Gravity-Assisted In the early 1960s, a graduate student named Michael Minovitch working at JPL developed a way to use a planet’s gravitation as a method of propulsion. Gravity-assisted maneuvers work by transferring angular momentum from an orbiting planet to a passing spacecraft. A spacecraft’s trajectory is adjusted so that it will make a fairly...
Electric (Ion) Propulsion Electric propulsion works by using electrical energy to accelerate a propellant to much higher velocities than is possible using chemical reactions. The most common propellant used in ion engines is xenon. Early experimental ion engines used mercury and caesium, but they proved hard to work with. At room temperature, mercury is...
Solid Fuel Solid-fuel rocket engines were the first engines created by man. They were invented by the Chinese in the 13th century and have been widely used since then. The “rocket’s red glare” in the American National Anthem, which was written in the early 1800′s, refers to the small solid-fuel rockets that were used...
Solar Propulsion Interplanetary Solar Sails A solar sail is a spacecraft that has an immense, lightweight mirror attached to it. It derives its propulsion by being pushed by light reflecting off of the mirror, instead of traditional rocket engines. The light used could be supplied by sunlight or lasers placed in orbit. Sunlight exerts...