How do I install the Orbit Dynamics skill?

Run npx skillmds@latest add ashfordeou/orbit-dynamics in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Orbit Dynamics safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Orbit Dynamics?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Orbit Dynamics free to use?

Yes. Installing skills from SkillMD is free. This skill is licensed under Apache-2.

Who published Orbit Dynamics?

ashfordeOU (@ashfordeou) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Orbit Dynamics by ashfordeou — Agent Skill

Name: Orbit Dynamics
Author: ashfordeOU

Orbit Dynamics

Use when analyzing spacecraft orbital mechanics with two-body and J2-perturbed motion: compute velocities with the vis-viva equation, size Hohmann transfer delta-v and transfer time between coplanar circular orbits, and sanity-check LEO-to-GEO transfer budgets (about 3.9 km/s total delta-v). Flags nodal-regression drift from J2 that exceeds an allowed rate for orbit maintenance planning. Uses Earth gravitational parameter 3.986004418e14 m^3/s^2. Trigger: orbit, orbital mechanics, hohmann transfer, delta-v, vis-viva, orbital elements, j2 perturbation, propagation, transfer time.

ashfordeOU 554c9a6 3 files · 8.3 KB Updated Sep 17, 2026

File contents

Orbit Dynamics (gnc-autonomy/space/orbit-dynamics)

Use when the task is two-body and J2-perturbed orbital mechanics: velocities, Hohmann transfer sizing, and drift checks.

Domain quick reference

Two-body dynamics with Earth gravitational parameter mu = 3.986004418e14 m^3/s^2.
Vis-viva: v = sqrt(mu * (2/r - 1/a)); a circular orbit (r == a) gives v = sqrt(mu/r), about 7.61 km/s at 500 km altitude (r = 6878 km).
Hohmann transfer between coplanar circular orbits: two burns at the ends of the half-ellipse transfer arc; total LEO (6878 km) to GEO (42164 km) about 3.9 km/s.
Transfer time is half the period of the transfer ellipse; LEO to GEO takes about 5.3 hours.
The J2 term drives secular nodal-regression drift (deg/day) that matters for repeat-ground-track and formation maintenance.

Workflow

Compute orbital speeds with the vis-viva equation.
Size Hohmann transfer delta-v (dv1, dv2, total) and transfer time for the two circular radii.
Check the total against the LEO-to-GEO sanity band (3.5-4.3 km/s) with scripts/orbit_dynamics_logic.py.
Compare the J2 nodal-regression drift rate against the allowed rate and flag orbit-maintenance needs.

Pitfalls

Using circular-orbit speed for elliptical segments.
Summing dv1 and dv2 with the wrong sign convention.
Forgetting that Hohmann applies to coplanar circular orbits.
Ignoring J2 drift in repeat-ground-track planning.

Behavior contract (gate 3)

The vis-viva, Hohmann, and J2-drift logic is exercised by the gate 3 contract test: scripts/test_orbit_dynamics.py against scripts/orbit_dynamics_logic.py (stdlib unittest, offline). Run: python3 scripts/test_orbit_dynamics.py

Compliance

ECSS series is freely downloadable (ESA); summary-only per standards-map.yaml and brief 06.
compliance: STANDARDS-REF, gated: false.

---name: orbit-dynamicsdescription: Use when analyzing spacecraft orbital mechanics with two-body and J2-perturbed motion: compute velocities with the vis-viva equation, size Hohmann transfer delta-v and transfer time between coplanar circular orbits, and sanity-check LEO-to-GEO transfer budgets (about 3.9 km/s total delta-v). Flags nodal-regression drift from J2 that exceeds an allowed rate for orbit maintenance planning. Uses Earth gravitational parameter 3.986004418e14 m^3/s^2. Trigger: orbit, orbital mechanics, hohmann transfer, delta-v, vis-viva, orbital elements, j2 perturbation, propagation, transfer time.license: Apache-2.0---# Orbit Dynamics (gnc-autonomy/space/orbit-dynamics)Use when the task is two-body and J2-perturbed orbital mechanics:velocities, Hohmann transfer sizing, and drift checks.## Domain quick reference- Two-body dynamics with Earth gravitational parameter mu = 3.986004418e14 m^3/s^2.- Vis-viva: v = sqrt(mu * (2/r - 1/a)); a circular orbit (r == a) gives v = sqrt(mu/r), about 7.61 km/s at 500 km altitude (r = 6878 km).- Hohmann transfer between coplanar circular orbits: two burns at the ends of the half-ellipse transfer arc; total LEO (6878 km) to GEO (42164 km) about 3.9 km/s.- Transfer time is half the period of the transfer ellipse; LEO to GEO takes about 5.3 hours.- The J2 term drives secular nodal-regression drift (deg/day) that matters for repeat-ground-track and formation maintenance.## Workflow1. Compute orbital speeds with the vis-viva equation.2. Size Hohmann transfer delta-v (dv1, dv2, total) and transfer time for the two circular radii.3. Check the total against the LEO-to-GEO sanity band (3.5-4.3 km/s) with scripts/orbit_dynamics_logic.py.4. Compare the J2 nodal-regression drift rate against the allowed rate and flag orbit-maintenance needs.## Pitfalls- Using circular-orbit speed for elliptical segments.- Summing dv1 and dv2 with the wrong sign convention.- Forgetting that Hohmann applies to coplanar circular orbits.- Ignoring J2 drift in repeat-ground-track planning.## Behavior contract (gate 3)The vis-viva, Hohmann, and J2-drift logic is exercised by the gate3 contract test: scripts/test_orbit_dynamics.py againstscripts/orbit_dynamics_logic.py (stdlib unittest, offline). Run:python3 scripts/test_orbit_dynamics.py## Compliance- ECSS series is freely downloadable (ESA); summary-only per standards-map.yaml and brief 06.- compliance: STANDARDS-REF, gated: false.

Frequently asked questions