Getting into Space

(Picture fromhere.)

The fundamental problem with getting into space isconservation of momentum.

Specifically, we need propellant. A space ship throw propellant out the back. Momentum must be conserved so when a mass is cast out in one direction, the ship moves in the opposite direction. Momentum is often defined in terms of mass (m) times velocity, such that:

m(1)v(1) = m(2)v(2)

Where m(1) and v(1) are, in this case, the mass and velocity of the propellant and m(2)v(2) is the mass and velocity of...