A good introductory discussion of chemical-rocket fuels can be found by clicking here . When the total kinetic energy of the rocket and its exhaust are taken into consideration, the highest efficiency occurs when the exhaust is equal to the instantaneous rocket velocity, as shown in the figure at right. See Sutton for a discussion. Ascent from planetary surfaces Effect Key effects that come into play during launch from planetary surfaces are shown at right. Gravity reduces the effective acceleration, and it is generally the most important force.
Atmospheric drag can create significant friction, both heating and slowing a rocket.
The coriolis and centrifugal forces due to the planet's rotation are usually small effects, but the planet's rotation can often be used to give the rocket an initial velocity in a desired direction. Various criteria are used to decide when to launch a rocket. The F-1 engine used in the first stage of the Saturn V rockets that launched the Apollo missions appears at right. Heat transfer Heat transfer presents a critical problem for rocket engine designers. Nozzles Rocket nozzles are usually of an expansion-deflection design.