What NASA thinks it takes to go to Mars

Consulting the tables I constructed with respect to masses that can be delivered based upon delta v and isp, and given that it will take up to 10 launches that can place 290k lbs per launch into LEO, my calculations show that NASA wants to put at 700k lbs into LMO.  Of that amount, perhaps all of that will have to land on the surface.  Hard to say what good leaving anything in orbit will do.

If I am not mistaken, 700k lbs is more than the mass of the entire ISS.  What in the world is the need for such a large amount of mass?  Are all of the astronauts to get their own Mercedes Benz and luxury suites on the surface of Mars?  It just seems like a helluva lot to me.  Even if you use a completely powered landing and no aerobraking, that will still land 388k lbs on the surface.  Or they can land half, and use the other half to get back.  That would leave 350k in orbit, and land the rest.  That would mean at least 160k lbs on the surface.  They could probably do better than that with aerobraking.

To get back would only require getting to orbit and then docking with the mass that is still in orbit that will take you home.  Only about 20k fuel would be needed to orbit a 20k lb return craft.  That leaves 120k for surface activities.  True, they'll have to stay on the surface for a year, but really, is this necessary?  

Zubrin ideas don't call for that much mass.

They will need a way to get back.  Either they make their own fuel on the surface of Mars, or carry it all with them.  Maybe carrying along the fuel is what they have in mind.  Maybe they think that is less risk.  But the 350k still in orbit will certainly be enough to get home.   You could ditch that last return to orbit craft once you are back in Mars orbit.  Using liquid hydrogen rockets, you'd still be able to get back to Earth's orbit and leave nearly 100k in mass in Earth's orbit before reentry.  Again, is this necessary?

There may be some details I'm missing somewhere.  If I'm missing it, so is Zubrin.  Zubrin's ideas didn't call for 10 big rocket launches.

What's the deal here?  Are they putting so much safety into it that they are going to minimize the risk to the point where everything has a backup and there may even be backups to backups.