Everyone knows that rockets are huge, expensive, complicated and
impractical. Everyone knows that rockets use ridiculous amount
of fuel. Ok. Challenging concept time: The underlying costs of
space travel are not much more than that of air travel. Space
travel is 'cheap'; or atleast it will be. First, rockets need a
lot of fuel. The amount of fuel is determined by the rocket
equation. If you plug in the figures into the rocket equation
you find that for every pound of rocket, you need maybe 20x that
mass of fuel! And in fact, typical modern-day rockets manage
nearer to 50x that. That's outrageous; it's obvious where the
cost goes right? But it turns out that fuel is cheap. For
example Liquid oxygen (LOX) and Kerosene, LOX is pennies per
pound, aviation fuel (kerosene) isn't much more expensive and
you need a lot less mass of that than you do LOX, because LOX is
pretty heavy. The propellent only costs a few tens of dollars
per pound of rocket max. Therefore if we can get to the point
where the fuel is the only