What are Some Proposed Means of Interplanetary Travel?
There are three proposed means of interplanetary travel which get the most attention – bipropellant liquid rockets, electric engines, most notably the ion engine or ion thruster, and the more experimental (but extremely promising) VASIMR, a variable specific impulse magnetoplasma rocket, which uses radio waves and magnetic fields to accelerate a propellant. These interplanetary propulsion systems have an exhaust velocity (i.e., top speed) of 3 – 5 km/s, 30 – 50 km/s, and 10 km/s – 300 km/s, respectively. Specific impulse (miles per gallon, basically) ranges on a similar scale. To get off the planetary surface initially, solid rocket boosters are often used. Bipropellant rockets have been extensively used throughout the space program, and took men to the Moon as well as being used as the primary means of interplanetary travel for satellites. Ion engines are new and were only first tested in space in 1998, onboard Deep Space I. VASIMR engines are even newer and have only been tested on t
