, hence the Hamlet reference.  Okay, so now it is starting to look good.  At first, I thought it bad, then I thought it good, then bad again.  Now good again.

What I like about it now?

Let's say you can find an asteroid that masses at 500k pounds.  If it is 1/3 water by mass, that's about 170 k pounds of water that can be mined from it.  Since water is 1/9 th hydrogen by mass, the water can then be mined further for 18519 lbs of water.  Assuming that it has plenty of carbon, you can make 74074 lbs of methane.  Now with the oxygen obtained from the water, and some from Loxleo from Earth, you can make
370370 lbs of fuel.  Since you will require about 50% fuel to go to Deimos using a methane lox engine means that you can carry along 370k lbs of mass to Mars.

Would that be enough for a mission?  Maybe not, if it takes a million per astronaut.  But maybe it wouldn't if you play your cards right.  But if there's no way around that problem, this won't be enough.

Anyway, the way they figure that is by starting from Earth.  From Earth, you have to overcome a lot and that is where the majority of your fuel use will occur.  The space shuttle used 3.8 million pounds of fuel just to get to orbit.  Over half a million pounds for each of the 7 astronauts.

The main idea is to use atmospheric oxygen from the edge of space plus the asteroidal mass for reaction mass so that less will be lifted off the surface of the Earth.

If you still use a half million to get the astronauts into low earth orbit, then the you will be a little short using the above method.  Unless some way is found to reduce the amount of mass needed, you are going to need more asteroids.

Hmm.  Maybe its running bad again.