Circular orbital velocity API

Returns the circular orbital speed v=sqrt(mu/r) and matching period for an orbit radius or altitude above a named body (Earth, Mars, Sun, etc.), with bundled standard gravitational parameters so no mass lookup is needed. Answers 'What speed for a circular orbit at 400 km?', 'How fast is LEO?'.

Price$0.04per request

MethodPOST

Route/v1/space/circular-orbit-velocity

StatusLive

MIME typeapplication/json

Rate limit120/minute

Cache0s public

spaceastronomyorbital-mechanicscircular-orbitorbital-velocityleosatelliteastrodynamics

API URLhttps://x402.hexl.dev/v1/space/circular-orbit-velocity

Integration docs

Example request

{
  "body": "earth",
  "altitudeM": 400000
}

Example response

{
  "body": "earth",
  "mu": 398600441800000,
  "orbitRadiusM": 6771000,
  "velocityMs": 7672.5986,
  "velocityKms": 7.6726,
  "periodS": 5544.855,
  "periodMin": 92.4143,
  "interpretation": "A circular orbit at 6771 km radius requires 7.673 km/s."
}

Input schema

{
  "type": "object",
  "properties": {
    "body": {
      "type": "string",
      "description": "Named central body (earth, sun, mars, ...)",
      "examples": [
        "earth"
      ]
    },
    "mu": {
      "type": "number",
      "description": "Standard gravitational parameter GM (m^3/s^2), overrides body"
    },
    "centralMassKg": {
      "type": "number"
    },
    "radiusM": {
      "type": "number",
      "description": "Orbit radius from body center (m)"
    },
    "altitudeM": {
      "type": "number",
      "description": "Altitude above surface (m); needs body or centralRadiusM",
      "examples": [
        400000
      ]
    },
    "centralRadiusM": {
      "type": "number"
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}