kilometre per second is an SI derived unit of both speed (scalar) and velocity (vector), signified by the symbol km/s or km s^-1. It is equal to 1,000 m/s.

1 km/s is about the top speed of a sub-orbital spacecraft.

A typical value for the specific impulse of current rockets is 4.5 km/s.

See also

• escape velocity
• delta-v budget.
• Hohmann transfer orbit for some examples of orbital speeds