Answer · confidence: partial
What is orbit speed, and how fast must you go to stay up?
Research question: What does 'orbital velocity' mean, and what speed is needed to stay in low Earth orbit?
Orbital velocity is the speed at which gravity supplies exactly the centripetal force needed to keep a body on a circular orbit, so the speed stays at a constant magnitude 1. For a circular orbit it is calculated as the square root of GM divided by r, and this is called the first cosmic velocity 3. A body in a low orbit around Earth needs a speed of about 7.9 km/s 2. The newest fact provided dates from 2006, so it is about 20 years old as of October 2026 and may not reflect current figures 78.
Checked 2026-10-20. Only documented and supported facts are used.
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[1] supported
For a circular orbit, gravitational attraction exactly supplies the centripetal force needed, which fixes the orbital speed at a constant magnitude.
"Für den Spezialfall eines kreisförmigen Orbits bringt die Anziehungskraft zwischen den Himmelskörpern jeweils gerade die für die Kreisbahn notwendige Zentripetalkraft auf, wodurch die Geschwindigkeit festgelegt (und betragsmäßig konstant) ist."Bahngeschwindigkeit (Astronomie)
[2] supported
The speed of about 7.9 km/s is the speed of a body in a low orbit around Earth, also called the first cosmic velocity.
"s: Geschwindigkeit eines Körpers in einer niedrigen Umlaufbahn um die Erde ( erste kosmische Geschwindigkeit )"Raumflugmechanik
[3] supported
The speed of a circular orbit is the first cosmic velocity, and it is calculated as the square root of GM divided by r.
"Kreisbahn, 1. kosmische Geschwindigkeit"Bahngeschwindigkeit (Astronomie)
[4] supported
The speed of 11.2 km/s is needed for a body to leave Earth's gravitational field, and is called the escape velocity or second cosmic velocity.
"11,2 km/s: Geschwindigkeit eines Körpers, um das Schwerefeld der Erde zu verlassen (Fluchtgeschwindigkeit oder zweite kosmische Geschwindigkeit )"Raumflugmechanik
[5] supported
Under gravity described by the two-body problem, a body with low energy moves on an elliptical orbit, with a circle as a special case.
"bei geringer Energie ist die Umlaufbahn elliptisch (mit dem Kreis als Spezialfall);"Raumflugmechanik
[6] supported
The escape velocity of Earth is not enough to leave the solar system, because of the Sun's own gravitational pull.
"Insbesondere ist diese Geschwindigkeit, aufgrund der Anziehungskraft der Sonne selbst, nicht ausreichend um das Sonnensystem zu verlassen."Raumflugmechanik
[7] documented
The CHAMP satellite operates in Low Earth Orbit (LEO).
"After an overview of approaches and results in precise orbit determination (POD) for the CHAMP satellite in the Low Earth Orbit (LEO) we focus on the relations between kinematic POD and gravity field determination."From Kinematic Orbit Determination to Derivation of Satellite Velocity and Gravity Field
[8] documented
Kinematic velocities derived from positions are used in gravity field determination as kinetic orbital energy.
"We discuss determination of kinematic velocities out of kinematic positions that enter the gravity field determination in the form of kinetic orbital energy."From Kinematic Orbit Determination to Derivation of Satellite Velocity and Gravity Field