Kilometer Per Second (km/s)

ScientificCurrent unit

1,000 m/s. Used for orbital velocities; low Earth orbit is about 7.7 km/s.

1 kilometer per second = 1,000 meters per second (exactly).

About the kilometer per second

Orbital mechanics is where kilometers per second become the everyday scale. A satellite in a circular low Earth orbit between 200 and 2,000 km altitude travels at 7.7 to 6.9 km/s, and the International Space Station and typical low orbit satellites move at about 7.7 km/s, which is 27,700 km/h. Earth itself circles the Sun at an average of about 29.8 km/s, roughly 3.9 times that low orbit speed, since 29.8 divided by 7.7 is 3.87.

The unit also suits escape velocities, such as 11.186 km/s from the surface of Earth and 2.38 km/s from the Moon, and the speed of sound in water, about 1.5 km/s. It is a thousand times the SI base speed of 1 m/s, so quoting orbital motion in meters per second would mean long strings of digits.

Sources: Wikipedia: Orbital speed; Wikipedia: Escape velocity; Wikipedia: Orders of magnitude (speed)

Kilometer Per Second conversion chart

1 kilometer per second expressed in every other speed unit:

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