Spacecraft

A spacecraft is a vehicle that travels through space using an external and passive method of propulsion, while a spaceship flies through space by means of active propulsion via an internal engine and propellant fuel. A spacecraft is a Type I technology used for sub-light impulse speeds before the invention of faster-than-light methods of travel. Initially spacecraft are for interplanetary travel but later can be used for close interstellar travel.

Spaceships can launch and land by themselves whereas spacecraft need launch-assist and land-assist mechanisms.

Land-assist mechanisms
First spacecraft used rocket or chemical engines that created a thrust reaction by expelling mass. Then electromagnetic, ion, plasma and pulse detonation engines came along until more advanced propulsion technology was invented. With field propulsion, no propellant is necessary but instead momentum of the spacecraft is changed by an interaction of the spacecraft with external force fields, such as gravitational and magnetic fields from stars and planets.

In the 1950s, the Orion Project proposed a nuclear rocket propelled by a succession of nuclear blast waves from a stream of atomic bombs. A spacecraft would drop a series of atomic bombs out its back, creating a series of powerful blasts of X-rays. This shock wave would then push the starship forward. It was estimated that an advanced version of Orion would weigh 8 million tons, with a diameter of 400 meters, and be powered by 1,000 hydrogen bombs. Eventually the Nuclear Test Ban Treaty of 1963, which prohibited aboveground testing of nuclear weapons. killed the idea of nuclear rockets.

The $100m Breakthrough Starshot is the first serious attempt to design and engineer an interstellar space probe that could reach the nearest star system within a generation. This involves a ground-based light beamer pushing ultra-light nanocrafts (miniature space probes attached to lightsails) to speeds of around 0.2c. Such a system would allow a flyby mission to reach Alpha Centauri in just over 20 years from launch. A number of hard engineering challenges remain to be solved before these missions can become a reality.

The lighthugger uses quantum mechanics.