Source: https://guthlabs.ai/docs/instruments/vis-viva-elliptical-orbit-energy-calculator/implementation/

instrument implementation / implementation-contract

# Vis-Viva / Elliptical Orbit Energy Calculator implementation

A source-bound implementation contract for Vis-Viva / Elliptical Orbit Energy Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t4-047

**Effect**: Computation or source lookup only

## Input and validation requirements

The advertised apoapsis and periapsis speeds cannot be computed from the stated inputs GM, current radius r, and semi-major axis a alone; eccentricity or both apsis radii are required. The calculator also needs explicit rejection handling for r=0 and for negative square-root radicands, especially at and beyond r=2a.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "GM": 398600.4418,
    "r": 7000,
    "a": 7000,
    "units": "km, km³/s²"
  },
  "expected_outputs": {
    "speed": 7.54605329,
    "specific_energy": -28.47146013,
    "apoapsis_speed": null,
    "periapsis_speed": null
  },
  "working": "v²=398600.4418×(2/7000−1/7000)=398600.4418×(1/7000)=56.9429202571 km²/s²; v=√56.9429202571=7.54605329 km/s. ε=−398600.4418/(2×7000)=−398600.4418/14000=−28.47146013 km²/s². Apoapsis and periapsis speeds are not determined because eccentricity or apoapsis/periapsis radius was not supplied."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/vis-viva-elliptical-orbit-energy-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/vis-viva-elliptical-orbit-energy-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/vis-viva-elliptical-orbit-energy-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`