Calculator Inputs
Use a preset body or switch to a custom mass and radius. Large screens show three columns, smaller screens collapse automatically.
Example Data Table
The sample below uses Earth as the central body and illustrates how speed drops while orbital period increases as altitude rises.
| Altitude (km) | Orbital Radius (km) | Speed (km/s) | Period (min) | Acceleration (m/s²) |
|---|---|---|---|---|
| 200.00 | 6,571.00 | 7.7885 | 88.35 | 9.2316 |
| 400.00 | 6,771.00 | 7.6726 | 92.41 | 8.6943 |
| 35,786.00 | 42,157.00 | 3.0749 | 1,435.70 | 0.2243 |
Formula Used
Circular orbit speed: v = √(GM / r)
Orbital period: T = 2π√(r³ / GM)
Centripetal acceleration: a = GM / r²
Escape speed at the same radius: ve = √(2GM / r)
Here, G is the gravitational constant, M is the body mass, and r is the distance from the body center. If you enter altitude, the calculator first converts it to radius by adding the body radius.
How to Use This Calculator
- Select a preset central body or choose the custom option.
- Pick whether your known input is orbital altitude or orbital radius.
- Enter the value and choose the matching distance unit.
- For a custom body, provide body mass and body radius.
- Choose the number of decimals for the displayed outputs.
- Press Calculate Orbit Speed to show results above the form.
- Use the export buttons to download CSV or PDF copies.
Assumptions and Scope
This page estimates ideal circular motion. It does not model atmospheric drag, body oblateness, third-body perturbations, or powered station-keeping.
Frequently Asked Questions
1. What does circular orbit speed mean?
It is the tangential speed needed to stay in a perfectly circular orbit at a chosen radius around a central body.
2. Why does altitude change the speed?
Higher altitude means larger orbital radius. Gravity weakens with distance, so the required circular speed becomes lower.
3. Can I use radius instead of altitude?
Yes. Switch the mode to orbital radius when you already know the distance from the body center.
4. What is the difference between orbit speed and escape speed?
Orbit speed keeps a circular path. Escape speed is higher and gives enough energy to avoid falling back without further propulsion.
5. Does this work for moons, planets, and stars?
Yes. You can use the built-in presets or enter custom body mass and radius for any spherical central body.
6. Does the calculator include atmosphere or drag?
No. It assumes ideal vacuum conditions and a clean two-body model, so low-altitude real missions may need more analysis.
7. Why must orbital radius exceed body radius?
A circular orbit cannot exist inside the body surface. The path must stay outside the radius of the central object.
8. Is this useful for mission planning?
It is useful for quick screening, education, and checks. Detailed mission design still needs perturbation, transfer, and propulsion analysis.