[ExI] Eyes on the Solar System

[spike at rainier66.com]

-----Original Message-----
From: spike at rainier66.com <spike at rainier66.com> 
...

>...On second thought, Stuart, scratch that.  The irony of using a hydrogen
first stage to lift a kerosene final stage, oh that is killing me...OK then.
There is a bright side in all this somewhere, but the argument above is an
epic fail, my apologies, sheesh how embarraskin...spike



Stuart as I am pondering the problem of carrying humans to Mars, I am
reminded of the ugliness of some of the solutions one must try.  Like that
business of lifting a kerosene burning stage using a hydrogen burning stage
for instance, from an engineering point of view, it is just uglier than
nudist colony day at the nursing home.

The problem is based on the need to fire a delta V from earth orbit, then
fire an orbit adjust burn when we get to Mars about 8 months later, then go
play on the surface of Mars for a few days, then when (or if) the humans
come back, you have another orbit adjust burn to get back to Earth, then
another burn 8 months after that to insert into LEO to get ready for
descent, then a descent initiation burn.

OK so even if you had those huge first stage motors in LEO... you wouldn't
use them.  Reason: there is no point in hauling all that stuff out to Mars
where you can't use it because we have no known technology for holding onto
liquid hydrogen for the 8 months it takes to get to Mars.  So... we need to
haul low-volatility fuel oxidizer (because can't hang onto LOX that long
either) so we get hydrazine and nitric acid thrusters for everything after
we leave Earth orbit.

Oh what an ugly solution that is.

spike