A point which no acceleration from gravity or other force can be detected.

A chemical mixture that is burned to produce thrust

A government agency responsible for the United States of America's space program and long-term general aerospace research.

A vehicle for driving over rough terrain

A proposed explanation for an observation

Vehicle, missile, or aircraft that obtains thrust by the reaction to the ejection of exhaust.

Spacecraft operated by automatic or remote control

A project which represents a permanent human presence in space.

A fixed or adjustable van or airfoil affixed longitudinally to a space craft for stabilizing purposes

A fixed point in a material body through which the resultant force of gravitational attraction acts

The path of an object moving through space

The part of the universe lying outside the limits of Earth's atmosphere.

The informal competition between the US and Soviet Union to launch unmanned satellites, send people to space and land them on the moon

A bowl-shaped depression formed in the soft soil of the moon by the impact of a meteorite or other object