Getting to orbit

• Consider the “specific energy” (energy per unit mass, KE + PE) of an object in space relative to an inertial point on the Earth's surface

• The V-2, moving slowly at the edge of space, had E = 1.5 MJ/kg (1.1 to 2.1 for different launches)

• An orbiting satellite at the same altitude needs E=31.6 MJ/kg. Getting to orbit is MUCH harder! It took 15 more years...