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Orbital Velocity — Why Satellites Keep Missing Earth - Leejohnston - 01-08-2026
## Orbital Velocity — Why Satellites Keep Missing Earth
### 1. The Equation
Orbital velocity:
v = √(GM ÷ r)
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### 2. What Each Symbol Means
- v = orbital velocity
- G = gravitational constant
- M = mass of the planet
- r = distance from the planet’s centre
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### 3. What the Equation Is Telling Us
An orbit is **continuous free fall** where forward speed causes the ground to curve away.
Satellites don’t avoid falling — they miss the planet.
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### 4. Where It Comes From (Intuition)
Gravity pulls inward while velocity carries the satellite forward.
At the right speed, these balance perfectly.
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### 5. Worked Example
For low Earth orbit:
v ≈ **7.8 km/s**
That’s fast enough to circle Earth every ~90 minutes.
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### 6. Real-World Applications
- Satellites
- Space stations
- Planetary motion
- Orbital mechanics
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### 7. Common Misconceptions
- Orbit means no gravity → false
- Higher orbits need more speed → false
- Rockets keep firing in orbit → false
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### Try It Yourself
Why do higher orbits actually move more slowly?